Question

I am working with collections. One thing which is bothering me is: where is the Implementations of the methods of java.util.Iterator Interface? In which class these methods are implemented?

 public abstract boolean hasNext();
 public abstract E next();
 public abstract void remove();

I searched the source code of the java API, but didn’t find the implementation of these methods in any class.

Answer 1

Iterator is an interface and it has around 50 implementations in the java api itself.
Since the iterator needs to compy with the iterating object type, for ex if you want to iterate an ArrayList the iterator instance which your iterator() method returns is of new Itr type. see the implementation in java.util.AbstractList class which forms the base class for ArrayList