练习1

package com.atguigu.exercise1;
//static关键字的应用
public class CircleTest {
    public static void main(String[] args) {
  Circle c1 = new Circle();
  Circle c2 = new Circle();
  Circle c3 = new Circle(3.4);
  System.out.println("c1的id:"+ c1.getId());
  System.out.println("c2的id:"+ c2.getId());
  System.out.println("c3的id:"+ c3.getId());
  System.out.println("创建的圆的个数为："+ Circle.getTotal());
    }
}
class Circle{
    private double radius;
    private int id;
    public Circle(){
  id = init++;
  total++;
    }
    public Circle(double radius){
  this();
//  id = init++;
//  total++;
  this.radius = radius;
    }
    private static int total;
    private static int init = 1001;//static声明的属性被所有的对象所共享
    public double findArea(){
  return Math.PI*radius*radius;
    }
    public double getRadius() {
  return radius;
    }
    public void setRadius(double radius) {
  this.radius = radius;
    }
    public int getId() {
  return id;
    }
    public void setId(int id) {
  this.id = id;
    }
    public static int getTotal() {
  return total;
    }
}