A First Simple Program

A First Simple Program

/*

This is a simple program Call this file “Example.java”.

*/

Class Example

{

//Your program begins with a call to main ().

Public static void main (String args[])

{

 System.out.println (“This is a simple Java program “);

}

}

Entering the program

-The name of a source file is very important

-In Java, all code must reside inside a class. By convention ,the name of that class should match the name of the file that holds the program

-A source file use the .java filename extension

Compilling the Program

C:>\javac Example .java

-The javac compiler creates a file called Example .class, that contain the Bytecode version of the program

-To actually run program, you must use the Java interpreter, called java

C:>\java Example

-When java source code is compiled, each individual class is put into its own output file named after the class and using the .class extension

A closer look at the first program

-All Java application begin execution by calling main()

-A complex program will have dozens of classes, only one of which will need to have a main() method to get things started

-Java applets don’t have any main() method

-Java interpreter run only main() method

-Java interpreter run only the class that have a main method

-println() is a built in method

-System is a predefined class that provides access to the system,and out is the output stream that is connected to the console.

      

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