显示日期格式 雪花算法 java

在Java中，可以使用雪花算法来生成唯一的ID，其中包含了时间戳信息。下面是一个示例代码，展示了如何使用雪花算法生成日期格式的ID：

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class SnowflakeExample {
    private static final long EPOCH = 1609459200000L;  // 设置起始时间戳，例如 2021-01-01 00:00:00

    private static final long WORKER_ID_BITS = 5L;
    private static final long SEQUENCE_BITS = 12L;

    private static final long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);
    private static final long MAX_SEQUENCE = ~(-1L << SEQUENCE_BITS);

    private static final long WORKER_ID_SHIFT = SEQUENCE_BITS;
    private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;

    private long workerId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;

    public SnowflakeExample(long workerId) {
        if (workerId < 0 || workerId > MAX_WORKER_ID) {
            throw new IllegalArgumentException("Worker ID must be between 0 and " + MAX_WORKER_ID);
        }
        this.workerId = workerId;
    }

    public synchronized long generateId() {
        long currentTimestamp = System.currentTimeMillis();
        if (currentTimestamp < lastTimestamp) {
            throw new RuntimeException("Invalid system clock");
        }

        if (currentTimestamp == lastTimestamp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0) {
                currentTimestamp = nextTimestamp();
            }
        } else {
            sequence = 0;
        }

        lastTimestamp = currentTimestamp;

        return (currentTimestamp - EPOCH) << TIMESTAMP_LEFT_SHIFT
                | workerId << WORKER_ID_SHIFT
                | sequence;
    }

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

    public static void main(String[] args) {
        SnowflakeExample snowflake = new SnowflakeExample(1L);
        long id = snowflake.generateId();
        LocalDateTime dateTime = LocalDateTime.ofEpochSecond((id >> TIMESTAMP_LEFT_SHIFT) + (EPOCH / 1000), 0, OffsetDateTime.now().getOffset());
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formattedDate = dateTime.format(formatter);
        System.out.println("Generated ID: " + id);
        System.out.println("Formatted date: " + formattedDate);
    }
}

在上面的示例中，我们使用了Java 8的`LocalDateTime`类来将时间戳转换为日期格式。我们通过位运算和位移操作，将生成的ID解析为时间戳、工作节点ID和序列号。最后，使用`DateTimeFormatter`将日期格式化为指定的格式。

请注意，这只是一个简单的示例代码，实际应用中可能需要根据具体需求进行修改和优化。同时，如需使用雪花算法生成唯一ID，请确保每个工作节点的workerId是唯一的。