public Boolean putIfNotFull(Integer key, Object value) {
    if (isFull()) {
      return false;
    } else {
      put(key, value);
      return true;
    }
  }
Puts new key-value pair in cache.
@param key
@param value
@return false if queue was full and put failed. True otherwise.
ql/src/java/org/apache/hadoop/hive/ql/exec/BoundaryCache.java