Java ArrayList String Selection Sort

Question

I'm struggling mightly on doing selection sort on an ArrayList of Strings to alphabetize them. I have no idea what I'm doing wrong. But its just not working properly for me. Heres my code.

    ArrayList<String> list = new ArrayList<String>();
    list.add("a");
    list.add("d");
    list.add("f");
    list.add("c");
    System.out.println(list);
    int i;
    int j;
    int minValue;
    int minIndex;

    for (i=0; i<list.size(); i++) {
        System.out.println(list.get(i));
        char iLetter = (list.get(i).charAt(0));
        int iValue = (int) iLetter;
        minValue = iValue;
        minIndex = i;
        for(j=i; j<list.size(); j++) {
            char jLetter = list.get(j).charAt(0);
            int jValue = (int) jLetter;
            if (jValue < minValue) {
                minValue = jValue;
                minIndex = j;
            }
        }
        if(minValue < iValue) {
            int temp = iValue;
            char idx = list.get(minIndex).charAt(0);
            int idxValue = (int) idx;
            iValue = idxValue;
            idxValue = temp;

        }
    }
    System.out.println(list);
}

It still prints it out as ["a", "d", "f", "c"]

Answer 1

You are not updating your list anywhere in your loop, so it remains unsorted.

In order to actually swap elements of the list, replace:

if(minValue < iValue) {
    int temp = iValue;
    char idx = list.get(minIndex).charAt(0);
    int idxValue = (int) idx;
    iValue = idxValue;
    idxValue = temp;
}

with:

if(minValue < iValue) {
    Collections.swap (list, i, minIndex);
}

Collections.swap performs the following modification:

list.set(i, list.set(minIndex, list.get(i)));

Now the output will be

[a, c, d, f]