Map implementation with duplicate keys

Question

I want to have a map with duplicate keys.

I know there are many map implementations (Eclipse shows me about 50), so I bet there must be one that allows this. I know

Answer 1

Multimap multimap = ArrayListMultimap.create();

multimap.put(1, "A");
multimap.put(1, "B");
multimap.put(1, "C");
multimap.put(1, "A");

multimap.put(2, "A");
multimap.put(2, "B");
multimap.put(2, "C");

multimap.put(3, "A");

System.out.println(multimap.get(1));
System.out.println(multimap.get(2));       
System.out.println(multimap.get(3));

Output is:

[A,B,C,A]
[A,B,C]
[A]

Note: we need to import library files.

http://www.java2s.com/Code/Jar/g/Downloadgooglecollectionsjar.htm

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

or https://commons.apache.org/proper/commons-collections/download_collections.cgi

import org.apache.commons.collections.MultiMap;
import org.apache.commons.collections.map.MultiValueMap;