Page 376 - Computer_Science_F5

(e) Final keyword
In the Java programming language, the “final” keyword is employed to indicate
constants. It can be applied to variables, methods, and classes. When any of these
entities is declared as final, it can only be assigned a value once. This means that a Chapter Five: Object oriented programming with Java
final variable cannot be reassigned with a different value. In this case, also a final
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method cannot be overridden by a subclass. As for variable and method, a final class
cannot be extended by another class.

(i) Final variable
In Java the value of a final variable cannot be changed, as shown in Program
Example 5.31.

Program Exampe 5.31:

Java program demonstrating final variable of a final keyword

class MyClass {
public static void main(String[] args) {
//this code show a final variable
final int age = 93;

// this code want to change the final variable
age = 39;
System.out.println(“Age: “ + age);
}
}

Output:

Figure 5.33: Output "final" keyword program

(ii) Final method
Program Example 5.32 demonstrate how the final method cannot be overridden. In
this case, the final method in parent class cannot be overridden by a child class. In
this example, a final method named show() is created inside the class FinalClass.
The Main class inherits the 'FinalClass' class. When you try to override the final
method in the Main class you might end up with compilation error.

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Student’s Book Form Five

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