The 2009 AP® Computer Science A Released Exam Contains: = Multiple-Choice Questions, Answer Key, and Diagnostic Guide = Free-Response Questions with: + Scoring Guidelines + Sample Student Responses + Scoring Commentary = Statistical Information About Student Performance on the 2009 Exam Materials included in this Released Bxam may not reflect the current AP Course Description and exam in this subject, and teachers are advised to take this into account as they tise these materials to support theit ation about this AP course and exam, please download the official AP Course Description from the AP Central* Web site at apcentral.collegeboard.com. anstructi ef students. For up-to-date infonshapter I: The AP’ Process Nhat Is the Purpose of the AP® Computer Science A ‘am? Who Develops the Exam? Jow Is the Exam Developed? Section I—Multiple Choice Section II—Free Response Question Types Multiple Choice Free Response icoring the Exam ‘Who Scores the AP Computer Science A Exam? Ensuring Accuracy How the Scoring Guidelines Are Created Training Readers to Apply the Scoring Guidelines Maintaining the Scoring Guidelines Preparing Students for the Exam Essential Features of Student Responses ‘Teaching Free-Response Writing + chapter will give you a brief overview of the slopment and scoring processes for the AP Computer nee A Exam. You can find more detailed information P Central® (apcentralcollegeboard.com) aat Is the Purpose of the ’ Computer Science A Exam? AP Computer Science A Exam is designed to allow lents to demonstrate that their knowledge, under- ding, and skills are equivalent to those gained by lents who have successfully completed an introductory 2ge-level course in computer science. The AP Computer nce A Exam includes material that is covered in a -semester computer science course in which the Java gramming language is used to illustrate an object- ited approach to problem solving and algorithm slopment. : he multiple-choice section of the exam is designed to zr the breadth of the curriculum in terms of knowledge, «ciples, and conceptual understanding. The free vonse section requires students to solve problems vlving more extended reasoning. In both sections, lents must demonstrate their ability to design, write, yyze, and document programs and subprogeams Lifying scores on the AP Computer Science A Exam * allow students to begin their college careers with credit an introductory computer science course and/or ribution credit for a computer science course Who Develops the Exam? ‘The AP Computer Science Development Committee, working with Assessment Specialists at ETS, develops the exam. This committee is appointed by the College Board and is composed of six teachers from secondary schools, colleges, and universities in the United States. The members provide different perspectives: high school teachers offer valuable advice regarding realistic expectations when ‘matters of content coverage, skills required, and clarity of phrasing are addressed. College and university faculty _members ensure that the questions are at the appropriate level of difficulty for students planning to continue their studies at colleges and universities. Committee members typically serve one to four years. ‘Also aiding in the exam development process is the Chief Reader, the college computer science professor responsible for supervising the scoring of the free-response questions at the AP Reading. The Chief Reader attends every committee ‘meeting to ensure that the free-response questions selected for the exam can be scored reliably. The expertise of the Chief Reader and the committee members who have scored exams in past years is notable: they bring to bear their valuable ‘experience from past AP Readings and suggest changes to improve the quality and the performance of the questions. In addition, ETS computer science Assessment Specialists offer their guidance and advice. How Is the Exam Developed? ‘The Development Committee sets the exam specifications, determining what will be tested and how it will be tested. also determines the appropriate level of dificulty for the exam, based on its understanding of the level of competence required for success in introductory computer science courses in colleges and universities. Each AP Computer Science A Exam is the result of several stages of development that together span two or more years. Section I—Multiple Choice 1. Development Committee members and other faculty ‘write and submit multiple-choice questions directed to the major topics outlined in the AP Computer Science A Course Description 2. ETS Assessment Specialists perform preliminary reviews to ensure that the multiple-choice questions are worded clearly and concisely3. At the committee meetings, which are held two or three timesa year, the committee members review, revise, and approve the draft questions for use on future exams, They ensure that the questions are clear and unambiguous, that each question has only one correct answer, and that the difficulty level ofthe questions is appropriate. 4, Most of the approved draft questions are pretested in college classes to obtain some estimate ofthe questions level of difficulty. 5. From the pool of approved questions, ETS Assessment Specialists select an appropriate mix of materials for the ‘multiple-choice section of an exam, making sure that the questions are distributed across the content areas as specified by the Development Committee in the AP Computer Science A Course Description. 6. The committee thoroughly reviews the draft exam in various stages of its development, revising the individual {questions and the mix of questions until itis satisfied with the result “The committee contls the difficulty le el ofthe multiple- choice section by selecting a wide range of questions, a sub- set of which has been used in an earlier form of the exam. Section IJ—Free Response 1. Wellin advance ofthe exam administration, the members of the Development Committee write free-response {questions for the exam, These are assembled into 9 free-response question pool 2. From this pool, the committee selects an appropriate ‘combination of questions tor a particular exam. It reviews and revises these questions at all stages of development of that exam to ensure that they are ofthe highest possible ‘quality. The committee considers, for example, whether the questions will offer an appropriate level of difficulty and whether they will elicit answers that will allow Readers, the high school and college computer science teachers who score the free-response questions, to discriminate among the responses along the scoring guidelines used for the different questions. An ideal question enables the stronger students to demonstrate their accomplishments while revealing the limitations of less proficient students. Question Types “The 2009 AP Computer Science A Exam contains a 75- minute multiple-choice section consisting of 40 questions and a 105-minute free-response section consisting of 4 questions. The two sections are designed to complement each other and to measure a wide range of skills. Multiple-choice questions are useful for measuring 2 student’ level of competence in a variety of contexts. In addition, they have three other strengths: 1. They are highly reliable, Reliability, or the likelihood the students of similar ability levels taking a different form ¢ the exam will receive the same scores, is controlled mon. effectively with multiple-choice questions than with free-response questions. 2. ‘They allow the Development Committee to include a selection of questions at various levels of difficulty, there ensuring that the measurement of differences in student achievement is optimized. For AP Exams, the most important distinctions are between students earning scores of 2 and 3 and those earning scores of 3 and 4. ‘These distinctions are usually best accomplished by usit ‘many questions of middle difficulty. 3. They allow comparison of the ability level ofthe current students with those from another year. A number of questions from an earlier exam ave included in the curre cone, allowing comparisons to be made between the scor of the earlier group of students and those of the current group. This information, along with other data, is used t establish AP scores that reflect the competence demand by the Advanced Placement Program® and that can be legitimately compared with scores from earlier years. Free-response questions on the AP Computer Science A. Exam require students to use thei analytical and organizational skills to reason about and write program, fragments that fit the specifications given. They allow students to demonstrate their understanding of program structure and their ability to translate that understanding into a concrete solution. The free-response format allows for the presentation of uncommon yet correct responses and permits students to demonstrate their mastery of ‘computer science by 2 show of creativity. ‘The free-response and multiple-choice sections are designed to complement each other and to meet the overal course objectives and exam specifications. After each exam administration, the questions in each section are analyzed both individually and collectively, and the findings are use to improve the following year’s exam. Scoring the Exam Who Scores the AP Computer Science A Exam? The multiple-choice answer sheets are machine scored. ‘The teachers who score the free-response section of the AP Computer Science A Exam are known as Readers. The majority of these Readers are experienced faculty member> teach either alhigh school AP Computer Science A se or an equivalent course ata college or university, fat care is taken to obtain a broad and balanced group of sders. Among the factors considered before appointing aeone to the role are school locale and setting (urban, al, and so on), as well as the potential Reader's gender, nicity, and years of teaching experience. University and h school computer science teachers who are interested plying to be a Reader at a future AP Reading can aplete and submit an online application via AP Central centsal.collegeboard,com/readers) or request more ormation by e-mailing apreader@ets.org, 1 June 2009, approximately 130 computer science :hers and professors gathered at the Duke Energy Center Zincinnati, Ohio, to participate in the scoring session the AP Computer Science A Exam. Some of the most rienced members of this group were invited to serve as estion Leaders and Table Leaders, and they arrived at the ding early to help prepare for the scoring session. The raining Readers were divided into groups, with each up advised and supervised by a Table Leader. Under the dance of the Chief Reader, Question Leaders and Table ders assisted in establishing scoring guidelines, selecting aple student responses that exemplified the guidelines, \ preparing for Reader training. All ofthe free-response stions on the 2009 AP Computer Science A Exam were uated by the Readers at this single, central scoring sion under the supervision of the Chief Reader. suring Accuracy primary goal of the scoring process is to have all ders score their sets of responses fairly, consistently, and h the same guidelines as the other Readers, This goal is, jeved through the creation of detailed scoring guidelines, thorough training ofall Readers, and the various checks balances that are applied throughout the AP Reading. 'w the Scoring Guidelines Are Created ‘As the questions are being developed and reviewed, the Development Committee and the Chief Reader discuss the scoring of the free-response questions to ensure that che questions can be scored validly and reliably. Before the AP Reading, the Chief Reader prepares a draft of the scoring guidelines for each free-response question. In the case of AP Computer Science A, a 10-point scale (0-9) is used. A score of 0 means the student received no credit forthe problem. The Chief Reader, Fxam Leaders, Question Leaders, Table Leaders, and ETS Assessment Specialists meet atthe Reading site afew days before the Reading begins. They discuss, review, and revise the draft scoring guidelines, and test them by pre-scoring randomly selected student responses. If problems or ambiguities become apparent, the scoring guidelines are revised and refined until a final consensus is reached, 3. Once the scoring of student responses begins, no changes ‘or modifications in the guidelines are made. Given the expertise of the Chief Reader and the analysis of many student responses by Question Leaders and Table Leaders in the pre-Reading period, these guidelines can be used to cover the whole range of student responses. Each Question Leader and Table Leader devotes a great deal of time and effort during the fist day of the Reading to ‘eeching the scoring guidelines for that particular question and to ensuring that everyone evaluating responses for that question understands the scoring guidelines and can apply them reliably. Training Readers to Apply the Scoring Guidelines Because Reader training is so vital in ensuring that students receive an AP score that accurately reflects their performance, the process is thorough: 1. nthe first day of the Reading, the Chief Reader provides, an overview of the exam and the scoting process to the entire group of Readers. The Readers then break into sinaller groups, with each group working on a particular question for which it receives specific training. 2. Question Leaders direct a discussion of the assigned question, commenting on the question requirements and student performance expectations. The scoring guidelines for the question are explained and discussed. 3. The Readers are trained to apply the scoring guidelines by reading and evaluating samples of student answers that were selected at the pre-Reading session as clear examples of the various score points and the kinds of responses Readers are likely to encounter. Question and ‘Table Leaders explain why the responses received particular scores 4, When the Question Leader is convinced the Readers understand the scoring guidelines and can apply them uniformly, the scoring of student responses begins. Reading teams are formed by pairing a more experienced Reader with a new or less experienced Reader. Each team is given a set of student exams to score. Both members of the team score each studert response independently. The resulting scores and differences in judgment ate discussed until agreement is reached, with the Table Leader, Question Leader, or Chief Reader acting as arbitrator when needed5. After a team shows consistent agreement on its scores, its members proceed to score papers individually. Readers are encouraged to seek advice from each other, the Table Leader, Question Leader, or Chief Reader when in doubt about a score. Throughout the course of the Reading, a student response that is problematic or inappropriate receives multiple readings and evaluations. Maintaining the Scoring Guidelines ‘Throughout the Reading, Table Leaders continue to reinforce the use of the scoring guidelines by asking their groups to review sample responses that have already been discussed as. clear examples of particular scores, or to score new samples and discuss those scores with them. This procedure helps the Readers adhere to the standards of the group and helps to ensure thata student response will get the same score whether itis evaluated at the beginning, middle, or end of the Reading ‘A potential problem is that a Reader could unintentionally score a student response higher or lower than it deserves because that same student performed well or poorly on other questions. The following steps are taken to prevent this so-called halo effect A different Reader scores each question and the student's identity is unknown to the Reader. Thus, each Reader can evaluate student responses without being prejudiced by knowledge about individual students. No marks of any kind are made on the students’ papers. ‘The Readers record the scores on a form that is identified only by the students AP number. Readers are unable to see the scores that have been given to other responses in the exam booklet. Here are some other methods that help ensure that everyone is adhering closely to the scoring guidelines: Table Leaders backread (reread) a portion of the student responses from each of the Readers in that Leader's group “This approach allows Table Leaders to guide their Readers toward appropriate and consistent interpretations of the scoring guidelines Readers are paired, so that every Reader has a partner with whom to check for consistency and to discuss problem cases. Table Leaders and Question Leaders are also paired up to help each other on questionable calls. ‘The Chief Reader and the Exam Leaders monitor use of the full range of the scoring scale for the group and for each Reader by checking data on score distributions, and they randomly read selected papers to check for scoring consistency. Reliability data are periodically collected by having Readers unknowingly rescore booklets. Scores resultin from the first and second readings are then compared and analyzed. Preparing Students for the Exam ‘The AP Computer Science A course is designed to be comparable to a typical introductory computer science course taught in a college ot university department of computer science. The course emphasizes object-oriented programming methodology with an emphasis on problen solving and algorithm development, and is meant to be th equivalent of a first-semester course in computer science. also includes the study of data structures and abstraction For allist of the topics covered, see the topic outline in the AP Computer Science A Course Description. The following, goals apply to the AP Computer Science A course: Students should be able to design and implement solutions to problems by writing, running, and debugging computer programs. 1% Students should be able to use and implement commonly-used algorithms and data structures. Students should be able to develop and select appropri algorithms and data structures to solve problems, Students should be able to code fluently in an object oriented paradigm using the programming language Java. Students are expected to be familiar with and be able to use standard Java library classes from the AP Java subset = Students should be able to read and understand a large program consisting of several classes and interacting objects, Students should be able to read and understan a description of the design and development process leading to such a program, (An example of such a program is the AP Computer Science Case Study.) ™ Students should recognize the ethical and social implications of computer use. As teachers focus on the above goals, they will not only be preparing their students for the AP Computer Science A Exam, they will be preparing them for future study and applications of computer science Essential Features of Student Responses ‘There is far more to computer science than just the syntax, of a programming language. Similarly there is much mon. to the exam than testing syntax. Student responses are evaluated as “good first drafts’ of the solution to a probler In a world where so many students (as well as professionaputer scientists) use tools such as IDEs to help in their gramming, itis foolish to expect students to worry about ing punctuation exactly right. As part of evaluating -response questions, Readers are provided with General ring Guidelines that describe how to penalize (or ignore) vor errors, such as missing braces, confusing = and using a class name as an instance of that class. In ring questions, Readers focus more on whether a Jent response adequately addresses the major issues of question (for example, array access, looping, class aipulation, etc.) than more minor issues (is the code amented, are the braces aligned, are parentheses used ead of brackets, etc.) Additionally, the ability of students in college classes is sssed by programming projects as well as test questions. ay professors consider programming projects lo be more vortant than test questions because they are more repre- tative of how computer science is actually done. Since ‘Computer Science A students are assessed with only questions, these questions may have more structure 1 those on a college test. For example, students on @ ege test may be asked simply to write code to determine xe values in an array are in increasing order. Instead ‘omething so straightforward, a question on the Computer Science A Exam may pose the problem as ting code to determine if a student’ scores have im- ved over the course of a term, where the scores are kept narray. This more complicated question can then assess tudents can do basic array manipulation and how they ald perform on programming projects. ‘Teaching Free-Response Writing It is important for teachers to devote some course time to having students answer questions like those on the free-response section in a timed environment. Students, accustomed to doing all their work in IDEs may have trouble writing code “from scratch.” Itis also important to have students experience the challenge of reading a description of a problem and understanding exactly what is being asked in the problem. Often, students are asked to use code for which they are given just an interface, not a complete implementation. They need to have experience with reading descriptions of code before taking the AP Exam Many successful AP Computer Science A teachers use «questions from past free-response exams on a regular basis, and go over the scoring in class. The most recent questions, along with the scoring guidelines used, are available on AP Centralvyhapter IT: The 2009 \P Computer Science A Exam sxam Content and Format Giving a Practice Exam Siving a Practice Exam “The following pages contain the instructions as they appeared structions for Administering the Exam in the 2009 AP Examination Instructions for administering ote the AP Computer Science A Exam. Following these . instructions are a blank 2009 answer sheet and the 2009 the Exam AP Computer Science A Exam, If you plan to use this, released exam to test your students, you may wish to use :am Content and Format these instructions to create an exam situation that closely 2009 AP Computer Science A Exam is 3 hours in length resembles an actual administration. If so, read only the haas two sections: indented, boldface directions to the students all other Instructions are for the person administering the exam and need not be read aloud, Some instructions, such as those referring to the date, the time, and page numbers, are no longer relevant and should be ignored. References to the AP Computer Science AB Exam, which was discontinued after the 2009 administration, should also be ignored. ‘The term “grades,” which appears in the exam and exam instructions that follow, refers to AP Exam scores of 1, 2,3, 4,0r5. Another publication you might find useful is the Packet of 10—ten copies of the 2009 AP Computer Science A Exam, each with a blank answer sheet. You can order this ttle online at the College Board Store (store.collegeboard.com). \ 75-minute multiple-choice section consisting of \0 questions accounting for 50 percent of the final score. 4 105-minute frée-response section consisting of i questions accounting for 50 percent of the final score. 2009 AP Computer Science A Exam Format Multiple Choice (Section I) 40 questions .... -75 minutes Free Response (Section I) 4 questions veeceeseees 105 minutesInstructions for Administering the Exam (from the 2009 AP Examination Instructions booklet) ‘The Computer Science A exam and the Computer Science AB exam should be administered simultaneously. They may be administered in separate rooms, or in the same room if it is more convenient. SECTION I: Multiple-Choice Questions J[ Do not begin the exam instructions below until you have completed the appropriate General Instructions for your group. Make sure you begin the exam at the designated time. When you have completed the General Instructions, say: Itis Tuesday morning, May 5, and you will be taking either the AP Computer Science A Exam or the AP Computer Science AB Exam. {na moment, you will open the packet that contains your exam materials. By opening this packet, you agree to all of the AP Program's policies and procedures outlined in the 2008-09 Bulletin for AP Students and Parents. Please check to make sure you have the correct exam: Computer Science A or Computer Science AB. Raise your hand if you do not have the correct exam. You may now apen your exam packet and take out the Section | booklet, but do not open the booklet or the shrinkwrapped Section II materials. Put the white seals aside. Read the statements on the front cover of Section | and look up when you have finished. .. . Now sign your name and write today's date. Look up when you have finished. ... Now print your full legal name where icated. Are there any questions? .. ‘Answer any questions. Then say: Now turn to the back cover and read it completely. Look up when you have finished. . Are there any questions? ‘Answer any questions. Then say: Section | is the multiple-choice portion of the exam. You may never discuss these multiple-choice questions at any time in any form with anyone, including your teacher and other students. If you disclose these questions through any means, your AP Exam grade will be canceled. Are there any questions? . Answer any questions. Then say: You must complete the answer sheet using a No. 2 pencil only. Mark all of your responses on your answer sheet, one response per question. Completely fill in the ovals. There are more answer ovals on the answer sheet than there are questions, so you will have unused ovals when you reach the end. Your answer sheet will be scored by machine; any stray marksor smudges could be read as answers. If you need to erase, do so carefully and completely. No credit will be given for anything written in the exam booklet. Scratch paper is not allowed, but you may use the margins or any blank space in the exam booklet for scratch work. Are there any questions? . .. Answer all questions regarding procedure, Then say: You may use the orange appendix booklet throughout the exam. Appendix A contains the AP Java Quick Reference, and appendixes B through G contain case study reference material. In the Computer Science A exam, the case study questions are 21 through 25. In the Computer Science AB exam, the case study questions are 20 through 25. You have 1 hour and 15 minutes for Section I. Open your Section | booklet now and begin. ® Note start Time here____ Note Stop Time here ____.. You and your proctors should make sure students are marking their answers in pencil on their answer sheets, and that they are not looking at their shrinkwrapped Section II booklets. After 1 hour and 15 minutes, say: ‘Stop working. Close both your exam booktet and orange appendix booklet and put your answer sheet on your desk, face up. | will now collect your answer sheet. ‘After you have collected an answer sheet from each student, say Take your seals and press one on each area of your exam booklet marked “PLACE SEAL HERE.” Fold them over the open edges and press them to the back cover. When you have finished, place the exam booklet on your desk with the cover face up. Keep your orange appendix booklet; you will need it for Section II of the exam. I will now collect your Section | booklet. {As you collect the sealed Section 1 booklets, check to be sure that each student has signed the front cover. There is a 10-minute break between Sections | and I. When all Section I materials have been collected and accounted for and you are ready for the break, say: Please listen carefully to these instructions before we take a break. Everything you placed under your chair at the beginning of the exam must remain there. You are not allowed to consult teachers, other students, or textbooks about the exam materials during the break. You may not make phone calls, send text messages, check e-mail, access a computer, calculator, cell phone, PDA, MP3 player, e-mail/messaging device, or any other electronic or communication device. Remember, you are not allowed to discuss the multiple-choice section of this exam with anyone at any time. Failure to adhere to any of these rules could result in cancellation of your grade. Please leave your shrinkwrapped Section II package and your orange appendix booklet on top of your desk during the break. You may get up, talk, go to the restroom, or get a drink. Are there any questions? ... Answer all questions regarding procedure. Then say: @® Let's bogin our break. Testing will resume atSECTION II: Free-Response Questions After the break, say May | have everyone's attention? Place your Student Pack on your desk. ... You may now open the shrinkwrapped Section Il package. ... Read the bulleted statements on the front cover of the pink booklet. Look up when you have finished. ... Now place an AP number label on the shaded box. If you don't place an ‘AP number label on this box, it may be impossible to identify your booklet, which could delay or jeopardize your AP grade. If you don’t have any AP number labels, write your AP number in the box. Look up when you have finished. .. Read the last statement... . 9 a pen with black or dark blue ink, print the first, middle, and last Is of your legal name in the boxes and print today's date where ‘ated. This constitutes your signature and your agreement to the conditions stated on the front cover... . ‘Tum to the back cover and read Item 1 under “Important Identification Information.” Print your identification information in the boxes. Note that you must print the first two letters of your last name and the first letter of your first name. Look up when you have finished. . In {tem 2, print your date of birth in the boxes... . Read Item 3 and copy the school code you printed on the front of your ‘Student Pack into the boxes. ... Read Item 4. . Are there any questions? . . . Answer all questions regarding procedure. Then say: I need to collect the Student Pack from anyone who will be taking another ‘AP Exam. If you are taking another AP Exam, put your Student Pack on your desk. You may keep it only if you are not taking any other AP Exams this year. If you have no other AP Exams to take, place your Student Pack under your chair now. ... While Student Packs are being collected, read the “At a Glance” column. and the instructions for Section Il on the back cover of the pink booklet. Do not open the booklet until you are told to do so. Look up when you have finished. . .. Collect the Student Packs. Then say: Are there any questions? . . . Answer all questions regarding procedure. Then say: Now open the Section II booklet and tear out the green insert that is in the center of the booklet. In the upper right-hand corner of the cover, print your name, your teacher's name, and your school’s name.Read the information on the front cover of the green insert. Look up when you have finishe ‘You will need the orange appendix booklet for Question 2 in both the A exam and the AB exam, although you may use it at any time during this period. You may make nates in the green insert, but you must write your answers in the pink booklet using a No. 2 pencil. You are responsible for pacing yourself, and may proceed freely from one question to the next. If you need more paper during the exam, raise your hand, At the top of each extra piece of paper you use, be sure to write your AP number and the number of the question you are working on. You have 1 hour and 45 minutes for Section Il. Are there any questions? .... Answer any questions. Then say: You may begin. @ Note start Time here Note Stop Time here __. You and your proctors should make sure students are writing their answers in their Section IT booklets, After I hour and 35 minutes, say: There are 10 minutes remaining. After 10 minutes, say: ‘Stop working and close your exam booklet, the orange appendix booklet, and the green insert. Put your pink booklet, your orange appendix booklet, and your green insert on your desk, face up. Remain in your seat, without talking, while the exam materials ate collected... . Collect a pink Section II booklet, an orange appendix booklet, and a green insert from every student. Check for the following: + Section II booklet front cover: The student placed an AP number label in the shaded box, and printed his or her initials and today’s date + Section II booklet back cover: The student completed the “Important Identification Information” area. + ‘The student wrote answers in the pink booklet and not in the orange appendix booklet or green insert. ‘The green inserts must be stored securely for no fewer than two school days. After the two-day holding time, the green inserts may be given to the appropriate AP teacher(s) for return to the students. The orange appendix booklets must be returned to the AP Program. When all exam materials have been collected and accounted for, say’ Your teacher will return your green inserts to you in about two days, You may not discuss the free-response questions with anyone until that time. Remember that the multiple-choice questions may never be discussed or shared in any way at any time. You should receive your grade report in the mail about the third week of July. You are now dismissed. Exam materials should be put in locked storage until they are returned to the AP Program after your school’s last administration, Before storing materials, check your list of students who are eligible for fee reductions and fill in the appropriate oval on their registration answer sheets. To receive a separate AP Instructional Planning Report or student grade roster for each AP class taught, fill in the appropriate ova} in the “School Use Only” section of the answer sheet. 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Use only No. 2 pencils to mark your answers on pages 2 and 3 (one response per question}. After you have determined your response, be sure to completely fil|n the oval corresponding to the number of the question you are answering. Stray marks. and smudges could be read as answers, $0 erase carefully and completely. Any improper griddi affect your grade. Answers written in the multiple-choice booklet will nt be scored. 1®OQOCO ezDOOOe 31 @OOOO PRCRORGRORG) 7@P®BOOG 2 BOOOG 3®@®@OOO 32 @OOOG 3 ®@GDOOO 1@OOOO 2 @OOOO 4 @OOOG 5®@OoOOO »@OOCOG 53 DOOCOG s®OOOO 31 @@OOG 5 @DOGO 7®@@2OOO 2@®OOO 7 @®OOO s®@®OOO@ 3 @®@®OOO 3 @®GOOO 2D®OOO x @®DOOO 3 @GBOOO 0 @OOOO 3s @OOCOO 2 ®@®OCOO 1 @®OOO OOOO 1 ®@OOOG 2@GCOeG 7 QDOOG 2 ®DOOOO 3 @®OCOO w@DOOOO aD®OOe u®@®DOOO »@®OOO #2DOOG 5 ®@OOOO 0 ®@®©CO® 5s ®OOCOO 6 @®DOOO 1 @®@GOG ®D@OOOO 7 @®OOO 2@®OOO DRCRCRCRORG) Bw ®®DOO 03 @OOO® 8 ®@OOCO 1 @OOOO “#@®®OOCO® 8 BOOOO n@OOCOO 6 ®DOOO n®®OOO 2 @GOO® #6 ®OOOO 1@®@OCOG 2@OOO®O 7 ®@®QOOO 2z@OOOO 232 @QODO #2 @ODOOO B@BOOOO 2 @O®OOO 2@®COO u@®COO ER ORORCRORG) »®@OCOG B@2OoCoO FOR QUESTIONS 76-151, SEE PAGE. 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Total Time ‘hour, 15 minutes Number of Questions 40 Percont of Total Grade 50%, Writing instrument Pencil required Electronic Device None allowed Instructions Te orange Appendix booklet i provided for use in both Section I and Section I Section I of this exam contains 40 multiple-choice questions. Fil in only the ovals for ‘numbers | through 40 on your answer sheet Indicate all of your answers to the multiple-choice questions on the answer sheet. No credit wil be given for anything written in this exam booklet, but you may use the booklet for notes or scratch work. After you have decided which of the suggested answers is best completely fill in the corresponding oval on the answer sheet. Give only one answer to each question. If you change an answer, be sure that the previous mark is erased ‘completely. Here is 2 sample question and answer. Sample Question, Sample Answer Chicago isa ®eooeo (A) state (B) city (© country (D) continent (&) village Use your time effectively, working as quickly as you can without losing accuracy. Do not spend too much time on any one question. Go on to other questions and come back to the ones you have not answered if you have time. It $ not expected that everyone will know the answers to all ofthe multiple-choice questions About Guessing Many students worcer whether or not to guess the answers to questions about which they are not certain. in this section of the examn, asa correction for random guessing ‘one-fourth of the number of questions you answer incorrectly will be subtracted from the number of questions you answer cosrecty. Ifyou are nat sure ofthe best answer but have some knowledge of the question and are able to eliminate one or more of the answer choices, your chance of answering correctly is improved, and it may be to your advantage to answer such a question, qw18 ‘COMPUTER SCIENCE A SECTION I ‘Time—I hour and 15 minutes Number of questions—40 Percent of total grade—S0 Directions: Determine the answer to each of the following questions or incomplete statements, using the available space for any necessary scratch work. Then decide which is the best of the choices given and fill in the corresponding oval on the answer sheet. No credit will be given for anything written in the examination booklet. Do not spend 100 much time on any one problem. Notes: «Assume that the classes listed in the Quick Reference found in the Appendix have been imported where appropriate ‘+ Assume that declarations of variables and methods appear within the context of an enclosing class. ‘+ Assume that method calls that are not prefixed with an object or class name and are not shown within a complete class definition appear within the context of an enclosing class. ‘+ Unless otherwise noted in the question, assume that parameters in method calls are not nul. Unauthorized copying o une a] [ny patel in pe eset GO ON TO THE NEXT PAG!1. Consider the following code segment. int value = 15; while (value < 28) { System.out .print1n(value) ; value++; y What are the first and last numbers output by the code segment? Est Last (a) 15 oa] (B) 15 28 ©) 16 a (D) 16 8 (16 29 GO ON TO THE NEXT PAGE. 192. A teacher put three bonus questions on a test and awarded 5 extra points to anyone who answered all three bonus questions correctly and no extra points otherwise. Assume that the boolean variables bonusOne, bonusTwo, and bonusThree indicate whether a student has answered the particular question correctly. Each variable was assigned true if the answer was correct and false if the answer was incorrect. Which of the following code segments will properly update the variable grade based on a student's, performance on the bonus questions? if (bonusOne && bonusTwo && bonusThree) grade += 5; I if (bonusOne || bonustwo || bonusThree) grade += 5; II if (bonusone) grade += 5 if (bonustwo grade += 5; if (bonusThree) grade += 5; (A) Lonly (B) Monly (C) Monly (D) Land IL (B) Wend UL sathorined copying oF 20 ny part of his pape eg GO ON TO THE NEXT PAGE‘Assume that an array of integer values has been declared as follows and has been initialized. int{] arr = new int{10}; Which of the following code segments correctly interchanges the value of arr (0] and arr{5] ? (A) arr[0] = 53 arr[5] = 0; (B) arr(0] = arr(s]; arr(5] = arr(0]; (© int k = arri5i; arr(0) = arr(5]; arr[5] = k; (D) int k = arr{o}; arr(Q] = arr(5]; arr(5] = k; (B) int k = are{5]; arr(5] = arr(0]; arr(0) = arri5]; ‘authori coping or eave al] pet of this page aga GO ON TO THE NEXT PAGE. a22, 4, Consider the following code segment. ArrayList items = new ArrayList(); items .add("A\ itens. items. fi items.add(0, "D*); items. remove (3): items.add(0, "E"); System.out .print1n (items) ; What is printed as 2 result of executing the code segment? (A) 1A, B,C, El (B) (A, B, D, B} © [£, D, a, BY (0) [z, D, a, C} (©) (8, D, C, B) When designing a class hierarchy, which ofthe following should be true of a superclass? (A) A superclass should contain the data and functionality that are common to all subclasses that inherit from the superclass. (B) A superclass should be the largest, most complex class from which all other subclasses are derived. (C) A superclass should contain the data and functionality that are only required for the most complex class. (D) A superclass should have public data in order to provide access for the entire class hierarchy. (E) A superclass should contain the most specific details of the class hierarchy. GO ON TO THE NEXT PAGE.Questions 6-7 refer to the following code segment. int k = arandom number such that 1S Sn; for (int p = 2; p <= k; p++) for (int r= 1; r < ki r+) System.out.print1n("Hello"); 6. What is the minimum number of times that He110_ will be printed? (a) 0 Bt ©2 (D) n=! ©) 1-2 7, What is the maximum number of times that Heo will be printed? (A) 2 Satoriged copying orreue ol] oft page eae. GO ON TO THE NEXT PAGE. 23“8, Consider the following instance variable and incomplete method. The method calcTotal is intended to ~ return the sum of all values in vals. private int(] vals; public int caleTotal() { int total = 0 /* missing code */ return total; } Which of the code segments shown below can be used to replace /* missing code */ sothat calcTotal will work as intended? L for (int pos = 0; pos < vals.length; post+) { total ) vals{pos] I. for (int pos = vals.length; pos > 0; pos ( total } vals{pos]; I. int pos = 0; while (pos < vals. length) { total post+ ) vals{pos]; (A) Lonly (B) only (C) Monty (D) Land ttl (E) Wand I 24 GO ON TO THE NEXT PAG!). Consider the following code segment. String str = ‘abcdef*; for (int rep = 0; rep < str.length() - 1; rept+) t system. out print (str.substring(rep, rep + 2)); } ‘What is printed as a result of executing this code segment? (A) abedet (B) aabbecddeeté (©) abbecddeet (D) abebcdcdedet is printed because an IndexOutOfBoundsExcept ion is thrown. GO ON TO THE NEXT PAGE. 2526 10. Consider the following method. public void numberCheck(int maxtum) { int typea = 0; int types = 05 int typec = 0; for { if (int k= 1 maxNum; (ka2 typeat+; if Ue 82 typea++ if (k a5 typeC++ 0 && kK 5 == 0) 0 ) system.out-printInitypea + * ) k++) Cr) “4 typen +" What is printed as a result of the call numberCheck (50) ? (A) 5 (B) (C) (D)5 ©) 205 5 20 10 5255 25 10 30 25 10 [Unauthorzad copying o aus o] any part of ts page legal s+ typec) ; GO ON TO THE NEXT PAG1. Consider the following method that is intended to modify its parameter nameList by replacing all occurrences of name with newValue. public void replace (ArrayList nameLi: String name, String newvalue) ce for (int j = 0; 3 < nameLis! t size(); j++) if ( /* expression */ ) { nameList.set(j, newvalue) ; } ) ) Which of the following can be used to replace /* expression */ sothat replace will work as intended? (A) nameList get (5) .equals (name) (B) nameList get (3) (C) nameList .remove (4) (D) nameList(j] == name (BE) nameList [j}.equals (name) \Siherzed copying or reuse of] ‘oar of ts pa fringe GO ON TO THE NEXT PAGE. a12, Consider the following incomplete method. public int someProcess(int n) t /* body of someProcess */ ) ‘The following table shows several examples of input values and the results that should be produced by calling someProcess, Input Value Value Returned by n_someProcess (1) 3 30 6 ® ee 7 Coe 80 9 | u “a pn | mo 14 u| 16 160 Which of the following code segments could be wsed to replace /* body of someProcess */ so that the method will produce the results shown in the table? Lif ((n 8 3 == 0) && (n & 4 == 0)) return n * 10; else return ni IL if ((n & 3 == 0) | return n * 10; o) return n; [Grautosad coping a uae of 28 [any part of ts page fog GO ON TO THE NEXT PAG!IL if @%3 if (n 8 4 == 0) return n * 10; return n; A) Lonly B) Monly ©) Monty D) Land ft E) Wand IM GO ON TO THE NEXT PAGE. 2913. Consider the following method. // precondition: x >= 0 public void mystery(int x) i if (x / 10) != 0) ( mystery(x / 10); ) System.out-print (x % 10); ) Which of the following is printed as a result of the call mystery (123456) ? (a) 16 (B) 56 (C) 123456 (D) 654321 (E) Many digits are printed due to infinite recursion. [Unauthorend copying or eure of [any part of bis pag egal GO ON TO THE NEXT PAGConsider the following instance variables and incomplete method that are part of a class that represents an item. ‘The variables years and months are used to represent the age of the item, and the value for months always between 0 and 11, inclusive. Method updateage is used to update these variables based on the parameter extratonths that represents the number of months to be added to the age. private int years; private int months; // 0 <= months <= 11 // precondition: extraMonths >= 0 public void updateage(int extraMonths) i /* body of updateage */ ) Which of the following code segments could be used to replace /* body of updateage */ so thatthe method will work as intended?” 1. int yrs = extraMonths % 12; int mos = extraMonths / 12; years = years + yrs; months = months + mos; Il, int totalMonths = years * 12 + months + extraMonths; years = totalNonths / 12; months = totalMonths % 12; Ill. int totalNonths = months + extraMonths; years = years + totalMonths / 12; months = totalNonths % 12; (A) Lonly {B) Ioniy (©) Mfonly (D) Hand IIT only (®) 1.1 and tt GO ON TO THE NEXT PAGE. at15, Consider the following method. public String inRangeMessage(int value) C if (value <0 [| value > 100) return "Not in range"; else return "In range"; ) Consider the following code segments that could be used to replace the body of inKangeMessage. 1 if (value < 0) { if (value > 100) return "Not in range"; else return In range"; ) else yeturn "In range"; I. if, (value < 0) return ‘Not in range"; else if (value > 100) return "Not in range"; else return ‘In range"; IM. if (value >= 0) return "In range"; else if (value <= 100} return "In range"; else return "Not in range"; Which of the replacements will have the same behavior as the original version of inRangeMessage ? (A) Lonly (B) Honly (C) Mtonly (D) Land tt (©) Wand 1 GO ON TO THE NEXT PAConsider the following class declaration. public class SomeClass { private int num; public SomeClass(int n) { num ) public void increment(int more) { num = num + more; ) public int getnum() ( return num; } d ‘The following code segment appears in another class. SomeClass one = new SomeClass(100); SomeClass two = new SomeClass(100); SomeClass three = one; one. increment (200) ; system.out.printIn(one.getNum() + * " + two.getNum() +" "+ three.getNum()); What is printed as a result of executing the code segment? (A) 100 100 100 (B) 300 100 100 (© 300 100 300 (P) 300 300 100 (©) 300 300 300 GOON TO THE NFYT PAGE aa4 17. The following incomplete method is intended te sort its array parameter rx’ in increasing order. // postcondition: arr is sorted in increasing order public static void sortarray(int[] arr) { int 3, k; for (j = arr.length - 1; j > 0; { int pos = j; for ( /* missing code */ } i if (arr[k] > arr[pos]) { pos = k } ) swap(arr, j, pos); 3 Assume that swap(arr, j, pos) exchanges the valuesof arr [4] and arc [pos]. Which of the following could be used to replace /* missing code */ so that executing the code segment sorts the values in array arr? yk = 5-1; > 07 kee (B) kK = 5-4; k >= 0; ke (C)k = 1; & < arr.length; k++ (D) k = 1; k > arrlength; ke+ (BE) k = 0; k <= arr.length; k++ Grauthorized copy ary part of tls page GO ONTO THE NEXT PA‘{Assume that 2 and y are boolean variables and have been properly initialized. (x 6& y) || 1Ge && y) The result of evaluating the expression above is best described as (A) always true (B) always false (©) true only when x is true and y is true (D) true only when x and y have the same value (2) true only when x and y have different values GO ON TO THE NEXT PAGE. 3536 19, Assume that the following variable declarations have been made. double @ = Math. random(); double x; Which of the following assigns a value to range 0.5 = 90) return true; if (testAverage return true; return false; = 75 && assignmentsCompleted >= 4) I, boolean pass = false; if (testAverage >= 90) pass = true; if (testAverage >= 75 && assignmentsCompleted >= 4) pass = true; return pass; Il, return (testaverage (testaverage 90) || 75 && assignmentsCompleted >= 4); Which of the implementations will correctly implement method isPassing ? (A) Lonly (B) Honly (©) Fand 11 only (D) Hand UL only (8) LU, and it GO ON TO THE NEXT PAGE. 3738 Questions 21-25 refer to the code from the GridWorld case study. A copy of the code is provided in the Appendix. 21. Consider the following code segment. Location loch Location loc2 new Location(3, new Location(3, i (1ocl equals (1oc2 .getadjacentLocation (Location. EAST) }) System. out.print ("aaa"); if (loc1.getRow() if (loc. getDirectionToward(1oc2) system. out .print ("555"); ‘What will be printed as a result of executing the code segment? (A) aaaxxx555 (B) aaaxxx (C) xxx555 (D) 555 (B) aaa = loc? .getRow()) System. out print ("XXX") ; Location. EAST) Unauhorzed copying ox ruse al any part of is ge a toga GO ON TO THE NEXT PAC1A RightTurningBug behaves like a Bug, except that when it turns, it turns 90 degrees to the right. The declaration for the RightTurningBug class is as follows. public class RightTurningBug extends Bug ( public void turn() /* missing implementation */ ) ) Consider the following suggested replacements for /* missing implementation */ I, int desiredDirection = (getDirection() + Location.RIGHT) % Location.FULL_CIRCLE; while (getDirection() != desiredDirection) { ) super.turn() ; I super.turn(); super. turn(); Ill. setDirection(getDirection(] + Location.RIGHT); Which of the replacements will produce the desired behavior? (A) Lonly (B) Honly (©) Land Il only (D) Land III only (B) LM and tt GO ON TO THE NEXT PAGE. 3940 23. Consider the following declarations, Actor a = new Actor(); Bug b = new Bug(); Rock r = new Rock(); Critter ¢ = new Critter(); Consider the following lines of code. Line: int dirl = c.getDirection(); Line2: int dir2 = a.getDirection(); Line 3: int dix3 = b.getDirection(); Line 4: ArrayList rLoc = r.getMoveLocations( ¢.getMoveLocations(); Line 5: ArrayList cLoc Which of the lines of code above will cause a compile time error? (A) Line 1 only (B) Lines 2 and 3 only (C) Line 4 only (D) Line 5 only (E) Lines 4 and 5 only GO ON TO THE NEXT PAGConsider the following TestBug class declaration. public class TestBug extends Bug public void act() t if (canMove()) { move () ; if (canMove()) move(); y else t setDirection(getDirection() + Location.HAL¥_CIRCLE) ; ) ) y The following code segment will produce @ grid that has a Rock object anda TestBug object placed as shown. Grid g = new PoundedGrid (5, 5); Rock r = new Rock(); x.putSelfInGrid(g, new Location(2, 1)); Bug t = new TestBug() t.putSelfIncrid(g, new Location(3, 2)); Fa Which of the following best describes what the TestBug object t does as a result of calling t.act () ? (A) Moves forward two locations and remains facing current direction (B) Moves forward two locations and turns 180 degrees (©) Moves forward one location and remains facing current direction (D) Moves forward one location and turns 180 degrees (B) Stays in the same location and turns 180 degrees GOON TO THE NEXT PAGE. aABA DancingCritter isa Critter that moves in the following manner. The DancingCritter ‘makes a left turn if at least one of its neighbors is another DancingCritter. It then moves like a Critter. Ifnone of its neighbors are DancingCritter objects, it moves likea Critter without making a left turn. In all other respects, a DancingCritter acts like a Critter by eating neighbors that are not rocks or critters. Consider the following implementations, I public class DancingCritter extends Critter { public ArrayList getActors() { ArrayList actors = new ArrayList(); for (Actor a : getGrid() .getNeighbors (getLocation())} ‘ if (a instanceof DancingCritter) actors.add(a) ; ) return actors; } public void processActors(ArrayList actors) ‘ae (actors.size() > 0) ‘ setDirection(getDirection() + Location.LEFT) ; buper. procosshetors actors) Il. public class DancingCritter extends Critter c public void processActors(ArrayList actors) € boolean turning = false; for (Actor a : actors) t if (a instanceof DancingCritter) turning = true; ) if (turning) setDirection(getDirection() + Location.LEFT) ; ) ) ) [Unauthorised copying o oun of 42 any part of is page a og GO ON TO THE NEXT PACI. public class DancingCritter extends critter ( public void maketfove(Location loc) { boolean turning = false; for (Actor a : getGrid() .getNeighbors (getLocation()}) « if (a instanceof DancingCritter) turning = true; d if (turning) ( setDirection(getDirection() + Location.LEFT) ; y super .makeMove (loc) ; ‘Thich of the proposed implementations will correctly implement the DancingCritter clas \) Lonly 3) Ionly 2) Ml only 9) Land I only 1,1, and It ‘Garza copying arousal] par ofthis pagel lege. GO ON TO THF NFXT PAGE aa26. Consider the following cade segment. int k = while (k < 10) C System.out.print((k % 3) +"); if ((e $3) == 0) kek +2; else kee; ) What is printed as @ result of executing the code segment? (Ayo 21 0 2 (Bo 20 20 2 o210210 (Po 20 202 0 @®o121212 GO ON TO THE NEXT PAGConsider the following method, Method al1Even isintended to retum true if all elements inamay arr are even numbers; otherwise, it should retum false. public boolean allsven(int{] arr) { boolean isEven = /* expression */ ; for (int k = 0; k < arr.length; k++) t /* loop body */ ) return isEven; ) Which of the following replacements for /* expression */ and /* loop body */ should be used so that method al1Bven will work as intended? * expression */ * loop body * A) false if ((arr(k) % 2) == 0) isEven = true; (B) false if ((arr[k] % 2) != 0) isBven = false; else isEven = true; © true if (arr(k] % 2) != 0) isEven = false; () true if ((arr{k] % 2) isEven = false; else isEven = true; © true if (larr{k] % 2) == 0) isEven = false; else isEven = true; GO ON TO THE NEXT PAGE. 4528. Consider the following code segment. int x = /* some integer value */ ; int y = /* some integer value */ ; boolean result = (x < y); result = ( (x >= y) && !result ); Which of the following best describes the conditions under which the value of result willbe true after the code segment is executed? (A) Only when x < y (B) Only when x >= y (© Only when x and y are equal (D) The value will always be true. (E) The value wilh never be true. 46 29. Consider the following code segment. for (int outer ( for (int inner = 0; inner <= outer; inner++) { 0; outer db) is equivalent to which of the following? (A) true (B) false © as=b @) at=b (©) "a b) GO ON TO THE NEXT PAGE. a732. Consider the following code segment, 48 int a int b while (b != 0) System.out.printin(a); What is printed as a result of executing the code segment? (ayo 8) 6 © (D) 24 © 30 (Unauthorized copying rouse a] any pat of is pagel Hegel GO ON TO THE NEXT PAGE3. Consider the following method. public int sol (int Lim) “int s = 0; for (int outer = 1; outer <= lim; outer++) fl for (int inner = outer; inner <= lim; inner++} ( st: } 3} return s; ) ‘What value is returned as a result of the call sol (10) ? (A) 20 (B) 45 © 55 () 100 (E) 385 GOON TOTHENEXTPAGE. 49.34. Consider the following incomplete method. Method £indNext. is intended to return the index of the first occurrence of the value val beyond the position start inamay arr. // returns index of first occurrence of val in arr // after position star! // xeturns arr. length if val is not found public int findNext(int[] arr, int val, int start) t int pos = start + 1; while ( /* condition */ } post; return pos; ) For example, consider the following code segmem. int(] arr = (11, 22, 100, 33, 100, 11, 44, 100); System. out .printin(findNext (arr, 100, 2)); The execution of the code segment should result im the value 4 being printed Which of the following expressions could be used to replace /* condition */ sothat findNext will work as intended? () {pes < arr. length) && (arr[pos) != val) (B) (arr[pos] != val) && (pos < arr.length} (© {pos < arr.length) || (arr{pos] != val) (D) (arr[pos} == val) && (pos < arr.length) () (pos < arr length) || (arr{pos] == val) [Uneuthorzad copying rouse a] 50 sry par hs pape fe Megs GO ON TO THE NEXT PAG!5. Consider the following code segments. Lo int k= 1; while (k < 20) if (k%3 == 1) system.out.print( k + * Ml, for (int k = 1; k < 20; k++) ( if (ce $3 == 1) System.out.print( k +" "); M1, for (int k = 1; k < 20; k=k +3) ( y System.out.print( k +" "); Which of the code segments above will produce the following output? 1 4 7 10 13 16 19 (A) Lonly (B) Ionly (©) Land I only (D) Hand 111 only (B) 1,1, and GO ON TO THE NEXT PAGE. 6152 a 36. Consider the following two methods that appear within 3s public void changeIt(int{] list, int num) ( list new int [5]; 0; for (int x list [x] 0; x < list.length; x++) 0 public void start() ( int{] nums = (1, 2, 3, 4, 5); int value = 6; changert (nums, value) ; for (int k = 0; k < nums.length System.out.print (nums[k] + " ket) System. out .print (value) ; ) What is printed as a result of the call start () ? (00000 00000 (1234 (12345 (E) changeTt. will throw an exception. [Unauthorised copying or euse a ary par of is pag a aga gle class. GO ON TO THE NEXT PAGE7, Consider the following declaration of the class NumSequence, which has a constructor that is intended to initialize the instance variable seq toan ArrayList of numberOfValues random floating-point values in the range [0.0, 1.0). public class NumSequence { private ArrayList seq: // precondition: numberOfValues > 0 // postcondition: seq has been initialized to an ArrayList of i" length numberOfValues; each element of seq uw contains a random Double in the range [0.0, 1.0) public Numgequence(int numberofValues) € /* missing code */ ) ) Which of the following code segments could be used to replace /* missing code */ so that the ‘constructor will work as intended? L ArrayList seq = new ArrayList (1; for (int k = 0; k < numberOfValues; k++) seq.add(new Double (Nath. random())); I seq = new ArrayList(); for (int k = 0; k < numberOfValues; k++) seq.add(new Double (Math, random())) ; I, ArrayList temp = new ArrayList(); for (int k = 0; k < numberOfValues; k++) temp.add(new Double (Math.random())) ; seq = temp; (A) Honly (B) Monty (©) Land tt (D) Land tt (E) Wand Ul GO ON TO THE NEXT PAGE. 53oa |any pert otis page egal 38. Consider the following code segment. double a double b = Bt 1.2; if ((a+b) * (a -b) { (a * a) - tb * by) system. out .printIn (‘Mathematical error!*); } Which of the following best describes why the phrase “Mathematical error!" would be printed? (Remember that mathematically (a +b) *(a-b) = a?-b?.) (A) Precedence rules make the if condition true. (B) Associativity rules make the if condition true. (©) Roundoff error makes the if condition tre. (D) Overflow makes the i£ condition true (©) A compiler bug or hardware error has occurred. 39. Consider the following recursive method. public static String recur{int val) i String dig = + (val 83); if (val / 3 > 0) return dig + recur(val / 3); return dig; ) What is printed as a result of executing the following statement? System.out.print1n (recur (32)}; (A) 20 (B) 102 © 210 (D) 1020 (©) 2101 Unaathorzed copying or rouse] GO ON TO THE NEXT PAG0. Consider the following method. public String goAgain(String str, int index) { if (index >= str.length()) return str; return str + goAgain(str.substring(index), index + 1); ¥ What is printed as a result of executing the following statement? System.out .printin(goagain(*"today", 1))+ (A) today (B) todayto (©) todayoday (D) todayodayay (E) todayodaydayayy END OF SECTION! IF YOU FINISH BEFORE TIME IS CALLED, YOU MAY CHECK YOUR WORK ON THIS SECTION. DO NOT GO ON TO SECTION Il UNTIL YOU ARE TOLD TO DO SO. 5556 NO TEST MATERIAL ON THIS PAGEContent of Appendixes Appendix A... A Exam Java Quick Reference Appendix B . Testable API Appendix C.. . Testable Code for APCS A/AB Appendix E. sess. Quick Reference A/AB Appendix Goeee.e ec cececeveeeeeeceeeeueeeeeeeeeeees Index for Source Code 875 Appendix A ‘A Java Quick Reference Appendix A — A Exam Java Quick Reference Accessible Methods from the Java Library That May Be Included on the Exam class java.lang.Object * boolean equals (Object other) © String tostring() class java-lang. Integer © Integer (int value) © int intvalue() clase java-lang.Double * Double (double value) * double doublevalue() class java-lang.string © int length() © String substring(int from, int to) // retums the substring beginning at from 17 and ending at to-1 © string substringlint from) // rewms substring (from, Length()) © int indexof (string str) 7/- seturns the index of the first occurrence of St; 1/ returns ~1 if not found © int compareTo(String other) 1/ returns a value <0 if this isless than other J/ retums.a value =0if this isequal to other 1/ returns a value >Oi€ this is greater than other class java.lang.Math * static int abs(int x) * static double abs (double x) * static double pow(double base, double exponent) * static double .¢ double // returns a double inthe range (0.0, 10) class java.util .arrayList © int size() * boolean add(E obi) 17 appends obj toend of list; retums true © void add(int index, © obj) 1/ inserts obj at position index (0 < index < size), 17 moving elements at position index and higher 77 to the ight (adds 110 their indices) and adjusts size * © get (int index) © E set(int index, £ obj) 11. replaces the element at position index with obj 17 returns the element formerly atthe specified position © E remove(int index) // removes element from position index, moving elements 1/ at position index + 1 and higher to the left // (subtracts | from their indices) and adjusts size //- returns the element formerly atthe specified position -Al-Appendix B Testable API Appendix B — Testable API info.gridworld.grid.Location class (implements Comparable) public Location(int r, int c) constructs a location with given row and column coordinates public int getRow() returns the row of this location public int getCol() returns the column of this location public Location getAdjacentLocation(int direction) returns the adjacent location in the direction that is closest to Airect ion public int getDirectionToward(Location target) returns the closest compass direction from this location toward target public boolean equals (Object other) retums true if other isa Location with the same row and column as this location; false otherwise public int hashCode() retums a hash code for this location public int compareTo(Object other) returns a negative integer if this location is less than other, zero ifthe two locations are equal, or a positive integer if this location is greater than other. Locations are ordered in row-major order. Precondition: other isa Location object. public String toString() retums a string with the row and column ofthis location, n the format (row, col) ‘Compass directions: public static final int NORTH = 0; public static final int BAST = 90; public static final int SOUTH = 180; public static final int WES? = 270 public static final int NORTHEAST = 45 public static final int SOUTHEAST = 135; public static final int SOUTHWEST = 225; public static final int NORTHWEST = 315; ‘Tum angles: public static final int public static final int public static public static public static public static public static RIGHT = 90; int BALF_LE int HALF_RIGHT = 45; int FULL_CIRCLE = 36 int HALF _CIRCLE int AHEAD = 0 -BI- 59Appendix B Testable API info.gridworld.grid.Grid interface int getNumRows () returns the number of rows, or-1 if this grid is unbounded int getwuncols() retums the number of columns, or -1 if this grid is unbounded boolean isValid(Location loc) retums true if Loc is validin this grid, false otherwise Precondition: loc isnot null put (Location loc, E obj) Puts obj at location 1oc in this grid and returns the object previously at that location (or null ifthe location was previously unoccupied). Precondition: (1) Loc is valid in this grid 2) obj js not null B remove(Location loc) removes the object at location Loc from this grid and returns the object that was removed (or nul if the location is unoccupied) Precondition: Loc is valid in this grid B get (Location loc) returns the object at location loc (or null ifthe location is unoccupied) Precondition: Loc is valid inthis grid ArrayList getOccupiedLocations() returns an array list of all occupied locations in this grid ArrayList getValidadjacentLocations (Location loc) returns an array list of the valid locations adjacent to Loc in this grid Precondition: Loc is valid in this grid ArrayList getEmptyAdjacentLocations (Location loc) rotums an array list ofthe valid empty locations adjacent to oc in this grid Precondition: loc is valid inthis grid ArrayList get0ccupiedAdjacentLocations (Location loc) retums an array list ofthe valid occupied locations adjacent to loc in this grid Precondition: Loc is valid in this grid ArrayList getNeighbors (Location loc) returns an array list of the objects in the occupied locations adjacent to Loc in this grid Precondition: Loc is valid in this grid -B2-Appendix B Testable API info.gridworld.actor.Actor class public Actor () constructs a blue actor that is facing north public Color getColor() retus the color of this actor public void setColor (Color newColor) sels the color of this actor to newColor public int getDirection() returns the direction of this actor, an angle between 0 and 359 degrees public void setDirection(int newDirection) sets the direction of this actor to the angle between 0 and 359 degreps that is equivalent to newDirection public GridcActor> getGrid() returns the grid ofthis actor, or nu. if this actor isnot contained in a grid public Location getLocation (} returns the location of this actor, or nul. if this actor is not contained in a grid public void putSelfinGrid(Gridcactor> gr, Location loc) puts this actor into location loc of grid gr. Ifthere is another actor at Loc, it is removed. Precondition: (1) This actor is not contained in a grid (2) Loc is valid in gx public void removeSelfFromGrid() removes this actor from its grid. Precondition: this actor is contained in a grid public void moveTo(Location newLocation) moves this actor to newLocation. Ifthere is another actor at newLocat ion, itis removed. Precondition: (1) This actor is contained in a grid (2) newLocat ion is valid in the grid ofthis actor public void act() reverses the direction of this actor. Override this method in subclasses of Actor to define types of actors with different behavior public String toString() returns a string with the location, direction, and color of this actor -B3- 662 Appendix B Testable API info.gridworld.actor.Rock class (extends Actor) public Rock() constructs a black rock public Rock(Color rockColor) constructs a rock with color rockColor public void act() overrides the act. method in the Actor class to do nothing info.gridworld.actor.Flower class (extends Actor) public Flower () constructs a pink flower public Flower (Color initialColer) constructs a flower with color initiaiColor public void act() causes the color of this lower to darken. -B4-\ppendix C Bug java Appendix C — Testable Code for APCS A/AB jug. java ackage info.gridvorld.actor; mport info.gridworld.grid.Grid; mport info.gridworld.grid. Location; mport java.awt Color; * A. Bug is an actor that can move and tur. It drops flowers as it moves. * The implementation of this class is testable on the AP CS A and AB Exams. +7 UbTICr Clade BUG Tex Pens ACTOR ” * Constructs a red bug. y SpubMe TRIER ¢ setColor (Color .RED) ; ) GREE in * Constructs a bug of a given color. * @param bugColor the color for this bug a Public Bug (CoLS¥ BugeolEH): ee AN setColor (bugColor) ; ) pe + Moves if it can move, turns otherwise. ” public void act () if (canMove()) move (1; else curn(); + Tums the bug 45 degrees tothe right without changing its location. ” public void turn() ( setDirection(getDirection|) + Location, ) -Cl- PaAppendix C Bug java ye * Moves the bug forward, puting flower into the location it previously occupied, + ‘SDaeE eka aae 85 EP RT ETS A RES RO Gridcactor> gr = getGria(): if (gr == null) return; Location loc = getLocation(); Location next = loc.getAdjacentLocation(getDirection()); if (gr. isValid(next) } moveTo (next); else removeSel {FromGrid() ; Flower flower = new FlowerigetColor(}}; flower.putSelfInGrid(gr, loc); ie Tests whether this bug can move forward into a location that is empty or contains a flower. * Greturn true if this bug can move. */ SopubLickbbreanieamtove 0 ee “ { Grid gr = getGrid(); SE (gr == null) return false; Location loc =’ getLocation(); Location next = loc.getAdjacentLocat ion (getDirection()): if (gr. isValid(next)) return false: Actor neighbor = gr.get (next): return (neighbor == null) || (neighbor instanceof Flower): 1. ok to move into empty location or onto flower J not ok to move onto any other actor -C2-\ppendix C BoxBug java joxBug. java mport info.gridworld.actor.Bug: + A BoxBug traces out a square “box” ofa given size. + The implementation of ths clas is testable on the AP CS A and AB Exams + SAS a A Ee Ae ES private int steps; private int sideLength; ee * Constructs a box bug that traces a squarc of a given side length * Qparam length the side length steps = 0; sideLength = Length; ye * Moves to the next location of the square. + if (steps < sideLength && canMove()) ( move() steps++; ) else ( turn (); turn (3; steps = 0. ? ) -C3- 65Appendix C Critter java Critter.java package info.gridworld.actor; import info.gridworld.gria.Lecation; import java.util.arrayList; io * A Critter isan actor that moves through its world, processing * other actors in some way and then moving to a new location. * Define your own critters by extending this class and overriding any methods of this class except for act.. * When you override these methods, be sure to preserve the postconditions, » The implementation of this class is testable on the AP CS A and AB Exams. . ei mmo tn eee public class Critter extends’ actor * Acritter acts by getting a list of other actors, processing that lis, geting locations to move to, * selecting one of them, and moving to the selected location, “7 public void act()- i if (getcria() return: ArrayList actors = getactors(); processActors (actors) ; ArrayList moveLocs = getMoveLocations(); Location loc = selectMoveLocation (moveLocs) ; makeMove(1o¢) ; null) es * Gets the ators for processing. Implemented to return the ators that occupy neighboring grid locations * Override this method in subclasses to look elsewhere for actors to process. + Postcondition: The sate of all actor is unchanged + Greturn a ist of actors that this critter wishes to process, “ public ArrayList getMoyenocations ( { return getGrid() .getEmptyAdjacentLocations (gettocation()); ) + Selects the location for the next move. Implemented to randomly pick one of the possible locations, * orto retum the current location if Locs has size 0, Override this method in subclasses that * have another mechanism for selecting the next move location, * Postcondition: (1) The retuned location is an element of Locs, this crtter’s eurrent location, or nul. + (2) The state of all actors is unchanged. + Gparam locs the possible locations for the next move + @return the location that was selected for the next move. * public’ Location selectMoveLocation(Arraybist - { int n = locs.size(); if (n == 0) return getLocation (); int r= (int) (ath-random(} * n); return locs.get (zr); -C5-68 Appendix C Critter java Moves this criter to the given location loc, or removes this critter from its grid if Loc is mulL. An actor may be added to the old location, If there isa different actor at location Loc, that actor is removed from the grid. Override this method in subclasses that want to earry out other actions (for example, turning this critter or adding an occupant in its previous location). Postcondition: (1) getLocation() == loc. (2) The state of all actors other than those at the old and new locations is unchanged. @param Loc the lecation to move to 1 SATEEN ca OS“ RR ete ETE if (loc == mull) removeSelfFromGrid() ; else moveTo (loc): a ) ) ChameleonCritter.java import info.gridworld.actor Actor; import info.gridworld actor Critter import info.gridworld. grid. Location; import java.util.ArrayList ion + A ChameleonCritter takes on the color of neighboring actors as it moves through the grid * The implementation of this class is testable on the AP CS A and AB Exams, * Pablie' clas’ Chameléoncritter: extendsi Crittexe igs { i Randomly selects a neighbor and changes this rittr’s color tobe the same as that neighbors + If there are no neighbors, no action is taken, ” 3 ‘Rue vp RaiRO REN aine faSTAUTatntt int n = actors.size(); if (n == 0) return int r= (int) (Math.random{) * n) Actor other = actors. get (x); setColor (other .getColor ()}; (eo * Turns towards the new location as it moves. i publ ic..void: makeMowe (Locations1oc) Sake setDirection (getLocation() .getDirectionToward(1oc) ); super .makeMove (1oc) ; ) -C6-Appendix E GridWorld Quick Reference A/JAB Appendix E — Quick Reference A/AB Location Class (implements Comparable’ public Location(int r, int c) public int getRow() public int getCol () public Location getAdjacentLocation(int direction) Sublic int getDirectiontoward (Location target) dublic boolean equals(Object other) dublic int hashcode() sublic int compareTo(Object other) vublic String tostring() JORTH, EAST, SOUTH, WEST, NORTHEAST, SOUTHEAST, NORTHWEST, SOUTHWEST JEFT, RIGHT, HALF_LEPT, HALF_RIGHT, FULLCTRCLE, HALF_CIRCLE, AHEAD 3rid_ Interface nt getNumRows () nt_getNumCols () voolean isValid(Location toc} } put (Location loc, E obj) ! remove (Location loc) 3 get (Location loc) wraybist getOccupiedLocations() rrayList getValidadjacentLocations (Location loc) rraylist getEmptyAdjacentLocations (Location loc) xrayList getOccupiedadjacentLocations (Location loc) rrayList getNeighbors(Location 10c) sctor Class ublie Actor() ublic Color getColor() ublic void setColor (Color newColor) ublic int getDirection() ublic void setDirection(int newDirection) vblic Grid«actor> getGrid() ublic Location getLocation () ublic void putseifinGrid(Gridcactor> ex, Location loc) ublic void removeselfFroncrid() ublic void moveTo(Location newLocation) ublic void act() ublic String toString() -El- a70 Appendix GridWorld Quick Reference A/AB Rock Class (extends Actor) public Rock() public Rock (Color rockCoior) public void act () Flower Class (extends Actor) public Flower () public Flower (Color initialColor) public void act () Bua Class (extends Actor) public Bug() public Bug (Color bugColor) public void act (} public void turn() public void move() public boolean canMove() BoxBug Class (extends Bug, public BoxBug(int 1) public void act () Critter Class (extends Actor) public void act () public ArrayList getActors() public void makevfove (Location loc] public void processActors (ArrayList actors) public ArrayList getWoveLocations () public Location selectoveLocation(ArrayList locs) | public void maketove (Location loc} ChameleonCri re Cli xtends Cri public void processActors (ArrayList actors)Appendix G Source Code Index Appendix G — Index for Source Code This appendix provides an index for the Java source code found in Appendix C, Bug.java Bug () Bug (Color bugColor) act () turn () move () canMove () BoxBug.java BoxBug(int length) act () Critter java act () getActors () processActors (ArrayList actors) getMoveLocations () selectMoveLocation (ArrayList locs) makeMove (Location loc) ChameleonCritter.java processActors (ArrayList actors) makeMove (Location loc) -Gl- C3 c4 ca cs cs cs C6 co C6 n72 The Exar AP* Computer Science A Exam 2009 DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. IMPORTANT Identification Information PLEASE PRINT WITH PEN: Thou mie 1 Fate terayou staan [[] 4 Us eke oc nga Wer Gesons lJ * tig don util ate 7 featotrtyourteeame |] rated oy seca Pere oT Gide Eats tien sna eo 2 natin Sivan sera tito a 1 putpotes. My name and tho name of ny Wetig beret [ School wil nt be used in ny way in encl ea Bayar Connection wth my fre-respoase Electronic Device aaa ‘materiale understand that am ree to None allowed Siig ‘markNo" wath efect on my grade or Weight T its reporting The questions are thee ans ‘ / Instructions The questions for Section I ae printed in the green insert and in this booket. You may use the inset to organize your answers and for scratch work, but you must waite your this pink Section Il booklet. No credit will be given for any work written in the the orange Appendix booklet is provided for use in Section Il ‘Write your answer to each question in the space provided in the Section Il booklet. Some questions require you to write program segments, and these must be written in Java. Show all your work. Credit for partial solutions will be given. Write clearly and legibly. Cross fou any errors you make. Erased or crossed-out work will not be graded. ‘Assume dss listed inthe Quick Reference found in the Appendix ar incladed in any program that wes a program segment you write If other dasses are to be included, that information will be specified in individual questions. Unless otherwise noted, assume that all methods are invoked oni when their preconditions are satisfied. A Quick Reference to required Java chess included inthe Appendix. Manage your time carefully. Do not spend too much time on any one question. You may proceed freely from one question to the next. You may review your responses if you finish before the end of the exam is announcedCOMPUTER SCIENCE A SECTION I ‘Time—1 hour and 45 minutes Number of questions—4 Percent of total grade—S0 rections: SHOW ALL YOUR WORK. REMEMBER THAT PROGRAM SEGMENTS ARE TO BE RITTEN IN JAVA. tes: ‘Assume that the classes listed in the Quick Reference found in the Appendix have been imported where appropriate. Unless otherwise noted in the question, assume that parameters in method calls are not nu11 and that methods are called only when their preconditions are satisfied. In writing solutions for each question, you may use any of the accessible methods that are listed in classes defined in that question. Writing significant amounts of code that can be replaced by a call to one of these methods may not receive full credit GO ON TO THE NEXT PAGE. 737 A statistician is studying sequences of numbers obtained by repeatedly tossing a six-sided number cube. On each side of the number cube is a single number in the range of 1 to 6, inclusive, and no number is repeated on the cube. The statistician is particularly interested in nuns of numbers. A run occurs when two or more consecutive tosses of the cube produce the same value. For example, in the following sequence of cube tosses, there are runs starting at positions 1, 6, 12, and 14. Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 : a Rest [1] [5] 4] 3][1]2]2[2]2]6][1]3][3]5]5|5]5 ‘The number cube is represented by the following class. public class NumberCube t /** @return an integer value between | and 6, inclusive Wi public int toss} (/* implementation not shown */ // There may be instance variables, constructors, and methods that are not shown, ) You will implement a method that collects the results of several tosses of a numbercube and another method that calculates the longest run found in a sequence of tosses. GO ON TO THE NEXT PACWrite the method getCubeTosses that takes 2 number cube and a number of tosses as parameters, The method should return an array of the values produced by tossing the number cube the given number of times. Complete method getCubeTosses below. /** Returns an array of the values obtained by tossing a number cube numTosses times. * @param cube a NumberCube * @param numTosses the number of tosses tobe recorded « Precondition: numfosses > 0 * @return anamay of nunfosses values 7 public static int[] getCubeTosses(NumberCube cube, int numTosses) GO ON TO THE NEXT PAGE. 676 (b) Write the method getLongestRun that takes as its parameter an array of integer values representing a series of number cube tosses. The method returns the starting index in the array of a run of maximum size. A run is defined as the repeated occurrence of the same value in two or more consecutive positions in the stray. For example, the following array contains two runs of length 4, one starting at index 6 and another starting at index 14. The method may retum either of those starting indexes. If there are no runs of any value, the method returns. ~1. Index 0 1 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 Resut [1] 5] s[4]3[1[2]2]2]2fe]ijajal{s|s sis WRITE YOUR SOLUTION ON THE NEXT PAGE. GO ON TO THE NEXT PAGimplete method getLongestRun below. * Returns the starting index of a longest run of two or more consecutive repeated values, inthe array values. @param values an array of integer values representing a series of number cube tosses Precondition: values. length > 0 @return the starting index of a run of maximum size; <1 if there is no run / blic static int getLongestRun(int[{] values) GO ON TO THE NEXT PAGE. 72. This question involves reasoning about the code from the GridWorld case study. A copy of the code is provided as part of this exam. A StockpileCritter isa Critter that uses other actors as a source of energy. Each actor represents one unit of energy. The StockpileCritter behaves likea Critter except in the way that it interacts with other actors. Each time the StockpileCritter acts, it gathers all neighboring actors by removing them from the grid and keeps track of them in a stockpile. The StockpileCritter then attempts to reduce its stockpile by one unit of energy. If the stockpile is emply, the StockpileCritter runs out of energy and removes itself from the grid. Consider the following scenario, INITIAL WORLD AFTER ONE ACT AFTER TWO ACTS IE He ka Stockpilecritter Gathered 3 actors, No actors gathered, is in location 2, 2), used L energy unit, used 1 energy unit, stockpile is empty 2 remaining in stockpile, 1 remaining in stockpile, moved to location (3, 3) moved to location (4, 3) AFTER THREE ACTS AFTER FOUR ACTS AFTER FIVE ACTS Gathered | actor, No actors gathered, Stockpile empty, used 1 energy unit, used I energy unit, removed self from grid remaining in stockpile, O remaining in stockpile, moved to location (3, 2) ‘moved to location (3, 3) Write the complete StockpileCritter class, including all instance variables and required methods. Do NOT override the act. method. Remember that your design must not violate the postconditions of the ‘methods of the Critter class and that updating an object’ instance variable changes the state of that object. 7 GO ON TO THE NEXT PACADDITIONAL WORK SPACE. GO ON TO THE NEXT PAGE. 793. An electric car that runs on batteries must be periodically recharged for a certain number of hours. The battery technology in the car requires thatthe charge time not be interrupted. ‘The cost for charging is based on the hour(s) during which the charging occurs. A rate table lists the 24 one-hour periods, numbered from 0 to 23, and the corresponding hourly cost for each period. The same rate table is used for each day. Each hourly cost is a positive integer. A sample rate table is given below. Hour Cost Hour — Cost Hour Cost 0 50 8 150 200 1 60 9 150 “17 | 200 2 160 | 10 130 18 180 3 60 | u 200 19 180 4 80 2 40 20 140 5 100 13 | 240 au 100 6 100 14 | 220 [2 80 \7 20 1s | 220 23 60. The class BatteryCharger below uses a rate table to determine the most economic time to charge the battery. You will write two of the methods for the BatteryCharger class. public class BatteryCharger /** rateTable has 24 entries representing the charging costs for hours 0 through 23. */ private int{]}-rateTable; /** Determines the total cost to charge the battery starting at the beginning of startHour. * @param startHour the hour at which the charge period begins * Precondition: 0 < startHour < 23 * Gparam chargeTime the number of hours the battery needs to be charged . Precondition: chargeTime > 0 * @return the total cost to charge the battery ” private int: getChargingcost (ints dtareHoun eS aUaReeIED { /* tobe implemented in part (a) */ } /** Determines start time to charge the battery at the lowest cost for the given charge time. * @param chargeTime the number of hours the battery needs to be charged Precondition: chargeTime > 0 * @return an optimal start time, with 0 < returned value < 23 “7 public int getChargeStartTime(int chargeTime) { /* tobe implemented in part (b) */ 1) There may be instance variables, constructors, and methods that are not shown, GO ON TO THE NEXT PAGE2) Writethe BatteryCharger method getChargingCost that returns the total cost to charge a battery given the hour at which the charging process will start and the number of hours the battery needs to be charged. For example, using the rate table given at the beginning of the question, the following table shows the resulting costs of several possible charges. Start Hour of Hours of Charge 1 Last Hour of Total Cost Charge Time Charge 12 i 12 0 [o 2 i 110 2 7 4 (the next day) 550 [2 30 3 (ewo days lates) 710 Note that a charge period consists of consecutive hours that may extend over more than one day. Complete method getChargingCost below. /** Determines the total cost 1o charge the battery starting at the beginning of startHour. * @param startHour the hour at which the charge period begins * Precondition: 0 < startHour < 23 * Gparam chargeTime the number of hours the battery needs to be charged Precondition: chargeTime > 0 @return the total cost to charge the battery private int getChargingCost (int startHour, int chargeTime) GO ON TO THE NEXT PAGE. at8& (b) Write the BatteryCharger method getChargeStartTime that retums the start time that will allow the battery to be charged at minimal cost. If there is more than one possible start time that produces the minimal cost, any of those start times can be returned. For example, using the rate table given at the beginning of the question, the following table shows the resulting minimal costs and optimal starting hour of several possible charges. Hours of Charge | Minimum Cost | Start Hour of |Last Hour of Charge Time Charge 1 40 2 2 0 1 2 110 or 2B O (the next day) 7 550 2 4 (the next day) 30 3,710 22 3 (two days later) WRITE YOUR SOLUTION ON THE NEXT PAGE. GO ON TO THE NEXT PAGAssume that getChargingCost works as specified, regardless of what you wrote in part (a) Complete method getChargeStartTime below. /** Determines start time to charge the battery at the lowest cost for the given charge time. * @param chargeTime the number of hours the battery needs to be charged. * Precondition: chargeTime > 0 * @return an optimal start time, with 0 < retumed value < 23 * public int getChargeStartTime(int chargeTime) GO ON TO THE NEXT PAGE. 834. A game uses square tiles that have numbers on their sides. Bach tile is labeled with a number on each ofits four sides and may be rotated clockwise, as illustrated below. INITIAL AFTER | AFTER 2 AFTER 3 (AFTER 4 ROTATION ROTATIONS ROTATIONS ROTATIONS. 4 4 7 foo3 A 4 3 7 4 3 4 4 7 4 3 1 3 4 4 7 The tiles are represented by the NumberTile class, as given below. public class NumberTile t J** Rotates the tile 90 degrees clockwise 7 public void rotate() { /* implementation not shown */ 7/** @return valueat left edge of tile public int getheft() ( /* implementation not shown */ /** @return value at right edge of tile +s public int, getRight() { /* implementationnot shown */ / 1 There may be instance variables, constructors, and methods that are not shown. ) Tiles are placed on a game board so that the adjoining sides of adjacent tiles have the same number. The following figure illustrates an arrangement of tiles and shows a new tile that is to be placed on the game board. GAME BOARD NEW TILE 4 6 1 3 5 Gees 4 3/]3 4] la 2) j2 2) f2 9 1 3 3 5 2 1 2 4 a4 GO ON TO THE NEXT PAGEits original orientation, the new tile can be inserted between the tiles at positions 2 and 3 or between the tiles positions 3 and 4. Ifthe new tile is rotated once, it can be inserted before the tile at position 0 (the first tie) or er the tile at position 4 (the last tile). Assume that the new tile, in its original orientation, is inserted between les at positions 2 and 3. As a result of the insertion, the tiles at positions 3 and 4 are moved one location to 2 right, and the new tile is inserted at position 3, as shown below. GAME BOARD AFTER INSERTING TILE 2 in) 1 2 partial definition of the TileGame class is given below. public class TileGame ( J** represents the game board; guaranteed never to be null */ private ArrayList board; public TileGame() { board = new Arraylist(); } /** Determines where to insert tile, in its current orientation, into game board @param tile the tile to be placed on the game board @return the position of tile where tile is to be inserted 0 if the board is empty; -1 if tile does not fit in front, at end, or between any existing tiles otherwise, 0 < position retuned < board.size() ”“ private int getIndexForFit (NumberTile tile) {/* tobe implemented in part (a) */ /** Places tile on the game board if it fits (checking all possible tile orientations if necessary) If there are no tiles on the game board, the tie is placed at position 0. The tile should be placed at most 1 time. + Precondition: board isnot null G@param tile the tile to be placed on the game board @return true if tile is placed successfully: false otherwise + Posteondition: the orientations of the other ties on the bord are not changed Postcondition: the order of the other tiles on the board relative to each other is not changed. ” public boolean insertTile(NumberTile tile) { /* tobe implemented in part (b) */ // There may be instance variables, constructors, and methods that are not shown, GO ON TO THE NEXT PAGE. 55