八股文(设计模式)

一. 设计模式类型

• 概念
  
• 分类
  

二. 单例模式

1. 概念

2. 静态常量饿汉式

构造器私有化(防止new)
类的内部创建对象
向外暴露一个静态的公共方法。getInstance

package Singleton;

public class test01 {
    public static void main(String[] args) {
        Singleton1 instance = Singleton1.getInstance();
        Singleton1 instance2 = Singleton1.getInstance();
        System.out.println(instance == instance2);
        System.out.println(instance.hashCode());
        System.out.println(instance2.hashCode());
//true
//668386784
//668386784
    }

}
class Singleton1{
    private Singleton1(){
        //构造器私有化
    }
    private final static Singleton1 instance = new Singleton1();
    public static Singleton1 getInstance(){
        return instance;
    }
}