Java OOP Concepts

Classes and Objects:
- A class is a blueprint or template that defines the properties and behavior of an object.
- An object is an instance of a class, and it has its own set of attributes (data) and methods (functions).
Inheritance:
- A mechanism that allows one class to inherit the properties and behavior of another class.
- The child class inherits all the fields and methods of the parent class and can also add new fields and methods or override the ones inherited from the parent class.
Polymorphism:
- The ability of an object to take on multiple forms.
- Method overriding: When a subclass provides a different implementation of a method that is already defined in its superclass.
- Method overloading: When multiple methods with the same name can be defined with different parameter lists.
Abstraction:
- The concept of showing only the necessary information to the outside world while hiding the internal details.
- Abstract classes and interfaces are used to achieve abstraction in Java.
Encapsulation:
- The concept of bundling data and methods that operate on that data within a single unit (class).
- Access modifiers (public, private, protected) are used to control access to the data and methods.

Single Responsibility Principle (SRP): A class should have only one reason to change.
Open-Closed Principle: A class should be open for extension but closed for modification.
Liskov Substitution Principle: Subtypes should be substitutable for their base types.
Interface Segregation Principle: A client should not be forced to depend on interfaces it does not use.
Dependency Inversion Principle: High-level modules should not depend on low-level modules, but both should depend on abstractions.

Class declaration: public class MyClass { // class body }
Method declaration: public void myMethod() { // method body }
Inheritance: public class ChildClass extends ParentClass { // class body }
Interface declaration: public interface MyInterface { // interface body }
Abstract class declaration: public abstract class MyAbstractClass { // abstract class body }

Use meaningful and descriptive class and variable names.
Keep classes and methods short and focused.
Use access modifiers to control access to data and methods.
Use interfaces and abstract classes to achieve abstraction and polymorphism.
Follow the SOLID principles to write robust and maintainable code.

Classes and Objects:
- Classes define properties and behavior of objects.
- Objects are instances of classes with their own attributes and methods.
Inheritance:
- Inheritance allows a class to inherit properties and behavior from another class.
- Child classes inherit all fields and methods from parent classes and can add new or override inherited ones.
Polymorphism:
- Polymorphism allows objects to take multiple forms.
- Method overriding: Subclasses provide different implementations of methods defined in superclasses.
- Method overloading: Multiple methods with the same name can be defined with different parameter lists.
Abstraction:
- Abstraction shows only necessary information to the outside world, hiding internal details.
- Abstract classes and interfaces achieve abstraction in Java.
Encapsulation:
- Encapsulation bundles data and methods that operate on that data within a single unit (class).
- Access modifiers control access to data and methods.

Single Responsibility Principle (SRP):
- A class should have only one reason to change.
Open-Closed Principle:
- A class should be open for extension but closed for modification.
Liskov Substitution Principle:
- Subtypes should be substitutable for their base types.
Interface Segregation Principle:
- A client should not be forced to depend on interfaces it does not use.
Dependency Inversion Principle:
- High-level modules should not depend on low-level modules, but both should depend on abstractions.

Class declaration:
- public class MyClass { // class body }
Method declaration:
- public void myMethod() { // method body }
Inheritance:
- public class ChildClass extends ParentClass { // class body }
Interface declaration:
- public interface MyInterface { // interface body }
Abstract class declaration:
- public abstract class MyAbstractClass { // abstract class body }

Use meaningful and descriptive class and variable names.
Keep classes and methods short and focused.
Use access modifiers to control access to data and methods.
Use interfaces and abstract classes to achieve abstraction and polymorphism.
Follow the SOLID principles to write robust and maintainable code.

Questions and Answers