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I know these 3 different kinds of declarations:

1) ClassParent var = new ClassParent ();
2) ClassChild var = new ClassChild();
3) ClassParent var = new ClassChild();
   Map<Character, Integer> hash = new HashMap<Character, Integer>();

Third case really common with collections. Could you let me know the difference between all of them, advantages, disadvantages and how you know when to use one of them over the others. Thanks

William
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  • Please have a look at the [help] to find out what are appropriate questions on StackOverflow. Asking for a broad tutorial, and not asking a specific question, is not appropriate and will likely be closed quickly as "too broad". – Erwin Bolwidt Jul 22 '18 at 01:27
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    I feel this is a duplicate of https://stackoverflow.com/q/1413543 – Dawood ibn Kareem Jul 22 '18 at 01:43

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