• • A map contains values based on the key i.e. key and value pair.Each pair is known as an entry.Map contains only unique elements.
• • The Map interface represents a mapping between a key and a value. The Map interface is not a subtype of the Collection interface. Therefore it behaves a bit different from the rest of the collection types.

Map Implementations:

Since Map is an interface you need to instantiate a concrete implementation of the interface in order to use it. We can choose between the following Map implementations in the Java Collections API:

• • java.util.HashMap
• • java.util.Hashtable
• • java.util.EnumMap
• • java.util.IdentityHashMap
• • java.util.LinkedHashMap
• • java.util.Properties
• • java.util.TreeMap
• • java.util.WeakHashMap

In my point of view, the most commonly used Map implementations are HashMap and TreeMap.Here are a few examples of how to create a Map instance: