Object-oriented Programming in Java

Key Principles:
- Encapsulation: Bundling data (attributes) and methods (functions) that operate on the data together.
- Inheritance: Mechanism to create a new class based on an existing class to promote code reuse.
- Polymorphism: Ability to treat objects of different classes through a common interface, allowing methods to perform differently based on the object that invokes them.
- Abstraction: Hiding complex implementation details and exposing only the necessary features of an object.

Basic Structure:
- Class definition: public class ClassName { }
- Main method: public static void main(String[] args) { }
Data Types:
- Primitive types: int, float, double, char, boolean
- Reference types: Objects and arrays.
Control Statements:
- Conditional: if, else if, else, switch
- Loops: for, while, do-while
Methods:
- Defined using: returnType methodName(parameters) { }
- Overloading: Multiple methods with the same name but different parameters.

Popular Frameworks:
- Spring: For building enterprise applications, offers dependency injection and aspect-oriented programming.
- Hibernate: ORM framework that simplifies database interactions by mapping Java classes to database tables.
- JavaServer Faces (JSF): For building user interfaces for web applications.
- Apache Struts: For creating MVC-based web applications.

Mechanism:
- Use try, catch, and finally blocks to manage exceptional conditions.
Exception Types:
- Checked Exceptions: Must be declared or handled, e.g., IOException.
- Unchecked Exceptions: Runtime exceptions, e.g., NullPointerException.
Custom Exceptions: Can be created by extending Exception or RuntimeException.

Core APIs:
- Java Collections Framework: Interfaces and classes for data structures (e.g., List, Set, Map).
- Input/Output (I/O): Classes for reading and writing data, e.g., File, InputStream, OutputStream.
- Concurrency: Utilities for multithreading, e.g., Thread, Runnable, ExecutorService.
Web APIs:
- Servlet API: For creating web applications.
- Java Persistence API (JPA): For managing relational data in Java applications.
Java Standard Library: Comprehensive set of pre-written classes and methods for various tasks.

Encapsulation: Combines data and methods within a class, promoting data hiding and integrity.
Inheritance: Facilitates code reuse by allowing new classes to inherit attributes and behaviors from existing classes.
Polymorphism: Enables objects of different classes to be treated as instances of a parent class, enhancing flexibility in method implementation.
Abstraction: Simplifies interactions by concealing complex internal workings and presenting only necessary functionalities to the user.

Class Structure: Classes are defined with the syntax public class ClassName { }, establishing the building blocks of Java programs.
Main Method: The entry point of any Java application is defined as public static void main(String[] args) { }, essential for program execution.
Data Types:
- Primitive types include int, float, double, char, and boolean, serving as basic building blocks.
- Reference types consist of objects and arrays for more complex data handling.
Control Statements:
- Conditional statements: if, else if, else, and switch allow for decision-making processes in code.
- Looping constructs: for, while, and do-while execute repetitive tasks based on conditions.
Methods:
- Method definition syntax: returnType methodName(parameters) { } allows for code modularity.
- Overloading enables multiple versions of a method name, distinguished by parameter types or counts, enhancing flexibility.

Spring Framework: Provides infrastructure support for enterprise-level applications, incorporating features such as dependency injection and aspect-oriented programming.
Hibernate: An Object-Relational Mapping (ORM) framework that simplifies database operations by connecting Java classes to database tables.
JavaServer Faces (JSF): A component-based framework for building user interfaces in web applications, facilitating easy interaction with server-side data.
Apache Struts: An MVC framework designed for developing web applications, promoting a clean separation between the model, view, and controller.

Structure: Manages exceptions using try, catch, and finally blocks, allowing for controlled error handling.
Exception Types:
- Checked Exceptions: Must be explicitly declared or caught during compilation, such as IOException.
- Unchecked Exceptions: Include runtime exceptions like NullPointerException, which do not require explicit handling.
- Custom Exceptions: Users can create exceptions by subclassing Exception or RuntimeException, offering tailored error handling.

Java Collections Framework: Comprises interfaces and classes aiding in the management of data structures, such as List, Set, and Map.
Input/Output (I/O): Provides classes for data reading and writing operations, including File, InputStream, and OutputStream.
Concurrency Support: Offers tools for managing multithreading with classes like Thread, Runnable, and ExecutorService.
Web APIs:
- Servlet API: Enables the development of web applications using Java as the back-end framework.
- Java Persistence API (JPA): Simplifies data management by providing an ORM solution for relational databases.
- Java Standard Library: A comprehensive collection of pre-written classes and methods for diverse programming tasks, facilitating development efficiency.