docs: public static int safeAdd(int val1, int val2) {
          int sum = val1 + val2;
          // If there is a sign change, but the two values have the same sign...
          if ((val1 ^ sum) < 0 && (val1 ^ val2) >= 0) {
              throw new ArithmeticException
                  ("The calculation caused an overflow: " + val1 + " + " + val2);
          }
          return sum;
      }