Difference Between final, finally And finalize In Java | Interview Question Explained

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final - keyword
finally - block
finalize() - method

final: 
used to apply restrictions on class, method and variable. 
  • final variable => value can not be changed
  • final method => you cannot override it
  • final class => you cannot extend it

Example: 
class FinalExample{  
    public static void main(String[] args){  
        final int x=10;  
        x=200;      //Compile Time Error  
}}  

finally:
  • used with try-catch
  • after try-catch block but before control transfers back to its origin
  • executes whether exception occurs or not
class FinallyExample{  
    public static void main(String[] args){  
        try{  
            int x=300;  
        }catch(Exception e){System.out.println(e);}  
        finally    {System.out.println("finally block is executed");}  
}}  

Garbage => unreferenced Object

A a = new A();

a = null; nullifying an object i.e. no reference

A a = new A();

A b = new A();

a = b; one of the object is useless as their is no point of 1 object

new A(); anonymous object and we are not assigning anything... unreferenced, nullifying



finalize:
  • invoked each time before garbage collection
  • System.gc() => used to invoke garbage collection
  • after try-catch block but before control transfers back to its origin
  • executes whether exception occurs or not
Example:
class C1{ 
    public static void main(String[] args){  
        C1 a=new C1();  
        C1 b=new C1();  
        a=null;  
        b=null;  
        System.gc();  
}
    public void finalize(){
        System.out.println("GC");
    }  
}  

Output: GC GC (2 times as 2 objects)


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