Question

I am converting an empty String array (which i may get from middleware) to List .

For Conversion process i used Arrays.asList (Please see below code ) which is throwing an java.lang.UnsupportedOperationException .

public class Ramddd {
    public static void main(String args[]) {
        String[] words = null;
        if (words == null) {
            words = new String[0];
        }
        List<String> newWatchlist = Arrays.asList(words);
        List<String> other = new ArrayList<String>();
        other.add("ddd");
        newWatchlist.addAll(other);
    }

}



Exception in thread "main" java.lang.UnsupportedOperationException
    at java.util.AbstractList.add(Unknown Source)
    at java.util.AbstractList.add(Unknown Source)
    at java.util.AbstractCollection.addAll(Unknown Source)
    at Ramddd.main(Ramddd.java:18)

I dont get this Error if i use

List<String> mylist = new ArrayList<String>();
        for (int i = 0; i < words.length; i++) {
            mylist.add(words[i]);
        }

This forms an proper List and any operations like addALL , removeALL seems good , but dont want to go to this for loop approach , as it may result in performance .
Please let me know what is the best and safe approach for converting a String array to ArrayList .

Answer 1

How about the following:

public class Ramddd {
    public static void main(String args[]) {
        String[] words = getWords();
        if (words == null) {
            words = new String[0];
        }
        List<String> other = new ArrayList<String>(Arrays.asList(words));
        other.add("ddd");
    }
}

In terms of performance, I don’t this this is something to worry about, unless you have a really gigantic array of Strings.