Java - using static class variables in various methods

Question

I'm new to programming, I need a little help understanding how to use the same variable in many methods. Thanks in advance!

I have a class with some static variable declared before the methods, after I have a first method which calculate some value and a second method which print the results. In the printing method I want to print the initial input but it's always 0. Can someone help me to understand how to update the global variable please?

I tried to return the value from the method but it doesn't update the "global" variable

import java.util.Scanner;

public class Main {
    public static boolean evenNumber = false;
    public static boolean positiveNumber = false;
    public static boolean positiveEvenNumber = false;
    public static int intInputNumber;


    public static void main(String[] args) {
            testEvenPositive();
            printMethod();
        }

        public static int testEvenPositive(){
            System.out.println("Please insert a number, it will be evaluated to even or not and id it's positive or not.");
            Scanner scanner = new Scanner(System.in);
            int intInputNumber = Integer.parseInt(scanner.nextLine());
            if (intInputNumber > 0) {
                positiveNumber = true;}
            if (intInputNumber % 2 == 0) {
                evenNumber = true;}
            if (intInputNumber % 2 == 0 && intInputNumber > 0) {
                positiveEvenNumber = true;}

            return intInputNumber;
        }

        public static void printMethod() {
            System.out.println(Main.intInputNumber + " is an even number: " + evenNumber);
            System.out.println(Main.intInputNumber + " is a positive number: " + positiveNumber);
            System.out.println(Main.intInputNumber + " is a positive even number: " + positiveEvenNumber);
        }
    }

Answer 1

The problem is that you have declared a local variable (intInputNumber) in your testEvenPositive() method. That is what is being changed. You are also ignoring what is being returned. You could instead not declare a local variable and make the method void

public static void main(String[] args) {
            testEvenPositive();
            printMethod();
        }

        public static void testEvenPositive(){
            System.out.println("Please insert a number, it will be evaluated to even or not and id it's positive or not.");
            Scanner scanner = new Scanner(System.in);
            intInputNumber = Integer.parseInt(scanner.nextLine());
            if (intInputNumber > 0) {
                positiveNumber = true;}
            if (intInputNumber % 2 == 0) {
                evenNumber = true;}
            if (intInputNumber % 2 == 0 && intInputNumber > 0) {
                positiveEvenNumber = true;}

            return intInputNumber;
        }

or you could return the variable and then assign it in the main method

public static void main(String[] args) {
            intInputNumber = testEvenPositive();
            printMethod();
        }

        public static int testEvenPositive(){
            System.out.println("Please insert a number, it will be evaluated to even or not and id it's positive or not.");
            Scanner scanner = new Scanner(System.in);
            int intInputNumber = Integer.parseInt(scanner.nextLine());
            if (intInputNumber > 0) {
                positiveNumber = true;}
            if (intInputNumber % 2 == 0) {
                evenNumber = true;}
            if (intInputNumber % 2 == 0 && intInputNumber > 0) {
                positiveEvenNumber = true;}

            return intInputNumber;
        }

I am also of the opinion that you shouldn't use global variables in this case. You can define the variables in your main methods and pass parameters.