设计如下界面，在界面上方有一个标签“I’m a able”,中间有一个随机颜色的圆形，下方有两个按钮，点击点击“change lable”后标签改变为“ouch!”。点击“change circle”后圆改变颜色。

以下是一个实现该界面的示例代码，使用了Java Swing库：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame("GUI Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel() {
            private static final long serialVersionUID = 1L;

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                Random rand = new Random();
                g.setColor(new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256)));
                g.fillOval(50, 50, 100, 100);
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(200, 200);
            }
        };
        panel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        JLabel label = new JLabel("I'm able");
        label.setHorizontalAlignment(JLabel.CENTER);

        JButton changeLabelButton = new JButton("Change label");
        changeLabelButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                label.setText("Ouch!");
            }
        });

        JButton changeCircleButton = new JButton("Change circle");
        changeCircleButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                panel.repaint();
            }
        });

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(changeLabelButton);
        buttonPanel.add(changeCircleButton);

        frame.add(panel, "Center");
        frame.add(label, "North");
        frame.add(buttonPanel, "South");
        frame.pack();
        frame.setVisible(true);
    }
}

运行该程序后，会弹出一个包含随机颜色的圆形、标签和两个按钮的界面。点击“Change label”按钮后，标签会变为“Ouch!”；点击“Change circle”按钮后，圆形的颜色会随机改变。