LeetCode 709 To Lower Case

class Solution {
    public String toLowerCase(String str) {
        char[] chars = str.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            char c = chars[i];
            if (c >= 65 && c <= 90) {
                chars[i] = (c += 32);
            }
        }
        return new String(chars);
    }
}