What is Java?

Java is a general-purpose, object-oriented programming language first released by Sun Microsystems in 1995 and now maintained by Oracle and the OpenJDK community. Almost three decades later it still runs a massive share of the world's serious software: banking backends, e-commerce platforms, telecom systems, Android apps and big-data tools like Hadoop and Kafka.

If you are deciding what to learn for a software career in India, that history matters for one practical reason: Java job volume. Product companies, service giants and startups all maintain enormous Java codebases, and they hire continuously for people who can work on them.

Java in one sentence

Java is a language where you write code once, compile it into an intermediate format called bytecode, and run that bytecode on any machine that has a Java Virtual Machine (JVM) installed.

That single design decision — compile to bytecode, not to machine code — is the answer to the most common beginner question: "Why is Java called platform independent?" Your .class file does not care whether the machine underneath is Windows, Linux or macOS. The JVM for that platform handles the translation.

Interview note: Interviewers love the phrase "Write Once, Run Anywhere" (WORA). Be ready to explain why it works: Java source compiles to bytecode, and a platform-specific JVM executes that bytecode. The bytecode is portable; the JVM is not. The full picture is covered in JDK vs JRE vs JVM.

Your first Java program

Here is the classic starting point. Save this in a file named exactly HelloWorld.java:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello from CodeBegun!");
    }
}

Compile and run it from a terminal:

javac HelloWorld.java
java HelloWorld

Notice three things. First, all code lives inside a class — Java is object-oriented from line one. Second, main is the fixed entry point; the JVM looks for exactly this signature. Third, javac produced a HelloWorld.class file — that is the bytecode we just talked about.

Common mistake: A common mistake beginners make is saving the file with a name that does not match the public class name. If your class is HelloWorld, the file must be HelloWorld.java — including capitalization. The compiler will refuse anything else.

What makes Java different from other languages

Statically typed

Every variable in Java has a declared type — int, String, boolean — and the compiler checks types before your program ever runs. Compare that with Python, where type errors surface only at runtime. Static typing means more keystrokes but far fewer surprises in production. You will meet the full type system in Java data types.

Object-oriented

Java organizes code into classes and objects. Real systems model concepts like Customer, Order and Payment as classes with data and behavior bundled together. The four pillars — encapsulation, inheritance, polymorphism and abstraction — are the backbone of every Java interview.

Automatic memory management

You create objects with new; you never delete them manually. The JVM's garbage collector reclaims memory that is no longer referenced. This removes an entire category of bugs (dangling pointers, double frees) that plague C and C++ developers.

Compiled and interpreted

Java sits between the two worlds. javac compiles source to bytecode ahead of time, then the JVM interprets that bytecode and its JIT (Just-In-Time) compiler converts hot code paths into native machine code while the program runs. Long-running Java servers get faster after warm-up because of this.

A slightly more realistic example

Printing one line does not show you what Java code feels like day to day. This program models a tiny fee calculator using a class, a method and a loop:

public class CourseFeeCalculator {

    static double totalWithGst(double baseFee) {
        double gstRate = 0.18;
        return baseFee + (baseFee * gstRate);
    }

    public static void main(String[] args) {
        double[] baseFees = {25000.0, 40000.0, 55000.0};

        for (double fee : baseFees) {
            System.out.printf("Base: %.2f -> Payable: %.2f%n",
                    fee, totalWithGst(fee));
        }
    }
}

Notice how the logic (totalWithGst) is separated from the data and the printing. Even in a 15-line program, Java nudges you toward structuring code into reusable units. Arrays, loops and variables like gstRate are the building blocks you will master in the first two weeks.

Where Java is actually used

Beginners often assume Java is "old" technology. Look at where it runs before you accept that:

In Hyderabad specifically, the service companies and global capability centers that dominate hiring run overwhelmingly on Java plus Spring Boot backends. That is why our Java full stack course treats core Java as the foundation and builds Spring Boot, SQL and React on top of it.

Which Java version should you learn?

Java releases a new version every six months, but only some are LTS (Long-Term Support) releases that companies actually standardize on: Java 8, 11, 17 and 21.

• Learn on Java 17 or 21. Modern syntax, records, better switch, and everything interviewers ask about.
• Know Java 8 features cold. Lambdas, streams and Optional arrived in Java 8 and remain the single most-asked interview topic area.
• Do not panic about version differences. Core syntax — classes, loops, collections — is essentially unchanged since the beginning.

Pro tip: Install an OpenJDK build such as Eclipse Temurin 21 rather than hunting for Oracle downloads. Run java -version in your terminal to confirm the install. Pair it with IntelliJ IDEA Community Edition, which is free and is what most professional Java developers use.

Is Java worth learning in 2026?

Yes — and the reasoning is practical, not sentimental.

First, demand: Java consistently sits in the top three languages in India by open job count, because the systems written in it over 25 years are not going anywhere and keep growing. Second, salary trajectory: Java backend and full stack roles in India typically pay in the same range as other backend stacks, with strong growth once you add Spring Boot and microservices experience. Third, transferability: once you understand Java's OOP, collections and concurrency, picking up C#, Kotlin or even Go becomes dramatically easier.

The honest counterpoint: for pure data science or quick scripting, Python is the better tool. If you are torn between the two as a fresher, read our detailed breakdown in Java vs Python for freshers before committing.

How to start learning Java this week

A realistic first-month sequence looks like this:

1. Day 1–2: Install JDK 21 and IntelliJ IDEA. Write and run HelloWorld. Understand what JDK, JRE and JVM each do.
2. Week 1: Data types, variables, operators, if/else and switch. Write small programs daily — calculators, grade checkers, unit converters.
3. Week 2: Loops, arrays and strings. Solve 20–30 basic problems by hand before touching any framework.
4. Week 3–4: Object-oriented programming — classes, objects, constructors, inheritance. This is where Java starts making sense as a system-building language.

The single biggest predictor of success we see in classrooms is typing code daily, not watching videos. Two hours of writing broken programs and fixing them beats six hours of passive tutorials.

Pro tip: From day one, read compiler error messages fully instead of skimming them. Java's errors are verbose but precise — they name the file, the line and usually the exact problem. Learning to decode them is a genuine professional skill, not a chore.

What comes after the basics

Core Java is the entry ticket, not the destination. The typical fresher-to-hired path stacks these layers: core Java → SQL → Spring Boot → a front-end basic (HTML/CSS/JS or React) → one or two real projects. If you want the full sequence with timelines, the step-by-step guide in how to become a Java developer maps it out month by month.

For now, your next reading in this series is JDK vs JRE vs JVM — the first "explain the difference" question almost every Java fresher faces in an interview.