by Five Java programs demonstrating the use of the final keyword in Java
:Below are five Java programs demonstrating the use of the final keyword, along with step-by-step explanations for each.
Program-1: Final Variable
java
public class FinalVariableExample {
public static void main(String[] args) {
final int MAX_VALUE = 100;
System.out.println("Max Value: " + MAX_VALUE);
// Uncommenting the following line will cause a compilation error
// MAX_VALUE = 200; // Cannot assign a value to a final variable
}
}
Explanation :
1. Declaration: The variable MAX_VALUE is declared as final, which means it cannot be changed after its initial assignment.
2. Output: The program prints the value of MAX_VALUE, which is 100.
3. Error Handling: Attempting to reassign MAX_VALUE will result in a compilation error, demonstrating that `final` prevents modification.
Program-2: Final Method
java
class Parent {
final void display() {
System.out.println("Final Method in java!!!!");
}
}
class Child extends Parent {
// Uncommenting the following method will cause a compilation error
// void display() {
// System.out.println("Trying to override final method.");
// }
}
public class FinalMethodExample {
public static void main(String[] args) {
Child child = new Child();
child.display(); // Calls the final method from Parent
}
}
Explanation
1. Final Method: The method display in the Parent class is declared as final, meaning it cannot be overridden in any subclass.
2. Child Class: The Child class attempts to override the display method. This is commented out, as it would lead to a compilation error if uncommented.
3. Execution: The main java method creates an instance of Child and calls display, which outputs the message from the `Parent` class.
Program-3: Final Class
java
final class FinalClass {
void show() {
System.out.println("This is a final class.");
}
}
// Uncommenting the following class will cause a compilation error
// class SubClass extends FinalClass {
// }
public class FinalClassExample {
public static void main(String[] args) {
FinalClass obj = new FinalClass();
obj.show(); // Calls the method in the final class
}
}
Explanation
1. Final Class: The FinalClass is declared with the final keyword, preventing it from being subclassed.
2. SubClass Attempt: Any attempt to create a subclass from FinalClass will result in a compilation error (commented out in the code).
3. Method Call: The main method creates an instance of FinalClass and calls its show method.
Program 4: Final Parameter
java
public class FinalParameterExample {
void calculate(final int number) {
// Uncommenting the following line will cause a compilation error
// number = number + 10; // Cannot modify final parameter
System.out.println("The number is: " + number);
}
public static void main(String[] args) {
FinalParameterExample example = new FinalParameterExample();
example.calculate(20); // Passing a final parameter
}
}
Explanation
1. Final Parameter: The method calculate takes a parameter number declared as final, which means it cannot be modified within the method.
2. Error Handling: Attempting to change the value of number inside the method results in a compilation error (commented out).
3. Output: The main method calls calculate with 20, which is printed without modification.
Program 5: Final with Constructors
java
class FinalField {
final int value;
// Constructor to initialize final field
FinalField(int value) {
this.value = value; // Assigning the value to the final field
}
void display() {
System.out.println("Final Field Value: " + value);
}
}
public class FinalFieldExample {
public static void main(String[] args) {
FinalField obj = new FinalField(50);
obj.display(); // Displays the value of the final field
}
}
Explanation
1. Final Field: The class FinalField has a final field value which must be initialized.
2. Constructor: The constructor initializes value when an object of FinalField is created.
3. Display Method: The display method prints the value of the final field.
4. Execution: In main, an instance of FinalField is created with a value of 50, which is then displayed.
