자바 의 추상 적 인 방법 과 추상 적 인 사례 에 대한 상세 한 설명

public abstract class Shape
{
  {
   System.out.println("  Shape     ...");
  }
  private String color;
  //              
  public abstract double calPerimeter();
  //              
  public abstract String getType();
  //   Shape    ，           Shape  ，
  //          
  public Shape(){}
  public Shape(String color)
  {
   System.out.println("  Shape    ...");
   this.color = color;
  }
  //   color setter getter  
  public void setColor(String color)
  {
   this.color = color;
  }
  public String getColor()
  {
   return this.color;
  }
}

public class Triangle extends Shape
{
  //         
  private double a;
  private double b;
  private double c;
  public Triangle(String color , double a
   , double b , double c)
  {
   super(color);
   this.setSides(a , b , c);
  }
  public void setSides(double a , double b , double c)
  {
   if (a >= b + c || b >= a + c || c >= a + b)
   {
     System.out.println("              ");
     return;
   }
   this.a = a;
   this.b = b;
   this.c = c;
  }
  //   Shape            
  public double calPerimeter()
  {
   return a + b + c;
  }
  //   Shape            
  public String getType()
  {
   return "   ";
  }
}

public class Circle extends Shape
{
  private double radius;
  public Circle(String color , double radius)
  {
   super(color);
   this.radius = radius;
  }
  public void setRadius(double radius)
  {
   this.radius = radius;
  }
  //   Shape            
  public double calPerimeter()
  {
   return 2 * Math.PI * radius;
  }
  //   Shape            
  public String getType()
  {
   return getColor() + "  ";
  }
  public static void main(String[] args)
  {
   Shape s1 = new Triangle("  " , 3 , 4, 5);
   Shape s2 = new Circle("  " , 3);
   System.out.println(s1.getType());
   System.out.println(s1.calPerimeter());
   System.out.println(s2.getType());
   System.out.println(s2.calPerimeter());
  }
}