Iterator

3 CURSORS OF JAVA

• Enumeration (I)
• Iterator (I)
• ListIterator (I) : Provides 2 way iteration with list.previous() adn list.next()

3 main methods of iterator API

 hasNext()
 next()
 remove(object) -> to avoid concurrent modification exception while iterating

List Iterator

Maps

Iterating a Map(TreeMap or HashMap) via KeySet

//Set keyset = map.keySet();
//iterator<E> itr= keyset.iterator();
iterator<E> itr= map.keySet().iterator();

while (itr.hasNext()){
	int key = itr.next
	int value = map.get(key)
}

Iterating a Map(TreeMap or HashMap) via EntrySet

//Set set = map.entrySet();
//Iterator<Map.Entry<Integer,String>> itr = set.iterator()
Iterator<Map.Entry<Integer,String>> itr = map.entrySet().iterator();
while (itr.hasNext()){
   //itr.getKey(), itr.getValue
	int key = itr.getKey();
	int value = itr.getValue();
}

For Each Loop (Read Only Loop)

For each loop for Map

//For Each Loop
for(Int key :map.keySet()){
	int value = map.get(key);
}