以秒为单位生成唯一的时间序列号

/**
 * 功能： 以秒为单位生成唯一的序列号 <br/>
 * 生成格式：YYMMddHHmmssXXXXXXX <br/>
 * XXXXXXX：代表序列号，从1开始
 * 例子: 1808312321280000001 或者 1808312321280001234 <br/>
 * <p>局限性： 每秒生成最大范围 (1000万-1) 个数</p>
 * Created by Administrator on 2018/8/31.
 */
public final class GenerateDateTimeUniqueID {

    private static final DateFormat DF = new SimpleDateFormat("yyMMddHHmmss");
    private static volatile long LAST_TIME = -1;
    private static final AtomicInteger COUNT = new AtomicInteger();
    private static final Object LOCK = new Object();

    //测试是否有生成重复的ID
    public static final ConcurrentMap<String, Boolean> MAP = new ConcurrentHashMap<String, Boolean>();

    //1 000 000
    private static final byte LEVEL = 7; //限定一秒钟最多产生1000万-1 个数
    private static final String ZERO_0 = "";
    private static final String ZERO_1 = "0";
    private static final String ZERO_2 = "00";
    private static final String ZERO_3 = "000";
    private static final String ZERO_4 = "0000";
    private static final String ZERO_5 = "00000";
    private static final String ZERO_6 = "000000";


    /*******
     *
     * 测试机器系统参数： Win7 64位 i5-4210M 4core 2.6GHz 内存8GB
     *
     * ********/


    /**
     * 测试10个线程并发产生，每秒可以产生310万左右个序列号
     * *
     */
    public static String generateDateTimeUniqueIdStr() throws Exception {
        Date date = new Date();
        String dateStr = DF.format(date);
        long curTime = Long.parseLong(dateStr);
        int curCount = 0;

        synchronized (GenerateDateTimeUniqueID.class) {
            if (curTime < LAST_TIME) {
                curTime = LAST_TIME;
            } else if (curTime > LAST_TIME) {
                LAST_TIME = curTime;
                System.out.println(Thread.currentThread().getName() + "-" + COUNT.get());
                COUNT.set(0);
            }
            curCount = COUNT.incrementAndGet();
        }

        return curTime + format(curCount);
    }

    /**
     * 测试10个线程并发产生，每秒可以产生290万左右个序列号
     * *
     */
    public static long generateDateTimeUniqueId() {
        Date date = new Date();
        String dateStr = DF.format(date);
        long curTime = Long.parseLong(dateStr);
        int curCount = 0;

        synchronized (GenerateDateTimeUniqueID.class) {
            if (curTime < LAST_TIME) {
                curTime = LAST_TIME;
            } else if (curTime > LAST_TIME) {
                LAST_TIME = curTime;
                System.out.println(Thread.currentThread().getName() + "-" + COUNT.get());
                COUNT.set(0);
            }
            curCount = COUNT.incrementAndGet();
        }

        return Long.parseLong(curTime + format(curCount));
    }


    private static String format(int value) {
        int temp = value;
        int count = 0;
        while (temp > 0) {
            temp = temp / 10;
            count++;
        }
        switch (LEVEL - count) {
            case 0:
                return ZERO_0 + value;
            case 1:
                return ZERO_1 + value;
            case 2:
                return ZERO_2 + value;
            case 3:
                return ZERO_3 + value;
            case 4:
                return ZERO_4 + value;
            case 5:
                return ZERO_5 + value;
            case 6:
                return ZERO_6 + value;
            default:
                return "9999999";
//                throw new IllegalStateException(); //再处理
        }
    }

    private GenerateDateTimeUniqueID() {
    }

    public static void main(String[] args) {

        long cur = System.currentTimeMillis();
        for (int i = 1; i < 1000000000; i++) {
            System.out.println(generateDateTimeUniqueId());

        }

//        int num = 6;
//        ExecutorService executorService = Executors.newFixedThreadPool(num);
//        for (int i = 0; i < num; i++) {
//            executorService.submit(new TestThread());
//        }
        System.out.println("spend " + (System.currentTimeMillis() - cur) + " ms");
    }

    static class TestThread implements Runnable {

        @Override
        public void run() {
            while (true) {
                String id = generateDateTimeUniqueIdStr();
                Boolean isHas = MAP.putIfAbsent(id, Boolean.TRUE);
                if (isHas != null) {
                    throw new IllegalArgumentException();
                }
            }
        }
    }
}