CLASS X
COMPUTER APPLICATIONS
LN 5(A) - INTRODUCTION TO JAVA
Write short answers
1. Name a Java package which is imported by default.
java.lang is imported by default in Java.
2. Explain the significance of the following Java library packages.
(a) java.awt
(b) java.io
(c) java.net
(a) java.awt — java.awt package contains classes for supporting abstract window tool kit
and managing Graphical User Interface (GUI) components.
(b) java.io — It contains the classes that handle fundamental input and output operations in
Java.
(c) java.net — It contains classes for supporting network operations in Java.
3(a) Java interpreter is called Java Virtual machine. Explain.
Java interpreter enables a computer to execute a Java program as well as a program written in
other language compiled into Java byte code. Hence, java interpreter is called Java Virtual machine.
3(b) Name two ways of writing Java programs.
Two ways of writing Java programs are:
1. Java Application
2. Java Applet
4. Define the terms:
(a) Source code
(b) Machine code
(c) Byte code
(a) Source code — A set of statements written in a High-Level programming language like Java,
C++, Python, etc. is called as Source Code.
(b) Machine code — Machine code is a low-level programming language. Instructions in machine
code are written as a sequence of 0s and 1s. It is directly understood and executed by the processor.
(c) Byte code — Java compiler converts Java source code into an intermediate binary code called
Byte code. Byte code can't be executed directly on the processor. It needs to be converted into
Machine Code first.
5. What is BlueJ? What are the features of BlueJ?
BlueJ is an integrated development environment for Java. It was created for teaching Object
Oriented programming to computer science students. Features of BlueJ include a simple beginner
friendly graphical user interface to develop Java programs. It allows creating objects of the class
dynamically, invoking their methods and also supplying data to the method arguments if present.
6 . Write down the syntax of output statement in Java with an example.
We commonly use two output statements in Java. Their syntax is as follows:
1. System.out.println(<output value>);
This statement displays the output of the program on the screen in different lines. The letters
'ln' in the statement act as a line feed which directs the cursor to move to the next line.
2. System.out.print(<output value>);
This statement is used to display the value enclosed within its braces. It leaves the cursor in
the same line on the screen.
As an example, the below statements will generate the following output:
System.out.println("JVM stands for");
System.out.print("Java ");
System.out.print("Virtual ");
System.out.print("Machine");
Output
JVM stands for
Java Virtual Machine
7. What is meant by Java reserved words? Name five Java reserved words which are commonly used
in Java programming.
There are some words that carry special meaning to the system compiler. These words can't
be used as variable names in the program. Such words are called Keywords or reserved words.
Five commonly used Java reserved words are:
1. public
2. class
3. int
4. double
5. char
8. Differentiate between the output statements System.out.println() and System.out.print().
System.out.println() System.out.print()
It prints data to the console and places It prints data to the console but the cursor
the cursor in the next line. remains at the end of the data in the same line.
Next printing takes place from next
Next printing takes place from the same line.
line.
9. A Java program uses a Compiler as well as an Interpreter. Explain.
Java compiler compiles Java source code to Byte code. Byte code cannot run on the processor
directly as processor only understands machine code. Java Virtual Machine (JVM) takes this byte
code as input and converts it into machine code line by line. So, JVM acts as an interpreter for
converting byte code to machine code. In this way, a Java program uses both a compiler as well as an
interpreter to get executed on the processor.
10. Write a package that is used for input/output operation in Java
java.io package is used for input/output operation in Java.
