单例模式

单例模式的多种实现方式

　　1.饿汉模式　

public class Singleton {

    private static Singleton singleton = new Singleton();

    private Singleton(){}

    public static Singleton getInstance(){
        return singleton;
    }

}

　　

　　2.懒汉模式

public class Singleton {

    private static Singleton singleton;

    private Singleton() {}

    synchronized public static Singleton getInstance(){
        if(singleton!=null){
        }else{
            singleton =  new Singleton();
        }
        return singleton;
    }

}

　　

　　3. 双重校验锁

public class Singleton {

    private static Singleton singleton;

    private Singleton() {}

     public static Singleton getInstance(){
        if(singleton!=null){
        }else{
            synchronized (Singleton.class){
                if(singleton==null){
                    Singleton =  new Singleton();
                }
            }

        }
        return Singleton;
    }
}

　　

　　4.静态内部类

public class Singleton {

    private static class SingletonHandle{
        private static Singleton singleton = new Singleton();
    }

    private Singleton(){}

    public static Singleton(){
        return SingletonHandle.singleton;
    }

}