вроде все правильно...
package com.javarush.task.task16.task1632;
import java.util.Scanner;
public class Fifth extends Thread{
@Override
public void run() {
Scanner scanner = new Scanner(System.in);
int sum = 0;
try {
while (Thread.currentThread().isInterrupted()) {
String s = scanner.nextLine();
if (s.equals("N")){
Thread.currentThread().interrupt();
System.out.println(sum);
}
sum = sum + Integer.valueOf(s);
}
}catch (NumberFormatException exception){}
}
}