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javaobjectjakarta-eeinstantiationsuperclass

Difference between two types of a super class instantiation in Java

I have an abstract super class called Document and two child classes called Magazine and Book. What is the difference between :

Document book = new Book(); and Book book = new Book();

Thank you in advance.

Solution

  • The difference is for example if you have any information about document only in the document class, like, say, price. By doing

    Book book = new Book();

    you won't be able to get the price of the book, so doing

    Document book = new Book();

    will give you additional information about your object. Note that price is not the best example. I only wanted to show you how the super-/subclass work.