final, finally and finalize () in Java

final

final is a keyword.
It is used to apply restriction on class, method and variables.
final class cannot be inherited, final method cannot be overridden and final variable cannot be changed.

finally

finally is a block followed by try or catch block.
finally block is executed whether exceptions are handled or not.
We put clean up code in finally block.

finalize ()

finalize is a method.
This method is associated with garbage collection, just before collecting the garbage by system.
It is called automatically.

Creating Custom Exceptions

The exceptions that we create on our own are known as custom exception.
These exceptions are created to generate a solution for anticipated errors as per programmer’s need.
A “Custom exception class” must be extended from “Exception class”.

Example : Program to create custom exception in Java

// CustomException.java

public class CustomException extends Exception
{
     public CustomException(String msg)
     {
          super(msg);
     }
}

// CustomDemo.java

public class CustomDemo
{
      public static void main(String args[]) throws Exception
      {
           CustomDemo custom = new CustomDemo();
           custom.display();
      }
      public void display() throws CustomException
      {
           for(int i=2;i<20;i=i+2)
           {
                 System.out.println("i= "+i);
                 if(i==8)
                 {
                       throw new CustomException("My Exception Occurred");
                 }
           }
      }
}

Output:
i= 2
i= 4
i= 6
i= 8
Exception in thread "main" CustomException: My Exception Occurred
at CustomDemo.display(CustomDemo.java:11)
at CustomDemo.main(CustomDemo.java:4)