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HashSet Examples

HashSet 1 - Construction, enumeration, rejection of duplicates.

HashSet 2 - Union, intersection, difference, symmetric difference, subset.

HashSet 3 - Counting, finding, removing.

HashSet 4 - Construction, enumeration, acceptance of duplicates.

HashSet 5 - Counting, finding, removing with duplicates allowed.

HashSet 6 - Bounds. Duplicates allowed.

HashSet 7 - Using another BinaryPredicate for matching

HashSet1 Example Code

// Copyright(c) 1996,1997 ObjectSpace, Inc.

import java.util.Enumeration;
import COM.objectspace.jgl.*;

/**
 * Construction, enumeration, rejection of duplicates.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet1
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet();
    set.add( new Integer( 6 ) );
    set.add( new Integer( 1 ) );
    set.add( new Integer( 4 ) );
    System.out.println( set );
    System.out.println();

    System.out.println( "Enumerate the HashSet" );
    Enumeration e = set.elements();
    while ( e.hasMoreElements() )
      System.out.println( e.nextElement() );
    System.out.println();

    System.out.println( "Iterate through the HashSet" );
    for ( HashSetIterator i = set.begin(); !i.atEnd(); i.advance() )
      System.out.println( i.get() );
    System.out.println();

    System.out.println( "Show that duplicates cannot be added." );
    Object value = set.add( new Integer( 8 ) );
    if ( value != null )
      System.out.println( "Could not add 8." );
    else
      {
      System.out.println( "Added 8" );
      System.out.println( "New contents are " + set );
      }

    value = set.add( new Integer( 4 ) );
    if ( value != null )
      System.out.println( "Could not add 4." );
    else
      {
      System.out.println( "Added 4." );
      System.out.println( "New contents are " + set );
      }
    }
  }

HashSet1 Example Output

HashSet( 1, 4, 6 )

Enumerate the HashSet
1
4
6

Iterate through the HashSet
1
4
6

Show that duplicates cannot be added.
Added 8
New contents are HashSet( 1, 4, 6, 8 )
Could not add 4.

HashSet2 Example Code

// Copyright(c) 1996,1997 ObjectSpace, Inc.

import COM.objectspace.jgl.*;

/**
 * Union, intersection, difference, symmetric difference, subset.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet2
  {
  public static void main( String[] args )
    {
    HashSet set1 = new HashSet();
    set1.add( "ape" );
    set1.add( "cat" );
    set1.add( "bat" );

    HashSet set2 = new HashSet();
    set2.add( "bat" );
    set2.add( "fox" );
    set2.add( "ape" );
    System.out.println( "set1 = " + set1 + ", set2 = " + set2 );

    HashSet set3 = set1.union( set2 );
    System.out.println( "set3 = set1.union( set2 ) = " + set3 );

    HashSet set4 = set1.intersection( set2 );
    System.out.println( "set4 = set1.intersection( set2 ) = " + set4 );

    HashSet set5 = set1.difference( set2 );
    System.out.println( "set5 = set1.difference( set2 ) = " + set5 );

    HashSet set6 = set1.symmetricDifference( set2 );
    System.out.println( "set6 = set1.symmetricDifference( set2 ) = " + set6 );

    System.out.println( "set4.subsetOf( set3 ) = " + set4.subsetOf( set3 ) );
    System.out.println( "set3.subsetOf( set4 ) = " + set3.subsetOf( set4 ) );
    }
  }

HashSet2 Example Output

set1 = HashSet( ape, bat, cat ), set2 = HashSet( ape, bat, fox )
set3 = set1.union( set2 ) = HashSet( ape, bat, fox, cat )
set4 = set1.intersection( set2 ) = HashSet( ape, bat )
set5 = set1.difference( set2 ) = HashSet( cat )
set6 = set1.symmetricDifference( set2 ) = HashSet( fox, cat )
set4.subsetOf( set3 ) = true
set3.subsetOf( set4 ) = false

HashSet3 Example Code

// Copyright(c) 1996,1997 ObjectSpace, Inc.

import COM.objectspace.jgl.*;

/**
 * Counting, finding, removing.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet3
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet();
    set.add( "cat" );
    set.add( "ape" );
    set.add( "dog" );
    set.add( "bat" );
    System.out.println( set );
    System.out.println( "set.count( dog ) = " + set.count( "dog" ) );
    HashSetIterator i = set.find( "dog" );
    if ( i.equals( set.end() ) ) // A simpler way: if ( i.atEnd() ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + i.get() );
    System.out.println( "set.remove( dog ) = " + set.remove( "dog" ) );
    HashSetIterator j = set.find( "dog" );
    if ( j.atEnd() ) // A simpler way: if ( j.equals( set.end() ) ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + j.get() );
    }
  }

HashSet3 Example Output

HashSet( ape, dog, bat, cat )
set.count( dog ) = 1
Found dog
set.remove( dog ) = 1
Could not find dog.

HashSet4 Example Code

import java.util.Enumeration;
import COM.objectspace.jgl.*;

/**
 * Construction, enumeration, acceptance of duplicates.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet4
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet( true ); // allow duplicates
    set.add( new Integer( 6 ) );
    set.add( new Integer( 1 ) );
    set.add( new Integer( 4 ) );
    set.add( new Integer( 1 ) );
    System.out.println( set );
    System.out.println();

    System.out.println( "Enumerate the HashSet" );
    Enumeration e = set.elements();
    while ( e.hasMoreElements() )
      System.out.println( e.nextElement() );
    System.out.println();

    System.out.println( "Iterate through the HashSet" );
    for ( HashSetIterator i = set.begin(); !i.atEnd(); i.advance() )
      System.out.println( i.get() );
    System.out.println();

    System.out.println( "Show that duplicates can be added." );
    set.add( new Integer( 8 ) );
    System.out.println( "set = " + set );

    set.add( new Integer( 4 ) );
    System.out.println( "set = " + set );
    }
  }

HashSet4 Example Output

HashSet( 1, 1, 4, 6 )

Enumerate the HashSet
1
1
4
6

Iterate through the HashSet
1
1
4
6

Show that duplicates can be added.
set = HashSet( 1, 1, 4, 6, 8 )
set = HashSet( 1, 1, 4, 4, 6, 8 )

HashSet5 Example Code

import COM.objectspace.jgl.*;

/**
 * Counting, finding, removing with duplicates allowed.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet5
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet( true ); // allow duplicates
    set.add( "cat" );
    set.add( "ape" );
    set.add( "dog" );
    set.add( "bat" );
    set.add( "dog" );
    System.out.println( set );
    System.out.println( "set.count( dog ) = " + set.count( "dog" ) );
    HashSetIterator i = set.find( "dog" );
    if ( i.equals( set.end() ) ) // A simpler way: if ( i.atEnd() ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + i.get() );
    System.out.println( "set.remove( dog ) = " + set.remove( "dog" ) );
    HashSetIterator j = set.find( "dog" );
    if ( j.atEnd() ) // A simpler way: if ( j.equals( set.end() ) ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + j.get() );
    }
  }

HashSet5 Example Output

HashSet( ape, dog, dog, bat, cat )
set.count( dog ) = 2
Found dog
set.remove( dog ) = 2
Could not find dog.

HashSet6 Example Code

import COM.objectspace.jgl.*;

/**
 * Bounds. Duplicates allowed.
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet6
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet( true ); // allow duplicates
    set.add( new Integer( 3 ) );
    set.add( new Integer( 8 ) );
    set.add( new Integer( 2 ) );
    set.add( new Integer( -2 ) );
    set.add( new Integer( 3 ) );
    set.add( new Integer( 10 ) );
    System.out.println( set );

    Range range = set.equalRange( new Integer( 3 ) );
    while ( !range.begin.equals( range.end ) )
      System.out.println( "match @ " + range.begin.nextElement() );
    }
  }

HashSet6 Example Output

HashSet( 2, 3, 3, 8, 10, -2 )
match @ 3
match @ 3

HashSet7 Example Code

import java.util.Enumeration;
import COM.objectspace.jgl.*;

/**
 * Using another BinaryPredicate for matching
 *
 * @see COM.objectspace.jgl.HashSet
 * @version 2.0.2
 * @author ObjectSpace, Inc.
 */

public class HashSet7
  {
  public static void main( String[] args )
    {
    HashSet set = new HashSet( new IdenticalTo() );
    set.add( new Integer( 6 ) );
    set.add( new Integer( 1 ) );
    set.add( new Integer( 4 ) );

    // this WILL work because it is a seperate object than the other Integer(1)
    set.add( new Integer( 1 ) );
    System.out.println( set );
    System.out.println();

    System.out.println( "Add an object Integer(100)" );
    Integer tryit = new Integer(100);
    System.out.println( "add returns: " + set.add( tryit ) );
    System.out.println( "set = " + set );
    System.out.println( "Try to add the EXACT same object Integer(100)" );
    System.out.println( "add returns: " + set.add( tryit ) );
    System.out.println( "set = " + set );
    }
  }

HashSet7 Example Output

HashSet( 1, 1, 4, 6 )

Add an object Integer(100)
add returns: null
set = HashSet( 1, 1, 4, 6, 100 )
Try to add the EXACT same object Integer(100)
add returns: 100
set = HashSet( 1, 1, 4, 6, 100 )

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