为什么我圆形的面积后面保留了那么多位？

package com.imooc.modle;

public abstract class Shape {

    public abstract double area();

   }

package com.imooc.modle;

public class Rectangle extends Shape {

private double length;

private double wide;

public Rectangle() {

}

public Rectangle(double length, double wide) {

     this.setLength(length);

     this.setWide(wide);

}

public double getLength() {

return length;

}

public void setLength(double length) {

this.length = length;

}

public double getWide() {

return wide;

}

public void setWide(double wide) {

this.wide = wide;

}

public double  area() {

// TODO Auto-generated method stub

       double area=this.getLength()*this.getWide();

       return area;

}

}

package com.imooc.modle;

public class Circle extends Shape{

   private double r;

   public Circle() {

   }

   public Circle(double r) {

  this.setR(r);

   }

public double getR() {

return r;

}

public void setR(double r) {

this.r = r;

}

public double area() {

// TODO Auto-generated method stub

double area=this.getR()*this.getR()*Math.PI;

return area;

}

}

package com.imooc.test;

import com.imooc.modle.Circle;

import com.imooc.modle.Rectangle;

import com.imooc.modle.Shape;

public class Test1 {

 public static void main(String[] args) {

Shape one=new Rectangle(5, 6);

Shape two=new Circle(4);

System.out.println(one.area());

System.out.println(two.area());

}

}