Access Modifier - Encapsulation

An access modifier is a Java keyword that indicates how a field or method can be accessed.

In Java, public, private, and protected are access modifiers. They determine the level of access that other classes have to the members (fields and methods) of a class.

public: This access modifier states that any other class can access the resource.
private: This access modifier indicates that only data within this class can access the resource.
protected: This modifier indicates that only classes in the current package or a class lower in the class hierarchy can access this resource.

By default, if no access modifier is specified, a member is considered to have package-private access, which means it can only be accessed within the same package.

Using these modifiers, you can control the visibility of class members, encapsulating implementation details and exposing a public interface for other classes to interact with.

Let's explain Java's access modifiers but with a real-world analogy:

Public: Imagine a public park. Anyone can come in and use the park, right? In Java, when something is marked as public, it's like this park. Any other part of your program can see and use this public part. It's completely open for all.
Private: Now think of your own bedroom in your house. Only you can enter it, right? In Java, when something is private, it's like your bedroom. Only the code within the same class (think of it as the same house) can access this private part. It's not visible or accessible to the outside world.
Protected: This one is like your living room at home. Your family and relatives (who live in the same house or are closely related) can come in, but not your neighbors or strangers. In Java, protected is similar. The code in the same class or in a subclass (think of them as family or relatives) can access a protected member, but other unrelated classes (like neighbors) cannot.

In Java, access modifiers (public, private, and protected) are keywords used to control the accessibility of classes, methods, and fields within a program. They define the level of visibility or accessibility from other parts of the program.

Here's an explanation of each access modifier:

public: When a class, method, or field is declared as public, it can be accessed from any other class or package. It has the highest level of visibility. For example:

public class MyClass {
    public int myPublicField;
    
    public void myPublicMethod() {
        // Method implementation
    }
}

private: When a class member (method or field) is declared as private, it can only be accessed within the same class. It is not accessible from outside the class or even from subclasses. This access modifier provides the highest level of encapsulation. For example:

public class MyClass {
    private int myPrivateField;
    
    private void myPrivateMethod() {
        // Method implementation
    }
}

protected: When a class member is declared as protected, it can be accessed within the same class, subclasses (even in different packages), and other classes within the same package. However, it is not accessible from classes in different packages that are not subclasses. For example:

public class MyClass {
    protected int myProtectedField;
    
    protected void myProtectedMethod() {
        // Method implementation
    }
}

Default (no access modifier): If no access modifier is specified, it is considered the default access level. A member with default access can be accessed within the same package but not from classes in other packages, even if they are subclasses.

Access modifiers are important for encapsulation, information hiding, and controlling the visibility of code elements. They allow you to restrict access to certain parts of your code and expose only what is necessary, improving security, maintainability, and code organization.