import org.apache.commons.collections4.BidiMap; import org.apache.commons.collections4.bidimap.TreeBidiMap; public class CommonsCollectionsExample { public static void main(String[] args) { BidiMap<String, Integer> bidiMap = new TreeBidiMap<>(); bidiMap.put("One", 1); bidiMap.put("Two", 2); bidiMap.put("Three", 3); int value = bidiMap.get("Two"); System.out.println("Value: " + value); String key = bidiMap.getKey(3); System.out.println("Key: " + key); } }