Leetcode 520 Detect Capital

Given a word, you need to judge whether the usage of capitals in it is right or not.

We define the usage of capitals in a word to be right when one of the following cases holds:

All letters in this word are capitals, like “USA”.
All letters in this word are not capitals, like “leetcode”.
Only the first letter in this word is capital if it has more than one letter, like “Google”.
Otherwise, we define that this word doesn’t use capitals in a right way.
天呐，终于做到了到目前为止感觉最简单的一道题。
题目表明以上三种情况返回true。
代码如下，只要分情况讨论即可。

public static boolean detectCapitalUse(String word) {        //全部为大写字母        int count1 = 0;        for (int i = 0; i < word.length(); i++) {            if (word.charAt(i)<='Z'&&word.charAt(i)>='A') {                count1++;            }        }        //全部为小写字母        int count2 = 0;        for (int i = 0; i < word.length(); i++) {            if (word.charAt(i)<='z'&&word.charAt(i)>='a') {                count2++;            }        }        //第一个为大写，其他的为小写        int flag = 0;        if (word.charAt(0)<='Z'&&word.charAt(0)>='A') {            flag = 1;        }        int count3 = 0;        if (flag==1) {            for (int i = 1; i <word.length(); i++) {                if (word.charAt(i)<='z'&&word.charAt(i)>='a') {                    count3++;                }            }        }        //判断返回        if (flag==1&&count3==word.length()-1) {            return true;        }        if (count1==word.length()||count2==word.length()) {            return true;        }        return false;    }

但是别人的答案是这样写的：

return word.matches("[A-Z]+|[a-z]+|[A-Z][a-z]+");

但是这样虽然简单，他的运行时间是我的五倍左右。