code: public static int[] validate2NonNegative(int[] data, boolean allowSz1, String paramName) {
          validateNonNegative(data, paramName);
          return validate2(data, allowSz1, paramName);
      }
docs: Reformats the input array to a length 2 array and checks that all values are >= 0.
  
  If the array is length 1, returns [a, a]
  If the array is length 2, returns the array.
  
  @param data An array
  @param paramName The param name, for error reporting
  @return An int array of length 2 that represents the input