追问大神---向上转型和向下转型的实现。
package com.syq.test; 

public class Shape { 

  public void draw() { 
  System.out.println("绘制图形…………"); 
  } 

  public double getPerimter() { 
  return 0; 
  } 

  public double getArea() { 
  return 0; 
  } 

  public void print() { 
  System.out.println("这是父类的print方法"); 
  } 

}

 

package com.syq.test;

public class Triangle extends Shape {
  private double sid1;
  private double sid2;
  private double sid3;

  public Triangle() {
  }

  public Triangle(double sid1, double sid2, double sid3) {
  this.setSid1(sid1);
  this.setSid2(sid2);
  this.setSid3(sid3);
  }

// 求三边中最长的边
  public double sidMax() {
  return (sid1 > sid2) ? sid1 : (sid2 > sid3) ? sid2 : sid1;
  }

// 重写toString方法，用于描述对象
  public String toString() {
  return "三角形周长：" + this.getPerimter() + "\n三角形面积：" + this.getArea()
  + "\n最长的边长："+this.sidMax();
  }

  public void draw() {
  System.out.println("绘制三角形…………三边长："+this.getSid1()+" "+this.getSid2()+" "+this.getSid3());
  }

  // 绘制三角形，返回是否符合三角形的定义
  public void draw(Triangle triangle) {
  if (this.sid1 + sid2 > sid3 & sid3 - sid1 < sid2) {
  this.setSid1(sid1);
  this.setSid2(sid2);
  this.setSid3(sid3);
  System.out.println("成功绘制三角形!");
  }else {
  System.out.println("不符合绘制三角形的条件!");
  }
  }
// 计算周长
  public double getPerimter() {
  return this.sid1 + this.sid2 + this.sid3;
  }

// 计算三角形面积
  public double getArea() {
  double p = this.getPerimter() / 2;
  double area = Math.sqrt(p * (p - sid1) * (p - sid2) * (p - sid3));
  return p;
  }

  public double getSid1() {
  return sid1;
  }

  public void setSid1(double sid1) {
  this.sid1 = sid1;
  }

  public double getSid2() {
  return sid2;
  }  

  public void setSid2(double sid2) {
  this.sid2 = sid2;
  }

  public double getSid3() {
  return sid3;
  }

  public void setSid3(double sid3) {
  this.sid3 = sid3;
  }

}

 

package com.syq.test;

public class Circle extends Shape {
  private double r;

  public Circle() {
  }

  public Circle(double r) {
  this.setR(r);
  }

// 计算圆的直径
  public double diameter() {
  return 2 * r;
  }

  public void draw() {
  System.out.println("绘制圆…………半径："+this.getR());
  }

// 绘制圆
  public void draw(Circle circle) {
  if (this.r > 0) {