code: public static String appendIfMissing(final String str, final CharSequence suffix, final CharSequence... suffixes) {
          return appendIfMissing(str, suffix, false, suffixes);
      }
docs: Appends the suffix to the end of the string if the string does not
  already end with any of the suffixes.
  
  <pre>
  StringUtils.appendIfMissing(null, null) = null
  StringUtils.appendIfMissing("abc", null) = "abc"
  StringUtils.appendIfMissing("", "xyz") = "xyz"
  StringUtils.appendIfMissing("abc", "xyz") = "abcxyz"
  StringUtils.appendIfMissing("abcxyz", "xyz") = "abcxyz"
  StringUtils.appendIfMissing("abcXYZ", "xyz") = "abcXYZxyz"
  </pre>
  <p>With additional suffixes,</p>
  <pre>
  StringUtils.appendIfMissing(null, null, null) = null
  StringUtils.appendIfMissing("abc", null, null) = "abc"
  StringUtils.appendIfMissing("", "xyz", null) = "xyz"
  StringUtils.appendIfMissing("abc", "xyz", new CharSequence[]{null}) = "abcxyz"
  StringUtils.appendIfMissing("abc", "xyz", "") = "abc"
  StringUtils.appendIfMissing("abc", "xyz", "mno") = "abcxyz"
  StringUtils.appendIfMissing("abcxyz", "xyz", "mno") = "abcxyz"
  StringUtils.appendIfMissing("abcmno", "xyz", "mno") = "abcmno"
  StringUtils.appendIfMissing("abcXYZ", "xyz", "mno") = "abcXYZxyz"
  StringUtils.appendIfMissing("abcMNO", "xyz", "mno") = "abcMNOxyz"
  </pre>
  
  @param str The string.
  @param suffix The suffix to append to the end of the string.
  @param suffixes Additional suffixes that are valid terminators.
  
  @return A new String if suffix was appended, the same string otherwise.
  
  @since 3.2