palindrome recursive

package ch.fhnw.claudemartin;

public class SomeClass {
  public static void main(final String[] args) {
    test("", true);
    test("12345", false);
    test("racecar", true);
    test("Madam", false);
    test("abcdefgfedcba", true);
    test("abcdefggfedcba", true);
    test("abcdefggxfedcba", false);

    // one symbol in two chars (surrogate pair):
    final String clef = "\uD834\uDD1E";
    test(clef + clef, true);
  }

  static void test(final String a, final boolean expected) {
    final boolean actual = testPalindrome(a);
    (actual == expected ? System.out : System.err).format("'%s' => %s%n", a, actual);
  }

  /**
   * is the given string a palindrome?
   *
   * Note: this doesn't work with surrogate pairs.
   *
   * @param str
   *          the string to be tested
   * @return true if it's a palindrome.
   */
  public static boolean testPalindrome(final String str) {
    final int last = str.length() - 1;
    if (-1 == last)
      return true;
    return testPalindrome(str, 0, last);
  }

  private static boolean testPalindrome(final String str, final int offset, final int last) {
    if (str.charAt(offset) != str.charAt(last - offset))
      return false;
    if (offset == last / 2)
      return true;
    return testPalindrome(str, 1 + offset, last);
  }

}