code: private static BigInteger checkAndReturn(String which,
                                               BigInteger expected,
                                               String asbigintcs)
      {
          BigInteger other =
                  BigIntStringChecksum.fromString(asbigintcs).asBigInteger();
  
          if (expected.equals(other))
          {
              return expected;
          }
          else
          {
              throw new SecretShareException(which + " failure");
          }
      }
docs: Guard against accidental changes to the strings.
  
  @param which caller
  @param expected value as biginteger
  @param asbigintcs value as big-integer-checksum string
  @return expected or throw exception
  @throws SecretShareException if expected does not match asbigintcs