JAVA SECOND EDITION Chapter 1 Introduction to Object- Oriented Programming and Problem Solving (© 2008 Jones snd Barlet PublishersKnowledge Goals Understand what a computer program is Know the three phases of the software life cycle Understand what an algorithm is Learn what a high-level programming language is Understand the difference between machine code and Bytecode (© 2008 fones snd Barlet PublishersKnowledge Goals Understand the compilation, execution, and interpretation processes Learn what the major components of a computer are and how they work together Understand the concept of an object in the context of computer problem solving (© 2008 fones snd Barlet PublishersSkills aS List the basic stages involved in writing a computer application Distinguish between hardware and software List the ways of structuring code in a Java application Name several problem-solving techniques Choose an applicable problem-solving technique Identify the objects in a problem statement How can you distinguish the knowledge goals from the skills goals? ot Date PublishersWhat is Programming? Computer A programmable device that can store, retrieve, and process data Computer programming The process of specifying objects and the ways in which those objects interact to solve problems Programming Writing out instructions for solving a problem or performing a task Computer program Instructions defining a set of objects and orchestrating their interactions to solve a problem 1d Ware PublishersHow do we write a Program ; PROBLEM-SOLVING PHASE IMPLEMENTATION PHASE Analysis and specification General solution Concrete solution (algorithm) | Verity Revise to address new requirements and correct errors discovered in use MAINTENANCE PHASEHow do we write a program ... Problem-Solving Phase « Understand (define) the problem and identify what the solution must do * Specify the objects and their interactions to solve the problem + Follow the steps exactly to see if the solution really does solve the problemHow do we write a program ... Implementation Phase « Translate the object specifications (the general solution) into a programming language + Have the computer carry out the solution and check the results What if the solution isn't correct?How do we write a program ... Maintenance Phase « Use the program + Modify the program to meet changing requirements, to enhance its functionality, or to correct any errors that show up in using itHow can a computer work with objects... Hat Size Magnification Travel Time (© 2008 fones snd Barlet PublishersNea do we ae a program ... (© 2008 fones snd Barlet PublishersHow can a computer work with objects? Information Any knowledge that can be communicated Data Information in a form that a computer can use Object Acollection of data values and associated operationsHow can a computer work with objects... Object Object Output of Contents Operation Operation Ms. Jane T. Leegle Esq. (© 2008 fones snd Barlet PublishersHow can a computer work with objects... Objects contain data and operations Consider a Name object What sort of data would this object contain? What sort of operations might we need to manipulate the data?What is an algorithm? Once we have the algorithm, then what? We translate the algorithm into statements in a programming language Say again? (© 2008 fones snd Barlet PublishersClasses of Objects Date class data: month, day, year operations: set and return month, day, year Date object (an instance of a class) June 23 2004 (© 2008 Jones an ware PublishersWhat is an algorithm? How are the operations specified? Algorithm Instructions for solving a problem ina finite amount of time using a finite amount of dataaORON> 6. What is an algorithm? Objects: Key, Transmission, Gas Pedal, Engine, Phone Insert the key. Make sure the transmission is in Park (or Neutral). Depress the gas pedal. Turn the key to the start position. If the engine starts within six seconds, release the key. If the engine doesn’t start within six seconds, release the key and gas pedal, wait ten seconds, and repeat Steps 3 through 6, but not more than five times. 7. If the car doesn’t start, phone your mechanic. (© 2008 fones snd Barlet PublishersWhat is a ve nae 9 Chip's Java Code b. Algorithm translated by different people 2 © 2008 jones and arte PaihersWhat kind of instructions ... Computer A programmable device that can store, retrieve, and process data [ers accept data, send data, perform arithmetic operations, perform logical operationsClasses of Objects What about multiple objects with the same properties? Class A specification of the representation of a particular kind of object, in terms of data and behavior (operations)What kind of instructions ... Control structures Statements that organize the instructions that specify the behaviors of objects - sequence - selection - repetition - subprograms - asynchronous (© 2008 fones snd Barlet PublishersWhat kind of instructions ... ‘SELECTION (also called branch or decison) fn IF ooditon THEN stalomentt ELSE statment2 (© 2008 Jones an ware PublishersWhat is a programming language? Programming language Aset of rules, symbols and special words used to construct a computer program Statements Specific combinations of symbols and special words that are defined by a programming language to be complete units within a program; analogous to sentences in a human language Code Instructions for a computer that are written programming language 20What kind of instructions ... LOOP (also called repetition or iteration) WHILE condition DO statamentt | 'SUBPROGRAM (also called method, procedure, function, or subroutine) ‘SUBPROGRAMT JBPROGRAM meaningful collection z any of the above ASYNCHRONOUS 25 (© 2008 fones snd Barlet PublishersHow It All Works (© 2008 Jones an ware PublishersSoftware Maintenance Maintaining software accounts for the majority of its live cycle (i.e., old programs never die, they just get modified) Where were you on January 1, 2000?Assembly Languages + Are machine dependent and run on only one specific type of computer + Are translated into machine code by assemblers - Are made up of English-like abbreviations such as LOAD, STORE, or ADDHow It All Works Assembly Language Machine Language Meaning 1001 001 014 101 Operation Result Operand1 Operand2 Operation Result Operand 1 Operand 2 High-level language: R1=R3+R5 R2=R6-R1 29 (© 2008 Jones an ware PublishersHigh-Level Languages Source code Instructions written in a high-level language Object code A machine language version derived from source code (© 2008 Jones andHow It All Works Machine language The language, made up of binary-coded instructions, that is used directly by the computer Assembly language A low-level programming language in which a mnemonic represents each machine language instruction for a particular computer 28Machine Language - Is not portable - Runs only on specific type of computer - Is made up of binary-coded instructions (strings of Os and 1s) - Is the language that can be directly used by the computerSoftware Maintenance Software maintenance tips - Check existing code - Make changes to a copy - Change related aspects to leave clean, consistent code for next change - Keep backup copiesHigh-Level Languages » Are portable - Are translated into machine code by compilers - Instructions are written in language similar to natural language - Examples -- FORTRAN, COBOL, Pascal, C, C++ » Many are standardized by ISO/ANSI to provide an official description of the languageHigh-Level Languages Direct execution The process by which a computer performs the actions specified in a machine-language program Interpretation The translation, while a program is running, of non- machine language instructions (such as Bytecode) into executable operations Virtual machine Aprogram that makes one computer act like another 37 (© 2008 fones snd Barlet PublishersWhat's inside the computer? Control unit The Manager Arithmetic/logic unit Does operationsWhat's inside the computer? ~<— Your program Memory unit Internal data storage inside a computer, made up of an ordered sequence of addressable cells 40 © 2008 fone a are PublishersJava's Road to Portability Bytecode A standardized machine language into which Java source code is compiled Windows PC: running JVMPortability opuect ‘COMPUTER ‘CODE EXECUTES: (MACHINE ‘TRANSLATOR LANGUAGE ‘compuTen SouRCE CODE ‘cope VERSION OF EXECUTES: (ces) (compuen) ‘SOURCE CODE) OBJECT CODE Windows PC Ces compiler z a (C++ compior 35 (© 2008 Jones an ware PublishersHigh-Level Languages Input Direct Execution Output Interpretation Phase es and arte PublishersWhat's inside the meWhat's inside the computer? Hardware The physical components of a computer Software Computer programs; the set of all programs available on a computer Clock An electrical circuit that sends out a train of pulses to coordinate the actions of the computer's hardware components; its speed is measured in hertz (cycles per second) 42Problem Solving How to Solve It: A New Aspect of Mathematical Method by George Polya "How to solve it list" written within the context of mathematical problems But the list is quite generalProblem Solving How ao you solve problems? Understand the problem Devise a plan Carry out the plan Look back (© 2008 Jones an ware PublishersWhat is system software? User/computer interface Aconnecting link that translates between the computer's internal representation of data and representations that humans are able to work with Interactive system A system that supports direct communication between the user and the computer System software The set of programs that simplifies the user/ communication interface Operating system Set of programs that manages all the computer's resources 43What is system Se See how it all fits together ? oureur (© 2008 Jones an ware PublishersProblem Solving Problem solving The act of finding a solution to a perplexing, distressing, vexing, or unsettled question How do you define problem solving?Problem-Solving Techniques (© 2008 Jones an ware PublishersProblem-Solving Techniques Ask questions! - What do | know about the problem? - What is the information that | have to process in order the find the solution? - What does the solution look like? - What sort of special cases exist? - How will | recognize that | have found the solution?Problem-Solving Techniques Never reinvent the wheel! Similar problems come up again and again in different guises A good programmer recognizes a task or subtask that has been solved before and plugs in the solution Can you think of two similar problems?Problem-Solving Techniques Hard problem |Problem-Solving Techniques Means: Fy, walk, hitchhike, bike, rive, sail, bus Revised Means: Fly to Chicago and then to Austin; fly to Newark and then to Austin: fly to Atlanta land then to Austin Start: Boston Means to Intermediate Goal: Commuter: Intermediate Goal: Newark walk, hitchhike, bike, drive, sail, bus Goal: Austin Solution: Take commuter flight to Newark and then catch cheap flight to Austin 52 (© 2008 fones snd Barlet PublishersProblem-Solving Techniques Existing Software New Program Inventory System Existing Software (© 2008 fones snd Harlet PublishersProblem-Solving Techniques List of Temperatures Use the same method to find these values in both cases. Highest = 95 Lowest = 18 50 List of Test Scores 27 14 55 98 72 66 45 12 39 70 68 Highest = 98 Lowest = 12 (© 2008 fones snd Barlet PublishersProblem-Solving Techniques ‘Summing Values on a File Summing and Counting Values on a File While data on file Read value Add value to sum. Add one to count Close file 55 (© 2008 Jones and ware PublishersProblem-Solving Techniques Object-Oriented Problem Solving Stages - Brainstorm List all objects that might contribute to solution - Filter Review the classes to find duplicates or remove unnecessary objects - Responsibilities Determine the operations associated with a class of objects - Collaborations Determine the interactions between classesProblem-Solving Techniques - Attributes Determine the values defined by a class that are used to represent its objects - Driver Write a program for creating the objects and coordinating their collaborations to solve the problem