String[] split(String line, int assertLen, String usage) {
    String[] ret = split(line);

    if (ret.length != assertLen) {
      error(usage);
      return null;
    }

    return ret;
  }
Split the line based on spaces, asserting that the
number of words is correct.

@param line
         the line to split
@param assertLen
         the number of words to assure
@param usage
         the message to output if there are an incorrect
         number of words.
@return the split lines, or null if the assertion failed.
beeline/src/java/org/apache/hive/beeline/BeeLine.java