Unmodifiable List in java

Question

I'm trying to set a List unmodifiable.

In my code, I have a method which returns a list.

This list shouldn't be modified, but I don't want to catch the exception returned by the unmodifiableList.

private List<T> listeReferenceSelectAll = null;
List<T> oListeRet = new ArrayList<T>();
oListeRet = listeReferenceSelectAll;
return new ArrayList<T>(oListeRet);

It is an existing code and I have to transform it to return an unmodifiable list, but if an "add" method has been called, no exception has to be caught.

First I have create a class which implements List to override "add" method to log the exception and not to catch it.

But I don't know how to correctly instantiate it...

Answer 1

Collections.unmodifiableList

Returns an unmodifiable view of the specified list. This method allows modules to provide users with "read-only" access to internal lists. Query operations on the returned list "read through" to the specified list, and attempts to modify the returned list, whether direct or via its iterator, result in an UnsupportedOperationException. The returned list will be serializable if the specified list is serializable. Similarly, the returned list will implement RandomAccess if the specified list does.

Answer 2

You need java.util.Collections:

return Collections.unmodifiableList(oListeRet);

If you have to write your own, have that class implement the List interface and throw exceptions for the methods that modify contents.