83 lines
1.9 KiB
Java
83 lines
1.9 KiB
Java
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Using a BitSet to demonstrate the Sieve of Eratosthenes
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import java.awt.*;
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import java.awt.event.*;
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import java.util.*;
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import javax.swing.*;
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public class BitSetTest extends JFrame
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{
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public BitSetTest()
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{
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super( "BitSets" );
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final BitSet sieve = new BitSet( 1024 );
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Container c = getContentPane();
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final JLabel status = new JLabel();
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c.add( status, BorderLayout.SOUTH );
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JPanel inputPanel = new JPanel();
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inputPanel.add( new JLabel( "Enter a value from " + "1 to 1023" ) );
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final JTextField input = new JTextField( 10 );
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input.addActionListener( new ActionListener()
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{
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public void actionPerformed( ActionEvent e )
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{
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int val = Integer.parseInt( input.getText() );
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if ( sieve.get( val ) )
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status.setText( val + " is a prime number" );
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else
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status.setText( val + " is not a prime number" );
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}
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} );
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inputPanel.add( input );
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c.add(inputPanel, BorderLayout.NORTH );
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JTextArea primes = new JTextArea();
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ScrollPane p = new ScrollPane();
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p.add( primes );
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c.add( p, BorderLayout.CENTER );
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// set all bits from 1 to 1023
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int size = sieve.size();
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for ( int i = 1; i < size; i++ )
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sieve.set( i );
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// perform Sieve of Eratosthenes
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int finalBit = ( int ) Math.sqrt( sieve.size() );
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for ( int i = 2; i < finalBit; i++ )
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if ( sieve.get( i ) )
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for ( int j = 2 * i; j < size; j += i )
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sieve.clear( j );
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int counter = 0;
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for ( int i = 1; i < size; i++ )
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if ( sieve.get( i ) )
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{
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primes.append( String.valueOf( i ) );
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primes.append( ++counter % 7 == 0 ? "\n" : "\t" );
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}
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setSize( 300, 250 );
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show();
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}
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public static void main( String args[] )
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{
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BitSetTest app = new BitSetTest();
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app.addWindowListener( new WindowAdapter()
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{
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public void windowClosing( WindowEvent e )
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{
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System.exit( 0 );
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}
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} );
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}
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}
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