Who owns Java? #

  • 1995: Sun Microsystems created Java.
  • 2009: Oracle Corporation acquired Sun Microsystems, gaining control over Java.
    • Oracle continues to develop and release new Java versions.

Java SE vs Java EE vs Java ME #

📌 Java SE (Standard Edition)

  • Core Java platform with fundamental libraries, JDK, JRE and JVM
  • Core Libraries: Includes java.lang, java.util, java.io, and java.net
  • Database Connectivity: Uses JDBC for interacting with databases
  • Earlier called J2SE

📌 Java EE (Enterprise Edition) → Now Jakarta EE

  • Built on Java SE to support enterprise-grade applications
  • Common Use Cases: Large-scale applications, APIs, and cloud services
    • Servlets & JSP: Enables dynamic web applications
    • JPA (Java Persistence API): Supports database ORM (Object-Relational Mapping)
    • Web Services: Provides REST (JAX-RS) and SOAP (JAX-WS) support
  • Renamed: J2EE > Java EE > Jakarta EE
    • Java EE (Enterprise Edition) was rebranded as Jakarta EE after being transferred from Oracle to the Eclipse Foundation in 2017

📌 Java ME (Micro Edition)

  • Lightweight Java version for mobile, embedded systems, and IoT devices
  • Optimized for Low-Memory Devices: Used in feature phones, smart cards etc.
  • Limited API Support: Subset of Java SE, designed for resource-constrained environments

How has Java evolved over the last few decades? #

📌 Embedded Systems (1990s)

  • Early Purpose: Developed as a platform-independent language for embedded systems
  • Oak to Java: Originally designed for interactive televisions, rebranded as Java in 1995 for general computing

📌 Web Applications (Early 2000s)

  • Adoption in Web Development: Became widely used with Java EE (now Jakarta EE)
  • Dynamic Web Pages: Servlets and JSP enabled interactive and data-driven web applications
  • Framework Evolution: Spring and Hibernate simplified development and improved scalability

📌 Mobile Development (Mid-2000s)

  • Java in Mobile: Became the dominant language for mobile applications
  • Android Boom: In 2008, Google adopted Java as the primary Android language
  • Rise of Kotlin: Introduced in 2017 as an official Android language, but Java remains widely used

📌 Microservices & Cloud (2010s–Present)

  • Shift to Cloud-Native: Java adapted to cloud-based and microservices architectures
  • Spring Boot Revolution: Improved modularity and scalability for microservices
  • Containerization: Java applications now run efficiently on Docker, Kubernetes, and cloud platforms

What is a JAR file? #

📌 Overview

  • What?: Single package containing .class files, images, configuration files, and libraries in one archive.
  • Why?: Makes Java applications easy to package, distribute, and run

📌 Why Use JAR Files?

Feature Why It Matters?
Easy Distribution Packages all dependencies into one file.
Compression Reduces storage and transfer size.
Executable Allows running Java applications with java -jar.
Create Sharable Libraries Used for sharing Java libraries (e.g., mysql-connector.jar).

📌 Creating and running a JAR file

jar cf MyApp.jar *.class #Create a JAR File
java -jar MyApp.jar #Run it (Needs `MANIFEST.MF`)

📌 Manifest File for an Executable JAR: META-INF/MANIFEST.MF

Main-Class: com.example.MainApp

Oracle JDK vs Amazon Corretto vs OpenJDK vs GraalVM #

📌 OpenJDK

  • Purpose: Open-source reference implementation of Java
  • Maintenance: Managed by the Java community and major vendors (IBM, Apple..)
  • Support: Regular updates but no built-in commercial support
  • Best For: Developers and organizations preferring open-source solutions

📌 Oracle JDK

  • Purpose: Official Java distribution from Oracle
  • Features: Premium support and security updates
  • Best For: Enterprises needing long-term support

📌 Amazon Corretto

  • Purpose: Free, OpenJDK-based distribution from Amazon
  • Optimization: Designed for AWS and cloud environments
  • Support: Includes long-term support and performance enhancements
  • Best For: Businesses on AWS seeking cost-effective Java solutions

📌 GraalVM

  • Purpose: An advanced JDK with ahead-of-time (AOT) Native Image compilation
  • Low Resource Usage: Native executables use only a fraction of memory and CPU resources required by a JVM, which improves utilization and reduces costs.
  • Fast Startup: Requires no warmup to run at peak performance
  • Compact Packaging: Native executables are small and easy to deploy in minimal container images
  • Support:
    • Community Edition – Free, open-source, maintained by Oracle
    • Enterprise Edition – Paid support with advanced optimizations and security updates from Oracle
  • Best For:
    • Microservices and serverless computing where fast startup time is critical
    • Cloud-native applications with low memory footprint

What is JCP? #

JCP ensures Java evolves through an open, community-driven process, with JSRs defining major new features.

  • JCP (Java Community Process)
    • Definition: The official process for defining and evolving Java standards
    • Participants: Oracle, corporations, developers, and Java experts
  • How It Works
    • Proposals: New Java platform features are proposed as JSRs (Java Specification Requests)
    • Review & Voting: The Executive Committee reviews, provides feedback, and votes
    • Reference Implementation: A working implementation is developed and tested
  • Example: JSR 330 (Dependency Injection for Java)
    • Purpose: Standardized annotations like @Inject for dependency injection
    • Approval: Passed through the JCP and became part of Java EE 6
    • Impact: Unified dependency injection across different frameworks like Spring and Jakarta EE

JSR vs JEP #

JEPs handle JDK enhancements, while JSRs define major Java standards that require JCP approval.

📌 JEP (JDK Enhancement Proposal)

  • Purpose: Proposes and tracks changes to the JDK (Java Development Kit)
  • Scope: Used for incremental improvements, like language enhancements and performance optimizations
  • Process: Proposed by developers, reviewed internally by the OpenJDK team
  • Approval: Requires review but does not need JCP approval
  • Example:
    • JEP 378: Text Blocks
    • JEP 359: Records
    • JEP 436: Virtual Threads (Project Loom)

📌 JSR (Java Specification Request)

  • Purpose: Defines new Java standards, including APIs, libraries, and frameworks
  • Scope: Used for major changes that require community consensus, such as Java EE (Jakarta EE) specifications
  • Process: Goes through the JCP (Java Community Process) for approval
  • Approval: Voted on by the JCP Executive Committee
  • Example:
    • JSR 330: Standardized Dependency Injection annotations (@Inject)
    • JSR 370: JAX-RS 2.1 (RESTful Web Services)

Java Release Numbering #

Currently - a sequential numbering system like Java 8, Java 9, Java 10,..., Java 21,.., Java 27, ...

Did Java Release Numbering follow a different standard earlier? #

📌 Pre-2017 Versioning (Major.Minor Format)

  • Java versions followed a Major.Minor format, such as Java 1.2, Java 1.4, Java 1.5.
  • Confusing Naming: Java 1.5 was also called Java 5, creating inconsistency.

📌 Post-2017 Versioning (Simplified Integer Format)

  • Format Change: Versioning switched to a simple integer format (Java 9, Java 10, Java 11, etc.).

📌 Why the Change?

  • Simplifies Naming: No more confusion between "Java 1.8" and "Java 8"—just Java 8, Java 9, Java 10, etc.

When are new Java versions released? #

📌 Pre-2017 Release Schedule

  • Irregular Releases: Java versions were released every few years, with long gaps between major versions
  • Notable Versions: Java 5 (2004), Java 6 (2006), Java 7 (2011), Java 8 (2014)
  • Unpredictable Upgrades: Developers had to wait several years for new features and improvements

📌 Post-2017 Release Schedule

  • Six-Month Cycle: Starting with Java 9 (2017), new versions were released every six months (March & September).
  • Predictable Updates: Developers now get regular feature releases without long delays.
  • LTS Every Two (or Three) Years: Java 11 (2018), Java 17 (2021), Java 21 (2023), Java 25 (2025)

📌 Why the Change?

  • Faster Innovation: Shorter cycles allow Java to keep up with modern programming needs.
  • Less Migration Pain: Regular, incremental updates reduce the burden of upgrading from older versions.
  • Clear Roadmap: Developers and businesses can plan ahead for new features and LTS versions.

Long-Term Support (LTS) vs Non-LTS Releases #

📌 Long-Term Support (LTS) Releases

  • Definition: LTS versions receive extended security updates and commercial support for a number of years
  • Major LTS Versions: Java 8 (2014), Java 11 (2018), Java 17 (2021), Java 21 (2023), Java 25 (2025), ....
  • Support Duration: Oracle and other vendors provide LTS support for at least 8 years.
  • Best For: Enterprises and production environments needing stability and long-term maintenance.

📌 Non-LTS Releases

  • Definition: Short-term versions released every six months with new features.
  • Examples: Java 22, 23, 24, 26, 27, ....
  • Support Duration: Typically six months, until the next feature release.
  • Best For: Developers who want early access to new features.

Why Java is Still Popular? #

Java remains a top choice because it is stable, scalable, secure, and works everywhere—making it ideal for enterprise, web, and cloud applications.

Feature Why It Matters? Example
Platform Independence No OS-specific code needed JVM executes bytecode everywhere
Strong Ecosystem Frameworks for every use case Spring Boot, Hibernate, Android SDK
Performance Faster than most interpreted languages Used in Big Data (Hadoop, Kafka)
Memory Management No manual malloc/free Garbage Collector handles memory
Security No direct memory access, strong encryption Used in banking and fintech apps
Community Support Millions of developers and active support Stack Overflow, GitHub
Scalability Powers large-scale cloud apps Netflix, Amazon use Java microservices
Backward Compatibility Avoids costly rewrites Java 8 apps still work in Java 17