import org.ops4j.util.collection.BoundedQueue; queue.offer("Element 2"); queue.offer("Element 3"); import org.ops4j.util.collection.BoundedMap; map.put("Key 2", 2); map.put("Key 3", 3); map.put("Key 4", 4); map.put("Key 5", 5); import org.ops4j.util.collection.WeakBoundedMap; String key = new String("Key 1");