java实现：加入按钮，可实现添加圆形，线条，实现一个简单的绘图板程序

好的，以下是一个简单的Java绘图板程序的实现，具体实现思路和代码注释在代码中已经给出。

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;

public class SimplePaint extends JFrame {

    // 定义绘图区
    private DrawingBoard drawingBoard;

    public SimplePaint() {
        super("SimplePaint");

        // 初始化绘图区
        drawingBoard = new DrawingBoard();
        getContentPane().add(drawingBoard, BorderLayout.CENTER);

        // 初始化工具栏
        JToolBar toolBar = new JToolBar();
        getContentPane().add(toolBar, BorderLayout.NORTH);

        // 添加圆形按钮
        JButton circleButton = new JButton("Circle");
        circleButton.addActionListener(e -> {
            // 在绘图区添加圆形
            drawingBoard.addShape(new Circle(drawingBoard.getMousePosition()));
        });
        toolBar.add(circleButton);

        // 添加线条按钮
        JButton lineButton = new JButton("Line");
        lineButton.addActionListener(e -> {
            // 在绘图区添加线条
            drawingBoard.addShape(new Line(drawingBoard.getMousePosition()));
        });
        toolBar.add(lineButton);

        // 设置窗口大小和可见性
        setSize(400, 400);
        setVisible(true);
    }

    public static void main(String[] args) {
        new SimplePaint();
    }

    // 自定义绘图区
    private static class DrawingBoard extends JPanel {

        // 保存绘制的图形
        private ArrayList<Shape> shapes = new ArrayList<>();

        public DrawingBoard() {
            // 添加鼠标监听器，实现绘图功能
            addMouseListener(new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    // 获取当前按钮状态
                    int button = e.getButton();
                    if (button == MouseEvent.BUTTON1) {
                        // 添加图形
                        addShape(new Circle(e.getPoint()));
                    }
                }
            });
        }

        // 添加图形
        public void addShape(Shape shape) {
            shapes.add(shape);
            repaint();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            // 绘制所有图形
            for (Shape shape : shapes) {
                shape.draw(g);
            }
        }
    }

    // 自定义图形接口
    private interface Shape {

        // 绘制图形
        void draw(Graphics g);
    }

    // 自定义圆形类
    private static class Circle implements Shape {

        // 圆心坐标
        private Point center;

        public Circle(Point center) {
            this.center = center;
        }

        @Override
        public void draw(Graphics g) {
            // 计算圆的左上角坐标和半径
            int x = center.x - 25;
            int y = center.y - 25;
            int r = 50;

            // 绘制圆形
            g.drawOval(x, y, r, r);
        }
    }

    // 自定义线条类
    private static class Line implements Shape {

        // 起点坐标
        private Point start;

        public Line(Point start) {
            this.start = start;
        }

        @Override
        public void draw(Graphics g) {
            // 获取当前鼠标位置
            Point end = MouseInfo.getPointerInfo().getLocation();

            // 绘制线条
            g.drawLine(start.x, start.y, end.x, end.y);
        }
    }
}