Sorting Parallel Arrays in Java

Question

I have two arrays, one stores the distance of the cities and the other stores the corresponding population. Everything works fine if the distance of the cities is in ascending o

Answer 1

The good way of doing this is having a city class:

class City{
    private int id;
    private long population;

    //... getters, setters, etc
}

a city comparator class:

class CityPopulationComparator implements Comparator {
    @Override
    public int compare(City c1, City c2) {
        return Long.compare(c1.getPopulation(), c2.getPopulation());
    }
}

And an array list of cities:

ArrayList cities;

and finally sort it using:

Collections.sort(cities, new CityPopulationComparator());

But if you need to have your cities and populations this way, you can write a sort method yourself (a bubble sort for example) and whenever you swap two cities, also swap corresponding pupulations.