Why the below code throws null pointer excetion in test.put(1,"sd")
public class HashMap {
@SuppressWarnings("null")
public static void main(String a[]){
Map test = null;
test.put(1, "sd");
System.out.println(test);
}
}
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dimo414
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user3839699
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This question is not related to maps. – user253751 Sep 18 '14 at 04:59
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1By the way. The warning you suppressed is warning you exactly about the mistake you made. – helios Sep 18 '14 at 05:00
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man you need to read about Map. first do that and then try something cause i see a huge gap here – vikeng21 Sep 18 '14 at 05:01
1 Answers
0
Because test is null.
Map test = null;
Try instantiating the map instead.
Map test = new HashMap();
Or try a parameterized map:
Map<Integer,String> test = new HashMap<Integer,String>();
nostromo
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but then i am inserting value -- test.put(1, "sd"); Then y an exception – user3839699 Sep 18 '14 at 04:59
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You can't insert a value into a null object. The object must exist before you can add a value. – nostromo Sep 18 '14 at 05:01
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@user3839699 what, exactly, do you think you are inserting a value *into*? You haven't created a `Map` to put your data in - you're explicitly using `null`.... – dimo414 Sep 18 '14 at 05:01