creating unmodifiable list

You can use an unmodifiable wrapper to create a collection that offers read-only access to

others, while allowing read/write access to yourself. You do this simply by giving others a

reference to the unmodifiable wrapper while retaining for yourself a reference to the

original collection.

1.package com.usr.collections;

2.

3.import java.util.Arrays;

4.import java.util.Collections;

5.import java.util.List;

6.

7.public class UnmodifiableList {

8.       public static void main(String[] args) {

9.

10.              String[] strArr = { "sunday", "monday", "tuesday", "wednesday",

                        "thursday", "friday", "saturday" };

11.              List<String> strList = Arrays.asList(strArr);

12.              List<String> unmodifiableList = Collections.unmodifiableList(strList);

13.              // unmodifiableList.add("sunday");

14.              for (String temp : unmodifiableList) {

15.                     System.out.println(temp);

16.              }

17.       }

18.}

In the above program if line 13 is uncommented then we get

Exception in thread "main" java.lang.UnsupportedOperationException

       at java.util.Collections$UnmodifiableCollection.add(Unknown Source)

                                                          at com.usr.collections.UnmodifiableList.main(UnmodifiableList.java:13)