How can I use one variable in different methods and classes?

Question

Java

public class Test {
    public static void main(String[] args) {
        int a = 10;
    }

    public static void G() {
        System.out.println(a);
    }
}

Answer 1

Declare it as a class field.

public class Test {
    private static int a;

    public static void main(String[] args) {
        int a = 10;
    }

    public static void G() {
        System.out.println(a);
    }
}