Hello, World

Every Java program lives inside a class, and every runnable program has one method the JVM hunts for at startup: public static void main(String[] args). That exact signature is the contract. Match it and your program runs. Deviate — wrong capitalization, missing static, a different parameter type — and the JVM refuses to launch.

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Read it from the outside in:

• public class Main — all Java code lives inside classes. There are no free-floating functions like in Python or JavaScript. The grader on this platform compiles your file as class Main, so keep that name exactly as the starter has it.
• public static void main(String[] args) — the entry point. public so the JVM can reach it from outside the class, static so it can run before any object exists, void because it returns nothing, and String[] args carries command-line arguments (unused here, but required in the signature).
• System.out.println(...) — writes its argument to standard output, then moves to the next line. System lives in java.lang, which is imported automatically, so this works with zero setup.

Why all the ceremony?

Compared to Python's print("hi"), this looks heavy. The trade is deliberate: Java makes structure explicit from line one. Every program has an unambiguous entry point, every piece of code has a home, and the compiler checks all of it before anything runs. Small scripts pay a tax; large codebases collect the refund — you always know where execution starts and what type everything is.

The idiom and the trap

The working statement:

System.out.println("Hello, World!");   // capital S, double quotes, semicolon

The classic beginner breakages, and what the compiler says about each:

system.out.println("hi");    // error: cannot find symbol — Java is case-sensitive; it's System
System.out.println("hi")     // error: ';' expected — every statement ends with a semicolon
System.out.println('hi');    // error — single quotes are for ONE char; text needs double quotes

And the sneakiest one: declaring public static void Main(...) with a capital M. That compiles — it is a perfectly legal method — but the JVM reports that no main method was found when you run it, because Main is not main.

println vs print

System.out.println("A");   // prints A, then a newline
System.out.print("B");     // prints B, the cursor stays on the same line

The grader compares your output character-for-character, including the newline at the end of the line — println produces exactly one complete line, which is what nearly every exercise on this platform expects.

Your exercise

Write a program that prints exactly:

Hello, Java!

One statement inside the provided main:

System.out.println("Hello, Java!");

The grader checks stdout byte-for-byte. The mistake it will catch: copying the lesson example and printing Hello, World! instead of Hello, Java! — or dropping the comma, lower-casing the J, or forgetting the exclamation mark. Exact text, println, done.