[Java筆記] Threads

• 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.