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STRUCTURE OF A JAVA PROGRAM

The program created in the previous section contains a single class named HelloWorld which is declared
by using the class keyword. The curly brackets ({ }) are used to start and end the body of the class. The
HelloWorld class has one method named main( ). The main( ) method is declared by using three Java
keywords, which are public, static, and void. The main() method must look like:

public static void main(String args[])
In the main method:

public means the method is accessible from outside the class.
static means the method belongs to the class rather than to instances of the class.

void means the method does not return a value.

The only term that you can change in the syntax of the main( ) method is the name of the parameter
args, which can be any valid identifier name. The array of strings (String []) will contain the command-
line arguments, if any, when the program is executed from the command prompt. In BlueJ, we can also
use main() method without any argument. The main() contains a single statement:

System.out.println("Hello from Touchpad");
This statement is used to display the message “Hello from Touchpad” on the output screen. System.
out represents the standard output of the device where the program is running, and the println()
method displays the given string along with a line feed.

Notice that the semicolon at the end of the System.out.println() statement terminates the line.
It is also known as the line terminator. The Java compiler ignores all whitespace and indenting, so
it is necessary to use a semicolon to denote the end of all statements in Java.

BASIC FUNDAMENTALS OF JAVA

Like other programming languages, Java also provides some fundamental concepts which are given
below:

Identifiers

Keywords

Data Types
Literals

Variables

Comments
Let us discuss these in detail.

Identifiers

An identifier is the name given to an object in a Java program. It is used to uniquely identify an object in
a program. For example, a class name or a method name.

Introduction to Programming in Java 91