I need help with my exercise

package Algorithms;
import java.util.Scanner;

public class exercise {
    public static void InterestMonthly (double n) {
        double AnnualInterest = 0;
        AnnualInterest / = 100.0;
        double MonthlyInterest = AnnualInterest / 12;
    }

    public static void KestiMujor (double n) {
        double Principal = 0, MonthlyInstallment = 0, MonthlyInterest = 0, NumberofMonths = 0;
        double MonthlyInstallment = Principal * MonthlyInterest / (1 - Math.pow (1 + MonthlyInterest, 
                    -NumberMonths));
    }

    public static void main (String [] args) {
        Scanner input = new Scanner (System.in);
        System.out.print ("Annual loan interest rate (in%):");
        double InterestAnnual = input.nextDouble ();
        System.out.println ("");
        System.out.print ("Loan maturity period (NumberofMonths):");
        int NumberofMonths = input.nextInt ();
        System.out.println ("");
        System.out.print ("Credit Principal: All");
        double Principal = input.nextDouble ();
        System.out.println ("");
        double n;
        System.out.println ("Monthly Credit Installment is Euro" + MonthlyInstallment);
        System.out.println ("Monthly loan interest in% is:" + MonthlyInterest (n) * 100.0 + "%");
        System.out.println ("Monthly cash loan interest is:" + MonthlyInterest (n) * 
                MonthlyInstallment + "Euro");
    }
}