code: private File getWriteLock() {
          File[] lckFiles = this.lockPath.listFiles(lockFilter);
          for (final File lckFile : lckFiles) {
              if (lockFilter.isWriterLockFile(lckFile)) {
                  return lckFile;
              }
          }
  
          return null;
      }
docs: Reads {@link LockAdviser#lockPath lock path directory} and finds the
  {@link File write lock file}, if any.
  
  @return the {@link write lock file}, or <tt>null</tt> if no write lock
  exists