Java Collection

Some key information on Collection:

• List can contain duplicate elements whereas Set contains only unique elements.
• Set contains values only whereas Map contains key and values both.
• HashSet maintains no order whereas TreeSet maintains ascending order.
• HashSet contains only values whereas HashMap contains entry(key,value). HashSet can be iterated but HashMap need to convert into Set to be iterated.
• HashMap maintains no order but TreeMap maintains ascending order.
• Collection is an interface whereas Collections is a class. Collection interface provides normal functionality of data structure to List, Set and Queue. But, Collections class is to sort and synchronize collection elements.