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package com.techempower.thread;
import java.util.*;
import java.util.concurrent.*;
import com.techempower.helper.*;
import com.techempower.util.*;
/**
* Provides a thin abstraction over the Java Concurrency API's CountDownLatch
* to provide a simple means to fan work out to multiple threads and then
* block, waiting for all these threads to complete.
*
* Runnables are added and then runAndWait is called to start all Runnables
* using the ThreadHelper's cached Executor. Thread management is therefore
* hidden from view.
*
* SimpleLatches are intended for one use only--that is, constructed, used,
* and then discarded. However, that pattern is not enforced and
* theoretically, the same workload could be repeated by calling runAndWait
* multiple times.
*/
public class SimpleLatch
{
//
// Member variables.
//
private final List runnables = new ArrayList<>();
//
// Member methods.
//
/**
* Constructor.
*/
public SimpleLatch()
{
// Does nothing.
}
/**
* Adds a Runnable. The Runnable is not executed on a thread until the
* runAndWait method is called.
*/
public SimpleLatch add(Runnable runnable)
{
this.runnables.add(runnable);
return this;
}
/**
* Adds a bunch of Runnables. The Runnables are not executed on threads
* until the runAndWait method is called.
*/
public SimpleLatch addAll(List runnablesToAdd)
{
this.runnables.addAll(runnablesToAdd);
return this;
}
/**
* Gets the number of Runnables that have been added.
*/
public int size()
{
return this.runnables.size();
}
/**
* Starts all Runnables using a cached Executor and awaits their completion.
* Waits a default of 24 hours for completion.
*/
public SimpleLatch runAndWait()
{
return runAndWait(UtilityConstants.DAY);
}
/**
* Starts all Runnables using a cached Executor and awaits their completion.
*/
public SimpleLatch runAndWait(long timeoutMs)
{
final CountDownLatch cdl = new CountDownLatch(size());
// Wrap each Runnable and start it up.
for (Runnable r : this.runnables)
{
final Runnable runnable = r;
final Runnable wrapped = new Runnable() {
@Override
public void run()
{
runnable.run();
cdl.countDown();
}
};
ThreadHelper.submit(wrapped);
}
// Wait for the completion.
try
{
cdl.await(timeoutMs, TimeUnit.MILLISECONDS);
}
catch (InterruptedException iexc)
{
// Do nothing.
}
return this;
}
}