JavaSE 23种 设计模式 之 单例模式，javase23种

JavaSE 23种 设计模式 之 单例模式，javase23种

package com.atweihai.javase;

/**
* JavaSE23种 设计模式 之 单例模式
* 饿汉式
*/
public class Singleton {

private Singleton(){}

private static Singleton singleton=new Singleton();

public  static Singleton getInstance(){
    return singleton;
}

}
/**
*懒汉式:线程不安全
*/
class Singleton1{

private Singleton1(){}

private static Singleton1 singleton1=null;

public static Singleton1 getInstance(){
    if(singleton1==null){
        singleton1=new Singleton1();
    }
    return singleton1;
}

}

/**
* 懒汉式:线程安全 “双重检查锁”
*/
class Singleton2{

private Singleton2(){}

private static Singleton2 singleton2=null;

public static Singleton2 getInstance(){
    if(singleton2==null){
        synchronized (Singleton2.class) {
            if(singleton2==null){
                singleton2=new Singleton2();
            }
        }
    }

    return singleton2;
}

}