Beginner Programming in Java - using an integer in a Dialog (JOptionPane) box from another method

I have just started using Java and I am trying to write some code which will take some Inputs using Dialogue boxes and then transform/manipulate those Inputs further

I can get the desired answer if I only use one method but I am trying to use multiple methods. I believe I am incorrectly trying to retrieve values from other methods but I am not sure where I am going wrong. here is what I have written so far - the objective is to take the input numbers and swap them and then add 100 and 50 to the swapped numbers and display in Dialogue boxes.

I believe the error is with the fourth method because when I try to refer to number1 or number2 in the

My code is as follows:

import javax.swing.JOptionPane; 

public class NumberSwap
{

   public static void main(String[] args)
   {
      greeting();
      getFirstNumber();
      getSecondNumber();
      swapNumber(); 
   } 

   public static void greeting()
   {
   // display a dialog box with a message and custom Title
   JOptionPane.showMessageDialog(null,"Welcome to my program!", "Welcome!", JOptionPane.PLAIN_MESSAGE);
   } 

   public static int getFirstNumber()
   {
   // obtain user input from JOptionPane input dialogs
   String firstNumber = JOptionPane.showInputDialog(null, "Please enter a number", "First number?", JOptionPane.QUESTION_MESSAGE);

   // convert String inputs to int values
   int number1 = Integer.parseInt(firstNumber);
   return number1;
   } 

   public static int getSecondNumber()
   {
   // obtain user input from JOptionPane input dialogs
   String secondNumber = JOptionPane.showInputDialog(null, "Please enter a number", "Second number?", JOptionPane.QUESTION_MESSAGE);

   // convert String inputs to int values
   int number2 = Integer.parseInt(secondNumber);
   return number2;
   } 

    public static void swapNumber()
   {
   // swap number1 and number2 in order and increment  the new first number by 100 and the new second number by 50   
   int swap1 = number2+100;
   int swap2 = number1+50;

   JOptionPane.showMessageDialog(null, "new value of first number is " +swap1, "Summary", JOptionPane.INFORMATION_MESSAGE);
JOptionPane.showMessageDialog(null, "new value of second number is " +swap2, "Summary", JOptionPane.INFORMATION_MESSAGE);
System.exit(0);
   }  

}// end class NumberSwap

Solution

In your posted code, you call methods, but you don't use their returned values. You also need to "pass" the returned values to swapNumber.

You should use something like this:

int num1 = getFirstNumber();
int num2 = getSecondNumber();
swapNumber(num1, num2);

with

public static void swapNumber(int number1, int number2)
{
   // swap number1 and number2 in order and increment  the new first number by 100 and the new second number by 50   
   int swap1 = number2+100;
   int swap2 = number1+50;
   // etc

Some related reading (Oracle tutorial):