【leetcode】709. To Lower Case

class Solution {
    public static String toLowerCase(String str) {
        char[] chs = str.toCharArray();
        for(int i=0; i<chs.length; i++) {
            if(Character.isUpperCase(chs[i])) {
                chs[i] = (char) (chs[i]+32);
            }
        }
        return String.valueOf(chs);
    }
}