refactor(music-houduan): 优化 SnowflakeIdUtil 和 TimeUtil 类

- 为 SnowflakeIdUtil 类添加详细注释，解释各个字段和方法的作用- 为 TimeUtil 类添加方法注释，说明各个方法的功能- 优化代码结构，提高可读性和可维护性

music-houduan/src/main/java/com/test/musichouduan/util/SnowflakeIdUtil.java

@@ -1,69 +1,98 @@
 package com.test.musichouduan.util;
 
+/**
+ * 雪花算法ID生成工具类
+ */
 public class SnowflakeIdUtil {
 
-    private static final long START_TIMESTAMP = 1609459200000L; // 2021-01-01 00:00:00
+    // 起始时间戳 (2021-01-01 00:00:00)
+    private static final long START_TIMESTAMP = 1609459200000L;
 
-    private static final long SEQUENCE_BIT = 12;
-    private static final long MACHINE_BIT = 5;
-    private static final long DATA_CENTER_BIT = 5;
+    // 各部分占用的位数
+    private static final long SEQUENCE_BIT = 12; // 序列号占用的位数
+    private static final long MACHINE_BIT = 5;   // 机器标识占用的位数
+    private static final long DATA_CENTER_BIT = 5; // 数据中心占用的位数
 
+    // 各部分的最大值
     private static final long MAX_SEQUENCE = ~(-1L << SEQUENCE_BIT);
     private static final long MAX_MACHINE_NUM = ~(-1L << MACHINE_BIT);
     private static final long MAX_DATA_CENTER_NUM = ~(-1L << DATA_CENTER_BIT);
 
+    // 各部分向左的位移
     private static final long MACHINE_LEFT = SEQUENCE_BIT;
     private static final long DATA_CENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
     private static final long TIMESTAMP_LEFT = DATA_CENTER_LEFT + DATA_CENTER_BIT;
 
-    private long dataCenterId;
-    private long machineId;
-    private long sequence = 0L;
-    private long lastStamp = -1L;
+    private long dataCenterId;  // 数据中心ID
+    private long machineId;     // 机器ID
+    private long sequence = 0L; // 序列号
+    private long lastStamp = -1L; // 上一次时间戳
 
     private static SnowflakeIdUtil instance;
 
+    /**
+     * 获取单例实例
+     * @return SnowflakeIdUtil实例
+     */
     public static synchronized SnowflakeIdUtil getInstance() {
         if (instance == null) {
+            // 默认数据中心ID和机器ID为1
             instance = new SnowflakeIdUtil(1, 1);
         }
         return instance;
     }
 
+    /**
+     * 构造函数
+     * @param dataCenterId 数据中心ID
+     * @param machineId 机器ID
+     */
     public SnowflakeIdUtil(long dataCenterId, long machineId) {
         if (dataCenterId > MAX_DATA_CENTER_NUM || dataCenterId < 0) {
-            throw new IllegalArgumentException("Data center ID can't be greater than " + MAX_DATA_CENTER_NUM + " or less than 0");
+            throw new IllegalArgumentException("数据中心ID不能大于 " + MAX_DATA_CENTER_NUM + " 或小于 0");
         }
         if (machineId > MAX_MACHINE_NUM || machineId < 0) {
-            throw new IllegalArgumentException("Machine ID can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
+            throw new IllegalArgumentException("机器ID不能大于 " + MAX_MACHINE_NUM + " 或小于 0");
         }
         this.dataCenterId = dataCenterId;
         this.machineId = machineId;
     }
 
+    /**
+     * 生成下一个ID
+     * @return 雪花ID
+     */
     public synchronized long nextId() {
         long currStamp = getNewStamp();
         if (currStamp < lastStamp) {
-            throw new RuntimeException("Clock moved backwards. Refusing to generate id");
+            throw new RuntimeException("时钟向后移动。拒绝生成ID");
         }
 
         if (currStamp == lastStamp) {
+            // 同一毫秒内，序列号自增
             sequence = (sequence + 1) & MAX_SEQUENCE;
+            // 如果序列号溢出，等待下一毫秒
             if (sequence == 0L) {
                 currStamp = getNextMill();
             }
         } else {
+            // 不同毫秒内，序列号重置为0
             sequence = 0L;
         }
 
         lastStamp = currStamp;
 
-        return (currStamp - START_TIMESTAMP) << TIMESTAMP_LEFT
-                | dataCenterId << DATA_CENTER_LEFT
-                | machineId << MACHINE_LEFT
-                | sequence;
+        // 拼接成64位ID
+        return (currStamp - START_TIMESTAMP) << TIMESTAMP_LEFT // 时间戳部分
+                | dataCenterId << DATA_CENTER_LEFT             // 数据中心部分
+                | machineId << MACHINE_LEFT                    // 机器标识部分
+                | sequence;                                    // 序列号部分
     }
 
+    /**
+     * 获取下一毫秒的时间戳
+     * @return 下一毫秒的时间戳
+     */
     private long getNextMill() {
         long mill = getNewStamp();
         while (mill <= lastStamp) {
@@ -72,6 +101,10 @@ public class SnowflakeIdUtil {
         return mill;
     }
 
+    /**
+     * 获取当前时间戳
+     * @return 当前时间戳
+     */
     private long getNewStamp() {
         return System.currentTimeMillis();
     }

music-houduan/src/main/java/com/test/musichouduan/util/TimeUtil.java

@@ -3,17 +3,34 @@ package com.test.musichouduan.util;
 import java.text.SimpleDateFormat;
 import java.util.Date;
 
+/**
+ * 时间工具类
+ */
 public class TimeUtil {
 
+    /**
+     * 获取当前时间，格式为 yyyy-MM-dd HH:mm:ss
+     * @return 当前时间的字符串表示
+     */
     public static String getCurrentTime() {
         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
         return sdf.format(new Date());
     }
 
+    /**
+     * 获取当前时间戳
+     * @return 当前时间戳（毫秒）
+     */
     public static long getTimestamp() {
         return System.currentTimeMillis();
     }
 
+    /**
+     * 根据指定格式格式化日期
+     * @param date   要格式化的日期
+     * @param format 格式字符串
+     * @return 格式化后的日期字符串
+     */
     public static String formatDate(Date date, String format) {
         SimpleDateFormat sdf = new SimpleDateFormat(format);
         return sdf.format(date);