additionapplet.java

一个java的APPLET小程序,可以将用户输入的两个数字相加

// Fig. 3.13: AdditionApplet.java
// Additing two floating-point numbers.

//Java packages
import java.awt.Graphics; // inmport class Graphics
import javax.swing.*; // import package javax.swing

public class AdditionApplet extends JApplet{

   double sum; // sum of values entered by user
   
   // initialize apple by obtaining values from user
   public void init()
   {
      String firstNumber;  // first string entered by user
      String secondNumber; // second string entered by user   

      double number1;         // first number to add
      double number2;         // second number to add

      // obtain first number from user
      firstNumber = JOptionPane.showInputDialog( "Enter first floating-point           value" );

      // obtain second number from user
      secondNumber = JOptionPane.showInputDialog( "Enter second floating-point           value" );

      // convert numbers from type string to type double
      number1 = Double.parseDouble( firstNumber );
      number2 = Double.parseDouble( secondNumber );

      // add numbers
      sum = number1 + number2;

   } // end method init

   // draw results in a rectangle on applet's background
   public void paint( Graphics g )
   {
      // call superclass version of method paint
      super.paint( g );

      // draw rectangle starting from (15,10) that is 270
      // pixels wide and 20 pixels tall
      g.drawRect( 15,10, 270, 20 );

      // draw results as a String at (25, 25)
      g.drawString( "The sum is " + sum, 25, 25 );

   } // end method paint

} // end class AdditionApplet