### Question:
StringUtil { public static boolean isNumeric(String string) { if (string == null || string.length() == 0) return false; int l = string.length(); for (int i = 0; i < l; i++) { if (!Character.isDigit(string.codePointAt(i))) return false; } return true; }  static String join(Collection strings, String sep); static String join(Iterator strings, String sep); static String padding(int width); static boolean isBlank(String string); static boolean isNumeric(String string); static boolean isWhitespace(int c); static boolean isActuallyWhitespace(int c); static String normaliseWhitespace(String string); static void appendNormalisedWhitespace(StringBuilder accum, String string, boolean stripLeading); static boolean in(String needle, String... haystack); static boolean inSorted(String needle, String[] haystack); static URL resolve(URL base, String relUrl); static String resolve(final String baseUrl, final String relUrl); static StringBuilder stringBuilder();  }### Answer:
@Test public void isNumeric() { assertFalse(StringUtil.isNumeric(null)); assertFalse(StringUtil.isNumeric(" ")); assertFalse(StringUtil.isNumeric("123 546")); assertFalse(StringUtil.isNumeric("hello")); assertFalse(StringUtil.isNumeric("123.334")); assertTrue(StringUtil.isNumeric("1")); assertTrue(StringUtil.isNumeric("1234")); }