What is Java? Your first program

1 Learn

Java is a programming language: a way of writing instructions that a computer can follow. Java code is written in files ending with .java.

Every Java program lives inside a class. To run it as an application, Java looks for a special method called main — this is the starting point.

System.out.println() prints a line of text on the screen. It is the easiest way to see what your program is doing.

Want more detail? Open the full lesson

2 See the Code

Java

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
        System.out.println("Day 1 done.");
    }
}

public class Hello — creates a class named Hello. The file is usually named Hello.java.
public static void main(String[] args) — the entry point where the program starts running.
System.out.println(...) — prints the text in quotes, then moves to a new line.
Each statement ends with a semicolon ;

Output

Hello, Java!
Day 1 done.

3 Practice

Change the program so it prints your first name on one line and your college name on the next.
Add a third line that prints: I am learning Java.

Try it in your own Java setup or write it in the Practice Notebook.

4 Quick Check

1. Where does a Java application start running?
2. What does System.out.println("Hi"); do?
3. Which symbol ends most Java statements?

Step 5

Answer and check the Quick Check above to unlock this.