gistfile1.txt

public class InterProcessSemaphoreMutex implements InterProcessLock
{
    private InterProcessSemaphore semaphore;
    private volatile Lease lease;

    public InterProcessSemaphoreMutex(InterProcessSemaphore semaphore)
    {
        this.semaphore = semaphore;
    }

    @Override
    public void acquire() throws Exception
    {
        Preconditions.checkState(lease == null, "Already acquired");

        lease = semaphore.acquire();
    }

    @Override
    public boolean acquire(long time, TimeUnit unit) throws Exception
    {
        Preconditions.checkState(lease == null, "Already acquired");

        lease = semaphore.acquire(time, unit);
        return (lease != null);
    }

    @Override
    public void release() throws Exception
    {
        Preconditions.checkState(lease != null, "Not acquired");

        try
        {
            lease.close();
        }
        finally
        {
            lease = null;
        }
    }

    @Override
    public boolean isAcquiredInThisProcess()
    {
        return (lease != null);
    }
}