How to shuffle characters in a string without using Collections.shuffle(…)?

Question

How do I shuffle the characters in a string (e.g. hello could be ehlol or lleoh or ...). I don\'t want to use the Collections.shuffle(...) method, is there anyt

Answer 1

Not sure why you wouldn't want to use shuffle, unless it's for school. ;)

And if you're concerned with performance, you definitely can't use any solution that concatenates strings with "+".

Here's the most compact solution I could come up with:

public static String shuffle(String string) {
    if (StringUtils.isBlank(string) {
        return string;
    }

    final List randomChars = new ArrayList<>();
    CollectionUtils.addAll(randomChars, ArrayUtils.toObject(string.toCharArray()));
    Collections.shuffle(randomChars);
    return StringUtils.join(randomChars, "");
}