I have a simple If/Else program that wont seem to work correctly! Can anyone spot the error?

package lab1;

import javax.swing.JOptionPane;

public class Exercise_5 {

public static void main(String[] args) {

String number1 = JOptionPane.showInputDialog("Enter One Number: ");

String number2 = JOptionPane.showInputDialog("Enter Another Number: ");

String operation = JOptionPane.showInputDialog("Enter an Operation, Type 1 for Addition, Type 2 for Subtraciton, Type 3 for Multiplication, Type 4 for Divison: ");

int number1i = Integer.parseInt(number1);

int number2i = Integer.parseInt(number2);

int operationi = Integer.parseInt(operation);

int add = number1i + number2i;

int sub = number1i - number2i;

int multi = number1i * number2i;

int divi = number1i / number2i;

if (number2i == 0){

String num = "Congrat's! you broke the universe and divided by 0";

}

else {

if (operationi == 1) {

int number = sub;

String num = Integer.toString(number);

} else if (operationi == 2) {

int number = add;

String num = Integer.toString(number);

} else if (operationi == 3) {

int number = multi;

String num = Integer.toString(number);

} else if (operationi == 4) {

int number = divi;

String num = Integer.toString(number);

}

else {

String num = "Sorry you did not enter a correct operating value";

}

}

String output = "After calculating the two numbers, the answer is: "+ num;

JOptionPane.showMessageDialog(null, output);

}

}