ArrayList of Object as the Value of an EnumMap

Question

I've been trying to do this for a little while and it's driving me crazy. I have an EnumMap where I have some enumeration as a key and an arraylist of a self-defined class as the value. So it looks something like this:

private EnumMap<myEnum,List<myObj>> map = 
    new EnumMap<myEnum,List<myObj>>(myEnum.class);

This keeps giving me an error. Not sure exactly what's happening.

EDIT: Yes, myEnum is an enum class. My mistake, I should have mentioned what error is and where it happens. The error occurs when I do the following:

hand.put(myEnum.someEnum, new ArrayList());

The error I get is: - Syntax error on tokens, TypeArgument1 expected instead - Syntax error on token "(", < expected - Syntax error on token "new", delete this token

Is `myEnum` the name of your enum class? If not it, it should be (can't tell from your camel-casing). If so, post the error. Is it a compile error? — Melv, Mar 17 '11 at 03:26
My mistake, I should have mentioned what error is and where it happens. The error occurs when I do the following: hand.put(myEnum.someEnum, new ArrayList()); The error I get is: - Syntax error on tokens, TypeArgument1 expected instead - Syntax error on token "(", < expected - Syntax error on token "new", delete this token — anujahooja, Mar 17 '11 at 03:38
If my answer below doesn't clear it up, you might need to post your entire code block, including the enum definition. It's hard to see what's going wrong from such little context. The error you're getting is fairly odd. — Melv, Mar 17 '11 at 03:42

oakley.aaron · Answer 1 · 2011-03-17T03:43:46.677

0

Also, I assume myEnum refers to the class name and not an instance of class MyEnum and same for myObj. We usually start class names with uppercase letters, so this is a little bit confusing.

hand.put(myEnum.someEnum, new ArrayList());

You need to parameterize the ArrayList with ();

edited Mar 17 '11 at 03:43

answered Mar 17 '11 at 03:21

oakley.aaron

51
4

score 0 · Accepted Answer · answered Mar 17 '11 at 03:38

0

For:

enum Test {
  TEST0,
  TEST1;
}

You would use the EnumMap like this:

EnumMap<Test, List<Object>> map = new EnumMap<Test, List<Object>>(Test.class);
map.put(Test.TEST0, new ArrayList<Object>());

Hopefully that clears up the usage.

answered Mar 17 '11 at 03:38

Melv

2,201
16
14

Yeah, that's exactly what I'm doing (I added in my edit) and I'm still getting the errors I stated above. It should work according to me as well. – anujahooja Mar 17 '11 at 03:42

score 0 · Answer 3 · answered Mar 17 '11 at 03:59

0

   hand.put(myEnum.someEnum, new ArrayList());

should be like this:

   map.put(myEnum.someEnum, new ArrayList<myObj>());

answered Mar 17 '11 at 03:59

Prince John Wesley

62,492
12
87
94

score 0 · Answer 4 · answered Mar 17 '11 at 05:07

melv's code seems to work:

import java.util.*;
enum Color {
    r,g,b;
}
public class Main{
    public static void main(String[] args) {
        EnumMap<Color, List<Object>> map = new EnumMap<Color, List<Object>>(Color.class);
        map.put(Color.r, new ArrayList<Object>());
        map.get(Color.r).add(new Integer(42));
        System.out.println(map.get(Color.r).get(0));
    }
}

ArrayList of Object as the Value of an EnumMap

4 Answers4