How to include duplicate keys in HashMap? [duplicate]

Answer 1

You can't have duplicate keys in a Map. You can rather create a Map>, or if you can, use Guava's Multimap.

Multimap multimap = ArrayListMultimap.create();
multimap.put(1, "rohit");
multimap.put(1, "jain");

System.out.println(multimap.get(1));  // Prints - [rohit, jain]

And then you can get the java.util.Map using the Multimap#asMap() method.