CODEWITHSUNDEEP
javabiginteger
WTRIX
WTRIX

Reputation: 95

Java's BigInteger implementation

I'm new here so please excuse my noob mistakes. I'm currently working on a little project of mine that sees me dealing with digits with a length in the forty thousands and beyond.

I'm currently using BigInteger to handle these values, and I need something that performs faster. I've read that BigInteger uses an array of integers in its implementation, and what I need to know is whether BigInteger is using each index in this array to represent each decimal point, as in 1 - 9, or is it using something more efficient.

I ask this because I already have an implementation in mind that uses bit operations, which makes it more efficient, memory and processing wise.

So the final question is - is BigInteger already efficient enough, and should I just rely on that? It would better to know this rather than putting it to the test unnecessarily, which would take a lot of time.

Thank you.

Upvotes: 4

Views: 7347

Answers (1)

Chai T. Rex
Chai T. Rex

Reputation: 3018

At least with Oracle's Java 8 and OpenJDK 8, it doesn't store one decimal digit per int. It stores full 32-bit portions per 32-bit int in the int[], which can be seen with its source code.

Bit operations are fast for it, since it's a sign-magnitude value and the magnitude is stored packed just as you'd expect, just make sure that you use the relevant BigInteger bitwise methods rather than implementing your own.

If you still need more speed, try something like GMP, though be aware that it uses a LGPL or GPL license. It would also be better to use it outside of Java.

Upvotes: 4

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