Java - AYUDA CON EJERCICIOS

public int multiplicar(int x, int y) {

    int m = 0;

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

        m += x;

    }

    return m;

}

public void numerosComprendidos(int x, int y) {

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

        //System.out.println(i);

        System.out.print(i + (i + 1 <= y ? ", " : "\n"));

    }

}

public void imprimirEstrellas(int n) {

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

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

            System.out.print("*");

        }

        System.out.println();

    }

}