Example usage for java.math BigInteger getLowestSetBit

Introduction

In this page you can find the example usage for java.math BigInteger getLowestSetBit.

Prototype

public int getLowestSetBit() 

Source Link

Document

Returns the index of the rightmost (lowest-order) one bit in this BigInteger (the number of zero bits to the right of the rightmost one bit).

Usage

From source file:Main.java

public static void main(String[] args) {

    BigInteger bi1 = new BigInteger("8");// 1000
    BigInteger bi2 = new BigInteger("7");// 0111

    // perform getLowestSetBit on bi1, bi2
    int i1 = bi1.getLowestSetBit();
    int i2 = bi2.getLowestSetBit();

    System.out.println(i1);//from   ww  w .ja  va2s. c  o  m
    System.out.println(i2);
}

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From source file:Util.java

public static boolean isEven(BigInteger number) {
    return number.getLowestSetBit() != 0;
}

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From source file:Main.java

private static boolean passesMillerRabin(BigInteger us, int iterations, Random rnd) {
    final BigInteger ONE = BigInteger.ONE;
    final BigInteger TWO = BigInteger.valueOf(2);
    // Find a and m such that m is odd and this == 1 + 2**a * m
    BigInteger thisMinusOne = us.subtract(ONE);
    BigInteger m = thisMinusOne;
    int a = m.getLowestSetBit();
    m = m.shiftRight(a);//from   ww  w .  j a  v a  2 s.  c o  m

    // Do the tests
    if (rnd == null) {
        rnd = new SecureRandom();
    }
    for (int i = 0; i < iterations; i++) {
        // Generate a uniform random on (1, this)
        BigInteger b;
        do {
            b = new BigInteger(us.bitLength(), rnd);
        } while (b.compareTo(ONE) <= 0 || b.compareTo(us) >= 0);

        int j = 0;
        BigInteger z = b.modPow(m, us);
        while (!((j == 0 && z.equals(ONE)) || z.equals(thisMinusOne))) {
            if (j > 0 && z.equals(ONE) || ++j == a)
                return false;
            z = z.modPow(TWO, us);
        }
    }
    return true;
}

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From source file:Util.java

public static BigInteger bitwiseGcd(BigInteger u, BigInteger v) {
    if (u.equals(BigInteger.ZERO))
        return v;
    if (v.equals(BigInteger.ZERO))
        return u;

    //      System.out.format("u=%s=%s\nu.getLowestSetBit()=%s\n%s>>%s=%s = %s\n", u, u.toString(2), u.getLowestSetBit(), u, u.getLowestSetBit(), u.shiftRight(u.getLowestSetBit()), u.shiftRight(u.getLowestSetBit()).toString(2));

    int uBit = u.getLowestSetBit();
    int vBit = v.getLowestSetBit();
    int k = (uBit <= vBit ? uBit : vBit);

    while (u.signum() > 0) {
        // first ensure that both are odd
        u = u.shiftRight(u.getLowestSetBit());
        v = v.shiftRight(v.getLowestSetBit());
        if (u.subtract(v).signum() >= 0) {
            u = (u.subtract(v)).shiftRight(1);
        } else {//from   w  w  w.  j  a  v  a 2  s .  c  o m
            v = (v.subtract(u)).shiftRight(1);
        }
    }

    return v.shiftLeft(k);
}

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