设计模式-单例模式

详细讲解请看：http://www.cnblogs.com/cielosun/p/6582333.html

饿汉模式：

public class Singleton {
    private static Singleton instance = new Singleton();

    private Singleton(){}

    public static Singleton getInstance(){
        return instance;
    }
}

懒汉模式：

public class Singleton {
    private static Singleton instance;

    private Singleton() {
    }

    public static Singleton getInstance() {
        if (instance == null)
            return new Singleton();
        else return instance;
    }
}

加锁的的单例：

public class Singleton {
    private static Singleton instance;

    private Singleton() {
    }

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