http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.pqc.math.ntru.euclid.test;

import java.math.BigInteger;

import junit.framework.TestCase;
import org.bouncycastle.pqc.math.ntru.euclid.BigIntEuclidean;

public class BigIntEuclideanTest
    extends TestCase
{
    public void testCalculate()
    {
        BigIntEuclidean r = BigIntEuclidean.calculate(BigInteger.valueOf(120), BigInteger.valueOf(23));
        assertEquals(BigInteger.valueOf(-9), r.x);
        assertEquals(BigInteger.valueOf(47), r.y);
        assertEquals(BigInteger.valueOf(1), r.gcd);

        r = BigIntEuclidean.calculate(BigInteger.valueOf(126), BigInteger.valueOf(231));
        assertEquals(BigInteger.valueOf(2), r.x);
        assertEquals(BigInteger.valueOf(-1), r.y);
        assertEquals(BigInteger.valueOf(21), r.gcd);
    }
}