What is “final” keyword in java

Java provides multiple keywords that can be used for different purposes such as abstract, for, do, final, etc. If we talk about the final keyword, it can be used with the java classes, variables, and methods. But why should we use it, and for what purpose is the final keyword used in Java? Well in Java, the final keyword restricts/stops the users from modifying the value of the variable, overriding the method, and inheriting the class.

This article will describe the following aspects of java’s “final” keyword:

What is final keyword in Java
final variables in Java
final Methods in Java
final Classes in Java
Examples

So, let’s begin!

What is final keyword in Java

It is a keyword that can be used with java classes, methods, and class attributes/variables. In java, the use of the final keyword makes the classes, variables, and methods non-changeable.

final variables in Java

If a variable is declared/created as final it means the value of that variable can’t be changed/modified. A final variable that is uninitialized can be initialized only using the java constructors.

Example 1

In this example, we will declare a variable as final, and we will try to modify the value of such variable:

publicclassFinalExample {
final String name = "Joe";
publicstaticvoidmain(String[] args) {
FinalExample obj = newFinalExample();
obj.name = "Alex";
}
}

In the main method, firstly, we created the object of “FinalExample” class and afterward, we tried to modify the variable value using the class’s object:

The output showed that we encountered a compile-time error.

final Methods in Java

If we utilize the final keyword with a java method, it can’t be overridden.

Example 2

In this example we will create a method “display()” using the final keyword:

classPersonClass{
finalvoiddisplay() {
System.out.println("This is PersonClass");
}
}
publicclassEmployeeClassextendsPersonClass {
voiddisplay() {
System.out.println("Trying to Override display method");
}
publicstaticvoidmain(String[] args) {

}
}

We created two classes: “PersonClass” and “EmployeeClass”.
The “PersonClass” has a method named “display()”.
The “EmployeeClass” inherits the “PersonClass”
Within “EmployeeClass” we tried to override the “display()” method of “PersonClass”:

The error proved that the final method couldn’t be overridden in java.

final Classes in Java

In Java, we can’t create an (outer class) class as private or protected because java is an object-oriented language, and declaring a class as private or protected means restricting the classes to be inherited. So, java doesn’t allow private or protected classes. However, if someone doesn’t want to make a class inheritable, then what to do?

How to stop a class from being inherited in java?

To solve this problem, the final keyword can be utilized with the java classes. In java, any class declared/created with a final keyword wouldn’t be available for the inheritance.

Example 3

In this example, we will create a PersonClass with the final keyword and we will try to inherit it from some other class:

finalclassPersonClass{
voiddisplay() {
System.out.println("This is PersonClass");
}
}
publicclassEmployeeClassextendsPersonClass {
voiddisplay() {
System.out.println("Overriding the display method");
}
publicstaticvoidmain(String[] args) {

}
}

In the above code snippet:

We created two classes: PersonClass, and EmployeeClass.
PersonClass is declared as final.
EmployeeClass tried to extend the PersonClass.

The above snippet verified that a compile-time error occurred when we tried to access the PersonClass.

Conclusion

In java, a final keyword can be used with a variable, class, or method. The purpose of the final keyword is to restrict the usage of the java variables, classes, and methods. It restricts/stops the users from modifying the value of the variables, overriding the methods, and inheriting the classes. This post presented an in-depth overview of java’s final keyword with suitable examples.

What is “final” keyword in java | Explained