Source of AdditionApplet.java


  1: // Fig. 20.10: AdditionApplet.java
  2: // Adding two floating-point numbers.
  3: import java.awt.Graphics;       // program uses class Graphics
  4: import javax.swing.JApplet;     // program uses class JApplet
  5: import javax.swing.JOptionPane; // program uses class JOptionPane
  6: 
  7: public class AdditionApplet extends JApplet 
  8: {
  9:    private double sum; // sum of values entered by user
 10: 
 11:    // initialize applet by obtaining values from user
 12:    public void init()
 13:    {
 14:       String firstNumber;  // first string entered by user
 15:       String secondNumber; // second string entered by user
 16: 
 17:       double number1; // first number to add
 18:       double number2; // second number to add
 19: 
 20:       // obtain first number from user
 21:       firstNumber = JOptionPane.showInputDialog(
 22:          "Enter first floating-point value" );
 23: 
 24:       // obtain second number from user
 25:       secondNumber = JOptionPane.showInputDialog(
 26:          "Enter second floating-point value" );
 27: 
 28:       // convert numbers from type String to type double
 29:       number1 = Double.parseDouble( firstNumber ); 
 30:       number2 = Double.parseDouble( secondNumber );
 31: 
 32:       sum = number1 + number2; // add numbers
 33:    } // end method init
 34: 
 35:    // draw results in a rectangle on applet’s background
 36:    public void paint( Graphics g )
 37:    {
 38:       super.paint( g ); // call superclass version of method paint
 39: 
 40:       // draw rectangle starting from (15, 10) that is 270 
 41:       // pixels wide and 20 pixels tall
 42:       g.drawRect( 15, 10, 270, 20 );
 43: 
 44:       // draw results as a String at (25, 25)
 45:       g.drawString( "The sum is " + sum, 25, 25 );
 46:    } // end method paint
 47: } // end class AdditionApplet
 48: 
 49: /**************************************************************************
 50:  * (C) Copyright 1992-2005 by Deitel & Associates, Inc. and               *
 51:  * Pearson Education, Inc. All Rights Reserved.                           *
 52:  *                                                                        *
 53:  * DISCLAIMER: The authors and publisher of this book have used their     *
 54:  * best efforts in preparing the book. These efforts include the          *
 55:  * development, research, and testing of the theories and programs        *
 56:  * to determine their effectiveness. The authors and publisher make       *
 57:  * no warranty of any kind, expressed or implied, with regard to these    *
 58:  * programs or to the documentation contained in these books. The authors *
 59:  * and publisher shall not be liable in any event for incidental or       *
 60:  * consequential damages in connection with, or arising out of, the       *
 61:  * furnishing, performance, or use of these programs.                     *
 62:  *************************************************************************/