com.sun.jini.thread

Class TaskManager

java.lang.Object

com.sun.jini.thread.TaskManager

public class TaskManager
extends Object

A task manager manages a single queue of tasks, and some number of worker threads. New tasks are added to the tail of the queue. Each thread loops, taking a task from the queue and running it. Each thread looks for a task by starting at the head of the queue and taking the first task (that is not already being worked on) that is not required to run after any of the tasks that precede it in the queue (including tasks that are currently being worked on).

This class uses the Logger named com.sun.jini.thread.TaskManager to log information at the following logging levels:

com.sun.jini.thread.TaskManager

Level	Description
SEVERE	failure to create a worker thread when no other worker threads exist
WARNING	exceptions thrown by TaskManager.Task methods, and failure to create a worker thread when other worker threads exist

Author:

Sun Microsystems, Inc.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	TaskManager.Task The interface that tasks must implement
private class	TaskManager.TaskThread

Field Summary

Fields

Modifier and Type	Field and Description
protected int	firstPending Index of the first pending task; all earlier tasks are active
protected float	loadFactor Threshold for creating new threads
protected static Logger	logger Logger
protected int	maxThreads Maximum number of threads allowed
protected List	roTasks Read-only view of tasks
protected ArrayList	tasks Active and pending tasks
protected boolean	terminated True if manager has been terminated
protected List	threads Active threads
protected long	timeout Idle time before a thread should exit

Constructor Summary

Constructors

Constructor and Description
TaskManager() Create a task manager with maxThreads = 10, timeout = 15 seconds, and loadFactor = 3.0.
TaskManager(int maxThreads, long timeout, float loadFactor) Create a task manager.

Method Summary

Methods

Modifier and Type	Method and Description
void	add(TaskManager.Task t) Add a new task.
void	addAll(Collection c) Add all tasks in a collection, in iterator order.
void	addIfNew(TaskManager.Task t) Add a new task if it is not equal to (using the equals method) to any existing active or pending task.
int	getMaxThreads() Return the maximum number of threads to use on tasks.
ArrayList	getPending() Return all pending tasks.
protected boolean	needThread() Return true if a new thread should be created (ignoring maxThreads).
boolean	remove(TaskManager.Task t)
boolean	removeIfPending(TaskManager.Task t) Remove a task if it is pending (not active).
private boolean	removeTask(TaskManager.Task t, int min) Remove a task if it has index >= min.
private boolean	runAfter(TaskManager.Task t, int i) Returns t.runAfter(i), or false if an exception is thrown.
void	terminate() Interrupt all threads, and stop processing tasks.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected static final Logger logger

Logger

tasks

protected final ArrayList tasks

Active and pending tasks

firstPending

protected int firstPending

Index of the first pending task; all earlier tasks are active

roTasks

protected final List roTasks

Read-only view of tasks

threads

protected final List threads

Active threads

maxThreads

protected final int maxThreads

Maximum number of threads allowed

timeout

protected final long timeout

Idle time before a thread should exit

loadFactor

protected final float loadFactor

Threshold for creating new threads

terminated

protected boolean terminated

True if manager has been terminated

Constructor Detail

TaskManager

public TaskManager()

Create a task manager with maxThreads = 10, timeout = 15 seconds, and loadFactor = 3.0.

TaskManager

public TaskManager(int maxThreads,
           long timeout,
           float loadFactor)

Create a task manager.

Parameters:

maxThreads - maximum number of threads to use on tasks

timeout - idle time before a thread exits

loadFactor - threshold for creating new threads. A new thread is created if the total number of runnable tasks (both active and pending) exceeds the number of threads times the loadFactor, and the maximum number of threads has not been reached.

Method Detail

addIfNew

public void addIfNew(TaskManager.Task t)

Add a new task if it is not equal to (using the equals method) to any existing active or pending task.

add

public void add(TaskManager.Task t)

Add a new task.

addAll

public void addAll(Collection c)

Add all tasks in a collection, in iterator order.

needThread

protected boolean needThread()

Return true if a new thread should be created (ignoring maxThreads).

runAfter

private boolean runAfter(TaskManager.Task t,
               int i)

Returns t.runAfter(i), or false if an exception is thrown.

removeIfPending

public boolean removeIfPending(TaskManager.Task t)

Remove a task if it is pending (not active). Object identity (==) is used, not the equals method. Returns true if the task was removed.

remove

public boolean remove(TaskManager.Task t)

removeTask

private boolean removeTask(TaskManager.Task t,
                 int min)

Remove a task if it has index >= min. If it is active and not being executed by the calling thread, interrupt the thread executing the task.

terminate

public void terminate()

Interrupt all threads, and stop processing tasks. Only getPending should be used afterwards.

getPending

public ArrayList getPending()

Return all pending tasks. A new list is returned each time.

getMaxThreads

public int getMaxThreads()

Return the maximum number of threads to use on tasks.