<dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>30.1-jre</version> </dependency> implementation 'com.google.guava:guava:30.1-jre' import com.google.common.collect.ArrayListMultimap; import com.google.common.collect.ListMultimap; ListMultimap<String, String> multimap = ArrayListMultimap.create(); multimap.put("key1", "value1"); multimap.put("key1", "value2"); multimap.put("key2", "value3"); multimap.put("key2", "value4"); List<String> valuesForKey1 = multimap.get("key1"); List<String> valuesForKey2 = multimap.get("key2"); for (Map.Entry<String, String> entry : multimap.entries()) { String key = entry.getKey(); String value = entry.getValue(); System.out.println(key + ": " + value); }