n 个整数扫描器的总和

Question

I have to enter an unknown amount of numbers using a scanner. Once the user enters -1, the program needs to print the sum of all the numbers entered and then end the program. The -1 needs to be included in the sum.

Scanner scanner = new Scanner(System.in);
int sum = 0;               

while (true) {
  int read = scanner.nextInt();
  if (read == -1) {
    break;
  }

 read = scanner.nextInt();
 sum += read;
}

System.out.println(sum);

I can't get the correct sum. Can someone help please?

Answer 1

In your while loop you're assigning read two times using scanner.nexInt() and this breaks your logic.

Scanner scanner = new Scanner(System.in);
int sum = 0;               

while (true) {
    int read = scanner.nextInt();
    if (read == -1) {
        sum += read; //have to include -1 to sum
        break;
    }

    //read = scanner.nextInt(); you have to delete this line

    sum += read;
}

System.out.println(sum);
}

Answer 2

Scanner scanner = new Scanner(System.in);
int sum = 0;               
int read = 0;
while (read != -1) {
   read = scanner.nextInt();
   sum += read;
}
scanner.close();
System.out.println(sum);

This works in my case. Closing the scanner will remove the warning too.

Answer 3

The following program will add -1 also in your sum. You are reading read = scanner.nextInt(); two times.

 Scanner scanner = new Scanner(System.in);
        int sum = 0;               

        while (true) {
            int read = scanner.nextInt();


            sum += read;
            if (read == -1) {
                break;
            }
        }

        System.out.println(sum);
    }

Answer 4

This should work

Scanner key = new Scanner(System.in);
int sum = 0;
int read;

while(read != -1) {
    read = key.nextInt();
    sum += read;
}

System.out.println("Sum is: " + sum);

You can't just specify while(true/false) you have to give the loop a proper expression so it can work