OOP Pitfalls in Java – Anti-patterns You Should Avoid

Introduction

Object-Oriented Programming (OOP) in Java is designed to promote modularity, reusability, and scalability. However, when misused, it leads to bloated, unmaintainable code. This article explores the common pitfalls and anti-patterns developers encounter while applying OOP principles in Java.

Understanding these missteps is crucial, especially in large-scale systems, where technical debt grows fast. In this guide, we’ll uncover real-world misuse examples and learn how to avoid or fix them using cleaner, extensible Java code.

What Are OOP Anti-patterns?

Anti-patterns are common but ineffective solutions to recurring problems in software design. In OOP, these usually result from misapplied principles like inheritance overuse, tight coupling, poor encapsulation, or unnecessary abstractions.

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Common OOP Pitfalls in Java

1. God Object Anti-pattern

Definition

A single class that knows too much or does too much.

Why It Happens

Developers pile responsibilities into a central class for convenience.

class GodClass {{
    void handleUI() {{}}
    void connectToDatabase() {{}}
    void processBusinessLogic() {{}}
}}
...
class Bird {{
    void fly() {{}}
}}
class Ostrich extends Bird {{
    void fly() {{ throw new UnsupportedOperationException(); }}
}}

Fix – Apply SRP (Single Responsibility Principle)

Break the class into smaller ones, each handling a specific responsibility.

...

7. Violating Liskov Substitution Principle

class GodClass {{
    void handleUI() {{}}
    void connectToDatabase() {{}}
    void processBusinessLogic() {{}}
}}
...
class Bird {{
    void fly() {{}}
}}
class Ostrich extends Bird {{
    void fly() {{ throw new UnsupportedOperationException(); }}
}}

Fix

Use abstract base classes with appropriate capabilities.

...

UML-style View

+-----------------+      uses      +------------------+
| OrderProcessor  |-------------->| Notification      |
+-----------------+               +------------------+
| - notification  |               | +send()          |
+-----------------+               +------------------+

...