Java String substring from middle

public class Main {
   public static void main(String[] args) {
      System.out.println("A       --> " + getMiddleString("A"));
      System.out.println("AB      --> " + getMiddleString("AB"));
      System.out.println("ABC     --> " + getMiddleString("ABC"));
      System.out.println("ABCD    --> " + getMiddleString("ABCD"));
      System.out.println("ABCDE   --> " + getMiddleString("ABCDE"));
      System.out.println("ABCDEF  --> " + getMiddleString("ABCDEF"));
      System.out.println("ABCDEFG --> " + getMiddleString("ABCDEFG"));
   }/*w ww . ja v a  2  s .  c  o m*/
   public static String getMiddleString(String str) {
     
      if (str== null || str.length() <= 2) {
         return str;
      }
      int beginIndex = (str.length() - 1) / 2;
      int endIndex = beginIndex + 2 - (str.length() % 2);
      return str.substring(beginIndex, endIndex);
   }
}

public class Main {
    public static void main(String[] argv) throws Exception {
        String str = "demo2s.com";
        int pos = 2;
        int len = 2;
        System.out.println(mid(str, pos, len));
    }//from  www .j a v a 2 s.  c om
    public static final String EMPTY = "";

    /**
     * <p>Gets <code>len</code> characters from the middle of a String.</p>
     *
     * <p>If <code>len</code> characters are not available, the remainder
     * of the String will be returned without an exception. If the
     * String is <code>null</code>, <code>null</code> will be returned.
     * An exception is thrown if len is negative.</p>
     *
     * <pre>
     * mid(null, *, *)    = null
     * mid(*, *, -ve)     = ""
     * mid("", 0, *)      = ""
     * mid("abc", 0, 2)   = "ab"
     * mid("abc", 0, 4)   = "abc"
     * mid("abc", 2, 4)   = "c"
     * mid("abc", 4, 2)   = ""
     * mid("abc", -2, 2)  = "ab"
     * </pre>
     *
     * @param str  the String to get the characters from, may be null
     * @param pos  the position to start from, negative treated as zero
     * @param len  the length of the required String, must be zero or positive
     * @return the middle characters, <code>null</code> if null String input
     */
    public static String mid(String str, int pos, int len) {
        if (str == null) {
            return null;
        }
        if (len < 0 || pos > str.length()) {
            return EMPTY;
        }
        if (pos < 0) {
            pos = 0;
        }
        if (str.length() <= (pos + len)) {
            return str.substring(pos);
        }
        return str.substring(pos, pos + len);
    }

}