Java HashTable

// Demonstrates the Hashtable class of the java.util package.

public class HashTableDemo extends JFrame {

	public HashTableDemo() {
		super(" Hashtable Sourcecode Example");
		final JLabel jlbStatus = new JLabel();
		final Hashtable hashTable = new Hashtable();
		final JTextArea display = new JTextArea(4, 20);
		display.setEditable(false);
		JPanel jplNorth = new JPanel();
		jplNorth.setLayout(new BorderLayout());
		JPanel jplNorthSub = new JPanel();
		jplNorthSub.add(new JLabel("Name (Key)"));
		final JTextField jtfFirstName = new JTextField(8);
		jplNorthSub.add(jtfFirstName);
		jplNorthSub.add(new JLabel("Phone No"));
		final JTextField jtfPhone = new JTextField(8);
		jplNorthSub.add(jtfPhone);
		jplNorth.add(jplNorthSub, BorderLayout.NORTH);
		jplNorth.add(jlbStatus, BorderLayout.SOUTH);
		JPanel jplSouth = new JPanel();
		jplSouth.setLayout(new GridLayout(2, 5));
		JButton jbnAdd = new JButton("Add");
		jbnAdd.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				String strNum = jtfPhone.getText().trim();
				String strName = jtfFirstName.getText().trim();
				if ((strNum != null && strNum.equals(""))
						|| (strName != null && strName.equals(""))) {
					JOptionPane.showMessageDialog(HashTableDemo.this,
							"Please enter both Name and Phone No");
					return;
				}
				int num = 0;
				try {
					num = Integer.parseInt(strNum);
				} catch (NumberFormatException ne) {
					ne.printStackTrace();
				}
				EmployeeDetails emp = new EmployeeDetails(strName, num);
				Object val = hashTable.put(strName, emp);
				if (val == null)
					jlbStatus.setText("Added: " + emp.toString());
				else
					jlbStatus.setText("Added: " + emp.toString()
							+ "; Replaced: " + val.toString());
			}
		});
		jplSouth.add(jbnAdd);
		JButton jbnGet = new JButton("Get");
		jbnGet.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				Object val = hashTable.get(jtfFirstName.getText().trim());
				if (val != null)
					jlbStatus.setText("Get: " + val.toString());
				else
					jlbStatus.setText("Get: " + jtfFirstName.getText()+ 
										" not in table");
			}
		});
		jplSouth.add(jbnGet);
		JButton jbnRemove = new JButton("Remove Name");
		jbnRemove.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				Object val = hashTable.remove(jtfFirstName.getText()
						.trim());
				if (val != null)
					jlbStatus.setText("Remove: " + val.toString());
				else
					jlbStatus.setText("Remove: " + jtfFirstName.getText()+
										" not in table");
			}
		});
		jplSouth.add(jbnRemove);
		JButton jbnIsEmpty = new JButton("Empty ?");
		jbnIsEmpty.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				jlbStatus.setText("Empty: " + hashTable.isEmpty());
			}
		});
		jplSouth.add(jbnIsEmpty);
		JButton jbnContains = new JButton("Contains key");
		jbnContains.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				jlbStatus.setText("Contains key: "+ 
					hashTable.containsKey(jtfFirstName.getText().trim()));
			}
		});
		jplSouth.add(jbnContains);
		JButton jbnClear = new JButton("Clear table");
		jbnClear.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				hashTable.clear();
				jlbStatus.setText("HashTable Emptied");
			}
		});
		jplSouth.add(jbnClear);
		JButton jbnDisplay = new JButton("List objects");
		jbnDisplay.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				StringBuffer buf = new StringBuffer();
				for (Enumeration enum = hashTable.elements();
									enum.hasMoreElements();)
					buf.append(enum.nextElement()).append('\n');
				display.setText(buf.toString());
			}
		});
		jplSouth.add(jbnDisplay);
		JButton jbnKeys = new JButton("List keys");
		jbnKeys.addActionListener(new ActionListener() {

		public void actionPerformed(ActionEvent e) {
				StringBuffer buf = new StringBuffer();
				for (Enumeration enum = hashTable.keys(); enum.hasMoreElements();)
					buf.append(enum.nextElement()).append('\n');
				JOptionPane.showMessageDialog(null, buf.toString(),
					"Display Keys of HashTable ",JOptionPane.PLAIN_MESSAGE);
			}
		});
		jplSouth.add(jbnKeys);
		Container c = getContentPane();
		c.add(jplNorth, BorderLayout.NORTH);
		c.add(new JScrollPane(display), BorderLayout.CENTER);
		c.add(jplSouth, BorderLayout.SOUTH);
		setSize(540, 300);
		setVisible(true);
	}
	
	public static void main(String args[]) {
		HashTableDemo hashTableDemo = new HashTableDemo();
		hashTableDemo.addWindowListener(new WindowAdapter() {

			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	}
}

class EmployeeDetails {

	private String name;
	private int phoneNp;
	public EmployeeDetails(String fName, int phNo) {
		name = fName;
		phoneNp = phNo;
	}
	public String toString() {
		return name + " " + phoneNp;
	}
}