Primitive Type

HashCode

How String hashCode is calculated?

s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

Reference

Parity

Giving a binary word, if the number of 1s is odd, return 1, otherwise 0

• (11010111) => (1101)^(0111)

public static short parity(long x) {
    x ^= (x >>> 32);
    x ^= (x >>> 16);
    x ^= (x >>> 8);
    x ^= (x >>> 4);
    x ^= (x >>> 2);
    x ^= (x >>> 1);
    return (short) (x & 1);
  }

50 Compute x^y

 private static double power(double x, int y){
    double result= 1.0;
    boolean isPositive = true;
    if (y < 0){
        isPositive = false;
        y = - y;
    }
    while( y > 0){
        if ( y%2 == 1){
            result *= x;
        }
        x *= x;
        y /= 2;
    }
    if(!isPositive){
        result = 1 / result;
    }
    return result;
}