New Thread State

• The state a newly created thread is in before it is started. For example,

  Thread newBorn = myThreadClass();

  A thread in this state can only be started or stopped. Calling any method other than start or stop makes no sense and causes an IllegalThreadStateException.

Runnable State

• The start method puts a thread in the runnable state. However, a runnable thread may not actually be running. For example, on a single CPU computer, many threads may be in the runnable state but only one can be running at a time.

Not Runnable

• A thread becomes not runnable when one of the following four events occurs:

  • Its sleep method is invoked.

  • Its suspend method is invoked.

  • The thread must wait for access to a monitored object as is done in the producer/consumer example.

  • The thread is blocking on I/O.
• A thread can transistion from the Not Runnable state to the Runnable state in the four following ways (one escape method for each of the four methods above):

  • The specified number of milliseconds has passed for a thread that had been put to sleep.

  • A suspended thread has its resume method called.

  • a thread is blocked on I/O and the I/O completes.

  • The thread is waiting for a monitored object, and the thread that owns the monitor for the condition variable, relinquishes it by calling notify or notifyAll.

    notify, for example, wakes up a single thread that is waiting on the object's monitor. A thread waits on an object's monitor by calling one of the wait methods.

    notify should only be called by a thread that is the owner of the object's monitor. A thread becomes the owner of the object's monitor in one of three ways:

    • By executing a synchronized instance method of that object.
    • By executing the body of a synchronized statement that synchronizes on the object.
    • For objects of type Class, by executing a synchronized static method of that class.

    Only one thread at a time can own an object's monitor.

Dead