Access Modifiers in Java- Types and Algorithms

Modifiers in Java are keywords that you can add to different definitions to change their meanings. In Java, you will come across access and non-access modifiers.

Access modifiers in Java are special keywords that control the visibility of class members, including variables, methods, and inner classes. They determine which parts of a class can be accessed from outside the class. These modifiers ensure data encapsulation, which means that sensitive information is hidden from unauthorized access.

Scroll through this article to learn about access modifiers in Java and their types. 

Table of Content:

1. What are Access Modifiers?
2. Types of Access Modifiers
3. Algorithms to Use Access Modifiers in Java
4. Quick Comparison of Types of Access Modifiers in Java
5. Conclusion
6. FAQs

What are Access Modifiers in Java?

Access modifiers in Java are like security guards for class members, such as variables and methods. They determine who gets to see and interact with these members. Think of them as virtual gates controlling access to different class parts. These modifiers ensure that only the right “authorized personnel” can access specific information or functions, enhancing data privacy and code integrity. Java offers four primary access modifiers: default, private, protected, and public.

The default modifier allows access within the same package, while private restricts access to the class itself. Protected extends access to subclasses as well, fostering controlled inheritance. Public, on the other hand, opens the gates for everyone. By strategically using these access modifiers, programmers can balance sharing what’s necessary and safeguarding sensitive data. They’re essential tools for designing well-structured, secure, and manageable Java programs.

You can limit the scope of any class, method, constructor, variable, or data member using access modifiers in Java. Depending on the chosen access specifiers in Java, you will come across different benefits like security and accessibility. The Java access specifiers are often referred to as visibility modifiers.

Let’s dive deep and understand the concept of Access Modifiers in Java in detail.

Access modifiers in Java are like the bouncers at a club entrance, managing who gets to enter and interact with different parts of a class. They work by setting boundaries on the visibility of class members like variables and methods. Each modifier determines which other classes or parts of the code can access these members. The public modifier acts like an open invitation, allowing any program part to freely interact with the associated class members.

The private modifier, on the other hand, keeps things exclusive, allowing only the class itself to access those members. Protected is a bit more flexible, allowing the class and its subclasses to engage with the protected members.  Lastly, the default modifier keeps things within the package, granting access to other classes in the same package but preventing outsiders from meddling.

By applying these modifiers thoughtfully, programmers can create a controlled environment for their code, safeguarding sensitive information and preventing unwanted interference.

Types of Access Modifiers in Java

Now that you have understood what is access modifiers in java. Let’s look at the four types of access modifiers in Java:

1. Public Access Modifier 

The public access modifiers in Java have no restriction on the instance members, methods, and classes of the particular class. When you fix classes with public access specifiers in Java, you will be able to access them in any package or class. The scope of the public Java access modifiers is extremely flexible compared to other access modifiers. This type of access modifier in java is accessible only within the class.

The public access modifier flings open the doors to class members, allowing unrestricted access from anywhere. It’s like having an open invitation to a public event. Members with public access can be accessed from any class, package, or even external applications. This is useful for creating reusable components and APIs.

Features:

• Members are accessible from anywhere in the program.
• Provides the broadest level of accessibility.
• Ideal for creating reusable components and exposing APIs.

public class PublicExample {

public int publicVar = 42;

}

2. Private Access Modifier 

The private access modifiers in Java are quite restricted. Data members and class methods prefixed with only private access modifiers can only be accessed inside the class. Even other classes inside the same package cannot reach the private methods or members.

Think of the private access modifier as a private chamber accessible only by the class itself. Private members are entirely shielded from external classes, ensuring strong encapsulation and preventing unauthorized access. This is particularly useful for securing sensitive data and hiding implementation details.

Features

• Members are accessible only within the same class.
• Ensures the highest level of encapsulation.
• Protects sensitive information from unauthorized access.

Example: class PrivateExample {private int privateVar = 42;}

You came across a lot of errors because you are trying to access the private methods and members in another class. 

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3. Protected Access Modifier

Protected access modifiers and instance members can be used in the same package. You will be able to access them in another package using a child class. Therefore, you are required to extend the class containing protected members in another package. You won’t get direct access by creating the class object containing protected functions and members. 

The protected access modifier strikes a balance between accessibility and controlled exposure. Members with protected access can be accessed within the same package and by subclasses, even in different packages. This facilitates the concept of controlled inheritance and extends visibility to specific classes.

Features

• Members are accessible within the same package and subclasses, regardless of package.
• Encourages controlled sharing among related classes and subclasses.
• Balances encapsulation with limited accessibility.

Example:

package mypackage;

class Parent {

protected int protectedVar = 42;

}

class Child extends Parent {

void someMethod() {

System.out.println(protectedVar); // Accessible in subclass

}

}

Suppose you have two packages, First and Second. The First package includes one public class and another protected prefixed method. You have two methods of accessing this method in another package:

Find out what will happen if you use these methods.

The line ob.print() created an error because you won’t be able to access the protected method beyond its own package. However, you will be able to access it by inheriting it in another class of different packages. That’s why obl.print() won’t lead to any errors. 

4. Default Access Modifier 

Default access modifiers in Java are given to instance members with no specified modifier. The methods and instance members with default access modifiers in Java can only be accessed in the same package. Therefore, you can call it the package private. 

The default access modifier is like having a “members-only” sign on a club entrance. It’s the default setting if no other access modifier is specified. Members with default access can only be accessed within the same package. This provides a controlled environment within a package, ensuring that only related classes can interact with each other.

Features

• Members are accessible only within the same package.
• Provides a level of encapsulation within the package.
• Helpful in creating package-level functionality or restricting access to certain components.

package mypackage;

class DefaultExample {

int defaultVar = 42; // Default access modifier

}

These are the major Access Modifiers in Java. Also read: 14 Machine Learning in Healthcare 

Understanding these access modifiers and their implications is crucial for designing robust and secure Java applications. By applying the right access modifier to each class member, you can ensure proper encapsulation, control access, and enhance the overall quality of your code.

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Java Access Modifiers with Method Overriding

When it comes to method overriding in Java, access modifiers continue to play a role in controlling visibility. Method overriding allows a subclass to provide its implementation for a method defined in its superclass. However, you can’t just arbitrarily change the overridden method’s visibility.

The rule is that you can’t reduce the visibility of an overridden method in the subclass. For example, if a method in the superclass is declared as public, you can’t make it protected or private in the subclass. But you can increase the visibility. If the superclass method is protected, you can override it with a public method in the subclass.

This ensures that the contract established by the superclass is still honored by the subclass, and no unintended exposure or restriction of methods occurs during the inheritance process.

Algorithm to Use Access Modifier in Java

The different algorithms for using access modifiers in Java are as follows:

• Define a class: It revolves around making a class that will signify the object you need to manage.
• Mention access modifiers in Java: You need to specify access modifiers in Java for every instance so that it can determine the visibility of the variable. 
• Define instance variables: You need to define instance variables within the class representing the data that needs to be managed. 
• Use public for variables that must be accessible from anywhere: The public java access modifiers are helpful for allowing access to a variable from anywhere. It is the least limited Java access modifier with the lowest amount of encapsulation.
• Use accessor and mutator approaches for managing variable access: You should use the accessor and mutator methods to access and modify variables. It delivers a level of abstraction and makes any code more testable and maintainable. 
• Identify Scope: Determine your class member’s intended level of visibility (e.g., variable, method).
• Apply Modifier: Select the appropriate access modifier (default, private, protected, public) based on your visibility requirement.
• Place Modifier: Add the chosen modifier before the member’s declaration.
• Consider Context: Consider the class’s role and interactions within your program.
• Balance Access: Use access modifiers to balance revealing enough for external use and keeping internal details secure.

By thoughtfully applying access modifiers, you ensure that your class members are accessible only to those who need them, contributing to a well-structured and secure codebase.

Quick Comparison of Types of Access Modifier in Java 

Below is the quick comparison of types of access modifier in java:

Let us see which all members of Java can be assigned with the Java Access Modifiers

Below are the key members of Java can be assigned with the Java Access Modifiers:

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Conclusion

Access modifiers in Java are primarily used for encapsulation. It allows us to control what part of a program is useful for accessing class members. The different access modifiers in Java can prevent the misuse of data. So, learn in detail about the different Java access specifiers. In this article we have understood about the java access modifiers, types of access modifiers in java and with their examples.