Challenge:

Swap positions in a list

Specifications:

Your program should accept as its first argument a path to a filename.
The file contains several test cases, one on each line.
Each test case is a list of numbers, supplemented with positions to be swapped.
List and positions are separated by a colon.
Positions start with 0.
There may be more than one position swaps, separated by a comma.
Positions swaps are processed left to right.

Solution:

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class SwapElements {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner input = new Scanner(new File(args[0]));

        while (input.hasNextLine()) {
            String[] temp = input.nextLine().split(":");
            printSwapped(swapList(temp[0], temp[1]));
        }
    }

    public static void printSwapped(List<String> list) {
        StringBuilder result = new StringBuilder();

        for (String s : list) {
            result.append(' ').append(s);
        }

        System.out.println(result.substring(1));
    }

    public static List<String> swapList(String input, String swapKey) {
        List<String> result = modifyToList(input);

        for (String s : swapKey.split(",")) {
            String[] keys = s.split("-");
            int index1 = Integer.parseInt(keys[0].substring(1));
            int index2 = Integer.parseInt(keys[1]);

            String target1 = result.get(index2);
            String target2 = result.get(index1);

            result.set(index1, target1);
            result.set(index2, target2);
        }

        return result;
    }

    public static List<String> modifyToList(String list) {
        List<String> result = new ArrayList<>(list.length());

        for (String s : list.split("\\s+")) {
            result.add(s);
        }

        return result;
    }   
}

Sample Input:

1 2 3 4 5 6 7 8 9 : 0-8
1 2 3 4 5 6 7 8 9 10 : 0-1, 1-3

Sample Output:

9 2 3 4 5 6 7 8 1
2 4 3 1 5 6 7 8 9 10

It's actually been a while since I did one of these and I get the feeling it shows. The solution itself, of course, works, but I get the sense that it's memory intensive and/or slow. I'd mostly like to focus on optimizing speed, what do you think?