Difference b/w Set,List and Map

Set (Interface)

• Set is an un-ordered collection which doesn’t allows duplicate (no-duplicate) elements
• We can iterate the values by calling iterator() method
  

Set s = new HashSet();
Iterator iter = s.iterator();

List (Interface)

• List is an ordered collection which allows duplicate elements
• We can iterate the values by calling iterator() method
  

List li = new ArrayList();
Iterator iter = li.iterator();

Map (Interface)

• In Map we used to store the data in key and value pairs, we may have duplicate values but no duplicate keys
• In Map we don’t have iterator() method, but we can get the keys by calling the method keySet()
  

Map m; // insert values
Set s = m.keySet();
// Get Map keys into the Set and then iterate this Set object normally
// m.keySet() returns Set object with Map keys
Iterator iter = s.iterator();