Finding a key in a hashmap

Question

i have created a hashmap with Color Objects as keys. My source code looks like this:

HashMap<Color,Integer> hm = new HashMap<Color,Integer>();

Now i would like to check if there is already a Color Object as a key in the HashMap. So i tried this:

if (hm.get(colorObject) != null){

Unfortunately it returns false, although the Color is the same. I print the color in the console and it is always java.awt.Color[r=254,g=0,b=0]. I also tried the method containsKey from HashMap.

So what is wrong? How can i check if there is an Object in the hashmap?

It should work if the `Color` object properly implements `equals` and `hashCode` (which i assume it does, since it's aparently `java.awt.Color`). — NilsH, May 12 '13 at 09:04
Its possible that you added null for this color in the map by mistake. — Ashwinee K Jha, May 12 '13 at 09:11

score 2 · Accepted Answer · answered May 12 '13 at 09:06

2

try if(hm.containsKey(colorObject))

answered May 12 '13 at 09:06

kelunik

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OP has already tried that. – NilsH May 12 '13 at 09:07
I tried containsKey again and it worked. Thanks. But i don't know why. – JavaForAndroid May 12 '13 at 09:09
It's magic, it works..^^ Sorry, I missed that @NilsH – kelunik May 12 '13 at 09:14

score 0 · Answer 2 · answered May 12 '13 at 09:22

I tried this:

final Map<Color, Integer> colors = new HashMap<>();
colors.put(new Color(3030), 1);
System.out.println(colors.get(new Color(3030)));

and the output was 1, as expected. Therefore your problem is not as general as you have scoped it in your question.

Finding a key in a hashmap

2 Answers2