code: @Override
      public synchronized void closeCompletionPort(long completionPort) {
          final int listSize = completionPorts.size();
          for (int i = 0; i < listSize; i++) {
              if (completionPorts.get(i).longValue() == completionPort) {
                  try {
                      aio_closeport2(completionPort);
                  } catch (AsyncException ae) {
                      // just log any errors and continue
                      if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                          Tr.debug(tc, "Error closing completion port: " + completionPort + ", error:" + ae.getMessage());
                      }
                  }
                  completionPorts.remove(i);
                  break;
              }
          }
      }
docs: /*
  @see com.ibm.io.async.IAsyncProvider#closeCompletionPort(long)