org.curjent.agent
Class DynamicTasks

java.lang.Object
  org.curjent.agent.DynamicTasks

All Implemented Interfaces:

AgentTasks

public abstract class DynamicTasks
extends Object
implements AgentTasks

Source for dynamically created tasks. This abstract class defines two method templates for subclasses: create and discard. This class is useful for creating and caching tasks that are too expensive in time or memory to create up front.

This implementation is not thread-safe.

Constructor Summary

protected

DynamicTasks(int acquireMax, int cacheMax, Collection<?> cacheSeed) Initializes the cache of tasks.

Method Summary

Object	acquire() Acquires a task.
protected abstract Object	create() Creates a new task.
protected void	discard(Object task) Discards a task.
void	release(Object task) Releases a task.

Methods inherited from class java.lang.Object

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

Constructor Detail

DynamicTasks

protected DynamicTasks(int acquireMax,
                       int cacheMax,
                       Collection<?> cacheSeed)

Initializes the cache of tasks. The cache is initialized with a copy of the given (possibly empty or null) cacheSeed. When a task is acquired, it is taken from the cache if available. If the cache is empty, a new task is created. As many as acquireMax tasks may be acquired. When a task is released, it is added to the cache. The cache can hold as many as cacheMax tasks. If the cache is full, the released task is discarded.

Parameters:

acquireMax - Maximum number of tasks that can be acquired.

cacheMax - Maximum number of tasks that can be cached.

cacheSeed - Initial cache of tasks. Possibly empty or null.

Throws:

IllegalArgumentException - acquireMax <= 0

IllegalArgumentException - acquireMax < cacheMax

IllegalArgumentException - cacheMax < 0

IllegalArgumentException - cacheSeed.size() > acquireMax

Method Detail

create

protected abstract Object create()
                          throws Throwable

Creates a new task. Called when the cache is empty. If this method returns null, the acquire method returns null, too. In this way the subclass can dynamically control how many tasks are created and acquired. This may be fewer than or equal to acquireMax but never more.

Throws:

Throwable

See Also:

acquire()

discard

protected void discard(Object task)
                throws Throwable

Discards a task. Called when the cache is full. The default implementation does nothing.

Throws:

Throwable

See Also:

release(Object)

acquire

public final Object acquire()
                     throws Throwable

Acquires a task. Returns a task from the cache if available. If the cache is empty, attempts to create and return a new task. If create() returns null, this method returns null, too.

Specified by:

acquire in interface AgentTasks

Throws:

Throwable - An unexpected error.

See Also:

create()

release

public final void release(Object task)
                   throws Throwable

Releases a task. Returns the task to the cache, or discards the task if the cache is full.

Specified by:

release in interface AgentTasks

Throws:

NullPointerException - task == null

IllegalStateException - acquireCount <= 0

Throwable - An unexpected error.

See Also:

discard(Object)