Java.math.BigInteger.modInverse() Method



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


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

public BigInteger modInverse(BigInteger m)


m − The modulus.

Return Value

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


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


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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