Shoot for the Win

import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class ShootForTheWin {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        List<Integer> targetsSequence = Arrays
                .stream(scanner.nextLine().split(" "))
                .map(Integer::parseInt)
                .collect(Collectors.toList());

        int shots = 0;
        String input = scanner.nextLine();
        while (!input.equals("End")) {
            int indexTarget = Integer.parseInt(input);

            if (isValidIndex(indexTarget, targetsSequence.size() - 1) && targetsSequence.get(indexTarget) != -1) {

                int currentNumber = targetsSequence.get(indexTarget);
                targetsSequence.set(indexTarget, -1);
                for (int i = 0; i <= targetsSequence.size() - 1; i++) {

                    if (targetsSequence.get(i) != -1) {
                        if (targetsSequence.get(i) > currentNumber) {
                            targetsSequence.set(i, targetsSequence.get(i) - currentNumber);
                        } else {
                            targetsSequence.set(i, targetsSequence.get(i) + currentNumber);
                        }
                    }
                }
                shots++;
            } else if (!isValidIndex(indexTarget, targetsSequence.size() - 1)) {

            }

            input = scanner.nextLine();
        }
        String output = "";
        for (int i = 0; i < targetsSequence.size(); i++) {
            output += targetsSequence.get(i) + " ";
        }
        System.out.println("Shot targets: " + shots + " -> " + output);
        scanner.close();
    }

    private static boolean isValidIndex(int indexTarget, int i) {
        return indexTarget >= 0 && indexTarget <= i;
    }
}