使用递归绘制“ Lo羽毛分形”

import java.awt.Color;

import java.awt.Dimension;

import java.awt.FlowLayout;/* 来自 N o w J a v a . c o m - 时  代  Java*/

import java.awt.Graphics;


import javax.swing.JButton;

import javax.swing.JColorChooser;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;


class FractalJPanel extends JPanel {

  private Color color; // stores color used to draw fractal

  private int level; // stores current level of fractal


  private static final int WIDTH = 400; // defines width of JPanel

  private static final int HEIGHT = 400; // defines height of JPanel


  public FractalJPanel(int currentLevel) {

    color = Color.BLUE;

    level = currentLevel; // set initial fractal level//来自 n o w  j a v a  . c o m

    setBackground(Color.WHITE);

    setPreferredSize(new Dimension(WIDTH, HEIGHT));

  }


  public void drawFractal(int level, int xA, int yA, int xB, int yB, Graphics g) {

    if (level == 0)

      g.drawLine(xA, yA, xB, yB);

    else {

      // calculate midpoint between (xA, yA) and (xB, yB)

      int xC = (xA + xB) / 2;

      int yC = (yA + yB) / 2;


      // calculate the fourth point (xD, yD) which forms an

      // isosceles right triangle between (xA, yA) and (xC, yC)

      // where the right angle is at (xD, yD)

      int xD = xA + (xC - xA) / 2 - (yC - yA) / 2;

      int yD = yA + (yC - yA) / 2 + (xC - xA) / 2;


      // recursively draw the Fractal

      drawFractal(level - 1, xD, yD, xA, yA, g);

      drawFractal(level - 1, xD, yD, xC, yC, g);

      drawFractal(level - 1, xD, yD, xB, yB, g);

    }

  }


  // start the drawing of fractal

  public void paintComponent(Graphics g) {

    super.paintComponent(g);

    g.setColor(color);

    drawFractal(level, 100, 90, 290, 200, g);

  }


  public void setColor(Color c) {

    color = c;

  }


  public void setLevel(int currentLevel) {

    level = currentLevel;

  }


  public int getLevel() {

    return level;

  }

}


public class Main extends JFrame {

  private static final int WIDTH = 400; // define width of GUI

  private static final int HEIGHT = 480; // define height of GUI

  private static final int MIN_LEVEL = 0, MAX_LEVEL = 15;


  private JButton changeColorJButton, increaseLevelJButton,

      decreaseLevelJButton;

  private JLabel levelJLabel;

  private FractalJPanel drawSpace;

  private JPanel mainJPanel, controlJPanel;


  public Main() {

    controlJPanel = new JPanel();

    controlJPanel.setLayout(new FlowLayout());


    changeColorJButton = new JButton("Color");

    controlJPanel.add(changeColorJButton);

    changeColorJButton.addActionListener(e -> {

      Color color = JColorChooser.showDialog(Main.this, "Choose a color",

          Color.BLUE);


      // set default color, if no color is returned

        if (color == null)

          color = Color.BLUE;


        drawSpace.setColor(color);

      });


    // set up decrease level button to add to control panel and

    // register listener

    decreaseLevelJButton = new JButton("Decrease Level");

    controlJPanel.add(decreaseLevelJButton);

    decreaseLevelJButton.addActionListener(e -> {

      int level = drawSpace.getLevel();

      --level;


      // modify level if possible

        if ((level >= MIN_LEVEL) && (level <= MAX_LEVEL)) {

          levelJLabel.setText("Level: " + level);

          drawSpace.setLevel(level);

          repaint();

        }

      }


      );


    // set up increase level button to add to control panel

    // and register listener

    increaseLevelJButton = new JButton("Increase Level");

    controlJPanel.add(increaseLevelJButton);

    increaseLevelJButton.addActionListener(e -> {

      int level = drawSpace.getLevel();

      ++level;


      // modify level if possible

        if ((level >=