Complete the getMiddle method that gets the middle character from a string if the string length is odd, or the middle character pair if it is even.

For example, getMiddle("Java") returns "av", and getMiddle("program")returns "g".

If the string parameter is empty, return the empty string.

Complete the following file:

public class Strings { /** Gets the middle character or character pair from this string when possible. @param str a string @return the middle character (if the string length is odd) or the middle two characters (if it is even), or the empty string if str is empty. */ public static String getMiddle(String str) {
. . .
} }