@Test
public synchronized void performance() throws InterruptedException {

    final String[][] results = new String[concurrency][];
    Thread[] threads = new Thread[concurrency];
    for (int i = 0; i < concurrency; i++) {
        final String[] result = new String[loop];
        results[i] = result;
        threads[i] = new Thread(new Runnable() {
            public void run() {
                for (int i = 0; i < loop; i++) {
                    result[i] = uuid.nextID();
                }
            }
        }, "t-" + (i + 1));
    }
    long start = System.currentTimeMillis();
    for (Thread thread : threads) {
        thread.start();
    }
    for (Thread thread : threads) {
        thread.join();
    }
    long duration = System.currentTimeMillis() - start;
    System.out.printf("%s: requests=%d, concurrency=%d%n", uuid.getClass().getSimpleName(), concurrency * loop,
            concurrency);
    System.out.printf("  Total time: %,d ms.%n", duration);
    System.out.printf("Average time: %,2.2f \u03BCs.%n", (double) duration / concurrency / loop * 1000);
    // 检查重复
    Set<String> allIDs = CollectionUtil.createHashSet();
    for (String[] result : results) {
        for (String id : result) {
            assertNotNull(id);
            assertTrue(id, !id.contains("+") && !id.contains("/") && !id.contains("="));
            allIDs.add(id);
        }
    }
    assertEquals(concurrency * loop, allIDs.size());
}