Question

I have an arraylist of arraylist, each inner arraylist contains 2 values, the first is an integer and the second is a string so essentially it would look like: {5, some text}, {12, some more text}, {3, even more text} etc, what I would like to do is take this and sort it so its in descending order of the largest integer to smallest, so the previous example then looks like: {12, some more text}, {5, some text}, {3, even more text}, any help would go a long way thanks in advance

Answer 1

your data structure sounds like it is a ‘Map’ actually.
Maybe you should look into data structures, and collection interfaces and classes in particular…

If you still think that what you have is a ‘List’, then you should make a Collections.sort operation with right kind of Comparator or Comparable

Here is a solution to your data structure if the List is the right one;

import java.util.ArrayList;
import java.util.Collections;

public class InnerObject implements Comparable<InnerObject> {
    Integer index;
    String  name;

    public InnerObject(Integer index, String name) {
        this.index = index;
        this.name = name;
    }

    @Override
    public int compareTo(InnerObject other) {
        return index.compareTo(other.index);
    }

    @Override
    public String toString() {
        return "{" + index + "," + name + "}";
    }

    public static void main(String[] args) {
        ArrayList<InnerObject> list = new ArrayList<InnerObject>();
        list.add(new InnerObject(666, "devil"));
        list.add(new InnerObject(1, "one"));
        list.add(new InnerObject(10, "ten"));

        System.out.println("list before order: " + list);

        Collections.sort(list);

        System.out.println("list after order: " + list);

    }   
}