单例模式的三种写法

这里介绍三种单例模式写法。
第一种：饿汉模式

类加载时就初始化

public class SingleTonHungry {
private static SingleTonHungry singleTonHungry = new SingleTonHungry();
private SingleTonHungry(){

}
public static SingleTonHungry getInstance(){
return singleTonHungry;
}
}

第二种：懒汉模式
类加载时不初始化，当调用getInstance方法时初始化

public class SingleTonIdler {
private static SingleTonIdler singleTonIdler;
private SingleTonIdler() {
}
public static SingleTonIdler getInstance(){
if(singleTonIdler == null){
singleTonIdler = new SingleTonIdler();
}
return singleTonIdler;
}
}
第三种：使用静态内部类

public class SingleTonStaticClass {
private SingleTonStaticClass(){
}

public static final SingleTonStaticClass getInstance(){
return SingleTon.singleTonStaticClass;
}

private static class SingleTon{
private static final SingleTonStaticClass singleTonStaticClass = new SingleTonStaticClass();
}
}