Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. Inheritance : For any bird, there are a set of predefined properties which are common for all the birds and there are a set of properties which are specific for a particular bird.
Therefore, intuitively, we can say that all the birds inherit the common features like wings, legs, eyes, etc. Therefore, in the object-oriented way of representing the birds, we first declare a bird class with a set of properties which are common to all the birds.
By doing this, we can avoid declaring these common properties in every bird which we create. Instead, we can simply inherit the bird class in all the birds which we create. The following is an example of how the concept of inheritance is implemented. According to Microsoft Polymorphism is one of the main concepts in object-oriented programming, after encapsulation and inheritance. In any program, objects of a derived class can be used as objects of a base class using functions parameters and collections or arrays.
Polymorphism is a very helpful concept when it comes to a single abstract idea used in different ways and shapes. Abstract classes are very simple and generic, and they are always used as base classes. Abstract classes have no meaning on their own, derived classes must be defined to complete the meaning, and they could contain abstract methods or abstract properties.
The following example will explain how we can define an abstract class to make a payroll system using Polymorphism. Worker is an abstract generic class that will be used later on for the other inherited classes. However, there is not much that you can do with them. Since every class is a subclass of Object, a variable of type Object can refer to any object whatsoever, of any type. Similarly, an array of type Object[] can hold objects of any type. The sample source code file ShapeDraw.
You might want to look at this file, even though you won't be able to understand all of it at this time. Even the definitions of the shape classes are somewhat different from those that I have described in this section. For example, the draw method has a parameter of type Graphics. This parameter is required because drawing in Java requires a graphics context.
I'll return to similar examples in later chapters when you know more about GUI programming. However, it would still be worthwhile to look at the definition of the Shape class and its subclasses in the source code. You might also check how an array is used to hold the list of shapes. Here is a screenshot from the program:. If you run the ShapeDraw program, you can click one of the buttons along the bottom to add a shape to the picture. The new shape will appear in the upper left corner of the drawing area.
The color of the shape is given by the "pop-up menu" in the lower right. Once a shape is on the screen, you can drag it around with the mouse. A shape will maintain the same front-to-back order with respect to other shapes on the screen, even while you are dragging it. However, you can move a shape out in front of all the other shapes if you hold down the shift key as you click on it. In the program, the only time when the actual class of a shape is used is when that shape is added to the screen.
Once the shape has been created, it is manipulated entirely as an abstract shape. The routine that implements dragging, for example, works with variables of type Shape and makes no reference to any of its subclasses.
As the shape is being dragged, the dragging routine just calls the shape's draw method each time the shape has to be drawn, so it doesn't have to know how to draw the shape or even what type of shape it is. The object is responsible for drawing itself. If I wanted to add a new type of shape to the program, I would define a new subclass of Shape, add another button, and program the button to add the correct type of shape to the screen.
No other changes in the programming would be necessary. Skip to main content. Side panel. Log in or Sign up. Getting Started. Discussion Forums. Course Introduction. Unit 4: Java Container Library. Unit 5: Exceptions. Unit 6: Recursion. Unit 7: Searching and Sorting. Course Feedback Survey. Certificate Final Exam. Saylor Direct Credit.
About Saylor Academy. Credit University Partners. Print book. Print this chapter. Back to '1. Log in or Sign up to track your course progress, gain access to final exams, and get a free certificate of completion! Objects and Classes Mark as completed. Object-Oriented OO concepts of modularity, abstraction, composition, and hierarchy are very powerful and require intense attention to detail. This chapter gives a detailed presentation of OO as implemented by Java. The terminology in this article is a little different; name-binding is called name-scope.
The chapter begins with an explanation of the data and procedures of a class called class variables and class methods. The class data can be fixed for all objects, in which case, it is called static. Static variables are common to all objects. There is only one copy and, thus only one value, stored in the class. Extending Existing Classes The topics covered in later subsections of this section are relatively advanced aspects of object-oriented programming.
Inheritance and Class Hierarchy The term inheritance refers to the fact that one class can inherit part or all of its structure and behavior from another class. Example: Vehicles Let's look at an example. Since cars, trucks, and motorcycles are types of vehicles, they would be represented by subclasses of the Vehicle class, as shown in this class hierarchy diagram: The Vehicle class would include instance variables such as registrationNumber and owner and instance methods such as transferOwnership.
This brings us to the following Important Fact: A variable that can hold a reference to an object of class A can also hold a reference to an object belonging to any subclass of A.
The test: if myVehicle instanceof Car But you could say: System. Polymorphism As another example, consider a program that deals with shapes drawn on the screen.
Whenever the statement someShape. A beveled rectangle has a triangle cut off each corner: To implement beveled rectangles, I can write a new subclass, BeveledRect, of class Shape and give it its own redraw method. Abstract Classes Whenever a Rectangle, Oval, or RoundRect object has to draw itself, it is the redraw method in the appropriate class that is executed.
Here is a screenshot from the program: If you run the ShapeDraw program, you can click one of the buttons along the bottom to add a shape to the picture. Mark as completed. Jump to Course Syllabus What is Computation?
Learn more. What is the difference between Abstraction and Polymorphism Ask Question. Asked 12 years, 11 months ago. Active 2 years, 5 months ago. Viewed 43k times. Thank you. Improve this question. Lawrence Dol Sambath Prum Sambath Prum 1, 8 8 gold badges 24 24 silver badges 33 33 bronze badges.
It's not homework, but just when I were discussing with my team, these concepts became a bit similar. That's why they make me confused. Abstraction refers to no specific detail of something, and Polymorphism refers to methods of different objects have the same, but do different task. Am I right?
Add a comment. Active Oldest Votes. Static Polymorphism happens at compile time: class colorizer: void colorize shirt s void colorize pants p That's called overloading. Improve this answer. Johannes Schaub - litb Johannes Schaub - litb k gold badges silver badges bronze badges. Here is a quick cheat sheet with one example: Data abstraction means information hiding.
Obviously you can define a class which is both abstract and polymorphic. So, do you feel better about being confused? Norman Ramsey Norman Ramsey k 57 57 gold badges silver badges bronze badges. So, what's the difference between data abstraction and ad-hoc polymorphism? These two are among the most important characteristics of Object Oriented paradigm.
Objects may behave differently depending on the "type" while keeping the same interface. What does this means? For instance an online store system may have two sub-classes of Employee A Internal employees. I hope this helps. SAbbasizadeh 10 10 silver badges 24 24 bronze badges. OscarRyz OscarRyz k gold badges silver badges bronze badges. Excellent explanation! Bill the Lizard Bill the Lizard k gold badges silver badges bronze badges.
Steven A. Lowe Steven A. Lowe While the above statement is correct, I find the "hides details" part misstated - I would rephrase it as something like Abstraction concerns with design details, deciding how the class hierarchy should look like, Encapsulation hides details implementation.
The term "abstraction" with this connotation is also seen in good books like Head First Object-Oriented Analysis and Design , and I quote a statement from there: Whenever you find common behavior in two or more places, look to abstract that behavior into a class, and then reuse that behavior in the common classes Notice the usage of abstraction here: " look to abstract that behavior into a class ".
Abstraction and Polymorphism are similar in nature with a different purpose. For ex. Farruh Habibullaev Farruh Habibullaev 2, 1 1 gold badge 22 22 silver badges 29 29 bronze badges. Or, alternatively, the design provides for polymorphism to the extent that abstraction makes it possible. Abstraction and Polymorphism basically deep down does almost same work in programming.
Now over to coding Part. As we all know that abstract classes, interfaces contains abstract methods We can only estimate how they will work. HENCE, abstract basically helps polymorphism.
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