final Method in Java
The final keyword in Java is used to indicate that a particular entity cannot be modified. This entity can be a class, method, or variable. When the final keyword is used with a method, it indicates that the method cannot be overridden by any subclass.
In this article, we will discuss,
- The final method in Java
- Final method and Inheritance
- A final method and Polymorphism
- Final Method and Performance
The final method in Java
A final method in Java is a method that cannot be overridden in the subclass. Once a method is marked as final, it cannot be changed or overridden by any subclass. Final methods are declared using the final keyword in the method signature.
Final methods differ from regular methods in that they cannot be modified or extended by any subclass. This adds security to the program because the parent class can ensure that no subclass changes certain critical methods. Additionally, final methods are also faster than regular methods, as the JVM can optimize them during runtime.
The advantages of using final methods include the ability to prevent unwanted modification of critical methods in the program. It also allows for better performance, as the JVM can optimize final methods during runtime. However, final methods cannot be modified or overridden, even if a subclass could benefit from doing so.
Overall, understanding the use of final methods in Java programming is important for creating secure and optimized code. Marking a method as final requires careful consideration, as it can significantly impact the program’s design and functionality.
Final method and Inheritance:
In Java, when a method is marked as final in a class, it means that it cannot be overridden by any subclass. This also means that the final method will have the same implementation in both the parent class and the subclass.
Final methods play an important role in inheritance, as they allow the parent class to prevent any modification of the method in the subclass. This can be helpful when the parent class needs to enforce specific behaviour and disallow modifications to the subclass method.
Final methods can’t be overridden by subclasses, even with the same method signature. This ensures that the implementation of the method remains consistent throughout the inheritance hierarchy.
Let’s take a look at an example to demonstrate the use of the final method in inheritance:
public class Parent {
public final void printMessage() {
System.out.println("This is a final method in Parent class");
}
}
public class Child extends Parent {
// This will result in a compile-time error
public void printMessage() {
System.out.println("This is an overridden method in Child class");
}
}
In the example above, the Parent class has a final method called printMessage(). The Child class attempts to override this method, but this will result in a compile-time error.
This is because the final keyword in the Parent class prevents any modification of the method in the Child class. The implementation of printMessage() will remain consistent in both classes.
Final methods can enforce consistent behaviour in an inheritance hierarchy, ensuring implementation remains uniform. However, it should be used with caution, as it can limit the flexibility and extensibility of the code.
Final method and Polymorphism:
In Java, polymorphism allows objects to take on different forms based on the context in which they are used. A final method in Java is a method that cannot be overridden by any subclass. When it comes to polymorphism, the final method behaves differently from a regular method.
Explanation of how the final method affects polymorphism in Java:
Polymorphism allows objects to take on different forms based on the context in which they are used. In Java, a subclass can override a method defined in its superclass to provide a different implementation. However, a final method cannot be overridden by any subclass. When a subclass object calls a final method, the implementation from the superclass will be used. This ensures that the behaviour of the final method cannot be changed by the subclass.
Example code snippets to demonstrate the use of the final method in polymorphism:
class Animal {
final void eat() {
System.out.println("Animal is eating.");
}
}
class Dog extends Animal {
void eat() { // will not compile as final method cannot be overridden
System.out.println("Dog is eating.");
}
}
public class Main {
public static void main(String[] args) {
Animal animal = new Dog();
animal.eat(); // Output: Animal is eating.
}
}
Output:
The animal is eating.
In the above code snippet, we have defined a class Animal with a final method, eat(). We have then defined a subclass Dog which tries to override the eat() method. But the code fails to compile as a final method cannot be overridden. In the main method, we have created an object of the Dog class but assigned it to a variable of the Animal type. When we call the eat() method on the animal object, the implementation defined in the superclass Animal is used.
The final method eats () defined in the superclass Animal is invoked, despite the object being an instance of the Dog class. Therefore, the Dog class is unable to offer a different implementation.
Overall, the final method in Java has a significant impact on polymorphism. When a method is marked as final in Java, it is not possible to override it in any subclass. Instead, the implementation-defined in the superclass is always used, regardless of the context in which the method is called.
Final Method and Performance
In Java, the final keyword can also be applied to methods to indicate that they cannot be overridden by subclasses. This can have an impact on the performance of the program.
A method marked as final is unmodifiable by subclasses, allowing the compiler to perform optimizations that would otherwise be impossible. For example, the compiler can inline the final method directly into the calling code, rather than making a separate method call. This can result in faster code execution and improved performance.
Additionally, when a method is marked as final, the JVM can also make certain optimizations at runtime. For example, it can cache the result of the final method so that it doesn’t need to be recalculated every time it is called. This can improve the overall performance of the program.
However, it’s important to note that using the final keyword on methods can also harm performance in certain cases. For example, if a frequently called method performs costly operations, inlining it can increase code size and slow down the program.
Example code snippets to demonstrate the use of the final method in improving performance:
public class MyClass {
private final int value;
public MyClass(int value) {
this.value = value;
}
public final int getValue() {
return value;
}
}
// in the calling code:
MyClass obj = new MyClass(42);
int val = obj.getValue();
Output:
Value = 42
In this example, the getValue() method is marked as final, indicating that it cannot be overridden by any subclasses. This allows the compiler to inline the method directly into the calling code, which can result in faster execution and improved performance.
Overall, the use of the final keyword on methods can have a significant impact on the performance of a Java program. By indicating that a method cannot be overridden, the compiler and JVM can make certain optimizations that can result in faster code execution. However, it’s important to carefully consider the use of the final keyword and weigh the potential performance benefits against any potential drawbacks.
Conclusion
Final methods in Java are an important concept for Java programmers to understand. In this article, we have explained the final keyword in Java and its purpose. We also provided a brief overview of what will be covered in the article.
We then went on to discuss the definition and characteristics of the final methods and how they differ from regular methods. We also discussed the advantages and disadvantages of using final methods.
We discussed how final methods impact inheritance and polymorphism in Java with code examples. We also discussed how final methods can improve performance in Java with example code snippets. Finally, We’ve covered the main points and stressed the importance of final methods in Java programming.