Java 101 – Everything You Need to Know: Basics, JDK Installation & First Code

📌 1. What is Java?

Java is a high-level, object-oriented programming language developed by Sun Microsystems (now owned by Oracle). It is widely used for web development, mobile apps (Android), enterprise applications, and competitive programming.

✅ Key Features of Java:
🔹 Write Once, Run Anywhere (WORA) – Java code runs on any platform with JVM (Java Virtual Machine).
🔹 Object-Oriented – Uses classes and objects for structured programming.
🔹 Secure & Robust – Handles memory management and exception handling efficiently.
🔹 Multithreaded – Can handle multiple tasks simultaneously for better performance.

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📌 2. Why Learn Java?

Java is used in various domains, making it a valuable skill for developers:
✅ Android Development – Used to build Android apps.
✅ Backend Development – Used in Spring Boot, Hibernate, and REST APIs.
✅ Competitive Programming & DSA – Fast execution and rich libraries.
✅ IoT & Embedded Systems – Used in smart devices and automation.

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📌 3. A Brief History of Java

🔹 1991: Java was originally called "Oak", created by James Gosling and his team at Sun Microsystems. The name Oak came from an oak tree outside Gosling’s office.

🔹 1995: Due to trademark issues, Oak was renamed to "Java", inspired by Java coffee beans from Indonesia. The name was chosen because it sounded dynamic, energetic, and unique.

🔹 1996: The first stable version, Java 1.0, was released with the Write Once, Run Anywhere (WORA) philosophy.

🔹 2009: Oracle Corporation acquired Sun Microsystems, making Java an Oracle product.

🔹 Present: Java is continuously updated, with Java 24 being the latest version.

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📌 4. How to Install Java (JDK) on Your System

🔹 Step 1: Download JDK

1️⃣ Go to the official Oracle JDK download page: https://www.oracle.com/java/technologies/javase-downloads.html
2️⃣ Choose the latest Java SE Development Kit (JDK) version.
3️⃣ Download the correct version for your OS (Windows, macOS, or Linux).

🔹 Step 2: Install JDK

1️⃣ Open the downloaded file and follow the installation steps.
2️⃣ Note the installation path (e.g., C:\Program Files\Java\jdk-XX.X.X).

🔹 Step 3: Set Up Java Environment Variables (Windows)

1️⃣ Search for "Environment Variables" in the Windows Start menu.
2️⃣ Under System Variables, select Path → Click Edit → Click New.
3️⃣ Add the Java bin path (C:\Program Files\Java\jdk-XX.X.X\bin).
4️⃣ Click OK and restart your PC.

🔹 Step 4: Verify Installation

Open Command Prompt (Windows) or Terminal (macOS/Linux) and type:

java -version

✅ If Java is installed correctly, it will show the Java version:

java version "23.0.2" 2025-01-21
Java(TM) SE Runtime Environment (build 23.0.2+7-58)
Java HotSpot(TM) 64-Bit Server VM (build 23.0.2+7-58, mixed mode, sharing)

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📌 5. Install an IDE (Optional but Recommended)

To make Java development easier, use an Integrated Development Environment (IDE):
✅ IntelliJ IDEA (Best for beginners)
✅ Eclipse (Popular for Java development)
✅ VS Code (With Java extensions – Lightweight alternative)

Download IntelliJ IDEA: https://www.jetbrains.com/idea/download/
Download VS Code: https://code.visualstudio.com/

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📌 6. Your First Java Program

Let's write and execute a simple "Hello, World!" program in Java.

🔹 Step 1: Write the Code

Create a file called HelloWorld.java and add the following code:

// Simple Java Program
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

🔹 Step 2: Compile the Code

Open Command Prompt or Terminal, navigate to the file location, and type:

javac HelloWorld.java

This compiles the file and creates a HelloWorld.class file.

🔹 Step 3: Run the Program

Execute the compiled program:

java HelloWorld

✅ Output:

Hello, Java!

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📌 7. Understanding the Code

🔹 public class HelloWorld {} → Defines a Java class named HelloWorld.
🔹 public static void main(String[] args) {} → The main method (entry point of Java programs).
🔹 System.out.println("Hello, Java!"); → Prints output to the console.

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📌 8. Common Errors & Fixes

❌ Error: 'javac' is not recognized as an internal or external command
✅ Fix: Add Java bin path to Environment Variables.

❌ Error: Main method not found in class HelloWorld
✅ Fix: Ensure the main method is correctly defined:

public static void main(String[] args)

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📌 9. Next Steps

🎯 Now that you've written your first Java program, here’s what to learn next:
✅ Understanding Java Syntax (Classes, Methods, main() method, Print Statements)
✅ Operators & Control Statements
✅ Loops, Arrays & Functions

Stay tuned for the next blog: "Understanding Java Syntax & Variables"! 🚀

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📌 Summary

📌 Java is platform-independent, object-oriented, and widely used.
📌 JDK (Java Development Kit) is needed to run Java programs.
📌 We wrote and executed our first Hello World Java program.

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