Introduction

Objects group data with related behavior. A class describes how to create those objects. Model a small concept first, such as a learner with a name and a greeting, and keep responsibilities clear.

Syntax & example

public class Main {
  public static void main(String[] args) {
    Learner learner = new Learner("Alex");
    System.out.println(learner.greet());
  }
  static class Learner {
    String name;
    Learner(String name) { this.name = name; }
    String greet() { return "Hello, " + name; }
  }
}

Expected output

Hello, Alex

Common mistakes

  • Using a variable before assigning a value to it.
  • Mixing text and numbers without converting deliberately.
  • Skipping an empty input or a boundary value when testing.

Practice

Create a second learner with a different name.

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