java实现绘制空心封闭半圆，空心圆形，空心矩形 ，空心三角形，空心梯形

以下是Java实现绘制空心封闭半圆、空心圆形、空心矩形、空心三角形、空心梯形的示例代码：

1. 绘制空心封闭半圆

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

public class HalfCirclePanel extends JPanel {

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        int centerX = getWidth() / 2;
        int centerY = getHeight() / 2;
        int radius = Math.min(getWidth(), getHeight()) / 2 - 10;

        g.drawArc(centerX - radius, centerY - radius, radius * 2, radius * 2, 0, 180);
    }
}

2. 绘制空心圆形

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

public class CirclePanel extends JPanel {

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        int centerX = getWidth() / 2;
        int centerY = getHeight() / 2;
        int radius = Math.min(getWidth(), getHeight()) / 2 - 10;

        g.drawOval(centerX - radius, centerY - radius, radius * 2, radius * 2);
    }
}

3. 绘制空心矩形

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

public class RectanglePanel extends JPanel {

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        int x = 10;
        int y = 10;
        int width = getWidth() - 20;
        int height = getHeight() - 20;

        g.drawRect(x, y, width, height);
    }
}

4. 绘制空心三角形

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

public class TrianglePanel extends JPanel {

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        int[] xPoints = {getWidth() / 2, 10, getWidth() - 10};
        int[] yPoints = {10, getHeight() - 10, getHeight() - 10};

        g.drawPolygon(xPoints, yPoints, 3);
    }
}

5. 绘制空心梯形

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

public class TrapezoidPanel extends JPanel {

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        int x1 = getWidth() / 4;
        int x2 = getWidth() * 3 / 4;
        int y1 = 10;
        int y2 = getHeight() - 10;
        int width1 = getWidth() / 2 - 20;
        int width2 = getWidth() / 2 + 20;
        int height = getHeight() - 20;

        int[] xPoints = {x1, x2, x2 - width2 / 2, x1 + width1 / 2};
        int[] yPoints = {y1, y1, y2, y2};

        g.drawPolygon(xPoints, yPoints, 4);
    }
}

以上示例代码均用Java Swing编写，可以在Java图形界面中运行。