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May 22, 2017 21:16
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Semaphore controller - Green vs Red light permission
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package br.com.ggdio.util.concurrent; | |
import java.util.concurrent.CountDownLatch; | |
import java.util.concurrent.locks.ReentrantLock; | |
/** | |
* Semaphore controller | |
* | |
* Red Signal - Blocks all threads controlled by this Semaphore | |
* Green Signal - All threads controlled by this Semaphore are allowed to proceed | |
* | |
* @author Guilherme Dio | |
* | |
*/ | |
public class Semaphore { | |
private final ReentrantLock lock = new ReentrantLock(); | |
private CountDownLatch latch; | |
public Semaphore() { | |
this(true); | |
} | |
public Semaphore(boolean green) { | |
if(green) { | |
setGreenSignal(); | |
} else { | |
setRedSignal(); | |
} | |
} | |
private CountDownLatch getLatch() { | |
try { | |
lock.lock(); | |
return latch; | |
} finally { | |
lock.unlock(); | |
} | |
} | |
/** | |
* Proceed the signal. | |
* <p>If it's red, then the current thread is locked until it turns green.</p> | |
* <p>If it's green, then the current thread is allowed to proceed and continue it's execution.</p> | |
* | |
*/ | |
public void proceed() { | |
try { | |
getLatch().await(); | |
} catch (InterruptedException e) { } | |
} | |
/** | |
* Releases the semaphore | |
*/ | |
public void setGreenSignal() { | |
lock.lock(); | |
if(latch != null) { | |
latch.countDown(); | |
} | |
latch = new CountDownLatch(0); | |
lock.unlock(); | |
} | |
/** | |
* Blocks the semaphore | |
*/ | |
public void setRedSignal() { | |
lock.lock(); | |
latch = new CountDownLatch(1); | |
lock.unlock(); | |
} | |
} |
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