Turning Learners into Developers
Introduction to Java
Java is a high-level, object-oriented, platform-independent programming language widely used for developing secure, scalable, and high-performance applications. Originally developed by Sun Microsystems and now maintained by Oracle, Java follows the principle Write Once, Run Anywhere (WORA), making it one of the most popular programming languages in the world.
- Java Architecture
Java architecture ensures portability and security through three core components:
- JDK (Java Development Kit)
The JDK is used by developers to write, compile, and debug Java programs. It includes the JRE and development tools like javac, java, and debugger utilities.
- JRE (Java Runtime Environment)
JRE provides the runtime libraries and environment required to run Java applications. It contains the JVM and core class libraries.
- JVM (Java Virtual Machine)
The JVM converts Java bytecode into machine-specific code, enabling Java programs to run on any operating system without modification.
- Core Java Concepts
- Java Basics
Core Java starts with understanding variables, data types (int, float, char, boolean), operators, and input/output operations. These fundamentals form the base of all Java programs.
- Control Statements
Control statements manage the flow of execution:
- if, if-else for decision making
- switch for multiple conditions
- Loops (for, while, do-while) for repetition
- Object-Oriented Programming (OOP)
Java is fully object-oriented and follows five major OOP principles:
Class & Object
A class is a blueprint, and an object is an instance of a class.
Inheritance
Allows one class to acquire properties of another, promoting code reuse.
Polymorphism
Enables methods to perform different tasks using the same name (method overloading and overriding).
Abstraction
Hides internal implementation and shows only essential features using abstract classes and interfaces.
Encapsulation
Wraps data and methods into a single unit and protects data using access modifiers.
- Constructors and Packages
Constructors initialize objects when they are created. Packages help organize Java classes into namespaces, improving maintainability and scalability.
- Access Modifiers
These modifiers ensure data security and controlled access. Java provides access control using:
publicprivateprotecteddefault
- Exception Handling
Exception handling prevents program crashes and ensures smooth execution. Java uses:
trycatchfinallythrowandthrows
- Multithreading in Java
Multithreading allows multiple threads to run simultaneously, improving performance and responsiveness. Threads can be created using:
ThreadclassRunnableinterface
Used heavily in real-time and high-performance applications.
- Java Collections Framework
Collections manage groups of objects efficiently:
List – ArrayList, LinkedList
Set – HashSet, TreeSet
Map – HashMap, TreeMap
Collections improve data handling and performance.
- File Handling in Java
Java supports reading and writing files using standard Java I/O classes.
- Advanced Java
- JDBC (Java Database Connectivity)
JDBC connects Java applications with databases like MySQL and Oracle, enabling CRUD(C – Create, R – Read, U – Update, D – Delete) operations.
- Servlets
Servlets are server-side Java programs that handle HTTP requests and generate dynamic responses.
- JSP (Java Server Pages)
JSP simplifies servlet development by allowing Java code within HTML.
- Session Management
Used to track user data across multiple requests using cookies and sessions.
- Java Frameworks
- Spring & Spring Boot
Used for building enterprise and microservices applications with minimal configuration.
- Hibernate
An ORM framework that simplifies database interactions.
- Microservices
Java supports microservices architecture for scalable cloud-based applications.
