Loop Ending With ESC Button

I'm doing old projects . This loop will take any number, sum it and when you press the ESC button the loop will end and you will be shown the sum.

Java Code:

import java.util.Scanner;
class Sum {
public static void main(String[] args) {
int sum = 0;
System.out.println("Please write a number, end with ESC button");
Scanner in = new Scanner(System.in);
int number = in.nextInt();

[Code] ....

Here is the error

Java Code:

Exception in thread "main" java.lang.Error: Unresolved compilation problem:

The operator != is undefined for the argument type(s) int, null mh_sh_highlight_all('java');

So well, the int ain't boolean says itself. also null ain't that for string ?

The original project was to get the number using one dialog box, convert the string to int and run the loop, so when you pressed ESC there then the return would be null.