You can create a simple wrapper class for the e-mail String:
public class EmailAddress {
@Pattern("\b[A-Z0-9._%+-]+@[A-Z0-9.-]+.[A-Z]{2,4}\b.")
String email;
//getters and setters
}
Then mark the field @Valid
in your existing object:
@NotNull
@Valid
List<EmailAddress> emailIds;
The validator will then validate each object in the list.