public class SwapWords {
    public static void main(String[] args) {
        String text = "London is the capital of Great Britain";
        String[] words = text.split(" ");
        String maxLength = Arrays.stream(words).max(Comparator.comparing(String::length)).get();
        String minLength = Arrays.stream(words).min(Comparator.comparing(String::length)).get();
        int idxOfMax = getWordIndex(words, maxLength);
        int idxOfMin = getWordIndex(words, minLength);
        words[idxOfMax] = minLength;
        words[idxOfMin] = maxLength;
        System.out.println(Strings.join(words, " "));
    }

    public static int getWordIndex(String[] array, String word) {
        int idx = 0;
        for (int i = 0; i < array.length; i++) {
            if (array[i].equals(word)) {
                idx = i;
            }
        }
        return idx;
    }
}