- Thread有5個狀態
- New
- Runnable
- Running
- Waiting/Sleeping/Blocked
- Dead
- Modifier synchronized 不能用在constructor/variables上.
- static synchronized method's lock is on the class-instance.
non-static synchronized method's lock is on the object instance. - Thread deadlocking is the situation when thread execution grinds to a halt
because the code is waiting for locks to be removed from objects.
It occurs when both threads are waiting for each others' locks to be released. - Method "long[] findDeadlockedThreads()" 用來查詢deadlock threads.
回傳thread IDs.
用於monitors或ownable synchronizers(e.g. ReentrantLock/ReentrantReadWriteLock).
http://docs.oracle.com/javase/7/docs/api/java/lang/management/ThreadMXBean.html#findDeadlockedThreads() - Memory consistency:理解 the happens-before relationship 可幫助避免 memory consistency error.
Happens-before relationship:
a guarantee that memory writes by one specific statement are visible to another specific statement.
複習:
- Constructors are never inherited.
