单例模式七种

最新推荐文章于 2025-11-24 23:10:56 发布

原创最新推荐文章于 2025-11-24 23:10:56 发布 · 119 阅读

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#单例模式 #java #开发语言

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// 饿汉式
class Singleton01{
    private Singleton01(){

    }

    private final static Singleton01 instance=new Singleton01();

    public  static Singleton01 getInstance(){
        return instance;
    }
}

// 饿汉式(静态方法)
class Singleton02{
    private Singleton02(){

    }

    private  static Singleton02 instance;

    static {
        instance =new Singleton02();
    }

    public  static Singleton02 getInstance(){
        return instance;
    }
}

// 懒汉式（线程不安全）
class Singleton03{
    private Singleton03(){

    }

    private static Singleton03 instance;

    public static Singleton03 getInstance(){
        if(instance==null){
            instance= new Singleton03();
        }
        return instance;
    }
}

// 懒汉式（线程安全,同步方法）
class Singleton04{
    private Singleton04(){

    }

    private static Singleton04 instance;

    public static synchronized Singleton04 getInstance(){
        if(instance==null){
            instance= new Singleton04();
        }
        return instance;
    }
}

// 懒汉式（双重检查）
class Singleton05{
    private Singleton05(){

    }

    private static volatile Singleton05 instance;

    public static  Singleton05 getInstance(){
        if(instance==null){
            synchronized(Singleton05.class){
                if(instance==null){
                    instance= new Singleton05();
                }
            }
        }
        return instance;
    }
}

// 静态内部类
class Singleton06{
    private Singleton06(){

    }
    private static class SingletonInstance{
        private  static final Singleton06 INSTANCE=new Singleton06();
    }

    public static Singleton06 getInstance(){
        return SingletonInstance.INSTANCE;
    }
}

// 枚举
class Singleton07 {
    private Singleton07(){
    }
    public static enum SingletonEnum {
        SINGLETON;
        private Singleton07 instance = null;
        private SingletonEnum(){
            instance = new Singleton07();
        }
        public Singleton07 getInstance(){
            return instance;
        }
    }
}