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Principal Of OOP:-
Object means a real-world entity such as a pen, chair, table,
computer, watch, etc. Object-Oriented Programming is a
methodology or paradigm to design a program using classes and objects. It
simplifies software development and maintenance by providing some concepts:
- Object
- Class
- Inheritance
- Polymorphism
- Abstraction
- Encapsulation
o Object
o
o Any entity that has state and behavior is
known as an object. For example, a chair, pen, table, keyboard, bike, etc. It
can be physical or logical.
o An Object can be defined as an instance of a
class. An object contains an address and takes up some space in memory. Objects
can communicate without knowing the details of each other's data or code. The only
necessary thing is the type of message accepted and the type of response
returned by the objects.
o Example: A dog is an object because it has states like color, name,
breed, etc. as well as behaviors like wagging the tail, barking, eating, etc.
·
Class
o Collection of objects is called class. It is a logical entity.
o A class can also be defined as a blueprint
from which you can create an individual object. Class doesn't consume any
space.
·
Inheritance
o When one object acquires all the properties
and behaviors of a parent object, it is known as inheritance. It provides code reusability. It
is used to achieve runtime polymorphism.
o
·
Polymorphism
o If one task is performed in different
ways, it is known as polymorphism. For example: to convince the customer differently,
to draw something, for example, shape, triangle, rectangle, etc.
o In Java, we use method overloading and method
overriding to achieve polymorphism.
o Another example can be to speak something; for
example, a cat speaks meow, dog barks woof, etc.
·
Abstraction
o Hiding internal details and showing
functionality is known as
abstraction. For example phone call, we don't know the internal processing.
o In Java, we use abstract class and interface
to achieve abstraction.
o
·
Encapsulation
o Binding (or wrapping) code and data together
into a single unit are known as encapsulation. For example, a capsule, it is wrapped with different
medicines.
o A java class is the example of encapsulation.
Java bean is the fully encapsulated class because all the data members are
private here.
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JVM(Java Virtual Machine):-
· What Is JVM
⇨ JVM, i.e., Java Virtual Machine.
⇨ JVM is the engine that drives the Java code.
⇨ Mostly in other Programming Languages, compiler produce code for a particular system but Java compiler produce Bytecode for a Java Virtual Machine.
⇨ When we compile a Java program, then bytecode is generated. Bytecode is the source code that can be used to run on any platform.
⇨ Bytecode is an intermediary language between Java source and the host system.
⇨ It is the medium which compiles Java code to bytecode which gets interpreted on a different machine and hence it makes it Platform/Operating system independent.
Platform Independent
Java is called platform independent because of Java Virtual Machine. As different computers with the different operating system have their JVM, when we submit a .class file to any operating system, JVM interprets the bytecode into machine level language.
⇨ JVM is the main component of Java architecture, and it is the part of the JRE (Java Runtime Environment)
⇨ A program of JVM is written in C Programming Language, and JVM is Operating System dependent.
⇨ JVM is responsible for allocating the necessary memory needed by the Java program.
⇨ JVM is responsible for deallocating memory space.
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