单例模式设计

饿汉式：坏处：对象加载时间过长；好处：线程安全

懒汉式：好处：延迟对象的创建；坏处：线程不安全

package com.atguigu.java;

public class SingleTest {
    public static void main(String[] args) {

        Bank bank = Bank.getInstance();
        Bank bank1 = Bank.getInstance();
        System.out.println(bank==bank1);
    }

}
class Bank{  //饿汉式单例模式设计
    private  Bank(){  //私有化构造器
        }
        private static Bank instance=new Bank(); //内部创建一个对象
    public static Bank getInstance(){   //创建一个公共的方法返回对象
        return instance;
    }
}

package com.atguigu.java;

public class SingleTest2 {
    public static void main(String[] args) {
        Order order = Order.getInstance();
        Order order1 = order.getInstance();
        System.out.println(order==order1);
    }
}
class Order{       //懒汉式单例模式设计
    private Order(){

    }
    private static Order instance =null;
    public static Order getInstance(){
        if (instance==null){
            instance=new Order();
        }
        return instance;
    }
}