What is Java?
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible.
Key Characteristics:
- Platform Independent
- Object-Oriented
- Robust & Secure
- Multithreaded
- High Performance
- Dynamic
Philosophy:
"Write Once, Run Anywhere"
WORA - This means that compiled Java code can run on all platforms that support Java without the need for recompilation.
Java History & Evolution
Modern Java Evolution
Current Status: Java 21 is the latest LTS (Long Term Support) version as of 2023
Key Java Features
1. Platform Independence
- Bytecode compilation
- JVM abstraction layer
- No platform-specific code
2. Object-Oriented
- Everything is an object
- Encapsulation, Inheritance, Polymorphism
- Abstraction support
3. Robust & Secure
- Strong memory management
- Exception handling
- No pointer arithmetic
- Bytecode verification
4. Multithreaded
- Built-in threading support
- Synchronized methods
- Thread-safe operations
5. High Performance
- Just-In-Time (JIT) compilation
- Optimized bytecode execution
- Garbage collection
6. Dynamic & Distributed
- Dynamic loading of classes
- Network-aware
- RMI, Web Services support
Java Application Domains
Enterprise Applications
- Banking systems (ICICI, HDFC)
- E-commerce platforms (Amazon, eBay)
- ERP systems (SAP, Oracle)
- Government applications
Web Development
- Server-side development
- Spring Framework applications
- RESTful web services
- Microservices architecture
Mobile Development
- Android applications
- Mobile enterprise apps
- Cross-platform solutions
Big Data & Analytics
- Apache Hadoop ecosystem
- Apache Spark
- ElasticSearch
- Apache Kafka
Desktop Applications
- Swing/JavaFX GUIs
- IDEs (NetBeans, Eclipse, IntelliJ)
- Cross-platform desktop apps
Java Ecosystem
Development Tools:
- IDEs: IntelliJ IDEA, Eclipse, NetBeans
- Build Tools: Maven, Gradle, Ant
- Testing: JUnit, TestNG, Mockito
Frameworks:
- Spring: Dependency Injection, Web MVC
- Hibernate: ORM framework
- Apache Struts: Web framework
Why Learn Java?
Industry Demand
- #1 programming language for enterprise
- High-paying job opportunities
- 3+ billion devices run Java
- Large developer community
Learning Benefits
- Strong OOP foundation
- Platform independence skills
- Memory management understanding
- Multithreading expertise
Career Paths
- Backend Developer
- Full-Stack Developer
- Android Developer
- Big Data Engineer
- DevOps Engineer
- Architect
Average Salary: ₹4-15 LPA for freshers in India
Previous Year Exam Questions
Q1. (GTU Summer 2022) Explain the features of Java programming language with suitable examples.
Solution:
1. Platform Independence: Java programs are compiled into bytecode, which runs on JVM. Same .class file runs on Windows, Linux, macOS.
// HelloWorld.java compiles to HelloWorld.class
// Runs on any platform with JVM installed2. Object-Oriented: Everything is treated as an object.
class Student {
private String name; // Encapsulation
public String getName() { return name; } // Method
}3. Robust: Strong memory management and exception handling.
try {
int result = 10/0; // Runtime exception handled
} catch(ArithmeticException e) {
System.out.println("Division by zero!");
}Q2. (GTU Winter 2021) Compare Java with C++ programming language.
Solution - Java vs C++ Comparison:
| Feature | Java | C++ |
|---|---|---|
| Platform | Platform Independent | Platform Dependent |
| Memory Management | Automatic (Garbage Collection) | Manual (new/delete) |
| Pointers | No explicit pointers | Supports pointers |
| Inheritance | Single inheritance only | Multiple inheritance |
| Compilation | Bytecode (.class) | Machine code (.exe) |
Q3. (GTU Summer 2020) Write a short note on "Write Once, Run Anywhere" concept of Java.
Solution:
"Write Once, Run Anywhere" (WORA) is Java's key philosophy that enables platform independence.
How WORA Works:
- Source Code: Written in .java files
- Compilation: javac compiles to bytecode (.class files)
- Execution: JVM interprets bytecode on any platform
HelloWorld.java → javac → HelloWorld.class → JVM → Output
(Platform Independent Bytecode)Benefits:
- Cost-effective development
- Reduced time-to-market
- Wide platform reach
- Maintenance efficiency
Example: A Java banking application developed on Windows can run on Linux servers and macOS development machines without any code changes.
Lecture Summary
Key Concepts Covered:
- Java definition and philosophy
- Historical evolution from Oak to Java 21
- Platform independence (WORA)
- Core features and characteristics
- Application domains and ecosystem
Learning Outcomes Achieved:
- ✅ Understand Java's history and evolution
- ✅ Comprehend platform independence
- ✅ Identify Java's key features
- ✅ Recognize Java application areas
- ✅ Compare Java with other languages
Next Lecture: Java Environment Setup & First Program
Topics: JDK installation, IDE setup, Hello World program, compilation process
Assignment & Lab Work
Lab Exercise 1:
- Research and create a timeline of Java versions with major features
- Identify 5 real-world applications built with Java
- Compare Java with one other programming language (Python/C#)
- Prepare a presentation on "Why Java for Enterprise Development?"
Assignment Questions:
- Explain how Java achieves platform independence with a detailed diagram.
- Discuss the role of JVM in Java's "Write Once, Run Anywhere" philosophy.
- Compare Java with C++ and Python in terms of features and use cases.
- Research and write about Java's role in modern big data technologies.
Preparation for Next Lecture:
- Download and install JDK from Oracle or OpenJDK
- Install an IDE (VS Code, IntelliJ IDEA Community, or Eclipse)
- Verify Java installation using command line