HashMap examples

HashMap1 Example Code





import com.sfdc.sss.*;

import java.util.Enumeration;



/**

 * Construction, enumeration, access, rejection of duplicates.

 */



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



//

import com.sfdc.sss.*;

import java.util.Enumeration;



/**

 * Accessing keys and values.

 */



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( dog, Woof ), Pair( ape, Squeak ), Pair( bat, Squeak ), Pair( cat, Meow ) )

Enumerate the HashMap: Woof Squeak Squeak Meow

map.keys() = dog ape bat cat

map.keys( Squeak ) = ape bat

map.values( bat ) = Squeak



HashMap3 Example Code



//

import com.sfdc.sss.*;



/**

 * Counting, finding, erasing.
 */



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: 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: if ( j.equals( map.end() ) ) ...

      System.out.println( "Could not find dog." );

    else

      System.out.println( "Found " + j.get() );

    }

  }

HashMap3 Example Output





HashMap( Pair( dog, Woof ), Pair( ape, Squeak ), 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



//

import com.sfdc.jgl.*;

import java.util.Enumeration;



/**

 * Construction, enumeration, access, acceptance of duplicates.

 */



public class HashMap4

  {

  public static void main( String[] args )

    {

    HashMap map = new HashMap( true ); // allow duplicates

    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



//

import com.sfdc.jgl.*;

import java.util.Enumeration;



/**

 * Accessing keys and values.

 */



public class HashMap5

  {

  public static void main( String[] args )

    {

    HashMap map = new HashMap( true ); // allow duplicates

    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 Code



//

import com.sfdc.jgl.*;



/**

 * Counting, finding, erasing.


 */



public class HashMap6

  {

  public static void main( String[] args )

    {

    HashMap map = new HashMap( true ); // allow duplicates

    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: 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: 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 Code



//

import com.sfdc.jgl.*;



public class HashMap7

  {

  public static void main( String[] args )

    {

    HashMap map = new HashMap( true ); // allow duplicates

    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 )