java sort list of objects by specifiable attribute

Question

I want to sort a List of objects by a specified attribute of those objects and I want to choose which attribute should be used for sorting. Example:

class          


        

Answer 1

It would be much simpler to use custom comparators:

To sort by name:

Arrays.sort(carArray, Comparator.comparing(Car::name));

To sort by colour:

Arrays.sort(carArray, Comparator.comparing(Car::colour));

So you could modify getSortedArray():

public static Car[] getSortedArray(Car[] carArray, Comparator comparator) {
    Car[] sorted = carArray.clone()
    Arrays.sort(sorted, comparator);
    return sorted;
}

And call it like this:

Car[] sorted = getSortedArray(carArray, Comparator.comparing(Car::name));

Edit:

If you use a language version that does not support these features, you can create the comparators by explicitly creating a nested class that implements the Comparator interface.

This, for example, is a singleton Comparator that compares Car instances by name:

static enum ByName implements Comparator {
    INSTANCE;

    @Override
    public int compare(Car c1, Car c2) {
        return c1.name().compareTo(c2.name());
    }
}

Then call:

Car[] sorted = getSortedArray(carArray, ByName.INSTANCE);