public boolean addOutputStream(OutputStream out) {
    synchronized (lock) {
      final Set<OutputStream> oldSet = streams;
      if (oldSet.contains(out)) {
        return false;
      } else {
        final Set<OutputStream> newSet = new HashSet<>(oldSet);
        final boolean added = newSet.add(out);
        streams = newSet;
        return added;
      }
    }
  }
@return <tt>true</tt> if this CompositeOutputStream did not already contain the specified
        OutputStream
geode-core/src/main/java/org/apache/geode/internal/io/CompositeOutputStream.java