BigInteger.valueOf() limits

Question

Does valueOf for BigInteger have any limitations ? I'm not sure but read somewhere, that given number can be of length = long only.

Solution 1

The BigInteger class itself is used to represent immutable arbitrary-precision integers. Meaning it can represent integers of any size (limited of course by the memory on your computer).

However the valueOf method returns a BigInteger whose value is equal to that of the specified long. So a BigInteger created in this way by definition can only be a large as Long.MAX_VALUE

BigInteger objects created by the other methods and constructors of the BigInteger class can of course be larger than Long.MAX_VALUE.

Take for example the code snipped below:

BigInteger big1 = BigInteger.valueOf(Long.MAX_VALUE);
BigInteger big2 = BigInteger.valueOf(Long.MAX_VALUE);
BigInteger big3 = big1.add(big2);

The BigInteger named big3 is larger than Long.MAX_VALUE even though its constituent parts were created using the valueOf method.

Solution 2

BigInteger's valueOf() method thakes a long as its sole parameter. So the maximum number you can pass to it is the maximum a long can represent (2^63-1 = 9223372036854775807).