// Fig. 20.6: PrintBits.java
// Printing an unsigned integer in bits 

// Java core packages
import java.awt.*;
import java.awt.event.*;

// Java extension packages
import javax.swing.*;

public class PrintBits extends JFrame {
   private JTextField outputField;

   // set up GUI
   public PrintBits()
   {
      super( "Printing bit representations for numbers" );

      Container container = getContentPane();
      container.setLayout( new FlowLayout() );

      container.add( new JLabel( "Enter an integer " ) );

      // textfield to read value from user
      JTextField inputField = new JTextField( 10 );

      inputField.addActionListener(

         new ActionListener() {

            // read integer and get bitwise representation
            public void actionPerformed( ActionEvent event )
            {
               int value = Integer.parseInt(
                  event.getActionCommand() );
               outputField.setText( getBits( value ) );
            }
         }
      );

      container.add( inputField );

      container.add( new JLabel( "The integer in bits is" ) );

      // textfield to display integer in bitwise form
      outputField = new JTextField( 33 );
      outputField.setEditable( false );
      container.add( outputField );

      setSize( 720, 70 );
      setVisible( true );
   }

   // display bit representation of specified int value
   private String getBits( int value )
   {
      // create int value with 1 in leftmost bit and 0s elsewhere
      int displayMask = 1 << 31;

      // buffer to build output
      StringBuffer buffer = new StringBuffer( 35 );

      // for each bit append 0 or 1 to buffer
      for ( int bit = 1; bit <= 32; bit++ ) {

         // use displayMask to isolate bit and determine whether
         // bit has value of 0 or 1
         buffer.append( 
            ( value & displayMask ) == 0 ? '0' : '1' );

         // shift value one position to left 
         value <<= 1;

         // append space to buffer every 8 bits
         if ( bit % 8 == 0 )
            buffer.append( ' ' );
      }

      return buffer.toString();
   }

   // execute application
   public static void main( String args[] )
   {
      PrintBits application = new PrintBits();

      application.setDefaultCloseOperation(
         JFrame.EXIT_ON_CLOSE );
   }

}  // end class PrintBits


/**************************************************************************
 * (C) Copyright 2002 by Deitel & Associates, Inc. and Prentice Hall.     *
 * All Rights Reserved.                                                   *
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 * DISCLAIMER: The authors and publisher of this book have used their     *
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 * development, research, and testing of the theories and programs        *
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