public class Solution {
    public boolean detectCapitalUse(String word) {
        if (word == null || word.length() == 0) return true;
        boolean firstUpperCase = Character.isUpperCase(word.charAt(0));
        if (firstUpperCase) { // in this case, all capital or neither capital
            boolean allCapital = true, neitherCapital = true;
            for (int i = 1; i < word.length(); i++) {
                if (Character.isUpperCase(word.charAt(i))) neitherCapital = false;
                else allCapital = false;
            }
            return allCapital || neitherCapital;
        } else { // neither capital!
            for (int i = 1; i < word.length(); i++) {
                if (Character.isUpperCase(word.charAt(i))) return false;
            }
        }
        return true;
    }
}