HashMap maintains key and value pairs and often denoted as HashMap<,Key, Value>, or HashMap<,K, V>,. HashMap implements Map interface. HashMap is similar to Hashtable with two exceptions – HashMap methods are unsynchornized and it allows null key and null values unlike Hashtable. It is used for maintaining key and value mapping. It is not an ordered collection which means it does not return the keys and values in the same order in which they have been inserted into the HashMap. It neither does any kind of sorting to the stored keys and Values. You must need to import java.util.HashMap or its super class in order to use the HashMap class and methods. In this example we have demonstrate almost all the important methods of HashMap class. For theoretical explanation of methods you can refer the HashMap documentation. Almost all the important methods I have covered in the above example. Still there are few lefts. Let’s discuss them – Do something so that your website can have more views………this is very much useful for beginners………………. Hi Chaitanya, This tutorial is really very understandable. I have been trying to learn Java from a long time but am not really able to get to undertsand the concepts well enough to use them wherever needed. Can you please suggest me how to learn so I can use the concepts in my day today job. Hello Sir, I don’t understand why have you used set for iterating while it can be easily done with keySet(),. Founder of beginnersBook.com, loves Java and open source stuff. BeginnersBook.com is a tech blog where he shares tutorials on programming (Java, C, CPP), WordPress, SEO and web development. Source.