Stop Making These 10 Java OOP Mistakes! Best Fixes Inside

Ramesh Fadatare

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Mar 17, 2025

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Object-Oriented Programming (OOP) is the foundation of Java development, but many developers — especially beginners — make avoidable mistakes that lead to bugs, performance issues, and bad design. 😨

In this article, we’ll explore the top 10 most common OOP mistakes in Java and how to fix them with best practices. Let’s dive in! 🚀

🔴 1️⃣ Not Following Encapsulation (Using Public Fields)

Mistake: Making class fields public violates encapsulation and exposes internal implementation.

❌ Bad Practice: Public Fields

class Person {
    public String name;  // ❌ No encapsulation
    public int age;
}

👉 Issue: Any external code can directly modify the fields, leading to unexpected behavior.

✅ Best Practice: Use Private Fields with Getters & Setters

class Person {
    private String name;  // ✅ Encapsulation applied
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

🔹 Fix: Always make fields private and expose them via getters & setters.