Java final keyword

One of the features of Java that is particularly important for programmers to understand is the “final” keyword.

In Java, the final keyword is used to denote constants. It can be used with variables, methods, and classes. we’ll take a look at what the final keyword means for classes, methods, and variables.

The “final” keyword in Java is used to indicate that once any entity (i.e, variable, method or class) is declared final, it can be assigned only once.

1. Final variable cannot be reinitialized.
2. Final method cannot be overridden.
3. Final class cannot be extended.

What is the final in Java

The “final” keyword can be used in various contexts such as variables, methods, and classes. In each context, the use of the “final” keyword indicates that the entity is immutable and cannot be changed.

Final with variable in Java

When the “final” keyword is used with a variable, it means that the value of the variable cannot be changed once it has been initialized. This can be useful when you want to define a constant value that should not be modified.

Here’s an example of using “final” with a variable:

final int MAX_COUNT = 10;

In this example, “MAX_COUNT” is a constant variable, and its value is set to 10. Once initialized, the value of “MAX_COUNT” cannot be changed.

Here are some of the benefits of using “final” with variables:

1. Preventing accidental changes: When you declare a variable as final, you are explicitly stating that its value should not be modified. This can help prevent accidental changes to the variable’s value later in the program, which can be difficult to debug.
2. Improving performance: The Java compiler can optimize code that uses final variables, since it knows that their value will not change. This can lead to faster execution times and more efficient use of memory.
3. Enforcing immutability: If you are working with immutable objects, such as strings or other reference types, you can use final variables to ensure that their values cannot be changed. This can help prevent bugs and improve the maintainability of your code.

It’s worth noting that the “final” keyword can also be used with instance variables and static variables.

In Java, “final” and “static” are both keywords used to define characteristics of variables and methods. The “final” keyword is used to define constants that cannot be changed after they are initialized, while the “static” keyword is used to define class-level variables and methods that can be accessed without creating an instance of the class. In other words, “final” is used to define unchangeable constants, whereas “static” is used to define variables and methods that can be accessed without creating an object of the class.

Final with method in Java

When the “final” keyword is used with a method, it means that the method cannot be overridden by any subclass. This can be useful when you want to ensure that a method’s behavior remains consistent throughout the program’s execution.

Here’s an example of using “final” with a method:

public final void display(String message) {
    System.out.println(message);
}

In this example, the “display()” method is declared as final. This means that the method cannot be overridden by any subclass, and its behavior will remain consistent throughout the program’s execution.

There are several benefits to using the “final” keyword with methods:

1. Preventing unintentional method overriding: By declaring a method as final, you can prevent sub-classes from accidentally overriding the method and changing its behavior. This can help to prevent bugs and unexpected behavior in your code.
2. Enhancing security: If a method in a class is declared as final, it cannot be changed by malicious code that may try to override it to introduce security vulnerabilities.
3. Improving performance: When a method is declared as final, the compiler can optimize the method invocation by inlining the method call. This can improve performance in some cases.

Note that only methods that are intended to be overridden by sub-classes should be declared without the final keyword. If a method is not meant to be overridden, it’s a good practice to declare it as final to prevent unintentional changes to its behavior.

Final with class in Java

When the “final” keyword is used with a class, it means that the class cannot be sub-classed. This can be useful when you want to ensure that a class’s behavior remains consistent throughout the program’s execution.

Here’s an example of using “final” with a class:

final class Demo{
    // class definition
}

In this example, the “Demo” class is declared as final. This means that the class cannot be sub-classed, and its behavior will remain consistent throughout the program’s execution.

Here are some benefits of using the “final” keyword with classes:

1. Preventing unwanted sub-classing: When a class is marked as “final”, you can be sure that no other class will extend it and modify its behavior in unexpected ways. This can be useful in situations where you want to provide a class with a fixed behavior that cannot be altered by external code.
2. Improving performance: Marking a class as “final” allows the compiler to optimize the code more aggressively, since it knows that the class cannot be sub-classed and that its behavior will not change at runtime.

Overall, the “final” keyword is an important feature of Java that allows you to define entities that cannot be modified after they have been initialized. This can be useful when you want to ensure that certain values or behaviors remain consistent throughout the program’s execution.