How to search an array for a part of string?

Question

I have an arraylist<string> of words. I sort it using Collections.sort(wordsList);

I'm using this array for an auto-suggest drop down box, so that when the user is typing in a letter, they are given a list of suggestions similar to what they are typing in.

How do I go about searching this array for a prefix of string, say the user types in "mount" and the array contains the word "mountain", how can I search this array and return similar values.

Here's my code so far:

public List<Interface> returnSuggestedList(String prefix) {
    String tempPrefix = prefix;
    suggestedPhrases.clear();
    //suggestedPhrases = new ArrayList<Interface>();
    //Vector<String> list = new Vector<String>();
    //List<Interface> interfaceList = new ArrayList<Interface>();
    Collections.sort(wordsList);
    System.out.println("Sorted Vector contains : " + wordsList);
    int i = 0;
    while (i != wordsList.size()) {
        int index = Collections.binarySearch(wordsList, prefix);
        String tempArrayString = wordsList.get(index).toString();
        if (tempArrayString.toLowerCase().startsWith(prefix.toLowerCase())) {
            ItemInterface itemInt = new Item(tempArrayString);
            suggestedPhrases.add(itemInt);
            System.out.println(suggestedPhrases.get(i).toString());
            System.out.println("Element found at : " + index);
        }
        i++;
    }
    return suggestedPhrases;
}

Answer 1

If wordList is fixed (does not change from one method call to the other) you should sort it somewhere else, because sort is costly, and store it in lowercase.

In the rest of the method you would do something like:

List<String> selected = new ArrayList<String>();

for(String w:wordList){
    if(w.startsWith(prefix.toLower())) // or .contains(), depending on 
        selected.add(w);     // what you want exactly 
}

return selected;