makeRandom.java

String makeRandom(String content)
{
    if(content == null)
        throw Exception("Null input vlaue");

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

String generateRandom(String content)
{
    StringBuilder builder = new StringBuilder();
    String[] wordList = content.split(" "); //split 浪费啊。。

    for(String word: wordList)
    {
        builder.append(randomizeWord(word));
        builder.append(' ');
    }//末尾会多一个 ' '的。。。

    return builder.toString();
}

String randomizeWord(String word)
{
    if(word.length <= 3)
        return word;
    else
    {
        StringBuilder builder = new StringBuilder(word);
        Random rnd = new Random();
        for(int i = 1; i < (word.length - 1) / 2; i++)
        {
            int randInt = rnd.nextInt(word.length - i) + 1;
            swap(builder, i, randInt);
        }
    }
}

void swap(StringBuilder builder, int i, int j) //这算滥用builder了吧，每次swap都会产生很多对象呢
{
    Char temp = builder[i];
    builder[i] = builder[j];
    builder[j] = temp;
}

StringBuilder可以数组方式使用？？