package strings;

public class Lower {

 /** Driver Code */
 public static void main(String[] args) {
 String[] strings = {"ABC", "ABC123", "abcABC", "abc123ABC"};
 for (String s : strings) {
 assert toLowerCase(s).equals(s.toLowerCase());
 }
 }

 /**
 * Converts all of the characters in this {@code String} to lower case
 *
 * @param s the string to convert
 * @return the {@code String}, converted to lowercase.
 */
 public static String toLowerCase(String s) {
 char[] values = s.toCharArray();
 for (int i = 0; i < values.length; ++i) {
 if (Character.isLetter(values[i]) && Character.isUpperCase(values[i])) {
 values[i] = Character.toLowerCase(values[i]);
 }
 }
 return new String(values);
 }
}