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

static interface

TaskManager.Task The interface that tasks must implement

Field Summary

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<TaskManager.Task>	tasks Active and pending tasks
protected boolean	terminated True if manager has been terminated
protected List<com.sun.jini.thread.TaskManager.TaskThread>	threads Active threads
protected long	timeout Idle time before a thread should exit

Constructor Summary

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.

TaskManager(int maxThreads, long timeout, float loadFactor, String threadName, int retriesOnIdle)

TaskManager(int maxThreads, long timeout, float loadFactor, String threadName, int retriesOnIdle, int threadPriority)

Method Summary

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.
List<TaskManager.Task>	getPending() Return all pending tasks.
String	getThreadName()
int	getTotalTasks() Returns the total number of tasks to be executed and currently executing.
boolean	isTerminated()
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).
void	setThreadName(String threadName)
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<TaskManager.Task> 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<com.sun.jini.thread.TaskManager.TaskThread> 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.

TaskManager

public TaskManager(int maxThreads,
                   long timeout,
                   float loadFactor,
                   String threadName,
                   int retriesOnIdle)

TaskManager

public TaskManager(int maxThreads,
                   long timeout,
                   float loadFactor,
                   String threadName,
                   int retriesOnIdle,
                   int threadPriority)

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.

setThreadName

public void setThreadName(String threadName)

getThreadName

public String getThreadName()

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).

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)

terminate

public void terminate()

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

isTerminated

public boolean isTerminated()

getPending

public List<TaskManager.Task> getPending()

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

getTotalTasks

public int getTotalTasks()

Returns the total number of tasks to be executed and currently executing.

getMaxThreads

public int getMaxThreads()

Return the maximum number of threads to use on tasks.