Your first Java program

Why this matters

You will see this entry-point structure in many beginner console programs, so understanding it makes lab exercises easier to follow.

Syntax

class ClassName {
    public static void main(String[] args) {
        // your statements go here
    }
}

Example

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, BCA student!");
        System.out.println("Welcome to OOPs Through Java.");
    }
}

Step by step

1. 1`public class Hello` — creates a class named Hello. The file must be saved as Hello.java.
2. 2`public` makes this entry method accessible to the Java launcher.
3. 3`static` lets the Java launcher call main without creating an object first.
4. 4`void` means main gives nothing back when it finishes.
5. 5`main(String[] args)` is the conventional application entry point; args can hold command-line values.
6. 6`System.out.println(...)` prints a line of text and then moves to the next line.
7. 7Every statement ends with a semicolon `;`. Every `{` must have a matching `}`.

Key points

• A standard launched class uses public static void main(String[] args) as its entry point
• A project can contain more than one class with a main method; the selected class determines where that run starts
• File name must match the public class name
• Java is case sensitive
• println adds a new line, print does not

Common mistakes

• Saving the file with a different name than the public class
• Writing `Public` or `Void` with a capital letter — Java is case sensitive
• Forgetting the semicolon at the end of a statement
• Using print instead of println and wondering why output is on one line

Try it yourself

• Print your name, your course and your college on three separate lines.
• Change println to print and observe the difference.