同步不同类（和不同包）中的两个方法 [英] Synchronize two methods in different classes (and different packages)

问题描述

我遇到了有关Java方法同步的问题。我希望我能简单解释一下：

I'm facing an issue regarding Java method synchronization. Let's hope I can explain it briefly:

我在两个不同的包中有两种不同的方法。类似于：

I have two different methods in two different classes, in two different packages. Something like:

Package1
     |_Class1
            \MethodA

Package2
     |_Class2
            \MethodB

好的，现在我需要同步这两种方法是非线程。到目前为止，我有两种不同的方法：

Ok, so now I need to synchronize these two methods, which are not threads. So far, I have two different approaches:

共享信号量 。

Shared semaphore.

在 Package1 和 Package2 之外创建共享静态信号量，类似于：

Create a shared static semaphore outside Package1 and Package2, something like:

 package Package3;

 public class SemaphoreClass {

    public static Semaphore;

}

我真的不知道JVM是否会认为这是一个无论如何，共享信号量。

I don't really know if JVM would consider this a shared semaphore, anyway.

同步（SharedClass.class） 。

Synchronized (SharedClass.class).

使用共享类来同步这两种方法，例如：

Using a shared class to synchronize those two methods, something like:

 public void MethodA() {
        synchronized (SharedClass.class) {
           //...
        }

和

public void MethodB() {
        synchronized (SharedClass.class) {
           //...
        }

无论如何，这些只是方法。我想知道实现我想要实现的目标的最佳方法是什么。拥有JVM的共享信号量会使事情变得更容易，但是，我知道必须有一个解决方案。在此先感谢。

Anyway, these are just approaches. I would like to hear what's the best way to implement what I'm trying to achieve. Having a shared semaphore for JVM would make things easier, but well, I know there must be a solution for this. Thanks in advance.

推荐答案

您的两种方法都应该有效，但我不认为锁定课程是推荐的做法。首选锁定 Object 的实例，或使用 java.util 中的正确锁定。另外，不要锁定字符串。

Both of your approaches should work, but I don't think locking on class is a recommended practices. Prefer locking on instances of Object, or use proper locks from java.util. Also, do not lock on String.

或者，您可以让类的实例 Class1 和 Class2 可以在实例化期间将锁作为参数：

Alternatively, you could let instances of classes Class1 and Class2 can take a lock as parameter during instantiation:

   class Class1 {
        private final Object lock;
        public Class1( Object lock ) { this.lock = lock }
        public method() { synchronize( lock ) { } );
   }

然后确保创建一个锁（使用 new Object（））并将其传递给 Class1 和 Class2 <的两个实例/ code>。

Then make sure that you create one lock (with new Object()) and pass it to the two instances of Class1 and Class2.

所以基本上，你把原来的问题分解为两个：1）这两个类没有静态地共享任何东西，它们只是接收一个参数。 2） Class1 和 Class2 的客户必须传递正确的锁。 Class1 和 Class2 的客户端充当orchestrator。

So basically, you've broken down the original problem in two: 1) the two classes do no share anything statically global, they just receive a parameter. 2) the clients of Class1 and Class2 must pass the correct lock. The client of Class1 and Class2 acts as the "orchestrator".

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