java实现绘制空心半圆，空心圆形，空心矩形 ，空心三角形，空心梯形

空心半圆：

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

public class HalfCircle extends JPanel {
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        // 画空心半圆
        g.drawArc(50, 50, 100, 100, 0, -180);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new HalfCircle());
        frame.setSize(200, 200);
        frame.setVisible(true);
    }
}

空心圆形：

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

public class Circle extends JPanel {
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        // 画空心圆形
        g.drawOval(50, 50, 100, 100);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new Circle());
        frame.setSize(200, 200);
        frame.setVisible(true);
    }
}

空心矩形：

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

public class Rectangle extends JPanel {
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        // 画空心矩形
        g.drawRect(50, 50, 100, 50);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new Rectangle());
        frame.setSize(200, 200);
        frame.setVisible(true);
    }
}

空心三角形：

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

public class Triangle extends JPanel {
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        // 画空心三角形
        g.drawLine(50, 100, 150, 100);
        g.drawLine(50, 100, 100, 50);
        g.drawLine(100, 50, 150, 100);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new Triangle());
        frame.setSize(200, 200);
        frame.setVisible(true);
    }
}

空心梯形：

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

public class Trapezoid extends JPanel {
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        // 画空心梯形
        g.drawLine(50, 100, 100, 50);
        g.drawLine(100, 50, 150, 50);
        g.drawLine(150, 50, 200, 100);
        g.drawLine(50, 100, 200, 100);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new Trapezoid());
        frame.setSize(250, 150);
        frame.setVisible(true);
    }
}