// Fig. 18.3: HashtableTest.java
// Demonstrates class Hashtable of the java.util package.
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class HashtableTest extends Applet
               implements ActionListener {
   private Hashtable table;
   private TextField fName, lName;
   private TextArea display;
   private Button put, get, remove, empty, containsKey, 
                  clear, listElems, listKeys;

   public void init()
   {
      table = new Hashtable();

      add( new Label( "First name" ) );
      fName = new TextField( 8 );
      add( fName );

      add( new Label( "Last name (key)" ) );
      lName = new TextField( 8 );
      add( lName );

      display = new TextArea( 4, 45 );
      add( display );

      put = new Button( "Put" );
      put.addActionListener( this );
      add( put );

      get = new Button( "Get" );
      get.addActionListener( this );
      add( get );

      remove = new Button( "Remove" );
      remove.addActionListener( this );
      add( remove );

      empty = new Button( "Empty" );
      empty.addActionListener( this );
      add( empty );

      containsKey = new Button( "Contains key" );
      containsKey.addActionListener( this );
      add( containsKey );

      clear = new Button( "Clear table" );
      clear.addActionListener( this );
      add( clear );

      listElems = new Button( "List objects" );
      listElems.addActionListener( this );
      add( listElems );

      listKeys = new Button( "List keys" );
      listKeys.addActionListener( this );
      add( listKeys );
   }

   public void actionPerformed( ActionEvent e )
   {
      if ( e.getSource() == put ) {
         Employee emp = new Employee( fName.getText(),
                                      lName.getText() );
         Object val = table.put( lName.getText(), emp );

         if ( val == null )
            showStatus( "Put: " + emp.toString() );
         else
            showStatus( "Put: " + emp.toString() +
                        "; Replaced: " + val.toString() );
      }
      else if ( e.getSource() == get ) {
         Object val = table.get( lName.getText() );
             
         if ( val != null )
            showStatus( "Get: " + val.toString() );
         else
            showStatus( "Get: " + lName.getText() +
                        " not in table" );
      }
      else if ( e.getSource() == remove ) {
         Object val = table.remove( lName.getText() );
             
         if ( val != null )
            showStatus( "Remove: " + val.toString() );
         else
            showStatus( "Remove: " + lName.getText() +
                        " not in table" );
      }
      else if ( e.getSource() == empty ) {
         showStatus( "Empty: " + table.isEmpty() );
      }
      else if ( e.getSource() == containsKey ) {
         showStatus( "Contains key: " +
            table.containsKey( lName.getText() ) );
      }
      else if ( e.getSource() == clear ) {
         table.clear();
         showStatus( "Clear: Table is now empty" );
      }
      else if ( e.getSource() == listElems ) {
         StringBuffer buf = new StringBuffer();

         for ( Enumeration enum = table.elements();
               enum.hasMoreElements(); )
            buf.append( enum.nextElement() ).append( '\n' );

         display.setText( buf.toString() );
      }
      else if ( e.getSource() == listKeys ) {
         StringBuffer buf = new StringBuffer();

         for ( Enumeration enum = table.keys();
               enum.hasMoreElements(); )
            buf.append( enum.nextElement() ).append( '\n' );

         display.setText( buf.toString() );
      }
   }
}

class Employee {
   private String first;
   private String last;

   public Employee( String fName, String lName )
   {
      first = fName;
      last = lName;
   }

   public String toString() { return first + " " + last; }
}