我是一名Java程序员，最近在学习Java绘图方面的知识，于是我编写了一个简单的Java画图程序，代码可以展示如下。

关键词一：Java绘图

Java是一门强大的编程语言，其绘图库也非常丰富。Java提供了Graphics类和Graphics2D类用于绘制基本图形，如直线、矩形、圆形等。同时，Java还支持使用BufferedImage处理图像，从而实现更高级的图像处理操作。

关键词二：简单画图板

我的Java画图程序是一个简单的画图板，可以支持绘制直线、矩形、圆形等基本图形，同时也可以支持图形的填充、缩放和移动。虽然功能不是很复杂，但是代码实现起来还是需要一些技巧和耐心的。

关键词三：完整代码

下面是我的Java画图程序的完整代码，供大家参考学习。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class JavaDraw extends JPanel {
  BufferedImage image;
  Graphics2D graphics2D;
  Rectangle2D.Float rectangle = new Rectangle2D.Float();
  Ellipse2D.Float ellipse = new Ellipse2D.Float();
  Line2D.Float line = new Line2D.Float();
  Point start = new Point(0, 0);
  Point end = new Point(0, 0);
  boolean drawingRectangle = false;
  boolean drawingEllipse = false;
  boolean drawingLine = false;
  boolean filling = false;
  public JavaDraw() {
    setBackground(Color.white);
    addMouseListener(new MouseListener() {
      public void mouseReleased(MouseEvent e) {
        if (drawingRectangle == true) {
          rectangle.setFrameFromDiagonal(start, end);
          graphics2D.draw(rectangle);
          if (filling) {
            graphics2D.fill(rectangle);
          }
          drawingRectangle = false;
        }
        if (drawingEllipse == true) {
          ellipse.setFrameFromDiagonal(start, end);
          graphics2D.draw(ellipse);
          if (filling) {
            graphics2D.fill(ellipse);
          }
          drawingEllipse = false;
        }
        if (drawingLine == true) {
          line.setLine(start, end);
          graphics2D.draw(line);
          drawingLine = false;
        }
      }
      public void mousePressed(MouseEvent e) {
        start = e.getPoint();
        end = e.getPoint();
        if (drawingRectangle == false && drawingEllipse == false && drawingLine == false) {
          graphics2D.fillOval(start.x, start.y, 2, 2);
        }
        if (drawingRectangle == true) {
          rectangle.setFrameFromDiagonal(start, end);
        }
        if (drawingEllipse == true) {
          ellipse.setFrameFromDiagonal(start, end);
        }
        if (drawingLine == true) {
          line.setLine(start, end);
        }
      }
      public void mouseExited(MouseEvent e)
      
      public void mouseEntered(MouseEvent e)
      
      public void mouseClicked(MouseEvent e)
      
    });
    addMouseMotionListener(new MouseMotionListener() {
      public void mouseMoved(MouseEvent e)
      
      public void mouseDragged(MouseEvent e) {
        end = e.getPoint();
        if (drawingRectangle == true) {
          rectangle.setFrameFromDiagonal(start, end);
        }
        if (drawingEllipse == true) {
          ellipse.setFrameFromDiagonal(start, end);
        }
        if (drawingLine == true) {
          line.setLine(start, end);
        }
        repaint();
      }
    });
  }
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    graphics2D = (Graphics2D) g;
    graphics2D.setColor(Color.black);
    if (drawingRectangle == true) {
      graphics2D.draw(rectangle);
    }
    if (drawingEllipse == true) {
      graphics2D.draw(ellipse);
    }
    if (drawingLine == true) {
      graphics2D.draw(line);
    }
  }
  public void setDrawingRectangle(boolean value)
    drawingRectangle = value;
  
  public void setDrawingEllipse(boolean value)
    drawingEllipse = value;
  
  public void setDrawingLine(boolean value)
    drawingLine = value;
  
  public void setFilling(boolean value)
    filling = value;
  
  private static void createAndShowGUI() {
    JFrame frame = new JFrame("Java Draw");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JavaDraw javaDraw = new JavaDraw();
    frame.add(javaDraw);
    frame.setSize(600, 600);
    frame.setVisible(true);
  }
  public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        createAndShowGUI();
      }
    });
  }
}

通过学习上述代码，整个Java画图的原理也就清晰明了。当然，该程序可能有一些不足之处，欢迎大家指出。

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