java实现三个箭头内红绿蓝每隔一秒交替，其余部分为白色的功能，可尝试在此基础上增加姓名水印

以下是使用Java Swing实现的三个箭头交替变色的代码，其中添加了姓名水印：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class ArrowPanel extends JPanel {
    private int colorIndex = 0;
    private Color[] colors = {Color.RED, Color.GREEN, Color.BLUE, Color.WHITE};
    private String name = "Watermark";
    private Font font = new Font("Arial", Font.BOLD, 20);

    public ArrowPanel() {
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                colorIndex = (colorIndex + 1) % colors.length;
                repaint();
            }
        }, 0, 1000);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int width = getWidth();
        int height = getHeight();
        int centerX = width / 2;
        int centerY = height / 2;

        // 绘制箭头
        g.setColor(colors[colorIndex]);
        g.drawLine(centerX, centerY - 40, centerX, centerY + 40);
        g.drawLine(centerX, centerY - 40, centerX - 10, centerY - 30);
        g.drawLine(centerX, centerY - 40, centerX + 10, centerY - 30);
        g.drawLine(centerX, centerY + 40, centerX - 10, centerY + 30);
        g.drawLine(centerX, centerY + 40, centerX + 10, centerY + 30);

        // 绘制水印
        g.setColor(colors[3]);
        g.setFont(font);
        g.drawString(name, width - 120, height - 20);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Arrow Panel");
        frame.setSize(400, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        ArrowPanel panel = new ArrowPanel();
        frame.add(panel);
        frame.setVisible(true);
    }
}

在这个例子中，我们使用了一个定时器来定期地调用`repaint()`方法，从而实现箭头的颜色交替。在`paintComponent()`方法中，我们首先绘制箭头，然后绘制水印。

要修改水印的内容，只需要将`name`变量赋值为所需的字符串即可。要修改水印的样式，可以修改`font`变量中的字体、大小和样式。