Java绘制高度可变的倒置矩形

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;

public class InvertedRectanglePanel extends JPanel {
    private int height;

    public void setHeight(int height) {
        this.height = height;
        repaint(); // 重新绘制面板
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int width = getWidth();
        int y = getHeight() - height; // 计算矩形的上边界位置
        g.setColor(Color.BLUE);
        g.fillRect(0, y, width, height); // 绘制矩形
    }
}

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class Main {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Inverted Rectangle");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            InvertedRectanglePanel panel = new InvertedRectanglePanel();
            frame.add(panel);

            frame.setSize(400, 400);
            frame.setVisible(true);

            // 设置矩形的高度为200
            panel.setHeight(200);
        });
    }
}