2.1 Introduction to Java

2.1.1 Explanation

Java is a high-level, object-oriented programming language designed for portability, reliability, and security. Created by Sun Microsystems (now owned by Oracle), Java compiles source code into an intermediate form called bytecode, which executes on the Java Virtual Machine (JVM).

This abstraction allows Java programs to be platform-independent, meaning they can run on any operating system that supports the JVM. Java’s architecture-neutral design, automatic memory management (garbage collection), and extensive standard library make it one of the most enduring technologies in software development.

By 2025, Java’s evolution — with versions like Java 21 and upcoming LTS releases — has added features such as pattern matching, records, virtual threads, and enhanced garbage collection (ZGC, G1GC), improving both developer productivity and runtime performance.

2.1.2 Code

public class HelloJava2025 {

public static void main(String[] args) {

System.out.println("Welcome to Java 2025!");

}

}

2.1.3 Example

Input: —
Output:

Welcome to Java 2025!

Explanation: The program defines a single class with a main() method, the entry point for Java applications. When executed, it prints a greeting to the console.

2.1.4 Use Cases

• Building enterprise-level applications (e.g., banking, retail, logistics).
  
• Creating Android applications.
  
• Developing backend microservices and RESTful APIs.
  

2.1.5 Relevant Table

2.2 Setting Up the Java Environment

2.2.1 Explanation

Before you can write and execute Java programs, you must install and configure your development environment properly. Java’s environment primarily consists of three components: JDK (Java Development Kit), JRE (Java Runtime Environment), and the JVM (Java Virtual Machine).

The JDK provides tools like the compiler (javac), debugger, and libraries required for development. The JRE is a subset of the JDK used for running programs, containing the JVM and core libraries. The JVM, in turn, is responsible for executing the compiled bytecode, handling memory, and ensuring platform independence.

Setting up Java involves installing the JDK, adding it to the system’s environment variables, and optionally using an Integrated Development Environment (IDE) like IntelliJ IDEA, Eclipse, or VS Code, which simplify coding, debugging, and project management. By configuring this correctly, developers ensure smooth compilation, execution, and version control.

2.2.2 Code

/*

Steps to verify your Java installation

*/

C:\> java -version

java version "21.0.2" 2025-01-17 LTS

Java(TM) SE Runtime Environment (build 21.0.2+13-LTS)

Java HotSpot(TM) 64-Bit Server VM (build 21.0.2+13-LTS, mixed mode)

C:\> javac -version

javac 21.0.2

2.2.3 Example

Example Process:

1. Download the latest JDK (e.g., from https://jdk.java.net/).
   
2. Install it to a directory such as C:\Program Files\Java\jdk-21.
   
3. Add the path to Environment Variables → System Variables → PATH.
   
4. Verify installation using java -version and javac -version.
   

Expected Output:
Both commands display the installed version, confirming proper setup.

2.2.4 Use Cases

• Ensuring version compatibility for enterprise builds.
  

• Setting up multiple JDKs for backward compatibility testing.
  

• Preparing local environments for CI/CD and automated build pipelines.
  

• Configuring IDEs for efficient debugging and code completion.

   

2.2.5 Relevant Table

2.3 Java Program Structure

2.3.1 Explanation

Every Java program follows a structured syntax that defines how classes, methods, and statements interact. A Java source file consists of a class declaration containing the main() method, which serves as the program’s entry point.
Within this method, execution begins from the first line and continues sequentially unless modified by control statements (loops, conditions, or exceptions).

A Java file’s structure is case-sensitive and follows strict conventions:

• Class names begin with a capital letter (PascalCase).
  
• Methods and variables follow camelCase naming.
  
• File name must match the public class name exactly.
  

Proper indentation, consistent naming, and use of comments are critical for readability and maintainability. As programs grow, modularization using packages and methods becomes essential to reduce complexity.

2.3.2 Code

public class StructureDemo {

// Main method - Entry point of every Java program

public static void main(String[] args) {

// Variable declaration

String language = "Java";

int year = 2025;

// Print statement

System.out.println("Welcome to " + language + " " + year);

}

}

2.3.3 Example

Input: —
Output:

Welcome to Java 2025

Explanation: The class StructureDemo contains one method main(). Inside, variables are declared and used within the System.out.println() statement to print a formatted message.

2.3.4 Use Cases

• Demonstrating program structure for beginners.
  
• Teaching naming conventions and syntax fundamentals.
  
• Illustrating compilation and execution flow.
  
• Introducing static methods and the JVM entry mechanism.
  

2.3.5 Relevant Table