Encapsulation and Access Modifiers

What is Encapsulation? Encapsulation is the practice of bundling an object's data (fields) and methods together within a class, and controlling access to that data from the outside world.

Data Hiding: A key part of encapsulation is data hiding. We achieve this by declaring the class's fields as private. A private member can only be accessed from within its own class.

Access Modifiers:

• public: The member is accessible from anywhere.

• private: The member is accessible only within its own class.

• protected: The member is accessible within its own package and by subclasses.

• default (no keyword): The member is accessible only within its own package.

Getters and Setters: To provide controlled access to private fields, we use public methods known as getters and setters.

• Getter: A method that retrieves the value of a private field. By convention, it is named getFieldName() (or isFieldName() for booleans).

• Setter: A method that modifies the value of a private field. It is named setFieldName(). Setters are crucial because they allow you to add validation logic before changing a field's value.

Benefits of Encapsulation:

• Control: You control how the data in your objects is used and modified.

• Security: You can protect your object from being put into an invalid state.

• Flexibility: You can change the internal implementation of a class without breaking the code that uses it, as long as the public methods remain the same.

Mini-Exercise: Create a BankAccount class with a private balance field. Add a public getBalance() method. Add a public deposit(double amount) method that only adds positive amounts. Add a public withdraw(double amount) method that only allows withdrawals if the amount is positive and there are sufficient funds.

public class Student {
    private String name;
    private int age;

    // Getter for name
    public String getName() {
        return this.name;
    }

    // Setter for name
    public void setName(String name) {
        if (name != null && !name.isBlank()) {
            this.name = name;
        }
    }

    // Getter for age
    public int getAge() {
        return this.age;
    }

    // Setter for age with validation
    public void setAge(int age) {
        if (age > 0) {
            this.age = age;
        }
    }
}