Suppose i try to instantiate an abstract class then a checked exception is thrown,but who handles it or how is it handled?

I don't think you can instantiate an abstract class.

Ok that thing i know ,i just want to throw an Instantiation Exception and wants to know who handles it and how is it handled . Now the other thing which i want to know is that can we avoid an exception through throws clause?

public void foo() throws Exception {
  //something happens and an exception is being thrown
}

With the throws you don't avoid the exception. By adding throws you don't have to catch it, but it is thrown to the method that calls foo. Meaning that you have to write something like this:

public void hoo() {
  try {
    foo();
  } catch (Exception e) {
  }
}

You can omit try-catch by adding throws Exception at the declaration of hoo() but you don't avoid it because it is thrown to the one that calls hoo(). You can do that until you reach main() where you will eventually have to catch it in the end