average.java

来自「32个java程序源代码」· Java 代码 · 共 169 行

// Exercise 5.16: Average.java
// Application that finds the average of three integers.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Average extends JFrame
{
   // JLabel and JTextField for user to input first number
   private JLabel firstNumberJLabel;
   private JTextField firstNumberJTextField;

   // JLabel and JTextField for user to input second number
   private JLabel secondNumberJLabel;
   private JTextField secondNumberJTextField;
   
   // JLabel and JTextField for user to input third number
   private JLabel thirdNumberJLabel;
   private JTextField thirdNumberJTextField;
   
   // JLabel and JTextField to display average
   private JLabel averageJLabel;
   private JTextField averageJTextField;
   
   // JButton to initiate average calculation
   private JButton calculateJButton;
   
   // no-argument constructor
   public Average()
   {
      createUserInterface();
   }
   
   // create and position GUI components; register event handlers
   private void createUserInterface()
   {
      // get content pane for attaching GUI components
      Container contentPane = getContentPane();

      // enable explicit positioning of GUI components
      contentPane.setLayout( null );
      
      // set up firstNumberJLabel
      firstNumberJLabel = new JLabel();
      firstNumberJLabel.setText( "Enter first number:" );
      firstNumberJLabel.setBounds( 20, 20, 125, 20 );
      contentPane.add( firstNumberJLabel );
      
      // set up firstNumberJTextField
      firstNumberJTextField = new JTextField();
      firstNumberJTextField.setText( "0" );
      firstNumberJTextField.setBounds( 165, 20, 40, 20 );
      firstNumberJTextField.setHorizontalAlignment( 
         JTextField.RIGHT );
      contentPane.add( firstNumberJTextField );

      // set up secondNumberJLabel
      secondNumberJLabel = new JLabel();
      secondNumberJLabel.setText( "Enter second number:" );
      secondNumberJLabel.setBounds( 20, 50, 125, 20 );
      contentPane.add( secondNumberJLabel );
      
      // set up secondNumberJTextField
      secondNumberJTextField = new JTextField();
      secondNumberJTextField.setText( "0" );
      secondNumberJTextField.setBounds( 165, 50, 40, 20 );
      secondNumberJTextField.setHorizontalAlignment( 
         JTextField.RIGHT );
      contentPane.add( secondNumberJTextField );
      
      // set up thirdNumberJLabel
      thirdNumberJLabel = new JLabel();
      thirdNumberJLabel.setText( "Enter third number:" );
      thirdNumberJLabel.setBounds( 20, 80, 125, 20 );
      contentPane.add( thirdNumberJLabel );
      
      // set up thirdNumberJTextField
      thirdNumberJTextField = new JTextField();
      thirdNumberJTextField.setText( "0" );
      thirdNumberJTextField.setBounds( 165, 80, 40, 20 );
      thirdNumberJTextField.setHorizontalAlignment(
         JTextField.RIGHT );
      contentPane.add( thirdNumberJTextField );
      
      // set up averageJLabel
      averageJLabel = new JLabel();
      averageJLabel.setText( "Average is:" );
      averageJLabel.setBounds( 20, 110, 130, 20 );
      contentPane.add( averageJLabel );
      
      // set up averageJTextField
      averageJTextField = new JTextField();
      averageJTextField.setText( "0" );
      averageJTextField.setEditable( false );
      averageJTextField.setBounds( 165, 110, 40, 20 );
      averageJTextField.setHorizontalAlignment( JTextField.RIGHT );
      contentPane.add( averageJTextField );
      
      // set up calculateJButton
      calculateJButton = new JButton ();
      calculateJButton.setText( "Calculate" );
      calculateJButton.setBounds( 225, 20, 90, 20 );
      contentPane.add( calculateJButton );
      calculateJButton.addActionListener( 
         
         new ActionListener() // anonymous inner class
         {
            // method called when calculateJButton is pressed
            public void actionPerformed( ActionEvent event ) 
            {
               calculateJButtonActionPerformed( event );
            }
         
         } // end anonymous inner class
	 
      ); // end call to addActionListener
            
      // set properties of window
      setTitle( "Average Three Numbers" ); // set window title
      setSize( 335, 180 );                 // set window size
      setVisible( true );                  // display window

   } // end method createUserInterface
   
   // calculate the average of the three values
   private void calculateJButtonActionPerformed( ActionEvent event )
   {
      // get values input by user
      int number1 = Integer.parseInt( 
         firstNumberJTextField.getText() );
      int number2 = Integer.parseInt( 
         secondNumberJTextField.getText() );
      int number3 = Integer.parseInt( 
         thirdNumberJTextField.getText() );
      
      // sum number1, number2 and number3 and divide by 3
      int result = number1 + number2 + number3 / 3;
      
      // display the result
      averageJTextField.setText( String.valueOf( result ) );
   
   } // end method calculateJButtonActionPerformed
   
   // main method
   public static void main( String[] args )
   {
      Average application = new Average();
      application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

   } // end method main
  
} // end class Average


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