import com.google.common.collect.ArrayListMultimap; import com.google.common.collect.Multimap; public class GuavaMultimapDemo { public static void main(String[] args) { Multimap<String, String> multimap = ArrayListMultimap.create(); multimap.put("key1", "value1"); multimap.put("key1", "value2"); multimap.put("key2", "value3"); } } import org.apache.commons.collections4.Bag; import org.apache.commons.collections4.bag.HashBag; public class ApacheCommonsBagDemo { public static void main(String[] args) { Bag<String> bag = new HashBag<>(); bag.add("apple", 3); bag.add("banana", 2); bag.add("apple"); } } import org.eclipse.collections.api.bag.primitive.MutableIntBag; import org.eclipse.collections.impl.bag.mutable.primitive.IntHashBag; public class EclipseCollectionsBagDemo { public static void main(String[] args) { MutableIntBag bag = new IntHashBag(); bag.addOccurrences(1, 3); bag.addOccurrences(2, 2); bag.add(1); } }