Strings { public static String capitalizeFirstLetter(@NonNull String src) { return src.substring(0, 1).toUpperCase(Locale.getDefault()) + src.substring(1); } private  Strings(); static String capitalizeFirstLetter(@NonNull String src);  }
@Test public void should_capitalize_first_letter() { String src = "hello"; String result = Strings.capitalizeFirstLetter(src); assertThat(result).isEqualTo("Hello"); }