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📜 WAYPOINT LESSON

Names, comments, and compiler errors

⭐ beginner⏳ 10 min read📍 Lesson 3 of 256

Naming conventions, comments, and how to read javac error messages.

Two commandments of Java style (the AP exam follows them too):

  1. Class names start with an uppercase letter, one word per part: Gradebook, StudentList.
  2. Variables and methods start lowercase, then capitalize: totalScore, findMax().

Identifiers may contain letters, digits, _, $, but may not start with a digit, and int, class, public are reserved keywords.

Comments are for humans and are ignored by the compiler:

// one-line comment

/* a comment
   spanning lines */

Reading compiler errors. javac reports the file, the line, and a (terse) reason:

Solution.java:4: error: ';' expected
        System.out.println("hi")
                                ^

The caret points where the compiler got confused — often after the real mistake. A missing ; on line 4 is reported on line 4; a missing } may be reported at the very end of the file.