code: private void setVariableRange(int start, int end) {
          if (start > end || start < 0 || end > 0xFFFF) {
              throw new IllegalIcuArgumentException("Invalid variable range " + start + ", " + end);
          }
  
          curData.variablesBase = (char) start; // first private use
  
          if (dataVector.size() == 0) {
              variableNext = (char) start;
              variableLimit = (char) (end + 1);
          }
      }
docs: Set the variable range to [start, end] (inclusive).