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Java BigInteger Class | modInverse() Method with Example

BigInteger Class modInverse() method: Here, we are going to learn about the modInverse() method of BigInteger Class with its syntax and example.
Submitted by Preeti Jain, on May 11, 2020

BigInteger Class modInverse() method

• modInverse() method is available in java.math package.
• modInverse() method is used to calculate the mod inverse by using the inverse of (this BigInteger) mod the given BigInteger (val).
• modInverse() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• modInverse() method may throw an exception at the time of returning mod inverse.
  ArithmeticException: This exception may throw when the given parameter holds value 0 or negative.

Syntax:

    public BigInteger modInverse(BigInteger val);

Parameter(s):

• BigInteger val – represents the object by which to calculate mod inverse.

Return value:

The return type of this method is BigInteger, it returns the mod inverse value by using [ inv (this BigInteger) mod (BigInteger val) ].

Example:

// Java program to demonstrate the example 
// of BigInteger modInverse(BigInteger val) method of BigInteger

import java.math.*;

public class ModInverseOfBI {
    public static void main(String args[]) {
        // Initialize three variables str1 , str2 and str3
        String str1 = "101";
        String str2 = "13";
        String str3 = "10";

        // Initialize three BigInteger objects  
        BigInteger b_int1 = new BigInteger(str1);
        BigInteger b_int2 = new BigInteger(str2);
        BigInteger b_int3 = new BigInteger(str3);

        // Display b_int1 , b_int2 and b_int3
        System.out.println("b_int1: " + b_int1);
        System.out.println("b_int2: " + b_int2);
        System.out.println("b_int3: " + b_int3);

        System.out.println();

        // Here, we are calculating modInverse between
        // two BigInteger values [inv(this BigInteger
        // b_int1) mod (BigInteger b_int3) ] by using
        // modInverse(BigInteger) method

        BigInteger modinv_val = b_int1.modInverse(b_int3);
        System.out.println("b_int1.modInverse(b_int3): " + modinv_val);

        // Here, we are calculating modInverse between
        // two BigInteger values [inv(this BigInteger
        // b_int2) mod (BigInteger b_int3) ] by using
        // modInverse(BigInteger) method
        modinv_val = b_int2.modInverse(b_int3);
        System.out.println("b_int2.modInverse(b_int3): " + modinv_val);
    }
}

Output

b_int1: 101
b_int2: 13
b_int3: 10

b_int1.modInverse(b_int3): 1
b_int2.modInverse(b_int3): 7