piyush121 piyush121 - 2 months ago 7
Java Question

How can I calculate modulo of a large number in String format in java

I am trying to calculate an expression in java which is in String
i.e

99999999999999999^99999999999999999

I want to calculate this number modulo
1000000007
.
I currently trying to store the big numbers as double but taking modulo with double gives me
NaN
.
Can somebody help ?

Answer

You can use BigInteger and modPow(BigInteger, BigInteger) like

BigInteger m = new BigInteger("1000000007");
BigInteger a = new BigInteger("99999999999999999");
BigInteger b = new BigInteger("99999999999999999");
BigInteger answer = a.modPow(b, m);
System.out.println(answer);

which gives

265859324