4.15. Basic Java syntax: Analysis of Access Modifiers (public, private, protected)

Basic Java Syntax: Analysis of Access Modifiers

Access modifiers in Java are fundamental elements that define the visibility of classes, methods, constructors and variables. They are the basis for encapsulation, one of the four pillars of object-oriented programming (OOP). The main access modifiers are public, private and protected, each with its own characteristics and particularities.

The public

Modifier

The public modifier is the most open among the three. When a class, method or variable is declared as public, it can be accessed from any other class in any package within the project. This means there are no access restrictions.

public class ExamplePublic {
    public int publicnumber;
    
    public ExamplePublic() {
        // public constructor
    }
    
    public void public method() {
        // Public method
    }
}

Using the public modifier is appropriate when you want the element to be universally accessible. However, this also means that you have less control over how and where the element is used, which can be a problem in terms of security and code maintenance.

The private

Modifier

On the other hand, the private modifier is the most restrictive. An element declared as private can only be accessed within the class in which it was defined. This is useful for hiding the implementation details of a class and forcing the use of public methods to interact with the class's data.

public class ExamplePrivate {
    private int privatenumber;
    
    public ExamplePrivate() {
        privatenumber = 1; // Access allowed within the class itself
    }
    
    private void private method() {
        // Private method, accessible only within this class
    }
    
    public int getPrivateNumber() {
        return privateNumber; // Public access to private value
    }
    
    public void setPrivateNumber(int newValue) {
        privatenumber = newValue; // Public method to change private value
    }
}

The getNumeroPrivado and setNumeroPrivado methods are examples of access methods, also known as getters and setters, that allow the reading and modification of private variables in a controlled manner.

The protected

Modifier

The protected modifier provides an intermediate level of access. An element declared as protected can be accessed by classes in the same package and by subclasses, even if they are in different packages. This is particularly useful when you want to allow a class to be extended and subclasses to have access to certain elements of the parent class.

public class ExampleBase {
    protected int protectednumber;
    
    protected ExampleBase() {
        // Protected constructor
    }
    
    protected void protectedmethod() {
        // Protected method
    }
}

public class DerivedExample extendsBaseExample {
    public DerivedExample() {
        numberProtected = 2; // Access allowed as it is a subclass
    }
    
    public void demonstrateAccess() {
        protectedmethod(); // Access allowed as it is a subclass
    }
}

It is important to note that using the protected modifier can create a dependency relationship between the base class and its subclasses, which can be a disadvantage in terms of encapsulation and code reuse.

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Additional Considerations

In addition to access modifiers, Java also has the concept of "default" or "package-private" access. If no access modifier is specified, the element has package visibility, meaning it can only be accessed by classes within the same package.

class ExampleDefault {
    int numberDefault; // Package visibility
    
    ExampleDefault() {
        // Builder with package visibility
    }
    
    void methodDefault() {
        // Method with package visibility
    }
}

Choosing the correct access modifier is essential for the security and integrity of your code. In general, it's good practice to start with the most restrictive level of access and increase it as needed. This is known as the principle of least privilege and helps maintain encapsulation and reduce interdependence between parts of your code.

In summary, understanding and correctly applying access modifiers is a crucial aspect of software development in Java. They not only help organize code logically, but also protect data and ensure that software components are used as intended.

Conclusion

The appropriate use of modifiersAccess is an important step in creating robust, secure, and easy-to-maintain applications. By learning about public, private, and protected, programmers can control how classes and members are exposed and interact with each other, following good encapsulation practices and object-oriented design.