java 如何在 Android 中创建锁 (concurrent.locks.Lock)？
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How do I create a Lock (concurrent.locks.Lock) in Android?
提问by Neil Townsend
This must be really obvious, but I can't spot the answer. I need to put a lock around a variable to ensure that a couple of race-hazard conditions are avoided. From what I can see, a pretty simple solution exists using Lock, according to the android docs:
这一定很明显，但我找不到答案。我需要在一个变量周围加一个锁，以确保避免一些竞争危险的情况。据我所见，根据 android 文档，使用 Lock 存在一个非常简单的解决方案：
Lock l = ...;
l.lock();
try {
// access the resource protected by this lock
}
finally {
l.unlock();
}
So far, so good. However, I can't make the first line work. It would seem that something like:
到现在为止还挺好。但是，我无法使第一行工作。似乎是这样的：
Lock l = new Lock();
Might be correct, but eclipse reports, "Cannot instantiate the type Lock" - and no more.
可能是正确的，但 eclipse 报告，“无法实例化锁类型”——仅此而已。
Any suggestions?
有什么建议？
回答by A--C
If you're very keen on using a Lock, you need to choose a Lockimplementation as you cannotinstantiate interfaces.
As per the docsYou have 3 choices:
如果您非常热衷于使用 a Lock，则需要选择一个Lock实现，因为您无法实例化接口。根据文档您有 3 个选择：
- ReentrantLock
- ConditionThis isn't a Lock itself but rather a helper class since
Conditions are bound toLocks. - ReadWriteLock
You're probably looking for the ReentrantLockpossibly with some Conditions
您可能正在寻找ReentrantLock带有一些Conditions的可能
This means that instead of Lock l = new Lock();you would do:
这意味着，而不是Lock l = new Lock();你会做：
ReentrantLock lock = new ReentrantLock();
However, if all you're needing to lock is a small part, a synchronized block/method is cleaner (as suggested by @Leonidos & @assylias).
但是，如果您需要锁定的只是一小部分，那么同步块/方法会更清晰（如@Leonidos 和@assylias 所建议的那样）。
If you have a method that sets the value, you can do:
如果您有设置值的方法，则可以执行以下操作：
public synchronized void setValue (var newValue)
{
value = newValue;
}
or if this is a part of a larger method:
或者如果这是更大方法的一部分：
public void doInfinite ()
{
//code
synchronized (this)
{
value = aValue;
}
}
回答by Andrey Atapin
Just because Lockis an interface and can't be instantiated. Use its subclasses.
只是因为它Lock是一个接口，不能被实例化。使用它的子类。
