### Question:
RandomUtil { public static String uuid() { UUID uuid = UUID.randomUUID(); String s = uuid.toString(); return s.substring(0, 8) + s.substring(9, 13) + s.substring(14, 18) + s.substring(19, 23) + s.substring(24); }  static int integer(int scopeMin, int scoeMax); static String number(int length); static String String(int length); static String MixString(int length); static String LowerString(int length); static String UpperString(int length); static String ZeroString(int length); static String toFixdLengthString(long num, int fixdlenth); static String toFixdLengthString(int num, int fixdlenth); static int getNotSimple(int[] param, int len); static T randomItem(T[] param); static String uuid(); static String UUID(); static String squid(String hostFeature); static T randomItem(T[] param, double[] percentum); static final String ALLCHAR; static final String LETTERCHAR; static final String NUMBERCHAR; }### Answer:
@Test public void testUuid() { System.out.println(RandomUtil.uuid()); System.out.println(RandomUtil.UUID()); System.out.println(RandomUtil.squid("1234")); System.out.println(RandomUtil.squid("1234")); System.out.println(RandomUtil.squid("1234")); for (int i = 0; i < 10; i++) { Set<String> set = new HashSet<>(100000); for (int j = 0; j < 100000; j++) { set.add(RandomUtil.squid("1234")); } assertEquals("出现重复主键", 100000, set.size()); } }