Iterators

Question 1

What is an Iterator?

Answer 1

Iterators are (usually) a special class/object that allows the user to easily traverse a data structure.

Question 2

What kind of methods does an Iterator have?

Answer 2

Iterators usually have methods to get the current item, go to the next item, or go to the previous item.

Question 3

How is an Iterator used?

Answer 3

The data structure itself implements the iterator (usually as an inner class or a private class).

Question 4

What needs to be done to have an Iterator in your class?

Answer 4

The class itself would implement the
Iterable interface (in the java.lang package), which has
just one method: iterator(). This method returns an
instance of the iterator for that data structure.

Question 5

What methods does the Iterator interface have?

Answer 5

The Iterator interface in Java has three methods:

hasNext(), next(), and remove().

Question 6

What does the hasNext() method do?

Answer 6

hasNext() tells you whether calling next() will return the
next item in the data structure (i.e. if there is at least one
more item).

Question 7

What does the next() method do?

Answer 7

next() returns the next item in the data structure.

Question 8

What does the remove() method do?

Answer 8

remove() removes the most-recently returned item.