Comparator接口（比较器）

自定义比较规则时使用 Comparator接口

class LengthComparator implements Comparator<String>{
    public int compare(String o1, String o2) {
        return o1.length() - o2.length();
    }
}

compare方法要在比较器对象上调用 ，而非比较对象本身

String[] words = {"a","ab","c"};
Comparator comparator = new LengthComparator();
if (comparator.compare(words[0],words[2]) > 0){
    //do someting
}