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Tech Funda
To make any changes to a program, double-click on the class icon. After making the
required changes, you need to compile the program again.
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 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 arguments. 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 the semicolon at the end of the System.out.println() statement; it terminates the line. It
is also known as the line terminator. The Java compiler ignores all white spacing and indentation,
so it is necessary to use a semicolon to denote the end of all statements in Java.
TOKENS
A token is the smallest element of a program that has a special meaning to the compiler. Tokens
can be classified as follows:
Identifiers
Keywords
Data Types
Literals
Variables
Comments
Let us discuss these in detail.
56 iPRIME (Ver. 2.2)–VIII

