java applet 雷达图

Java Applet 是一种运行在网页上的小程序，可以实现动态效果和交互功能。要画雷达图，可以使用Java Graphics2D API来绘制图形，其中包括多边形、线条、文本等元素。以下是一个简单的Java Applet雷达图示例代码：

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Polygon;

public class RadarChart extends Applet {
    private int centerX, centerY;   //雷达图中心坐标
    private int radius;             //雷达图半径
    private String[] labels = {"A","B","C","D","E","F"};  //雷达图各维度标签
    private int[] data = {80, 60, 50, 40, 70, 90};        //雷达图各维度数据

    public void init() {
        setBackground(Color.white);
        setSize(400, 400);
        centerX = getWidth() / 2;
        centerY = getHeight() / 2;
        radius = (int) (Math.min(getWidth(), getHeight()) * 0.4);
    }

    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.black);

        // 画雷达图多边形
        for (int i = 0; i < labels.length; i++) {
            int x = (int) (centerX + radius * Math.sin(i * 2 * Math.PI / labels.length));
            int y = (int) (centerY - radius * Math.cos(i * 2 * Math.PI / labels.length));
            g2d.drawLine(centerX, centerY, x, y);
        }

        // 画雷达图数据区域
        g2d.setColor(Color.blue);
        Polygon dataArea = new Polygon();
        for (int i = 0; i < labels.length; i++) {
            int x = (int) (centerX + data[i] / 100.0 * radius * Math.sin(i * 2 * Math.PI / labels.length));
            int y = (int) (centerY - data[i] / 100.0 * radius * Math.cos(i * 2 * Math.PI / labels.length));
            dataArea.addPoint(x, y);
        }
        g2d.fill(dataArea);

        // 画雷达图各维度标签
        g2d.setColor(Color.black);
        for (int i = 0; i < labels.length; i++) {
            int x = (int) (centerX + (radius + 20) * Math.sin(i * 2 * Math.PI / labels.length));
            int y = (int) (centerY - (radius + 20) * Math.cos(i * 2 * Math.PI / labels.length));
            g2d.drawString(labels[i], x, y);
        }
    }
}

在HTML文件中，需要将Applet标签引用Java Applet程序，并设置参数：

<applet code="RadarChart.class" width="400" height="400">
</applet>

这样就可以在网页上显示雷达图了。