1. A Java Program: // Fig. 2.1: Welcome1.java // Text-printing program.
public class Welcome1 {
// main method begins execution of Java application
public static void main( String args[] ) {
System.out.print ("Hello " );
System.out.println(" World! ");
System.out.println( "Welcome to Java Programming!" );
} // end method main
} // end class Welcome1
/*********************************************************
*(C) Copyright by Deitel & Associates, Inc. and *
* Prentice Hall. All Rights Reserved *
**********************************************************/

2. Escape sequence: // Escape sequence public class Welcome1 {
// main method begins execution of Java application
public static void main( String args[] ) {
System.out.print ("Hello World!\nWelcome ");
System.out.print ( "to Java Programming!\n" );
} // end method main
} // end class Welcome1
/*********************************************************
\n \t \\ \“ \r
**********************************************************/

3. Package: collection of classes
// Java API: Java Application Programming Interface
// (java., javax.)
// GUI: Graphical User Interface //
// using swing package, JOptionPane class
// showMessageDialog method
import javax.swing.JOptionPane;
public class TestPane{
public static void main(String args[]){
JOptionPane.showMessageDialog(
null,
"Welcome\nTo\nswing\nPackage");
System.exit(0); }

4. A Java program package classes methods arguments Variable declaration
import javax.swing.JOptionPane;
public class time{
public static void main(String args[]){
int x,y,z;
String X,Y;
X = JOptionPane.showInputDialog("Input x");
Y = JOptionPane.showInputDialog("Input y");
x = Integer.parseInt(X);
y = Integer.parseInt(Y);
z = x*y;
JOptionPane.showMessageDialog(
null,
x + " * " + y + " = " + z,
"The product of " + x + " and " + y,
JOptionPane.PLAIN_MESSAGE );
System.exit(0); }
Variable declaration
classes
methods
arguments