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Why do I get null pointer exception in map?
map is declared as Map map. If this is the case, then your if statement doesn’t do what you think it does. It actually gets the Boolean object from the map and tries to unbox it to a primitive bool. If there is no value with the key “A”, then you will get a NullPointerException.
Where do I find the null reference exception?
A good place to do that is in the class constructor. Assuming you use the default constructor : Is DbNull is not the same as Is NULL! You need to check for ‘IS NULL’, instead. That is why you are getting Null Reference Exceptions.
When does a nullreferenceexception occur in a class?
NullReferenceException or Object reference not set to an instance of an object occurs when an object of the class you are trying to use is not instantiated. For example: Assume that you have a class named Student.
How to avoid null reference when adding object to list?
You have it defined as a List type but you never initialize it to an instance of that type. Try initializing it in a constructor: OrderiTems is null. Try implementing set/get or storing an empty list into OrderiTems in the constructor. You need to instanciate the list before starting using it.
When do hashmaps throw the null pointer exception?
If nextLine [0] and nextLine [6] aren’t null, because the println call above worked, then that leaves dataMap. Did you do dataMap = new HashMap (); somwehere? My case was different as Usually, hashmaps throw the null pointer exception when trying to read a key that is not there e.g I have a
Why do I get NullPointerException in Java?
What is strange is that I have run this code without the above line and the call to nextLine [0] and nextLine [6] work exactly as expected – that is they give me back elements of a csv file. I declare and initialise the HashMap with the code
What happens if nextline is NOT NULL in Java?
Well, there are three objects accessed on that line. If nextLine [0] and nextLine [6] aren’t null, because the println call above worked, then that leaves dataMap. Did you do dataMap = new HashMap (); somwehere?