1 / 9

Polymorphism

Polymorphism. Overriding Methods refers to when a method in a child class has the same name as a method in a parent class. (know the difference: Overloading Methods refers to two methods in the same class that have the same name.)

neron
Download Presentation

Polymorphism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Polymorphism • Overriding Methods refers to when a method in a child class has the same name as a method in a parent class. • (know the difference: Overloading Methods refers to two methods in the same class that have the same name.) • Sometimes, you create an object of the parent class, but assign it a value of the child class. This is called polymorphism. • When an overridden method in one of those classes is then called, Java decides at run-time which method to call. This run-time decision by Java is called dynamic binding.

  2. Open: • Animal • Dog • Cat • PolymorphismClient

  3. for-each loop • When going through (“traversing”) every element in an array or ArrayList, an efficient way to do so is by using a for-each loop. • Syntax: for (type element : array) { // body of loop } • Demo: ForEachLoopDemo

  4. Static Methods • A static method can be called by using the name of the class itself. You do not need to create an object in order to call the method. • We have been using static methods for a long time: SavitchIn.readLine(); Math.pow(), etc. • This explains why you don’t have to “connect” (create an object of) the SavitchIn class in order to use it. • Open: StaticMethodClass, StaticMethodClient

  5. Static variables • A variable can also be declared with the keyword static • Just like a static method, a static variable is not accessed through an object. It is accessed by using the name of the class itself. • A static variable is also known as a class variable. • Example: see StaticMethodClass & StaticMethodClient

  6. Arrays of Objects • An array is not limited to holding just ints, or chars, or Strings, etc. • An array can hold objects. • Remember, when you connect to (instantiate) a class, you create an object, for example: Numbers x = new Numbers(); • In this example, x is an object. • Demo: Person, ArrayOfObjectsDemo

  7. Types of errors • There are 3 types of errors: • Compiler error: An error that the compiler will point out to you before you can run it • Run-time error: Will not be noticed by the compiler; will crash the program when it runs • Logic Error: does not cause either of the above errors, but makes your program run in a way you do not want it to

  8. Restricting the values in an Arraylist • By default, an ArrayList can store any type of Object. • You can, if you wish, restrict the type of thing that an ArrayList can hold, by using the < > symbols. • Example: ArrayList<Person> z = new ArrayList<Person>;

  9. Assignment • Continue working on Practice Tests and the Case Study.

More Related