docs: public synchronized void setHandler(Handler handler) {
          String handlerId = CollectorManagerUtils.getHandlerId(handler);
          HandlerManager hdlrMgr;
          if (!handlerMgrs.containsKey(handlerId)) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isEventEnabled()) {
                  Tr.event(tc, "Adding handler to the list", handler.getClass());
              }
              hdlrMgr = new HandlerManager(handler);
              handlerMgrs.put(hdlrMgr.getHandlerId(), hdlrMgr);
              hdlrMgr.getHandler().init(this);
          }
      }