How to find and handle binary/numerical overflow in J2ME

Question

Hi

I am building a unit convertor program that uses the MathFP library. Typically unit conversion occurs in the formula of:

U1 (unit1) * K (constant) = U2 (unit2)

I want to be able to detect when the an int has over/underflowed? How can I detect when this has occured and gracefully handle the problem. Ideally I would be looking for a generic solution, as I would want to handle overflow with primitives of type long:

The only idea I have is:

int largeOne = bigNum;
int largeTwo = anotherbigNum;

//complete math operation
long l = largeOne * largeTwo;
if(l > Integer.MAX_SIZE){
    System.out.println("Overflow");
    //handle error
}

Should I be using a different primitive data type for these conversions, such as double?

Thanks in advance for your help

Answer 1

You could check if the result is negative, or positive (depending on largeOne and largeTwo signs) but it would be a guess work.

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I found another way, you could manually multiply your two numbers with an algorithm.

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Resources :

• Wikipedia - Multiplication algorithm

On the same topic :

• how to write own multiplication of big numbers ?

Answer 2

You could switch to using the BigDecimal class which has much better handling for overflow/underflow than the int/long primitives in Java. The int/long values are a special case that are not classes and as a result miss out on advantages of OOP.