Accessing non-static methods containing variables from the class inside the main method?

Question

I'm learning java and was trying to create a simple program to help me find a way (if there is one) to access non-static methods inside the main method of the same class. This is what I have so far

import java.util.Scanner; public class MethodVariables { public int num1; public int num2; public int add = (num1 + num2); public int sub = (num1 - num2); public static void main(String[] args) { Scanner input = new Scanner (System.in); System.out.println("Please enter the first number: "); String num1 = input.nextLine(); System.out.println("Please enter the second number: "); String num2 = input.nextLine(); input.close(); // I know these wouldn't work this way but this is just to show what I am trying to accomplish addition(add); subtraction(sub); } public void addition(int add) { System.out.println("The sum of the two is: " +add); } public void subtraction(int sub) { System.out.println("The diference of the two is: "+sub); } }

If anyone knows what I am overlooking I'd appreciate the help.

Make the addition() and subtraction() methods static as well. You cannot access instance data from a static context in Java. Alternative: create an instance of MethodVariables in main() and use that instance to get at addition() and subtraction() members. — Patrick87
– Patrick87, Commented Sep 18, 2012 at 15:56

pb2q · Accepted Answer · 2012-09-18 16:01:02Z

Sure, just create an instance of the class in main:

MethodVariables instance = new MethodVariables(); instance.addition(num1); instance.subtraction(num2);

Since addition and subtraction are instance methods, then you'll always need an instance of the class to call them on.

ryan0 · Accepted Answer · 2012-09-18 16:06:27Z

This is not related to the original question, but is worth pointing out:

public int add = (num1 + num2);

This will not work as you expect. If you want a function that adds two numbers, just make a function that adds two numbers.

public int add(int num1, int num2) { return num1 + num2; } public int subtract(int num1, int num2) { return num1 - num2; }

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