// Addition program
import java.applet.Applet;
import java.awt.*;    // import the java.awt package
import java.awt.event.*;  // import the java.awt.event package


public class Addition extends Applet implements ActionListener {
   Label prompt;      // message that prompts user to input
   TextField input;   // input values are entered here
   int number;        // variable that stores input value
   int sum;           // variable that stores sum of integers

   // setup the graphical user interface components
   // and initialize variables
   public void init()
   {
      prompt = new Label( "Enter integer and press Enter:" );
      add( prompt );  // put prompt on applet 

      input = new TextField( 10 );
      add( input );   // put input TextField on applet

      sum = 0;        // set sum to 0

      // "this" applet handles action events for TextField input
      input.addActionListener( this );
   }

   // process user's action in TextField input 
   public void actionPerformed( ActionEvent e )
   {
      // get the number and convert it to an integer
      number = Integer.parseInt( e.getActionCommand() );

      sum = sum + number;   // add number to sum
      input.setText( "" );  // clear data entry field
      showStatus( Integer.toString( sum ) );  // display sum
   }
}