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final in java

Final variable in Java

In java, we can not change the value of final variable.

 class FinalVarExample
   {
    public static void main(String args[])
     {
       final double pi=3.14;
       int i=100;
       i=200; // we can change i value because it is not final variable
       // pi=4.13; as pi is final variable so we can not change its value.
       System.out.println("i= "+i +" pi= "+pi);
    }
  }

output : i=200 pi=3.14

Final class in Java

Declaring final class in preventing the inheritance .So if we declare a class as final no other clas may inherit it . A class me be declared as final by keyword final before class.

 final class A
  {
   
  }
 
 class B  //extends A  [As A class is final no class may inherit A class]
 {
  
 }

final Method in java

final method is used to prevent the override the methods in sub classes . Means if we declare a method final then sub class may not have same name method or we can say final method may not be overridden.

 class A
  {
   void display()
   {
     System.out.println("final method in super class");
   }
  final void show()
   {
    System.out.println("Not final method so it may be overridden");
   }
  }
 class B extends A
  {
   void display()
   {
    System.out.println("Overridden method in sub class");  
   }
   /*void show() 
   {
    System.out.println("This method will give error as we cannot override final method"); 
   } */
 }
class Main
 {
  public static void main(String args[])
  {
   B obj= new B();
   obj.display();
   obj.show();
  }
 }

output : final method in superclass

overridden method in subclass

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final in java

Final variable in Java

Final class in Java

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