Java Concurrency
为何要同步线程？
Since all threads run in the same address space, they all have access to the same data and variables. If two threads simultaneously attempt to update a global counter variable, it is possible for their operations to interleave in such way that the global state is not correctly modified. Although such a case may only arise only one time out of thousands, a concurrent program needs to coordinate the activities of multiple threads using something more reliable that just depending on the fact that such interference is rare.
Executor: An object that executes submitted Runnable tasks.ExecutorService: A more extensive interface.ThreadPoolExecutor: Provides an extensible thread pool implementation.Executors: Provides convenient factory methods for these Executors.
AbstractExecutorService: Provides default implementations of ExecutorService execution methods.ScheduledExecutorService: An ExecutorService that can schedule commands to run after a given delay, or to execute periodically.
ExecutorService的生命周期
- Active
- Shutting Down
- Shutdown
Synchronizers (synchronization aids)
- CyclicBarrier循环屏障: A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.
- Phaser
- CountDownLatch: 当counter为1时为被用作start signal，为N时为complete signal。
- Exchanger
- Semaphore
- SynchronousQueue
Potential threading problems
- Deadlock
- Starvation
- Livelock
- Race conditions