Java8 Lambda expression to iterate over enum values and initialize final member

Question

I have a static enum like this:

private static enum standardAttributes {
    id, gender, firstname, lastname, mail, mobile
}

I need all the values as String. Therefore I have a method like this:

public static List<String> getStandardRecipientsAttributes() {
    List<String> standardAttributesList = new ArrayList<String>();
    for (standardAttributes s : standardAttributes.values())
        standardAttributesList.add(s.toString());

    return standardAttributesList;
}

There is no need to create the same List everytime this method is called. So I created a static member:

static final List<String> standardAttributesList;
static {
    standardAttributesList = getStandardRecipientsAttributes();
}

This is all fine, but I wonder if there is a fancy Lambda expression to replace the method. Something like this:

Arrays.asList(standardAttributes.values()).forEach((attribute) -> standardAttributesList.add(attribute.toString()));

Two questions:

1. Can I avoid the Arrays.asList wrapper?
2. How can I handle the compiler error: The blank final field standardAttributesList may not have been initialized?

Answer 1

You can do

static final List<String> standardAttributesList = 
                                           Stream.of(values())
                                                 .map(Enum::name)
                                                 .collect(Collectors.toList());

This will create a Stream from an the array of values, apply the .name() method to each one and finally collect all the results into a List.