primenumbers.java

来自「32个java程序源代码」· Java 代码 · 共 177 行

// Exercise 12.17: PrimeNumbers.java
// Determines all prime numbers between a user-specified range.
import java.awt.*;
import java.awt.event.*;
import java.text.*;
import javax.swing.*;

public class PrimeNumbers extends JFrame
{
   // JLabel and JTextField for lower bound
   private JLabel lowerBoundJLabel;
   private JTextField lowerBoundJTextField;

   // JLabel and JTextField for upper bound
   private JLabel upperBoundJLabel;
   private JTextField upperBoundJTextField;

   // JLabel, JTextArea and JScrollPane for displaying prime numbers
   private JLabel primeNumbersJLabel;
   private JTextArea primeNumbersJTextArea;
   private JScrollPane primeNumbersJScrollPane;

   // JButton initiates calculation and display of prime numbers
   private JButton calculatePrimesJButton;

   // no-argument constructor
   public PrimeNumbers()
   {
      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 lowerBoundJLabel
      lowerBoundJLabel = new JLabel();
      lowerBoundJLabel.setBounds( 16, 16, 80, 21 );
      lowerBoundJLabel.setText( "Lower bound:" );
      contentPane.add( lowerBoundJLabel );

      // set up lowerBoundJTextField
      lowerBoundJTextField = new JTextField();
      lowerBoundJTextField.setBounds( 104, 16, 56, 21 );
      lowerBoundJTextField.setHorizontalAlignment(
         JTextField.RIGHT );
      contentPane.add( lowerBoundJTextField );

      // set up upperBoundJLabel
      upperBoundJLabel = new JLabel();
      upperBoundJLabel.setBounds( 16, 56, 80, 21 );
      upperBoundJLabel.setText( "Upper bound:" );
      contentPane.add( upperBoundJLabel );

      // set up upperBoundJTextField
      upperBoundJTextField = new JTextField();
      upperBoundJTextField.setBounds( 104, 56, 56, 21 );
      upperBoundJTextField.setHorizontalAlignment(
         JTextField.RIGHT );
      contentPane.add( upperBoundJTextField );

      // set up primeNumbersJLabel
      primeNumbersJLabel = new JLabel();
      primeNumbersJLabel.setBounds( 16, 100, 96, 21 );
      primeNumbersJLabel.setText( "Prime numbers:" );
      contentPane.add( primeNumbersJLabel );

      // set up primeNumbersJTextArea
      primeNumbersJTextArea = new JTextArea();
      primeNumbersJTextArea.setEditable( false );
      
      // set up primeNumbersJScrollPane
      primeNumbersJScrollPane = new JScrollPane(
         primeNumbersJTextArea );
      primeNumbersJScrollPane.setBounds( 16, 120, 144, 96 );
      contentPane.add( primeNumbersJScrollPane );

      // set up calculatePrimesJButton
      calculatePrimesJButton = new JButton();
      calculatePrimesJButton.setBounds( 16, 232, 144, 23 );
      calculatePrimesJButton.setText( "Calculate Primes" );
      contentPane.add( calculatePrimesJButton );
      calculatePrimesJButton.addActionListener(

         new ActionListener() // anonymous inner class
         {
            // event handler called when
            // calculatePrimesJButton is clicked
            public void actionPerformed( ActionEvent event )
            {
               calculatePrimesJButtonActionPerformed( event );
            }

         } // end anonymous inner class

      ); // end call to addActionListener

      // set properties of application's window
      setTitle( "Prime Numbers" ); // set title bar string
      setSize( 184, 296 );         // set window size
      setVisible( true );          // display window

   } // end method createUserInterface

   // calculate and display primes using method prime
   private void calculatePrimesJButtonActionPerformed(
      ActionEvent event )
   {
      // declare variables and get values
      int lowerBound = Integer.parseInt(
         lowerBoundJTextField.getText() );
      int upperBound = Integer.parseInt(
         upperBoundJTextField.getText() );
      int counter;
      primeNumbersJTextArea.setText( "" );

      if ( ( lowerBound <= 0 ) || ( upperBound <= 0 ) )
      {
         JOptionPane.showMessageDialog( null,
            "Bounds must be greater than 0", "Invalid Bounds",
            JOptionPane.ERROR_MESSAGE );
      }

      else if ( upperBound < lowerBound )
      {
         JOptionPane.showMessageDialog( null,
            "Upper bound cannot be less than lower bound",
            "Invalid Bounds", JOptionPane.ERROR_MESSAGE );
      }

      else
      {
         // loop from lower bound to upper bound
         for ( counter = lowerBound; counter <= upperBound;
            counter++ )
         {
            // if prime number, display in primeNumbersJTextArea
            if ( true )
            {
               primeNumbersJTextArea.append( counter + "\n" );
            }
         
         } // end for loop

      } // end else

   } // end method calculatePrimesJButtonActionPerformed

   // main method
   public static void main( String[] args )
   {
      PrimeNumbers application = new PrimeNumbers();
      application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
   
   } // end method main

} // end class PrimeNumbers

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 * (C) Copyright 1992-2004 by Deitel & Associates, Inc. and               *
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