How to raise a BigInteger to the power of something without pow()

Question

My Java Professor wants me to write a program where the user gives a value for x and a value for y, and then computes the value of x^y (x to the power of y), and prints it to the console. I'm not allowed to use the pow() method for this. x and y are int values.

My code, after the user gives x and y values:

BigInteger solution = BigInteger.valueOf(0);
    for (int i=0; i<y; i++) {
        solution = solution.add(BigInteger.valueOf((x+solution.intValue())*x));
    }

But it never works properly. The answer it gives is usually waaaay off. If anyone has code that would correct this problem, your assistance would be much appreciated!

Answer 1

You just need to multiply x by itself y times.

BigInteger solution;

if (y == 0) {
    solution = BigInteger.valueOf(1);
}
else if (y > 0) {        
    solution = BigInteger.valueOf(x);
    for (int i=0; i<y-1; i++) {
        solution = solution.multiply(BigInteger.valueOf(x));
    }
}
else {
    // Negative powers left as exercise to the reader
}

Answer 2

You can do something like this:

public void function(int x, int y){

    BigInteger sol = BigInteger.ONE;

            for (int i = 0; i < x; i++) {

                sol = sol.multiply(BigInteger.valueOf(y));

            }

            System.out.println(sol);

    }