MultiSet<String> multiSet = new HashMultiSet(); multiSet.add("Albama"); multiSet.add("Albama"); multiSet.add("Albama"); System.out.println(multiSet); // Prints [Albama:3] UnmodifiableMultiSet<String> unmodifiablemultiSet = (UnmodifiableMultiSet<String>) MultiSetUtils.unmodifiableMultiSet(multiSet); unmodifiablemultiSet.add("Albama"); // throws java.lang.UnsupportedOperationException