code: protected synchronized boolean contains(Object id) {
          boolean found = false;
          if (this.explicitBuffer.containsKey(id) || this.scanBuffer.contains(id)) {
              found = true;
          }
          return found;
      }
docs: Call this method to check whether a specified id exists in the invalidation explicit or scan buffer.
  
  @param id
  - cache id.
  @return boolean - true means a specified id is found.