javatools.thread
Class ThreadPool

java.lang.Object
  |
  +--javatools.thread.ThreadPool

public class ThreadPool

extends java.lang.Object

Implements a pool of threads. Only a limited number of threads can execute at once. If you try to exceed the thread limit you will block waiting. This avoids overloading a machine with threads.

Field Summary

(package private) java.util.List	jobs
(package private) java.lang.ThreadGroup	threadGroup
(package private) java.util.List	threads

Constructor Summary

ThreadPool(java.lang.String name, int maxThreads)

Method Summary

boolean	anyReadyThreads() Check whether any pool threads are currently available for use.
protected void	finalize()
(package private) java.lang.Runnable	getJob() Get a job to execute and remove it from the job queue.
void	join() Wait for all threads to complete.
int	numberOfActiveThreads() How many threads are active right now? This number can change at any time, so it is not particularly useful except for providing interesting diagnostics.
int	numberOfReadyThreads()
void	queueJob(java.lang.Runnable runnable) Execute the given procedure when a thread slot becomes available.
void	shutdown() Shutdown all pool threads safely.
void	startNow(java.lang.Runnable runnable) Start a job now.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

threads

java.util.List threads

threadGroup

java.lang.ThreadGroup threadGroup

jobs

java.util.List jobs

Constructor Detail

ThreadPool

public ThreadPool(java.lang.String name,
                  int maxThreads)

Parameters:

name - the name of the ThreadGroup

maxThreads - the maximum number of threads we allow at once.

Method Detail

getJob

java.lang.Runnable getJob()

Get a job to execute and remove it from the job queue.

Returns:

Job that needs executing.

startNow

public void startNow(java.lang.Runnable runnable)

Start a job now. If no threads are available, start a new thread to make sure it gets going now.

Parameters:

runnable -

queueJob

public void queueJob(java.lang.Runnable runnable)

Execute the given procedure when a thread slot becomes available.

Parameters:

runnable - the runnable that represents the work that shall be done.

Returns:

false if there was no slot available. Try again later.

join

public void join()

Wait for all threads to complete. Make sure you call shutdown() first.

numberOfActiveThreads

public int numberOfActiveThreads()

How many threads are active right now? This number can change at any time, so it is not particularly useful except for providing interesting diagnostics.

Returns:

Description of the Returned Value

anyReadyThreads

public boolean anyReadyThreads()

Check whether any pool threads are currently available for use. If the next available thread is unstarted we start it. This allows us to start the pool on an as-needed basis. If true is returned there is a thread available. If false is returned there is not a thread available unless one finished half-way through the function.

Returns:

whether there are currently available threads.

numberOfReadyThreads

public int numberOfReadyThreads()

shutdown

public void shutdown()

Shutdown all pool threads safely. This does not wait for them to complete. Call join() if you want that.

finalize

protected void finalize()
                 throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

java.lang.Throwable