要求能关闭窗口、点击按钮改变窗口背景颜色。

package GUI;
import javax.swing.;
import java.awt.;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
public class BGCUITest {
public BGCUITest() {
JFrame jf = new JFrame("Change BGC");
jf.setSize(400, 400);
jf.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
jf.setLocationRelativeTo(null);
jf.setResizable(false);

JPanel jp = new JPanel(new FlowLayout());

JButton post = new JButton("Change");

post.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent actionEvent) {
        Random random = new Random();
        int r = random.nextInt(256);
        int g = random.nextInt(256);
        int b = random.nextInt(256);
        Color c = new Color(r, g, b);
        jf.getContentPane().setBackground(c);
        System.out.println(c);
    }
});

jp.add(post);
jf.setContentPane(jp);
jf.setVisible(true);

}
public static void main (String[] args){
new BGCUITest();
}

}