java单例模式创建

最新推荐文章于 2025-12-05 17:02:52 发布

原创最新推荐文章于 2025-12-05 17:02:52 发布 · 89 阅读

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#java

饿汉式（可阻止反射）

public class Singleton {
    private Singleton(){
        if (INSTANCE!=null){
            throw new RuntimeException("单例已经创建！");
        }
    }
    private static final Singleton INSTANCE=new Singleton();
    public static Singleton getInstance(){
        return INSTANCE;
    }
}

2.枚举饿汉式

public enum Singleton {
    INSTANCE;
    Singleton(){};
    public static Singleton getInstance(){
        return INSTANCE;
    }
}

3.懒汉式（多线程不安全）

public class Singleton {
    private Singleton(){}
    private static Singleton INSTANCE=null;
    private static Singleton getInstance(){
        if (INSTANCE==null){
            INSTANCE=new Singleton();
        }
        return INSTANCE;
    }
}

4.双检锁懒汉式（线程安全）

public class Singleton {
    private Singleton(){}
    private static volatile Singleton INSTANCE=null;
    private static Singleton getInstance(){
        if (INSTANCE==null){
            if (INSTANCE==null){
                synchronized(Singleton.class){
                    INSTANCE=new Singleton();
                }
            }
        }
        return INSTANCE;
    }
}

5.内部类懒汉式（线程安全）

public class Singleton {
    private Singleton(){}
    private static class Holder{
        static Singleton INSTANCE=new Singleton();
    }
    public static Singleton getInstance(){
        return Holder.INSTANCE;
    }
}