When we talk about access modifiers in programming, especially when working with inheritance and polymorphism, it’s important to know when to use private access instead of protected access.

What Are Access Modifiers?

Let's break down what these modifiers mean:

• Public: You can access these members from anywhere.
• Protected: You can access these from the class itself and from classes that inherit from it.
• Private: You can only access these from within the same class.

When to Use Private Instead of Protected

1. Keeping Things Safe and Hidden
   If you want to keep things private, using private access is a smart move. This means other classes (even the ones that inherit from it) can't change variables or methods directly. Keeping things hidden helps you maintain control over how an object works.

   Example: Think about a BankAccount class:

   class BankAccount {
       private double balance;
   
       public void deposit(double amount) {
           balance += amount;
       }
       
       public double getBalance() {
           return balance;
       }
   }
   

   Here, the balance is private. The only way to change it is through the deposit method. Other classes can't change the balance directly, which keeps the BankAccount safe and trustworthy.

2. Avoiding Mistakes with Inheritance
   If you think that other classes might misuse or misunderstand parts of your class, keeping them private can help avoid problems. This reduces the chance of bugs caused by mistakes in the way classes interact with each other.

   Example: Imagine a Shape class with a private method that calculates the area:

   class Shape {
       private double calculateArea() {
           return 0.0; // Just a placeholder
       }
   }
   
   class Circle extends Shape {
       // Can't access calculateArea() here
   }
   

   By making calculateArea() private, you ensure that other classes cannot use it. This helps avoid confusion or mistakes.

3. Building User-Friendly Designs
   When you create systems for other developers to use, keeping certain parts private is helpful. It lets you define a clear "public contract" while keeping some details hidden. This way, you can change private parts later without breaking existing code.

   Example: Picture a Configuration class:

   class Configuration {
       private String setting;
   
       public void setSetting(String setting) {
           this.setting = setting;
       }
   
       public String getSetting() {
           return setting;
       }
   }
   

   Here, any changes to how the setting works won’t interfere with other classes using the setSetting and getSetting methods.

Conclusion

In short, while protected access can be flexible when you have classes that need to use or change each other's parts, private access offers many advantages. It helps keep data safe, reduces chances of bugs, and creates clear designs for how classes can work together. Using private access can lead to better and more reliable code in object-oriented programming.