Series 4: Object-Oriented Programming

Lessons

4.1: What Are Objects?

~18 min · Week 8 · Prereq: Lesson 2.1

From parallel arrays to bundled data. Classes vs objects, the new keyword, object references, null, and objects you have already used (Scanner, String).

4.2: Writing Your First Class

~20 min · Week 8 · Prereq: Lesson 4.1

Fields, constructors, the this keyword, instance methods, and toString(). Building a complete Student class from scratch.

4.3: Encapsulation and Access Control

~18 min · Week 8 · Prereq: Lesson 4.2

Private fields, public methods, getters/setters with validation, and information hiding. Why encapsulation protects your objects from invalid states.

4.4: toString, equals, and hashCode

~20 min · Week 8 · Prereq: Lesson 4.3

The three methods every Java class needs. Custom toString(), equals() with instanceof, and hashCode() with Objects.hash().

4.5: Unit Testing with JUnit

~18 min · Week 9 · Prereq: Lesson 4.4

JUnit 5 basics: @Test, assertEquals, assertThrows. The Red-Green-Refactor TDD cycle and running tests with Gradle.

4.6: Interfaces and Comparable

~20 min · Week 9 · Prereq: Lesson 4.4

Interface contracts, the Comparable<T> interface, writing compareTo(), and implementing natural ordering on custom classes.

4.7: Sorting Objects

~18 min · Week 9 · Prereq: Lessons 4.6, 2.3

Arrays.sort() and Collections.sort() with Comparable objects. Selection sort on object arrays, multi-field sorting, and Comparator intro.

4.8: Objects in Memory

~20 min · Week 9 · Prereq: Lesson 4.2

Stack vs heap, object references and aliasing, == vs .equals(), null and NullPointerException, passing objects to methods, and garbage collection.

4.9: Capstone Review and APE Preparation

~22 min · Week 10 · Prereq: All previous lessons

Connecting all 10 weeks by theme. Complete integration example, the full toolkit quick reference, APE preparation tips, and what comes next in CSCD 211.

Previous series: ← Series 3: File I/O