Java.math.BigInteger.modInverse() Method

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Description

The java.math.BigInteger.modInverse(BigInteger m) returns a BigInteger whose value is (this-1 mod m).

Declaration

Following is the declaration for java.math.BigInteger.modInverse() method

public BigInteger modInverse(BigInteger m)

Parameters

  • m - the modulus

Return Value

This method returns a BigInteger object whose value is this-1 mod m.

Exception

  • ArithmeticException - if m ≤ 0, or this BigInteger has no multiplicative inverse mod m (that is, this BigInteger is not relatively prime to m).

Example

The following example shows the usage of math.BigInteger.modInverse() method

package com.tutorialspoint;

import java.math.*;

public class BigIntegerDemo {

public static void main(String[] args) {

        // create 3 BigInteger objects
        BigInteger bi1, bi2, bi3;

	// Two numbers are relatively prime if they have no
	// common factors, other than 1.
        bi1 = new BigInteger("7");
        bi2 = new BigInteger("20");

        // perform modInverse operation on bi1 using bi2
	bi3 = bi1.modInverse(bi2);

        String str = bi1 + "^-1 mod " + bi2 + " is " +bi3;

	// print bi3 value
	System.out.println( str );
    }
}

Let us compile and run the above program, this will produce the following result:

7^-1 mod 20 is 3



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