java递归实现科赫雪花

今天来写k阶科赫雪花的递归实现，(K值需要你手动输入)至于科赫雪花是什么请大家自行百度。

首先来思考这个程序怎么写，当 count = 0 时就应该是一个三角形，这三个点是你一开始就确定的，以后的改变都依据这三个点发展的。当不是0的时候就需要计算相对于这个三角形的9个点，分别是每条边上的两个点，和它对应的三角形第三个顶点。

首先在JFrame中添加一个panel，我们需要在这个panel上画图。

大家再来看这个图片，这张图介绍了通过两个点来计算其他三个点的过程。

现在开始在panel中画图：

static class showpanel extends JPanel{
    int number = 0;
    public void setNumber(int number) {
      this.number = number;
      repaint();
    }
    public void paintComponent(Graphics g) {
      super.paintComponent(g);//画一个简单的panel 

      int side =(int)(Math.min((int)getWidth(),(int)getHeight())*0.8);
      int high =(int)(side*Math.cos(Math.toRadians(30))); 

       Point p1 = new Point(getWidth() / 2, 10);
       Point p2 = new Point(getWidth() / 2 - side / 2, 10 + high);
       Point p3 = new Point(getWidth() / 2 + side / 2, 10 + high); 

       playKochSnowFlake(g, number, p1, p2);
       playKochSnowFlake(g, number, p2, p3);
       playKochSnowFlake(g, number, p3, p1); 

    }

现在开始写递归函数。

public static void playKochSnowFlake(Graphics g,int number,Point p1,Point p2) {
      if(number == 0){
        g.drawLine(p1.x, p1.y,p2.x, p2.y);
      }
      else{
         int deltaX = p2.x - p1.x;
          int deltaY = p2.y - p1.y; 

          Point x = new Point(p1.x + deltaX / 3, p1.y + deltaY / 3);
          Point y = new Point(p1.x + deltaX * 2 / 3, p1.y + deltaY * 2 / 3);
          Point z = new Point(
           (int)((p1.x + p2.x) / 2 + Math.sin(Math.toRadians(60)) * (p1.y - p2.y) / 3),
           (int)((p1.y + p2.y) / 2 + Math.sin(Math.toRadians(60)) * (p2.x - p1.x) / 3));
          playKochSnowFlake(g, number - 1, p1, x);
          playKochSnowFlake(g, number - 1, x, z);
          playKochSnowFlake(g, number - 1, z, y);
          playKochSnowFlake(g, number - 1, y, p2);
      }
    } 

然后在主面板中加入一个JTextField   jta 它输入的数据要传入到number中。所以为其添加一个监听器。 已有数据输入就调用其中的setNumber()函数设置number变量。

jta.addActionListener(new ActionListener() { 

      public void actionPerformed(ActionEvent arg0) {
        spl.setNumber(Integer.parseInt(jta.getText()));
      }
    }); 

所以总体已经完成了，剩下的就是简答的窗体设置。

下面贴一个完整的java代码：

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField; 

public class SnowFlake extends JFrame { 

  private JTextField jta = new JTextField(5);
  private showpanel spl = new showpanel(); 

  static class showpanel extends JPanel{
    int number = 0;
    public void setNumber(int number) {
      this.number = number;
      repaint();
    }
    public void paintComponent(Graphics g) {
      super.paintComponent(g);//画一个简单的panel 

      int side =(int)(Math.min((int)getWidth(),(int)getHeight())*0.8);
      int high =(int)(side*Math.cos(Math.toRadians(30))); 

       Point p1 = new Point(getWidth() / 2, 10);
       Point p2 = new Point(getWidth() / 2 - side / 2, 10 + high);
       Point p3 = new Point(getWidth() / 2 + side / 2, 10 + high); 

       playKochSnowFlake(g, number, p1, p2);
       playKochSnowFlake(g, number, p2, p3);
       playKochSnowFlake(g, number, p3, p1); 

    }
    public static void playKochSnowFlake(Graphics g,int number,Point p1,Point p2) {
      if(number == 0){
        g.drawLine(p1.x, p1.y,p2.x, p2.y);
      }
      else{
         int deltaX = p2.x - p1.x;
          int deltaY = p2.y - p1.y; 

          Point x = new Point(p1.x + deltaX / 3, p1.y + deltaY / 3);
          Point y = new Point(p1.x + deltaX * 2 / 3, p1.y + deltaY * 2 / 3);
          Point z = new Point(
           (int)((p1.x + p2.x) / 2 + Math.sin(Math.toRadians(60)) * (p1.y - p2.y) / 3),
           (int)((p1.y + p2.y) / 2 + Math.sin(Math.toRadians(60)) * (p2.x - p1.x) / 3));
          playKochSnowFlake(g, number - 1, p1, x);
          playKochSnowFlake(g, number - 1, x, z);
          playKochSnowFlake(g, number - 1, z, y);
          playKochSnowFlake(g, number - 1, y, p2);
      }
    }
  } 

  public SnowFlake() {
    JPanel panel = new JPanel();
    panel.setLayout(new FlowLayout());
    panel.add(new JLabel("Please input the number"));
    panel.add(jta);
    add(spl,BorderLayout.CENTER);
    add(panel,BorderLayout.SOUTH);
    jta.addActionListener(new ActionListener() { 

      public void actionPerformed(ActionEvent arg0) {
        spl.setNumber(Integer.parseInt(jta.getText()));
      }
    });
  }
  public static void main(String args[]) {
    SnowFlake snowFlake = new SnowFlake();
    snowFlake.setSize(300, 300);
    snowFlake.setTitle("SnowFlake");
    snowFlake.setLocationRelativeTo(null);
    snowFlake.setVisible(true);
  }
} 

效果图：

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