受限的文本框——限制可输入字符个数的文本框

import java.awt.EventQueue;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
public class LimitTextNum extends JFrame{
	 private JTextField textField;
	 
	 public LimitTextNum() {
	        super();
	        setTitle("限制可输入字符个数的文本框");
	        getContentPane().setLayout(null);
	        setBounds(100, 100, 337, 243);
	        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	        
	        textField = new JTextField();
	        textField.addKeyListener(new KeyAdapter() {
	            public void keyTyped(final KeyEvent e) {
	                if (textField.getText().length() == 8) { // 限制最多只能在文本框中输入8个字符
	                    e.consume(); // 销毁本次输入的字符
	                    JOptionPane.showMessageDialog(null, "不能超出可输入的最大字符个数");
	                }
	            }
	        });
	        textField.setBounds(31, 41, 160, 22);
	        getContentPane().add(textField);

	        final JLabel label = new JLabel();
	        label.setText("限制文本框中可输入字符的个数");
	        label.setBounds(32, 17, 207, 18);
	        getContentPane().add(label);
	        //
	    }
	 
	 public static void main(String args[]) {
	        EventQueue.invokeLater(new Runnable() {
	            public void run() {
	                try {
	                    LimitTextNum frame = new LimitTextNum();
	                    frame.setVisible(true);
	                } catch (Exception e) {
	                    e.printStackTrace();
	                }
	            }
	        });
	    }
}