Exception when working with Map collections

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We have some questionable code. It's time to deploy an agent to intercept (catch) exceptions. Here's the code: HashMap<String, String> map = new HashMap<String, String>(null); map.put(null, null); map.remove(null); Agent, your task, as usual, is to catch the exception and display it on the screen. Don't forget to only display the exception type.

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Michael

Level 10 , Dresden, Germany

28 August 2021, 08:15

Hello Kent, concerning the null value in a HashMap I found this on stackoverflow (see: HashMap with null as a key) "HashMap does not call hashcode when null is passed." As I understand this statement, you cannot remove something from a null value (even if it is 'null' which you want to remove) in a HashMap and therefore an error is created.

Kent Hervey Software Engineer/Consult at Zeal IT Consultants

Expert

6 February 2020, 19:58

I don't know what this does: HashMap<String, String> map = new HashMap<String, String>(null); I thought this was a clue: HashMap public HashMap(int initialCapacity) Constructs an empty HashMap with the specified initial capacity and the default load factor (0.75). Parameters: initialCapacity - the initial capacity. Throws: IllegalArgumentException - if the initial capacity is negative.

Kent Hervey Software Engineer/Consult at Zeal IT Consultants

Expert

6 February 2020, 19:59

but running it showed the exception was different I still don't know what the null does, but I have passed this task