LintCode 字符大小写排序题目分析代码

public class Solution {
    /** 
     *@param chars: The letter array you should sort by Case
     *@return: void
     */
    public void sortLetters(char[] chars) {
        int i = 0, j = chars.length - 1;
        char tmp ;
        while ( i <= j) {
            while (i <= j && Character.isLowerCase(chars[i]) ) i++;
            while (i <= j && Character.isUpperCase(chars[j]) ) j--;
            if (i <= j) {
                tmp = chars[i];
                chars[i] = chars[j];
                chars[j] = tmp;
                i++; j--;
            }
        }
        return ;
    }
}