### Question:
StringUtil { public static String format(String format, Object... arguments) { return MessageFormatter.arrayFormat(format, arguments).getMessage(); }  static String format(String format, Object... arguments); static String randomString(int length);  }### Answer:
@Test public void format() { String a = "A"; String placeholder = "{}"; String b = "B"; String c = "C"; assertEquals(a + b + c, StringUtil.format(a + placeholder + c, b)); }