Question

I am new to java, I have seen in the code at many places where my seniors have declared as

List myList = new ArrayList(); (option1)

Instead of

ArrayList myList = new ArrayList(); (option2)

Can you please tell me why people use Option1, is there any advantages?

If we use option2, do we miss out any advantages or features?

Answer 1

The advantage of using option1, ie, List myList = new ArrayList(); is to have polymorphic behaviour with respect to methods. Say, for example, you can have a method which takes arguments of type List,

someMethod(List lst)
{
   lst.doSomething();
   //do somethng else.....
}

In this method lst can be of type Linked List, ArrayList or CopyOnWriteArrayList.