要求：2个英文字符串中，取相同的大于等于4个字母的词组

比如：

字符串1：" xingMeiLingabcdef WorldHello",

字符串2："mnjqlup WorldLingLing xingMeiLingHello"

获取交接：

[xingMeiLing, Hello, World]

实现方式：递归 

// 前提是对比两个文本的长短，参数1，是短的； 参数2,是长的
private static Set<String> getNewWords(String shortWord, String longWord){
    Set<String> result = new HashSet<>();
    while (shortWord.length()>=5) {
        String wordFirst = shortWord.substring(0,4);
        if(longWord.contains(wordFirst)){
            for (int i = 4; i < shortWord.length() ; i++) {
                if (longWord.contains(wordFirst+shortWord.charAt(i))){
                    wordFirst = wordFirst+shortWord.charAt(i);
                }else {
                    break;
                }
            }
            result.add(wordFirst);
            shortWord =shortWord.substring(wordFirst.length());
            getNewWords(shortWord,longWord);
        }else {
            shortWord =shortWord.substring(1);
        }
    }
    return result;
}

 闲言碎语： 递归比较适合数据量不大的，毕竟它比较占内存