How to sort an ArrayList?

Question

I have a List of doubles in java and I want to sort ArrayList in descending order.

Input ArrayList is as below:

List testList = new Arr         


        

Answer 1

You can use Collections.sort(list) to sort list if your list contains Comparable elements. Otherwise I would recommend you to implement that interface like here:

public class Circle implements Comparable {}

and of course provide your own realization of compareTo method like here:

@Override
    public int compareTo(Circle another) {
        if (this.getD()

And then you can again use Colection.sort(list) as now list contains objects of Comparable type and can be sorted. Order depends on compareTo method. Check this https://docs.oracle.com/javase/tutorial/collections/interfaces/order.html for more detailed information.