Another method to multiply two numbers without using the “*” operator [duplicate]

Answer 1

If you don't have integer values, you can take advantage of other mathematical properties to get the product of 2 numbers. Someone has already mentioned log10, so here's a bit more obscure one:

public double multiply(double x, double y) {
    Vector3d vx = new Vector3d(x, 0, 0);
    Vector3d vy = new Vector3d(0, y, 0);
    Vector3d result = new Vector3d().cross(vx, vy);
    return result.length();
}