Question

I have 3 lists so the order of their elements is important:

names: [a, b, c, d]
files: [a-file, b-file, c-file, d-file]
counts: [a-count, b-count, c-count, d-count]

I need to sort all of them alphabetically based on the List<String> names elements.
Can someone explain me how to do this?

Answer 1

Create a class to hold the tuple:

class NameFileCount {
    String name;
    File file;
    int count;

    public NameFileCount(String name, File file, int count) {
        ...
    }
}

Then group the data from the three lists into a single list of this class:

List<NameFileCount> nfcs = new ArrayList<>();
for (int i = 0; i < names.size(); i++) {
    NameFileCount nfc = new NameFileCount(
        names.get(i),
        files.get(i),
        counts.get(i)
    );
    nfcs.add(nfc);
}

And sort this list by name, using a custom comparator:

Collections.sort(nfcs, new Comparator<NameFileCount>() {
    public int compare(NameFileCount x, NameFileCount y) {
        return x.name.compareTo(y.name);
    }
});

(Property accessors, null checking, etc omitted for brevity.)