第85集：太阳系模型Planet类的实现构造器的优化和调用

今天遇到了一件恶心事，被人钓鱼执法了，心情不太好，后续估计还有很多麻烦事，但是，我不能允许它影响我的学习进度，加油，王涛！没有什么事情能阻止你实现目标！

本集知识点

1. 重构代码，让构造函数互相调用，前期虽然麻烦，但后期非常省事，例如本例对Star类的重构。

       package com.test084_087_solar;  import java.awt.Graphics; import java.awt.Image;  import com.test084_087_util.GameUtil;  public class Star {     Image img;     double x,y;     int width,height;          public void draw(Graphics g){         g.drawImage(img,(int)x,(int)y,null);         }          public Star(){              }          public Star(Image img){         this.img = img;         this.width = img.getWidth(null);         this.height = img.getHeight(null);     }          public Star(Image img,double x,double y){         this(img);         this.x = x;         this.y = y;     }          public Star(String imgpath,double x,double y){         this(GameUtil.getImage(imgpath),x,y);     }      } 

2. 关注Planet类如何沿着椭圆路径飞行。

   //Planet类的实现  package com.test084_087_solar;  import java.awt.Graphics; import java.awt.Image;  import com.test084_087_util.GameUtil;  public class Planet extends Star{     //除了图片，坐标。行星沿着某个椭圆运行：长轴、短轴、速度。绕着某个Star飞。     double longAxis;     //椭圆长轴     double shortAxis;    //椭圆短轴     double sPEed;        //飞行的速度     double degree;     Star center;                  public Planet(Star center,String imgpath,double longAxis,double shortAxis,double speed){         super(GameUtil.getImage(imgpath));                  this.center = center;         this.x = center.x + longAxis;         this.y = center.y;          this.longAxis = longAxis;         this.shortAxis = shortAxis;         this.speed = speed;         this.center = center;             }           public Planet(Image img,double x,double y){         super(img,x,y);     }          public void draw(Graphics g){         g.drawImage(img,(int)x,(int)y,null);         //沿着椭圆轨迹飞行         x = (center.x + center.width/2) + longAxis*Math.cos(degree);         y = (center.y + center.height/2) + shortAxis*Math.sin(degree);                  degree += speed;     }          } 

       package com.test084_087_solar;  import java.awt.Graphics; import java.awt.Image;  import com.test084_087_util.Constant; import com.test084_087_util.GameUtil; import com.test084_087_util.MyFrame;  public class SolarFrame extends MyFrame {     Image bg = GameUtil.getImage("images/bg.jpg");     Star sun = new Star("images/sun.jpg",Constant.GAME_WIDTH/2,Constant.GAME_HEIGHT/2);     Planet earth = new Planet(sun,"images/earth.jpg",150,100,0.1);          public void paint(Graphics g){         g.drawImage(bg,0,0,null);         sun.draw(g);         earth.draw(g);     }          public static void main(String[] args){          new SolarFrame().launchFrame();     } }