自动完成功能Java

Question

I am working on a Displaykeyboard for disabled peaople and i am thinking about to adding a auto word completion function. I found a example from oracle that works as i need it. Its the Another Example: TextAreaDemo. The problem is i dont really understand the search algorithm and the problem is when i add some word to the arraylist the search algorithm stops working properly.

String prefix = content.substring(w + 1).toLowerCase();
int n = Collections.binarySearch(words, prefix);
if (n < 0 && -n <= words.size()) {
    String match = words.get(-n - 1);
    if (match.startsWith(prefix)) {
        // A completion is found
        String completion = match.substring(pos - w);
        // We cannot modify Document from within notification,
        // so we submit a task that does the change later
        SwingUtilities.invokeLater(
        new CompletionTask(completion, pos + 1));
}
} else {
// Nothing found
mode = Mode.INSERT;
}

Is there a way to modify the example so it will work with any words?

Answer 1

Make sure you're not just adding the word to the end of the list and then using binarySearch() . It's documentation says the following

The list must be sorted into ascending order according to the natural ordering of its elements (as by the sort(List) method) prior to making this call.

Read more about it here: https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#binarySearch(java.util.List,%20T)