要求写一个程式， 当鼠标在左边程式窗口时背景色变成红色， 当鼠标指在右边程式窗口时背景色变成绿色。

希望高手可以写出来给我这个新手看看， 我刚接触java一个礼拜， 基本什么也不懂， 谢谢大家帮忙

是不是要这样的效果？

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;

public class MouseEventTest extends JFrame{
    private Container container;
    private JLabel label1,label2;
    
    public MouseEventTest(){
        super("MouseEventTest");
        container = getContentPane();
        
        label1 = new JLabel("绿色");
        label1.addMouseListener(
                new MouseAdapter(){
                    public void mouseEntered(MouseEvent event){
                        container.setBackground(Color.GREEN);
                    }
                    public void mouseExited(MouseEvent event){
                            container.setBackground(Color.WHITE);
                        }
                }
                );
        label2 = new JLabel("红色");
        label2.addMouseListener(
                new MouseAdapter(){
                    public void mouseEntered(MouseEvent event){
                        container.setBackground(Color.RED);
                    }
                    public void mouseExited(MouseEvent event){
                            container.setBackground(Color.WHITE);
                        }
                }
                );
        container.setLayout(new FlowLayout());
        container.add(label1);
        container.add(label2);
        
        setSize(400,400);
        setResizable(false);
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        Dimension frameSize = getSize();
        setLocation((screenSize.width - frameSize.width)/2,(screenSize.height - frameSize.height)/2);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public static void main(String[] args) {
        new MouseEventTest();
    }
}

差不多了， 但是为什么两个方框特别小？？ 我想要鼠标移到整个窗口的左边和右边， 不知道如何改进， 请指教，谢谢

这个可以了

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;

public class MouseEventTest extends JFrame{
    private Container container;
    private JLabel label1,label2;
    
    public MouseEventTest(){
        super("MouseEventTest");
        container = getContentPane();
        
        label1 = new JLabel("绿色",javax.swing.SwingConstants.CENTER);
        label1.addMouseListener(
                new MouseAdapter(){
                    public void mouseEntered(MouseEvent event){
                        container.setBackground(Color.GREEN);
                    }
                    public void mouseExited(MouseEvent event){
                            container.setBackground(Color.WHITE);
                        }
                }
                );
        label2 = new JLabel("红色",javax.swing.SwingConstants.CENTER);
        label2.addMouseListener(
                new MouseAdapter(){
                    public void mouseEntered(MouseEvent event){
                        container.setBackground(Color.RED);
                    }
                    public void mouseExited(MouseEvent event){
                            container.setBackground(Color.WHITE);
                        }
                }
                );
        container.add(label1,BorderLayout.WEST);
        container.add(label2,BorderLayout.EAST);
        
        setSize(400,400);
        setResizable(false);
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        Dimension frameSize = getSize();
        setLocation((screenSize.width - frameSize.width)/2,(screenSize.height - frameSize.height)/2);
        label1.setPreferredSize(new Dimension(200,400));
        label2.setPreferredSize(new Dimension(200,400));
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public static void main(String[] args) {
        new MouseEventTest();
    }
}

动作事件  选项事件 鼠标移动事件 鼠标事件 键盘事件 组件焦点事件 调整事件 组件改变事件 窗口事件  都记住就好了