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Final Class Java: Java Explained

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Java is a widely used programming language that is used to create complex applications and programs. However, if you are new to Java programming, you may come across the concept of a final class and wonder what it is and how it works. This article will explain the concept of final classes in Java, the benefits and drawbacks of using them, as well as how to declare and use them effectively.

What is Final Class Java?

A final class in Java is a class that is defined with the final keyword. This means that once a class has been declared as final, it cannot be extended or modified. This means that the fields of the class, as well as its public and protected methods, become immutable. An immutable class is a class that cannot be changed once it is created.

Final classes also limit the ability for other classes to inherit from them. Because of this, all methods and fields in a final class are treated as static and can only be accessed directly from the class, rather than from any other class that inherits from it.

Final classes are useful for ensuring that the code within them is not modified or changed in any way. This can be beneficial for security purposes, as it prevents malicious code from being injected into the class. Additionally, final classes can help to improve the performance of an application, as the code within them is not subject to change.

Benefits of Final Classes

There are several advantages to using final classes. First, since final classes cannot be modified, they can help reduce errors caused by unintentional changes to code. Additionally, they can limit the ability for other classes to access data and methods, providing a layer of robustness to code that is intended to remain constant. Finally, final classes can provide an additional level of security by restricting who has access to sensitive data or methods.

In addition, final classes can help improve the performance of an application by reducing the amount of code that needs to be processed. This is because the compiler can optimize the code more efficiently when it knows that the class will not be modified. Furthermore, final classes can help improve the readability of code by making it easier to identify which classes are intended to remain constant.

How to Declare a Final Class in Java

Declaring a class as final is simple. All you need to do is add the keyword “final” before the word “class” in the class declaration. For example:

final class MyClass {    // Fields    // Methods    // Constructors} 

Once declared, all fields, methods, and constructors will become immutable. This means they cannot be changed or modified in any way.

Declaring a class as final is beneficial in many ways. It prevents the class from being extended or subclassed, which can help protect the integrity of the code. Additionally, it can help improve the performance of the program, as the compiler can make certain optimizations when a class is declared as final.

Using the Final Keyword With Methods and Variables

You can also use the final keyword on individual methods and variables. Doing so prevents these elements from being changed or redefined in any subclass. For example:

class MyClass {    // Fields    final int x = 10;    // Methods    final void myMethod() {         // Implementation     }    // Constructors} 

Here, the variable “x” and the method “myMethod” will be immutable for any subclasses of MyClass.

Using the final keyword is a great way to ensure that your code is secure and that any changes made to the code are intentional. It also helps to make your code more readable and easier to debug.

Understanding Constructors in a Final Class

Constructors in a final class also become immutable once the class has been declared as final. This means that none of the parameters supplied to the constructor can be changed or modified in any way. Furthermore, the body of the constructor will not be altered when called by any subclass.

In addition, any methods that are declared within the final class cannot be overridden by any subclass. This is because the final class is considered to be the ultimate version of the class, and any changes to the class would be considered invalid. As a result, any methods declared within the final class must be used as-is.

The Effects of Finalizing a Class on Inheritance

Declaring a class as final has a significant effect on inheritance. While you can create subclasses of a non-final class, this is not possible for final classes. If a class is declared as final, any attempt to create a subclass will result in a compiler error.

In addition to preventing the creation of subclasses, final classes also prevent the overriding of methods. This means that any methods declared as final in a class cannot be overridden by subclasses. This can be beneficial in certain situations, as it ensures that the original method is always used, regardless of the subclass.

The Impact of Finalizing a Class on Polymorphism

Final classes also affect polymorphism. While it is possible for non-final classes to use polymorphism using inheritance, this is not possible for final classes. Since final classes cannot be extended, the compiler does not consider them for polymorphic behavior.

In addition, final classes can be used to prevent certain methods from being overridden. This can be useful in situations where the programmer wants to ensure that a certain method is always used in a certain way. By making the class final, the programmer can guarantee that the method will not be changed by any other class.

Practical Applications of Final Classes in Java

Given their characteristics, final classes are most commonly used when the programmer wants the code to remain constant and prevent any modification by a subclass. This means they can be used when creating an API or library that must remain consistent across all developers using it. Final classes can also prevent malicious code from being injected into a program, since all methods and fields become immutable.

In addition, final classes can be used to improve the performance of a program. Since the compiler knows that the class cannot be extended, it can optimize the code more efficiently. This can lead to faster execution times and improved memory usage. Final classes can also be used to create a more secure environment, as they can help to prevent unauthorized access to sensitive data.

Troubleshooting Common Issues With Final Classes

Final classes can cause errors if not used correctly. This is because some features of Java are not supported by final classes. For instance, you may encounter problems when using reflection to access variables or methods in a class declared as final. Similarly, since there is no polymorphism with final classes, you may encounter errors if you attempt to call methods using polymorphic behavior.

In addition, if you attempt to override a method declared as final, you will encounter an error since the method is immutable. Finally, if an enum declared as final is used within code, any attempt to modify it will throw errors.

Anand Das

Anand Das

Anand is Co-founder and CTO of Bito. He leads technical strategy and engineering, and is our biggest user! Formerly, Anand was CTO of Eyeota, a data company acquired by Dun & Bradstreet. He is co-founder of PubMatic, where he led the building of an ad exchange system that handles over 1 Trillion bids per day.

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