What is the difference between calling
? Also, in what instances would you call either method?
The Java platform uses the multithreading facilities of the host
OS to implement multithreading.
There are two flavors of multithreading
facilities: preemtive and non-preemptive. In a non-preemptive system all
runnable threads wait in a ready queue for the currently running thread
to release the CPU. This happens either because the thread terminates,
requests I/O, or calls
In a preemptive system, the CPU is allocated to a thread for a time slice
(e.g. one second). If a thread doesn't release the CPU before its time
slice expires, it will be interrupted, sent back to the ready queue, and
the CPU will be allocated to the "next" thread waiting in the ready queue.
Most host multithreading systems are preemptive, but some are not (e.g.
Solaris' "Green Threads"). This means multithreaded Java programs can
exhibit platform-dependent behavior. One way to mitigate this problem is
to write COOPERATIVE THREADS. A thread is cooperative if it
occasionally releases the CPU specifically so other threads can run.
There are two ways to do this: by calling
sleep(t) where t is
sleep(t) causes the thread to suspend itself for at least t
yield() causes the thread to rejoin the ready
Warning: The Java ready queue is a priority queue. This means threads are
inserted according to their priority. The maximum priority of a Java
thread is 10. The minimum priority is 1, and the normal priority is 5. A
thread with priority n is inserted into the ready queue ahead of all
threads with priority < n, but behind all threads with priority >= n.
Hence, if a co-operative thread with priority n calls
yield(), this only
means ready threads with priority >= n will get a chance to run.
Thread.setPriority to learn and modify a