Introduction to Programming

Immutable versus unmodifiable

There are eight static methods in the Collections class that make a collection unmodifiable:

• Set<T>  unmodifiableSet(Set<? extends T> set)
• List<T>  unmodifiableList(List<? extends T> list)
• Map<K,V>  unmodifiableMap(Map<? extends K, ? extends V> map)
• Collection<T> unmodifiableCollection (Collection<? extends T> collection)
• SortedSet<T>  unmodifiableSortedSet(SortedSet<T> sortdedSet)
• SortedMap<K,V>  unmodifiableSortedMap(SortedMap<K,? extends V> sortedMap),
• NavigableSet<T>  unmodifiableNavigableSet(NavigableSet<T> navigableSet)
• NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K,? extends V> navigableMap)

Here is an example of code that creates an unmodifiable list:

List<String> list = Arrays.asList ...