jlab0401b.java

计算机系学习java的专用ppt

class JLab0401B{
   public static void main(String[] args){
     Circle mycircle1=new Circle();
     Circle mycircle2=new Circle(4.3);
     String mess1=mycircle1.toString();
     System.out.println(mycircle1.toString());
     System.out.println( "周长为:"+mycircle1.circumference());
     System.out.println( "面积为:"+mycircle1.area());
     System.out.println(mycircle2.toString());
     System.out.println( "周长为:"+mycircle2.circumference());
     System.out.println( "面积为:"+mycircle2.area());
     }
    }
    
 class Circle{
     double radius=1;
     final double pi=3.1415;
     public Circle(double r){   
          radius=r;}
     public Circle(){}
     public double area(){
        double a;
        a=pi*radius*radius;
        return a;}
     public double circumference(){
        double a;
        a=2*pi*radius;
        return a;}
     public double getRadius(){
        return radius;}
     public String toString(){
        String mes="Circle with radius ";
        StringBuffer messb=new StringBuffer(mes);
        messb.append(radius);
        String mess=new String(messb);
        return mess;
         }
     public void setRadius(double r1){
        radius=r1;
        }
    }