import java.awt.*;
import java.awt.event.*;
public class Java extends Frame implements KeyListener{
    static Label l= new Label("A");
    
    public static void main(String args[]) {
        Java j = new Java();
        l.addKeyListener(j);
        j.setSize(200,200);
        j.add(l);
        j.setVisible(true);
    }
    
        public void keyPressed(KeyEvent e) 
        {
            if (e.getKeyCode()==e.VK_LEFT) {
                l.setText("B");
            }    
            if(e.getKeyCode()==e.VK_RIGHT) {
                l.setText("A");
            }    
             
        }
    public void keyTyped(KeyEvent e) {
    }
    public void keyReleased(KeyEvent e) {
    }
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Java extends JFrame implements KeyListener{
    static JLabel l= new JLabel("A");
    static JTextField tf=new JTextField(15);

    public static void main(String args[]) {
        Java j = new Java();

        j.setSize(200,200);
        j.getContentPane().setLayout(new FlowLayout());
        j.getContentPane().add(l);
        j.getContentPane().add(tf);
        tf.addKeyListener(j);
        j.setVisible(true);
        j.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

        public void keyPressed(KeyEvent e){
            if (e.getKeyCode()==KeyEvent.VK_LEFT) {
                System.out.println("-------");
                l.setText("B");
                
            }
            if(e.getKeyCode()==KeyEvent.VK_RIGHT) {
                l.setText("A");
            }

        }
    public void keyTyped(KeyEvent e) {
//        System.out.println("-------");
    }
    public void keyReleased(KeyEvent e) {
//        System.out.println("-------");
    }
}

------解决方案--------------------
探讨

        l.addKeyListener(j);


------解决方案--------------------
把label放到JPanel里，给JPanel添加事件

------解决方案--------------------
探讨


引用:
l.addKeyListener(j);

改成
        j.addKeyListener(j);

道理是1楼说的。


------解决方案--------------------
l.setFocusable(true);

------解决方案--------------------
添加一个键盘监听事件,由键盘触发时,,,,,对Label做响应.设置植!!!

------解决方案--------------------
大牛们，你们把需求理解错误了。楼主应该是想要按右键，当前字符+1，比如A变成B，B变成C。按左键则少1。
Java code

public void keyPressed(KeyEvent e){
            if (e.getKeyCode()==KeyEvent.VK_LEFT) {
                System.out.println("-------");
                String txt = l.getText();
                char c = txt.charAt(0);
                if(!txt.equals("A"))
                    l.setText(String.valueOf((char)(c-1)));
                
            }
            if(e.getKeyCode()==KeyEvent.VK_RIGHT) {
                String txt = l.getText();
                char c = txt.charAt(0);
                if(!txt.equals("Z"))
                    l.setText(String.valueOf((char)(c+1)));
            }

        }