Unit 3

OOP Concepts

The core of OOP in Java: classes and objects, constructors and overloading, memory and garbage collection, modifiers, encapsulation, inheritance, polymorphism, abstraction, abstract classes and interfaces.

What you will learn

After this unit you can:

Model real-world things as classes
Declare attributes and methods
Create objects and access members
Write constructors and overloaded methods
Explain destructors and object lifecycle
Explain heap allocation and garbage collection
Apply access and non-access modifiers
Encapsulate data with getters and setters
Build inheritance hierarchies and override methods
Use polymorphism
Apply abstraction with abstract classes and interfaces
Give real-world examples of encapsulation and abstraction

Topics in this unit

3.1Classes and Objects✓3.1.1Classes and objects in the real world1 diagram✓3.1.2Attributes and methods1 code example✓3.1.3Creating objects and accessing members1 code example · 1 diagram✓3.1.4The this keyword and constructors3 code examples✓3.1.5Destructors and releasing resources2 code examples✓3.1.6Overloading1 code example · 1 diagram✓3.1.7Static members and a complete program1 code example✓3.1.8Self-check and practice✓3.2Memory Management in OOP✓3.2.1Stack, heap and dynamic allocation2 code examples · 1 diagram✓3.2.2Garbage collection and the object lifecycle1 code example · 1 diagram · interactive lab✓3.2.3Self-check and practice✓3.3Modifiers✓3.3.1Access modifiers1 code example · 1 diagram · interactive lab✓3.3.2Non-access modifiers2 code examples · 1 diagram✓3.3.3Self-check and practice✓3.4Encapsulation1 diagram✓3.4.1Getters, setters and validation1 code example✓3.4.2Self-check and practice✓3.5Inheritance✓3.5.1The extends and super keywords1 code example · 1 diagram✓3.5.2Hierarchies and types of inheritance2 diagrams✓3.5.3Multiple inheritance and the diamond problem1 code example · 1 diagram✓3.5.4Method overriding1 code example✓3.5.5Constructor order1 code example · 1 diagram✓3.5.6Self-check and practice✓3.6Polymorphism✓3.6.1Compile-time and run-time polymorphism✓3.6.2Run-time polymorphism in action1 code example · 1 diagram✓3.6.3Upcasting, downcasting and instanceof1 code example · 1 diagram✓3.6.4Self-check and practice✓3.7Abstraction1 diagram✓3.8Abstract Classes and Interfaces✓3.8.1Abstract classes1 code example✓3.8.2Interfaces1 code example✓3.8.3Abstract class or interface?1 diagram✓3.8.4Self-check and practice✓3.9Real-World Examples of Encapsulation and Abstraction1 code example · 1 diagram✓