Prerequisite : BigInteger Basics
The modPow() method returns modular multiplicative inverse of this, mod m. This method throws an ArithmeticException if m <= 0 or this has no multiplicative inverse mod m (i.e., gcd(this, m) != 1).
public BigInteger modInverse(BigInteger m)
Parameters: m – the modulus.
Return Value: This method returns a BigInteger object whose value is ((this)^(-1) mod m).
- ArithmeticException – m <= 0, or this BigInteger has no multiplicative inverse mod m (that is, this BigInteger is not relatively prime to m).
Below programs illustrate the BigInteger.modInverse() method:
Program 1 :
8 ^ -1 % 21 = 8
Program 2 :
Exception in thread "main" java.lang.ArithmeticException: BigInteger not invertible. at java.math.MutableBigInteger.modInverse(Unknown Source) at java.math.MutableBigInteger.mutableModInverse(Unknown Source) at java.math.BigInteger.modInverse(Unknown Source) at BigInteger.GFG2.main(GFG2.java:23)
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