Tutorials

final keyword

The final keyword in java is used to restrict the user. The final keyword can be

final variable

final method

final class

final variable

final variables are the constants which cannot change the value of a final variable once it is initialized.

Program to use of final variable

class FinalDemo{  
   final int MAX=89;
   void me(){  
      MAX=110;
   }  
   public static void main(String args[]){  
      FinalDemo obj=new  FinalDemo();  
      obj.me();  
   }  
}

Output

D:\javap>javac FinalDemo.java
FinalDemo.java:4: error: cannot assign a value to final variable MAX
      MAX=110;
      ^
1 error

Here we got a compilation error because we tried to change the value of a final variable

final method

A final method cannot be overridden which means even though a subclass can call the final method of parent class but we cannot override it.

 
class FinalMethod{  
   final void demo(){
      System.out.println("FinalMethod Class 
Method");
   }  
}  
         
class ABC extends FinalMethod{  
   void demo(){
      System.out.println("ABC Class Method");
   }  
         
   public static void main(String args[]){  
      ABC obj= new ABC();  
      obj.demo();  
   }  
}

Output

D:\javap>javac FinalMethod.java
FinalMethod.java:8: error: demo() in ABC cannot override demo() in FinalMethod
   void demo(){
        ^
  overridden method is final

final class

A class is declared as final then this class cannot be inherited.

final class A{  
}  
         
class B extends A{  
   void demo(){
      System.out.println("I am in A");
   }  
   public static void main(String args[]){  
      A obj= new A(); 
      obj.demo();
   }  
}
Output
error: cannot inherit from final A
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