3-11随机结果有时候不是5个

package com.three.eleven;

public class Animal {

private String kind;//种类

public Animal() {

}

public Animal(String kind) {

this.setKind(kind);

}

public void cry() {

}

//get set方法

public String getKind() {

return kind;

}

public void setKind(String kind) {

this.kind = kind;

}

}

中间Cat Dog Sheep的不复制了

package com.yu.test;

import com.three.eleven.Animal;

import com.three.eleven.Cat;

import com.three.eleven.Dog;

import com.three.eleven.Sheep;

public class Test_3_11 {

public static void main(String[] args) {

Animal[] arr;

arr=new Animal[5];

for(int i=0;i<arr.length;i++) {

if((int) (Math.random()*3)==0) 

arr[i]=new Cat();

if((int) (Math.random()*3)==1) 

arr[i]=new Dog();

if((int) (Math.random()*3)==2) 

arr[i]=new Sheep();

}

for(int i=0;i<arr.length;i++) {

if(arr[i] instanceof Cat) {

Cat temp=(Cat)(arr[i]);

temp.cry();}

if(arr[i] instanceof Dog) {

Dog temp=(Dog)(arr[i]);

temp.cry();}

if(arr[i] instanceof Sheep) {

Sheep temp=(Sheep)(arr[i]);

temp.cry();}

}

}

}

 为啥有时候只出现2个3个动物 不是5个值么，老师帮忙看看哪出错了