Java Programming: Lesson 38 - Overloaded Abstract Methods and Abstract Data Structures смотреть онлайн

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In the previous video (https://youtu.be/vrjGwTGksl8), we reviewed a lot of OOP fundamentals and discussed return methods that print, as well as the instanceof keyword. We wrap up our OOP discussion in this video once and for all by reviewing the instanceof keyword again, as well as making a note about overloaded abstract methods as well as arrays or ArrayLists that are defined as type abstract.

y instanceof C returns true if and only if y is instantiated in C or a subclass of C (can be declared in a superclass).

Abstract methods in an abstract class or interface can be overloaded. You could also have some concrete and other abstract versions of an overloaded method. Any VERSIONS of an overloaded method that are abstract in an abstract method or interface must be formally defined in any concrete class that extends the abstract methods (or implements the interface).

We've said that we can declare an object as belonging to an abstract class or interface, as long as it is instantiated in a concrete class that extends it (or extends a subclass of it, ...) For an abstract class A, we can write
A[ ] abstractArray = new A[ ];

It seems like we're instantiating an abstract object, but as long as the elements coming into A are instantiated concretely, this is a valid data structure. We can then apply the instanceof keyword to check the particular data types of objects within the data structure. (All of this applies for ArrayLists as well, but YouTube won't let me have angled brackets which are the less than and greater than signs, required punctuation for an ArrayList. Remember to import java.util.ArrayList; if you take that approach.)

2:20 NEW: Overloaded Abstract Methods
12:58 NEW: Data Structures that Accept An Abstract Class or Interface

Next up? Sorting algorithms! https://youtu.be/jLAw4w5Va7s

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