枚举单例（如果枚举类实例参数有多个，那么枚举单例将失效）

/**
 * 枚举单例 线程池 如果多处使用该方法，则不可以shutDown
 */
public enum EnumThread {

    /**
     * 线程（单例不可以创建两个枚举实例，如果常见两个枚举实力，执行是，会调用两次想要单例的方法）
     */
    EXECUTOR_POOL;//因为枚举实例变量需要枚举类的构造器创建，所以，构造器没有形参，枚举实例参数EXECUTOR_POOL 也不用写成 
                  //EXECUTOR_POOL("参数") 该形式,;                    

    /**
     * ExecutorService 接口作为返回类型
     */
    private final ExecutorService maxExecutor;
    private final ExecutorService minExecutor;

    EnumThread() {
        System.out.println("11");
        ThreadFactory namedThreadFactory = new ThreadFactoryBuilder().setNameFormat("funinbook-pool-%d").build();
        maxExecutor = new ThreadPoolExecutor(
                CORE_POOL_SIZE67,
                CORE_POOL_SIZE87,
                10,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingDeque<Runnable>(1024),
                namedThreadFactory,
                new ThreadPoolExecutor.AbortPolicy()
        );
        minExecutor = new ThreadPoolExecutor(
                CORE_POOL_SIZE7,
                CORE_POOL_SIZE27,
                10,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingDeque<Runnable>(1024),
                namedThreadFactory,
                new ThreadPoolExecutor.AbortPolicy()
        );
    }

    /**
     * 线程数最大77 最小 57
     *
     * @return
     */
    public ExecutorService getMaxExecutor() {
        return maxExecutor;
    }

    /**
     * 线程数最大7 最小 7
     *
     * @return
     */
    public ExecutorService getMinExecutor() {
        return minExecutor;
    }
}

下面是测试，用两个枚举实例变量会调用两次想要单例的方法实例

class Test{

//main 方法调用枚举类10次，会发现“会调用两次”会输出两次，所以，想要用枚举类写单例，一定要像上面那样，只用一个枚举实例
public static void main(String[] args) {
    for (int i = 0; i <10 ; i++) {
        for (int j = 0; j < 10; j++) {
            ThreadPoolManager.EnumThread.EXECUTOR_POOL.getMaxExecutor();
        }
    }
}

/**
 * 枚举单例 线程池 如果多处使用该方法，则不可以shutDown
 */
public enum EnumThread {

    /**
     * 线程（单例不可以创建两个枚举实例，如果常见两个枚举实力，执行是，会调用两次想要单例的方法）
     */
    EXECUTOR_POOL,
    EXECUTOR_POOL_MAX;

    /**
     * ExecutorService 接口作为返回类型
     */
    private final ExecutorService maxExecutor;
    private final ExecutorService minExecutor;

    EnumThread() {
        System.out.println("会调用两次");
        ThreadFactory namedThreadFactory = new ThreadFactoryBuilder().setNameFormat("funinbook-pool-%d").build();
        maxExecutor = new ThreadPoolExecutor(
                CORE_POOL_SIZE67,
                CORE_POOL_SIZE87,
                10,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingDeque<Runnable>(1024),
                namedThreadFactory,
                new ThreadPoolExecutor.AbortPolicy()
        );
        minExecutor = new ThreadPoolExecutor(
                CORE_POOL_SIZE7,
                CORE_POOL_SIZE27,
                10,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingDeque<Runnable>(1024),
                namedThreadFactory,
                new ThreadPoolExecutor.AbortPolicy()
        );
    }

    /**
     * 线程数最大77 最小 57
     *
     * @return
     */
    public ExecutorService getMaxExecutor() {
        return maxExecutor;
    }

    /**
     * 线程数最大7 最小 7
     *
     * @return
     */
    public ExecutorService getMinExecutor() {
        return minExecutor;
    }
}

}