单态设计模式

package com.cn;

public class Test {
    public static void main(String agrs[]){
        Person p1 = Person.getInstances();
        Person p2 = Person.getInstances();
        System.out.println(p1==p2);
    }
}
class Person{
    static Person person = new Person();
    private Person(){
        
    }
    public static Person getInstances(){
        return person;
    }
}

打印结果为 ：true

保证了Person类在内存中只能被创建一个实例对象