com.threecrickets.creel.util.Jobs Maven / Gradle / Ivy
/**
* Copyright 2015-2016 Three Crickets LLC.
*
* The contents of this file are subject to the terms of the LGPL version 3.0:
* http://www.gnu.org/copyleft/lesser.html
*
* Alternatively, you can obtain a royalty free commercial license with less
* limitations, transferable or non-transferable, directly from Three Crickets
* at http://threecrickets.com/
*/
package com.threecrickets.creel.util;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Phaser;
import com.threecrickets.creel.util.internal.Job;
/**
* Powerful utility to avoid repeating concurrent identical jobs.
*
* @author Tal Liron
*/
public class Jobs
{
//
// Operations
//
/**
* Checks if we are already doing the job. If we are not, then mark that we
* have begun it. If we are, then hook a task to run when that job finishes.
*
* @param id
* The job ID
* @param executor
* The executor
* @param phaser
* The phaser or null
* @param onEnd
* The task to submit or run when the job finishes
* @return True if not already doing the job
*/
public synchronized boolean beginIfNotBegun( int id, ExecutorService executor, Phaser phaser, Runnable onEnd )
{
Job job = jobs.get( id );
if( job == null )
{
// New job
jobs.put( id, new Job( executor ) );
return true;
}
else
{
// Another thread has already started this job, so let's wait until
// they're done
if( phaser != null )
phaser.register();
job.onEnd( onEnd );
return false;
}
}
/**
* Mark the job finished, which may trigger tasks to be submitted.
*
* @param id
* The job ID
* @return True if the job existed
*/
public synchronized boolean notifyEnd( int id )
{
Job job = jobs.remove( id );
if( job != null )
{
job.end();
return true;
}
else
return false;
}
/**
* Submits the task to run when the job finishes. If already finished, runs
* the task now.
*
* @param id
* The job ID
* @param onEnd
* The task
*/
public synchronized void onEnd( int id, Runnable onEnd )
{
Job job = jobs.get( id );
if( job != null )
// Do later
job.onEnd( onEnd );
else
// Do now
onEnd.run();
}
// //////////////////////////////////////////////////////////////////////////
// Private
private Map jobs = new HashMap();
}