code: public void addChild(LockedObject newChild) {
          if (_children == null) {
              _children = new LockedObject[0];
          }
          int size = _children.length;
          LockedObject[] newChildren = new LockedObject[size + 1];
          System.arraycopy(_children, 0, newChildren, 0, size);
          newChildren[size] = newChild;
          _children = newChildren;
      }
docs: adds a new child lock to this lock
  
  @param newChild
  new child