单例模式的写法

最新推荐文章于 2025-04-04 02:48:17 发布

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最新推荐文章于 2025-04-04 02:48:17 发布

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分类专栏： Java 文章标签： singleton class

本文链接：https://blog.youkuaiyun.com/asdfayw/article/details/52815939

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本文介绍了五种不同的单例模式实现方式：静态内部类、枚举、双重校验锁、饿汉式及懒汉式实现。每种实现都有其特点，适用于不同场景。


/**
 * Created by yanwen.ayw on 2016/10/14.
 * desc:静态内部类实现
 */
public class Singleton {
    private static Singleton ourInstance = new Singleton();

    private static class InstanceHolder{
        private static final Singleton INSTANCE = new Singleton();
    }

    public static Singleton getInstance() {
        return InstanceHolder.INSTANCE;
    }

    private Singleton() {
    }

    private int counter = 0;
}



/**
 * Created by yanwen.ayw on 2016/10/14.
 * desc:枚举类实现
 */
public enum EnumSingleton {
    INSTANCE;
    public void doAnything(){}
}


/**
 * Created by yanwen.ayw on 2016/10/14.
 * desc:双重校验锁实现
 */
public class DoubleCheckSingleton {
    private static final String TAG = "DoubleCheckSingleton";

    private static volatile DoubleCheckSingleton instance ;
    private DoubleCheckSingleton(){}

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


/**
 * Created by yanwen.ayw on 2016/10/14.
 * desc:恶汉式实现
 */
public class HungurySingleton {
    private static final String TAG = "HungurySingleton";

    private static HungurySingleton instance = new HungurySingleton();
    private HungurySingleton(){}

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


/**
 * Created by yanwen.ayw on 2016/10/14.
     * desc:懒汉式
 */
public class LazySingleton {
    private static final String TAG = "LazySingleton";

    private static LazySingleton instance;
    private LazySingleton() {}

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