code: private static final void checkComparators(int[] pos1, int[] pos2, 
  							Class<? extends Key<?>>[] types1, Class<? extends Key<?>>[] types2)
  	{
  		if (pos1.length != pos2.length || types1.length != types2.length) {
  			throw new IllegalArgumentException(
  				"The given pair of RecordComparators does not operate on the same number of fields.");
  		}
  		for (int i = 0; i < types1.length; i++) {
  			if (!types1[i].equals(types2[i])) {
  				throw new IllegalArgumentException(
  				"The given pair of RecordComparators does not operates on different data types.");
  			}
  		}
  	}
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