RandUtil { public static String nextNumeric(int digits) { StringBuffer buffer = new StringBuffer(); for (int i = 0; i < digits; i++) { buffer.append((char) nextInt('0', '9')); } return buffer.toString(); } private  RandUtil(); static boolean nextBoolean(); static int nextInt(); static int nextInt(int lower, int upper); static long nextLong(long n); static long nextLong(long lower, long upper); static long nextLong(); static String nextAlphabetic(int characters); static String nextNumeric(int digits); static E nextItem(E[] array);  }
@Test @DisplayName("Test numeric string generation") void nextNumeric_1() { assertEquals("", RandUtil.nextNumeric(0)); assertDoesNotThrow(() -> new BigInteger(RandUtil.nextNumeric(1000))); }