Collections

Question 1

What is an iterator?

Answer 1

Use it to cycle through elements in collection. Each collection class provides an iterator() method.

Iterator itr = myList.iterator();
While(itr.hasNext()){
Object e = itr.next();
}

Question 2

What are comparable and comparator?

Answer 2

Comparable implemented by class, overrides compareTo(T t). Used by calling compares to.”

Comparator requires extra comparator class created that implements comparator. Overrides compare(a, b). Used by Collections.sort(list, new comparator());

Question 3

Types of collections?

Answer 3

List, Set and Map. List include ArrayList, LinkedList, Vector. Map includes HashMap, TreeMap. Set includes HashSet and TreeSet.

Question 4

Some basic List methods?

Answer 4

add()
Size()
Remove()
Clear()