HashMap Examples

HashMap 1 - Construction, enumeration, access, rejection of duplicates.

HashMap 2 - Accessing keys and values.

HashMap 3 - Counting, finding, erasing.

HashMap 4 - Construction, enumeration, access, acceptance of duplicates.

HashMap 5 - Accessing keys and values.

HashMap 6 - Counting, finding, erasing.

HashMap1 Example Code// Copyright(c) 1996 ObjectSpace, Inc.

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

/**
 * Construction, enumeration, access, rejection of duplicates. 
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap1
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap();
    map.add( new Integer( 2 ), "two" );
    map.add( new Integer( 4 ), "four" );
    System.out.println( map );
    System.out.println();

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

    System.out.println( "Iterate through the HashMap" );
    for( HashMapIterator i = map.begin(); !i.atEnd(); i.advance() )
      System.out.println( i.get() + ", key = " + i.key() + ", value = " + i.value() );
    System.out.println();

    System.out.println( "Demonstrate access" );
    System.out.println( "map.get( 2 ) = " + map.get( new Integer( 2 ) ) );
    System.out.println( "map.get( 5 ) = " + map.get( new Integer( 5 ) ) );
    System.out.println( "map = " + map );
    System.out.println();

    System.out.println( "Show that duplicates cannot be added." );
    Object value = map.add( new Integer( 8 ), "eight" );
    if( value != null )
      System.out.println( "Could not add 8." );
    else
      System.out.println( "Added 8." );
    System.out.println( "map = " + map );

    value = map.add( new Integer( 4 ), "FOUR" );
    if( value != null )
      System.out.println( "Could not add 4." );
    else
      System.out.println( "Added 4." );
    System.out.println( "map = " + map );
    System.out.println();

    System.out.println( "Demonstrate modification" );
    map.put( new Integer( 4 ), "FOUR" );
    System.out.println( "map = " + map );
    }
  }

HashMap1 Example Output
HashMap( Pair( 2, two ), Pair( 4, four ) )

Enumerate the HashMap
two
four

Iterate through the HashMap
Pair( 2, two ), key = 2, value = two
Pair( 4, four ), key = 4, value = four

Demonstrate access
map.get( 2 ) = two
map.get( 5 ) = null
map = HashMap( Pair( 2, two ), Pair( 4, four ) )

Show that duplicates cannot be added.
Added 8.
map = HashMap( Pair( 2, two ), Pair( 4, four ), Pair( 8, eight ) )
Could not add 4.
map = HashMap( Pair( 2, two ), Pair( 4, four ), Pair( 8, eight ) )

Demonstrate modification
map = HashMap( Pair( 2, two ), Pair( 4, FOUR ), Pair( 8, eight ) )

HashMap2 Example Code// Copyright(c) 1996 ObjectSpace, Inc.

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

/**
 * Accessing keys and values. 
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap2
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap();
    map.add( "cat", "Meow" );
    map.add( "ape", "Squeak" );
    map.add( "dog", "Woof" );
    map.add( "bat", "Squeak" );
    System.out.println( "map = " + map );    

    System.out.print( "Enumerate the HashMap: " );    
    Enumeration e = map.elements();
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " ");
    System.out.println();

    System.out.print( "map.keys() = " );
    e = map.keys();
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " ");
    System.out.println();

    System.out.print( "map.keys( Squeak ) = " );
    e = map.keys( "Squeak" );
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " ");
    System.out.println();

    System.out.print( "map.values( bat ) = " );
    e = map.values( "bat" );
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " ");
    System.out.println();
    }
  }

HashMap2 Example Output
map = HashMap( Pair( ape, Squeak ), Pair( dog, Woof ), Pair( bat, Squeak ), Pair( cat, Meow ) )
Enumerate the HashMap: Squeak Woof Squeak Meow 
map.keys() = ape dog bat cat 
map.keys( Squeak ) = ape bat 
map.values( bat ) = Squeak

HashMap3 Example Code// Copyright(c) 1996 ObjectSpace, Inc.

import jgl.*;

/**
 * Counting, finding, erasing. 
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap3
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap();
    map.add( "cat", "Meow" );
    map.add( "ape", "Squeak" );
    map.add( "dog", "Woof" );
    map.add( "bat", "Squeak" );
    System.out.println( map );
    System.out.println( "map.count( dog ) = " + map.count( "dog" ) );
    HashMapIterator i = map.find( "dog" );
    if( i.equals( map.end() ) ) // A simpler way of saying this is: if( i.atEnd() ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + i.get() );
    System.out.println( "map.remove( dog ) = " + map.remove( "dog" ) );
    HashMapIterator j = map.find( "dog" );
    if( j.atEnd() ) // A simpler way of saying: if( j.equals( map.end() ) ) ...
      System.out.println( "Could not find dog." );
    else
      System.out.println( "Found " + j.get() );
    }
  }

HashMap3 Example Output
HashMap( Pair( ape, Squeak ), Pair( dog, Woof ), Pair( bat, Squeak ), Pair( cat, Meow ) )
map.count( dog ) = 1
Found Pair( dog, Woof )
map.remove( dog ) = Woof
Could not find dog.

HashMap4 Example Code// Copyright(c) 1996 ObjectSpace, Inc.

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

/**
 * Construction, enumeration, access, acceptance of duplicates. 
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap4
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap( true );
    map.add( new Integer( 2 ), "two" );
    map.add( new Integer( 4 ), "four" );
    System.out.println( map );
    System.out.println();

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

    System.out.println( "Iterate through the HashMap" );
    for( HashMapIterator i = map.begin(); !i.atEnd(); i.advance() )
      System.out.println( i.get() + ", key = " + i.key() + ", value = " + i.value() );
    System.out.println();

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

    map.add( new Integer( 4 ), "FOUR" );
    System.out.println( "map = " + map );

    System.out.println( "Show that even with duplicates, put() does a replacement." );
    map.put( new Integer( 4 ), "FoUr" );
    System.out.println( "map = " + map );

    }
  }

HashMap4 Example Output
HashMap( Pair( 2, two ), Pair( 4, four ) )

Enumerate the HashMap
two
four

Iterate through the HashMap
Pair( 2, two ), key = 2, value = two
Pair( 4, four ), key = 4, value = four

Show that duplicates can be added.
map = HashMap( Pair( 2, two ), Pair( 4, four ), Pair( 8, eight ) )
map = HashMap( Pair( 2, two ), Pair( 4, four ), Pair( 4, FOUR ), Pair( 8, eight ) )
Show that even with duplicates, put() does a replacement.
map = HashMap( Pair( 2, two ), Pair( 4, FoUr ), Pair( 4, FOUR ), Pair( 8, eight ) )

HashMap5 Example Code// Copyright(c) 1996 ObjectSpace, Inc.

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

/**
 * Accessing keys and values.
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap5
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap( true );
    map.add( "cat", "Meow" );
    map.add( "ape", "Squeak" );
    map.add( "ape", "Whoop" );
    map.add( "bat", "Squeak" );
    System.out.println( "map = " + map );    
    System.out.println();    

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

    e = map.keys();
    System.out.print( "map.keys() = " );
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " " );
    System.out.println();

    e = map.keys( "Squeak" );
    System.out.print( "map.keys( Squeak ) = " );
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " " );
    System.out.println();

    e = map.values( "ape" );
    System.out.print( "map.keys( ape ) = " );
    while( e.hasMoreElements() )
      System.out.print( e.nextElement() + " " );
    System.out.println();
    }
  }

HashMap5 Example Output
map = HashMap( Pair( ape, Squeak ), Pair( ape, Whoop ), Pair( bat, Squeak ), Pair( cat, Meow ) )

Enumerate the HashMap
Squeak
Whoop
Squeak
Meow

map.keys() = ape ape bat cat 
map.keys( Squeak ) = ape bat 
map.keys( ape ) = Squeak Whoop

HashMap6 Example Codeimport jgl.*;

/**
 * Counting, finding, erasing. 
 * 
 * @see jgl.HashMap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap6
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap( true );
    map.add( "cat", "Meow" );
    map.add( "ape", "Squeak" );
    map.add( "ape", "Whoop" );
    map.add( "bat", "Squeak" );
    System.out.println( map );

    System.out.println( "map.count( ape ) = " + map.count( "ape" ) );
    HashMapIterator i = map.find( "ape" );

    if( i.equals( map.end() ) ) // A simpler way of saying this is: if( i.atEnd() ) ...
      {
      System.out.println( "Could not find dog." );
      }
    else
      {
      while( !i.atEnd() && i.key().equals( "ape" ) )
        {
        System.out.println( "Found " + i.get() ); 
        i.advance();
        }
      }
    System.out.println( "map.remove( ape ) = " + map.remove( "ape" ) );
    HashMapIterator j = map.find( "ape" );
    if( j.atEnd() ) // A simpler way of saying: if( j.equals( map.end() ) ) ...
      System.out.println( "Could not find ape." );
    else
      System.out.println( "Found " + j.get() );
    }
  }

HashMap6 Example Output
HashMap( Pair( ape, Squeak ), Pair( ape, Whoop ), Pair( bat, Squeak ), Pair( cat, Meow ) )
map.count( ape ) = 2
Found Pair( ape, Squeak )
Found Pair( ape, Whoop )
map.remove( ape ) = Squeak
Could not find ape.

HashMap7 Example Codeimport jgl.*;

/**
 * Bounds. 
 * 
 * @see jgl.Hashmap
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class HashMap7
  {
  public static void main( String[] args )
    {
    HashMap map = new HashMap( true );
    map.add( new Integer( 3 ), "three" );
    map.add( new Integer( 8 ), "eight" );
    map.add( new Integer( 2 ), "two" );
    map.add( new Integer( 3 ), "THREE" );
    System.out.println( map );
 
    Range range = map.equalRange( new Integer( 3 ) );
    while( !range.begin.equals( range.end ) )
      System.out.println( "match @ " + range.begin.nextElement() );
    }
  }

HashMap7 Example Output
HashMap( Pair( 2, two ), Pair( 3, three ), Pair( 3, THREE ), Pair( 8, eight ) )
match @ Pair( 3, three )
match @ Pair( 3, THREE )

HashMap Examples

`HashMap1 Example Code`

HashMap1 Example Output

`HashMap2 Example Code`

HashMap2 Example Output

`HashMap3 Example Code`

HashMap3 Example Output

`HashMap4 Example Code`

HashMap4 Example Output

`HashMap5 Example Code`

HashMap5 Example Output

`HashMap6 Example Code`

HashMap6 Example Output

`HashMap7 Example Code`

HashMap7 Example Output