JAVA单例模式

1.懒汉模式

//Singleton.java
public class Singleton {
    //防止多次实例 new
    private Singleton() {}
    //保证线程安全(两个线程同时获取实例)
    private static class SingletonInstance {
        private static final Singleton INSTANCE = new Singleton();
    }
    //获取实例
    public static Singleton getInstance() {
        return SingletonInstance.INSTANCE;
    }
}

//--------------QAQ---------------
//other.java
Singleton.getInstance()

2.饥汉模式(一)

//Singleton.java
public class Singleton {
    private final static Singleton INSTANCE = new Singleton();
    private Singleton(){}
    public static Singleton getInstance(){
        return INSTANCE;
    }
}
//--------------QAQ---------------
//other.java
Singleton.getInstance()

3.饥汉模式(二)

//Singleton.java
public class Singleton {
    public final static Singleton INSTANCE = new Singleton();
    private Singleton(){}
}
//--------------QAQ---------------
//other.java
Singleton.INSTANCE