我在数据库前面使用了LinkedBlockingQueue。一个线程写入队列，另一个从队列读取。
我认为不可能同时进行两次写入。但是一个线程是否有可能同时从队列中读取另一个线程呢？如果没有，是否有Java队列来提供呢？
最佳答案
是的，有可能一个线程正在读取而一个线程正在同时写入。LinkedBlockingQueue为此使用两个锁。一种用于从队列中取出物品，另一种用于放置物品。
/** Lock held by put, offer, etc */
private final ReentrantLock putLock = new ReentrantLock();
/** Lock held by take, poll, etc */
private final ReentrantLock takeLock = new ReentrantLock();
在
LinkedBlockingQueue上的实现方式也在其source file (line 77)中进行了讨论。/*
* A variant of the "two lock queue" algorithm. The putLock gates
* entry to put (and offer), and has an associated condition for
* waiting puts. Similarly for the takeLock. The "count" field
* that they both rely on is maintained as an atomic to avoid
* needing to get both locks in most cases. Also, to minimize need
* for puts to get takeLock and vice-versa, cascading notifies are
* used. When a put notices that it has enabled at least one take,
* it signals taker. That taker in turn signals others if more
* items have been entered since the signal. And symmetrically for
* takes signalling puts. Operations such as remove(Object) and
* iterators acquire both locks.
*/