There have multiple solusions to convert list to a collection
Solution 1
List<Contact> CONTACTS = new ArrayList<String>();
// fill CONTACTS
Collection<Contact> c = CONTACTS;
Solution 2
private static final Collection<String> c = new ArrayList<String>(
Arrays.asList("a", "b", "c"));
Solution 3
private static final Collection<Contact> = new ArrayList<Contact>(
Arrays.asList(new Contact("text1", "name1")
new Contact("text2", "name2")));
Solution 4
List<? extends Contact> col = new ArrayList<Contact>(CONTACTS);