makeRandom.java

package im.dante.Typoglycemia;

import java.util.Objects;
import java.util.Random;

public class Randomize {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {
        Randomize r = new Randomize();

        String content = "I couldn't believe that I could actually understand "
            + "what I was reading: the phenomenal power of the human mind. "
            + "According to a research team at Cambridge University, it "
            + "doesn't matter in what order the letters in a word are, the "
            + "only important thing is that the first and last letter be "
            + "in the right place. The rest can be a total mess and you "
            + "can still read it without a problem. This is because the "
            + "human mind does not read every letter by itself, but the "
            + "word as a whole. Such a condition is appropriately called "
            + "Typoglycemia. Amazing, huh? Yeah and you always thought "
            + "spelling was important.";

        System.out.println(r.produceTypoglycemia(content));
    }

    private String produceTypoglycemia(String content) {
        Objects.requireNonNull(content);

        if (content.length() <= 3) {
            return content;
        }

        // one array which has the same length with the original string's internal array
        char[] contentChars = content.toCharArray();

        // reuse these
        int indexSpace = 0;
        int indexStart = 0;
        int indexEnd = 0;
        char temp;
        Random random = new Random();

        // first level loop: looking for spaces
        for (int i = 0; i < contentChars.length; i++) {
            if (contentChars[i] != ' ') {
                continue;
            }

            indexStart = indexSpace;
            indexSpace = i;
            indexEnd = indexSpace;

            // search for the last letter.
            // some occasions hasn't been taken into consideration
            for (int j = indexEnd; j > indexStart; j--) {
                if (Character.isLetter(contentChars[j])) {
                    break;
                }

                indexEnd = j;
            }

            indexStart += 2;
            indexEnd -= 2;

            int length = indexEnd - indexStart + 1;

            if (length <= 1) {
                continue;
            }
            else if (length == 2) {
                // shortcut for 2 chars inside the word, avoid using Random.
                temp = contentChars[indexStart + 1];
                contentChars[indexStart + 1] = contentChars[indexEnd -1];
                contentChars[indexEnd - 1] = temp;

                continue;
            }
            else {
                for (int j = indexStart; j <= indexEnd; j++) {
                    int randPos = random.nextInt(length) + indexStart;

                    temp = contentChars[j];
                    contentChars[j] = contentChars[randPos];
                    contentChars[randPos] = temp;
                }
            }
        }

        // finally one string with the same length of the array
        return String.valueOf(contentChars);
    }

}