In Object Oriented Programming abstraction concept the actual implementation is hidden from the user and only required functionality will be accessible or available to the user. Abstraction is a powerful methodology to manage complex systems. Abstraction is managed by well-defined objects and their hierarchical classification.
For example, people do not think of a car as a set of tens of thousands of individual parts. They think of it as a well-defined object with its own unique behavior. This abstraction allows people to use a car to drive to the grocery store without being overwhelmed by the complexity of the parts that form the car. They can ignore the details of how the engine, transmission, and braking systems work. Instead, they are free to utilize the object as a whole.
A powerful way to manage abstraction is through the use of hierarchical classifications. This allows you to layer the semantics of complex systems, breaking them into more manageable pieces.
Binding (or wrapping) code and data together into a single unit are known as encapsulation. It also means to hide your data in order to make it safe from any modification. One way to think about encapsulation is as a protective wrapper that prevents the code and data from being arbitrarily accessed by other code defined outside the wrapper. Access to the code and data inside the wrapper is tightly controlled through a well-defined interface.
In Java, the basis of encapsulation is the class. A class defines the structure and behavior (data and code) that will be shared by a set of objects. Each object of a given class contains the structure and behavior defined by the class, as if it were stamped out by a mold in the shape of the class. For this reason, objects are sometimes referred to as instances of a class. Thus, a class is a logical construct; an object has physical reality.
Inheritance is the process by which one object acquires the properties of another object. This is important because it supports the concept of hierarchical classification. Most people naturally view the world as made up of objects that are related to each other in a hierarchical way, such as animals, mammals, and dogs.
If you wanted to describe animals in an abstract way, you would say they have some attributes, such as size, intelligence, and type of skeletal system. Animals also have certain behavioral aspects; they eat, breathe, and sleep. This description of attributes and behavior is the class definition for animals. If you wanted to describe a more specific class of animals, such as mammals, they would have more specific attributes, such as type of teeth and mammary glands. This is known as a subclass of animals, where animals are referred to as mammals’ superclass.
Inheritance interacts with encapsulation as well. If a given class encapsulates some attributes, then any subclass will have the same attributes plus any that it adds as part of its specialization.
Polymorphism means taking many forms, where ‘poly’ means many and ‘morph’ means forms. It is the ability of a variable, function or object to take on multiple forms. In other words, polymorphism allows you define one interface or method and have multiple implementations.
the concept of polymorphism is often expressed by the phrase “one interface, multiple methods.” This means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler’s job to select the specific action (that is, method) as it applies to each situation.
Polymorphism in java is of two types:
- Run time polymorphism:In Java, runtime polymorphism refers to a process in which a call to an overridden method is resolved at runtime rather than at compile-time. In this, a reference variable is used to call an overridden method of a superclass at run time. Method overriding is an example of run time polymorphism.
- Compile time polymorphism: In Java, compile time polymorphism refers to a process in which a call to an overloaded method is resolved at compile time rather than at run time. Method overloading is an example of compile time polymorphism. Method Overloading is a feature that allows a class to have two or more methods having the same name but the arguments passed to the methods are different. Unlike method overriding, arguments can differ in:
- Number of parameters passed to a method
- Datatype of parameters
- Sequence of datatypes when passed to a method.