Question

So I just learnt today how to make a secondary class take into account a variable from the main class.

But how do I do the reverse that is a variable with a value in the secondary class have that same value in the main class?

here the code:

package maiN;

public class nintodec {
    public static void convertToDec(String number) {
        number = new StringBuffer(number).reverse().toString();
        int numero = 0;
        int mult = 1;
        for (int i = 0; i < number.length(); i++) {
            int digit = number.charAt(i);
            digit = Character.getNumericValue(digit);
            numero = numero + (mult * digit);
            mult = mult * 9;
        }
    }
}

as you can see numero is calculated in the secondary class and i want the value returned to this main class:

package maiN;

import java.util.Scanner;

public class director {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner keyboard = new Scanner(System.in);
        System.out.println("enter a base nine number");
        String number = keyboard.next();
        nintodec.convertToDec(number);
        System.out.println(numero); // here numero is not recognized for is from
                                    // the other class
    }
}

Answer 1

you want to make convertToDec() return an int, so change the void you have there to int. Then you will want to add return numero; to the end of your convertToDec method.

This will make it so that int will get passed back and you can use it later.

then in main you want to do

//other code..
String number=keyboard.next();
int numero = nintodec.convertToDec(number);  
System.out.println(numero)

Also, please try reading & learning about some of Java's standards in terms of naming and the like, it will make your code much easier to maintain and read in the future.

Answer 2

Your issue is about variable scope ,and you can rectify that with following.

You have two options:

Print out the value inside the convertToDec if you are done with your calculation, as a result, numero variable no need to be visible there in order to be printed.
Instead of return void, you should return int so you can use it for further calculation inside director class

your function signature change from

public  static void convertToDec(String number){

to

public  static int convertToDec(String number){

Note: do not forget to use return numero in your function.

When you return a type int , the value of numero variable can be visible to your secondary class so you expand its scope

how to return a variable to the main class from anot main class

2 个答案: