What are the 4 pillars of Object Oriented Programming?

You will learn about the four pillars that hold together the object oriented programming, which are:

Abstraction.

Encapsulation.

Polymorphism.

Inheritance.

What are four principles of OOP, How aggregation is different than Composition ?

Encapsulation. Encapsulation is the mechanism of hiding of data implementation by restricting access to public methods.

Abstraction.

Inheritance.

Polymorphism.

The “three pillars” of OOP are generally taken to be:

Encapsulation.

Inheritance.

Polymorphism.

Real Life Difference Between Encapsulation and Abstraction: Encapsulate means to hide. Encapsulation is also called data hiding.You can think Encapsulation like a capsule (medicine tablet) which hides medicine inside it. Encapsulation is wrapping, just hiding properties and methods.

Generally, the ability to appear in many forms. In object-oriented programming, polymorphism refers to a programming language’s ability to process objects differently depending on their data type or class. More specifically, it is the ability to redefine methods for derived classes.

Difference between Static methods and Instance methods. Instance method are methods which require an object of its class to be created before it can be called. Static methods are the methods in Java that can be called without creating an object of class. Static method means which will exist as a single copy for a class

Encapsulation is one of the fundamental concepts in object-oriented programming (OOP). It describes the idea of bundling data and methods that work on that data within one unit, e.g., a class in Java. This concept is also often used to hide the internal representation, or state, of an object from the outside.

Overloading occurs when two or more methods in one class have the same method name but different parameters. Overriding means having two methods with the same method name and parameters (i.e., method signature). One of the methods is in the parent class and the other is in the child class.

Abstraction is one of the key concepts of object-oriented programming (OOP) languages. Its main goal is to handle complexity by hiding unnecessary details from the user. That’s a very generic concept that’s not limited to object-oriented programming. You can find it everywhere in the real world.

Inheritance. In object-oriented programming, inheritance enables new objects to take on the properties of existing objects. A class that is used as the basis for inheritance is called a superclass or base class. A class that inherits from a superclass is called a subclass or derived class.

Abstraction is process of hiding the implementation details and showing only the functionality. Abstraction in java is achieved by using interface and abstract class. Interface give 100% abstraction and abstract class give 0-100% abstraction. A class that is declared as abstract is known as abstract class.

Yes when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class. Same case applies to abstract classes.

Likewise in Object-oriented programming, abstraction is a process of hiding the implementation details from the user, only the functionality will be provided to the user. In Java, abstraction is achieved using Abstract classes and interfaces.

3) It must be overridden. An abstract class must be extended and in a same way abstract method must be overridden. 4) A class has to be declared abstract to have abstract methods. Note: The class which is extending abstract class must override all the abstract methods.

1.Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior. 2.Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

The ability of a subclass to override a method allows a class to inherit from a superclass whose behavior is “close enough” and then to modify behavior as needed. The overriding method has the same name, number and type of parameters, and return type as the method that it overrides.

Abstract classes cannot be instantiated, but they can be subclassed. In other words, a class that is declared with abstract keyword, is known as abstract class in java. It can have abstract(method without body) and non-abstract methods (method with body).

Abstract classes are similar to interfaces. You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation. However, with abstract classes, you can declare fields that are not static and final, and define public, protected, and private concrete methods.

There is only static fields in interface that dosen’t need to initialized during object creation in subclass and the method of interface has to provide actual implementation in subclass .So there is no need of constructor in interface. That’s why we can not define constructor in the interfaces.