Java生成11位的纯数字非0开头的唯一userid

以下是使用Java实现生成11位纯数字非0开头的唯一userID的示例代码:

import java.util.concurrent.atomic.AtomicLong;

public class UniqueIDGenerator {
    private static final int MACHINE_ID = 1; // 机器ID
    private static final long START_TIMESTAMP = 1577808000000L; // 起始时间戳（2020-01-01 00:00:00）
    private static final int SEQUENCE_BITS = 12; // 序列号占用的位数
    private static final int MAX_SEQUENCE = (1 << SEQUENCE_BITS) - 1; // 序列号最大值
    private static final int MACHINE_BITS = 10; // 机器ID占用的位数
    private static final int MACHINE_SHIFT = SEQUENCE_BITS; // 机器ID左移位数
    private static final int TIMESTAMP_SHIFT = MACHINE_BITS + SEQUENCE_BITS; // 时间戳左移位数
    private static final AtomicLong SEQUENCE = new AtomicLong(0); // 序列号生成器
    private static long lastTimestamp = 0; // 上次生成ID的时间戳

    public static long generateUserID() {
        while (true) {
            long timestamp = System.currentTimeMillis();
            if (timestamp < lastTimestamp) {
                throw new RuntimeException("Clock moved backwards");
            } else if (timestamp == lastTimestamp) {
                long sequence = SEQUENCE.incrementAndGet() & MAX_SEQUENCE;
                if (sequence == 0) {
                    timestamp = waitNextMillis(lastTimestamp);
                }
                lastTimestamp = timestamp;
                long userID = (timestamp - START_TIMESTAMP) << TIMESTAMP_SHIFT | MACHINE_ID << MACHINE_SHIFT | sequence;
                if (String.valueOf(userID).charAt(0) != '0') {
                    return userID;
                }
            } else {
                SEQUENCE.set(0);
                lastTimestamp = timestamp;
            }
        }
    }

    private static long waitNextMillis(long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }
}

该代码使用AtomicLong类型的SEQUENCE变量作为序列号生成器，同时使用AtomicLong的incrementAndGet方法实现线程安全的序列号生成。使用AtomicLong类型的变量可以避免多线程竞争导致的序列号重复问题。在生成唯一ID的过程中，如果开头为0，则重新生成ID，直到生成的ID符合要求为止。由于使用了Snowflake算法，生成的ID是唯一的，并且按照时间顺序递增。