package strings;

public class Upper {

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

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