GatekeeperSemaphore.java

public boolean tryAcquire(int timeout) {

 SemaphorePermit permit = new SemaphorePermit(semaphoreName, groupName,
     acquirerName, null);
     
    // Delegate to the gatekeeper which enforces the permit rules based
    // on the semaphore definition. The gatekeeper might be a local library
    // or a call to a remote service.
 permit = gatekeeperGateway.tryAcquire(permit);
 Date expirationDate = permit.getExpirationDate();
 
 if (expirationDate == null) {
   // We didn't get the permit. Either sleep or expire the attempt.
   // ...
 }
 else {
   // We got the permit. Return true.
   // ...
 }
}