How to cast ArrayList> to Comparable?

Question

I want to add y to the x:

x.put("y", (Comparable) y);

y is defined as:

ArrayList<LinkedHashMap<String, Comparable>> y = new ArrayList<LinkedHashMap<String, Comparable>>();

Output example of

y =[{c=32,a=1, b=2 }, {c=33,a=4, b=5 }]

x is defined as:

LinkedHashMap<String, Comparable> x = new LinkedHashMap<String, Comparable>();

I am getting this error: java.util.ArrayList cannot be cast to java.lang.Comparable where i am trying to : x.put("y", (Comparable) y); and if I remove the comparable it shows that error exist in the eclipse. Any suggestion?

/Elham

Also `Comparable` should usually be typed as well (to define what it can be compared with). — Thilo, May 16 '16 at 08:51
You are trying to assign a type of ArrayList to Comparable.That would not be possible. What exactly do you want to do ? — rootExplorr, May 16 '16 at 09:26

score 1 · Answer 1 · answered May 16 '16 at 09:29

If this is what you want, you can create a class likes so

private static class CompArrayList extends ArrayList<LinkedHashMap<String, Comparable>> implements Comparable
{

    @Override
    public int compareTo(Object o)
    {
        return 0;
    }
}

define whatever you want in the compareTo() method and define y using this class

CompArrayList y = new CompArrayList ()

now y is Comparable and you can add it to your map

score 0 · Answer 2 · answered May 16 '16 at 12:13

0

Well, Thanks for your answers. This problem is solved by replacing x and y with the following: ArrayList> y = new ArrayList<>(); Map x = new HashMap<>();

And then just use: x.put("y", y);

answered May 16 '16 at 12:13

Elham

1

How to cast ArrayList> to Comparable?

2 Answers2