Conversion from ArrayList to Collection

Question

I am having difficulty in this conversion. I don't know if there is a syntax error or this is not even possible.

I need to convert from--

private static final List<Contact> CONTACTS = Arrays.asList(
        new Contact("text1", "name1"),
        new Contact("text2", "name2"),
        new Contact("text3", "name3"));

To--

Collection c = new ArrayList(Arrays.asList(--?--))

--?-- --> (I don't understand what comes here)

By doing this, I intend to avoid UnsupportedOperationException. Any help appreciated, thanks!

Hey thank you all, i got it! This worked--
Solution:

List<? extends Contact> col = new ArrayList<Contact>(CONTACTS);

Solution 1

I am updating it as an answer I was looking for. Thank you all for your responses!

List<? extends Contact> col = new ArrayList<Contact>(CONTACTS);

Solution 2

public interface List
extends Collection

You don't need to do anything. Or is there some particular operation you need that the ArrayList doesn't support?

Solution 3

You don't have to do anything to perform that conversion, this works:

List<Contact> CONTACTS = new ArrayList<String>();
// fill CONTACTS
Collection<Contact> c = CONTACTS;

Collection is the super-interface of List, if an object implements List it will also implement Collection.

Solution 4

Doing this works:

private static final Collection<String> c = new ArrayList<String>(
                                                Arrays.asList("a", "b", "c"));

Thus I'd suggest something like:

private static final Collection<Contact> = new ArrayList<Contact>(
                       Arrays.asList(new Contact("text1", "name1")
                                     new Contact("text2", "name2")));

View more solutions

Comments

[Prince]

I cannot apply CONTACT.remove(index); operation on the ArrayList.

[Yuushi]

@Prince That's because the Collection interface doesn't have a Collection.remove(index) method, only a Collection.remove(Object o) method. See docs.oracle.com/javase/6/docs/api/java/util/Collection.html

[Prince]

Thanks but this will not work for me bcoz i consistently need to update contact from previously updated contact list and this would give me the original list everytime.