Hashmap contains key return false even when key exists

Question

I have made a hashmap Map percentages= new HashMap();, I have entered values and keys into it and that was successful, but when I try to get the or try ContainsKey method then it returns false.

Please see the attached screen shot: enter image description here

Without code, we can't tell what you did wrong. For all we know, maybe you have a string of `42` as a key in the `HashMap`, and are trying to do a `ContainsKey()` with an integer `42`. That's just one way you could have gotten it wrong. And if your post is to be believed, doesn't look like you are using a typed `HashMap`, so it is quite possible. Or maybe you are experiencing a subtle bug related to auto boxing. Who knows? — sstan, Jun 25 '15 at 02:31

score 1 · Answer 1 · answered Jun 25 '15 at 02:17

1

you are calling contains on new ArrayList object and not on Map

answered Jun 25 '15 at 02:17

Juned Ahsan

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But that new ArrayList is supposed to contain map key set right ? – Rookie007 Jun 25 '15 at 02:18
I tried calling containsKey on the map at first see the image – Mr_Hmp Jun 25 '15 at 02:20

score 0 · Accepted Answer · answered Jun 25 '15 at 02:35

When assigning values to Map, you may used different datatype and when checking for key, you are using integer, it won't work.

Map a = new HashMap();
    a.put("1", 12);
    a.put("2", 32);

    System.out.println(a.containsKey(1));

This will always return false.

Hashmap contains key return false even when key exists

2 Answers2