How to clear a text field when a button is pressed

Clearer.java

import javax.swing.*;
import javax.swing.text.*;
import java.awt.*; 
import java.awt.event.*;

public class Clearer {
  public static void main(String[] args) {
		JFrame mainframe = new JFrame("test");
		mainframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		mainframe.setSize(300,200);
		final JTextField tf = new JTextField(20);
		JButton button = new JButton("clear");
		button.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				try {
					// here it is, get the document and call remove on it
					// pass 0 (the starting point)
					// and the length of the document
					tf.getDocument().remove(0,tf.getDocument().getLength());
				} catch(BadLocationException err1) {
					err1.printStackTrace();
				}
			}
		});
		mainframe.getContentPane().setLayout(new FlowLayout());
		mainframe.getContentPane().add(tf);
		mainframe.getContentPane().add(button);
		mainframe.setVisible(true);
	}
}