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Run your first Java program

Meet the main method and print a message from a Java class.

14 min 4-question quiz 1 code exercise

By the end of this lesson you can

Recognize a Java class and print a line of output.

Java programs are organized into classes. A program starts at the main method, whose familiar signature is public static void main(String[] args). System.out.println writes a line to standard output. Java source is compiled to bytecode and run by a Java Virtual Machine (JVM).

Main.java

1class Main {
2    public static void main(String[] args) {
3        System.out.println("Hello, Java!");
4    }
5}

Output

Hello, Java!

Statements end with semicolons, and braces group class and method bodies. These exercises use a package-private Main class because the online compiler gives source files a generic name; in a local project, a public class name normally matches its .java filename.

Key takeaways

Recognize a Java class and print a line of output.
Java checks types as it compiles your source.
Use compiler messages as clues about what needs fixing.

Lesson quiz

4 questions · pass with 3 correct · up to 50 XP

Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.

Practice: write Java

Write Java in the editor and run it against sample input with a remote compiler. Your code is sent to Compiler Explorer to compile and run.

Exercise 1

Print a greeting

+25 XP

Print exactly Hello, Java! on one line from the main method.

Greeting

Main.java

Loading editor…

Java is compiled and run by Compiler Explorer (godbolt.org), a free public service. Your source code and test input are sent to that service.

Questions about this lesson

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