Java 日期格式化方法：SimpleDateFormat 和 DateTimeFormatter

一、SimpleDateFormat（传统方式）

1. 基本用法

importjava.text.SimpleDateFormat;importjava.util.Date;publicclassDateFormatExample{publicstaticvoidmain(String[]args){// 创建 SimpleDateFormat 实例SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-dd HH:mm:ss");// 格式化当前日期StringformattedDate=sdf.format(newDate());System.out.println("当前时间: "+formattedDate);// 2023-12-15 14:30:25}}

2. 常用模式字符

SimpleDateFormatsdf1=newSimpleDateFormat("yyyy年MM月dd日");// 2023年12月15日SimpleDateFormatsdf2=newSimpleDateFormat("yyyy/MM/dd");// 2023/12/15SimpleDateFormatsdf3=newSimpleDateFormat("dd-MM-yyyy");// 15-12-2023SimpleDateFormatsdf4=newSimpleDateFormat("HH:mm:ss");// 14:30:25SimpleDateFormatsdf5=newSimpleDateFormat("hh:mm:ss a");// 02:30:25 下午SimpleDateFormatsdf6=newSimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");// 2023-12-15T14:30:25.123+0800SimpleDateFormatsdf7=newSimpleDateFormat("EEEE, MMMM dd, yyyy");// 星期五, 十二月 15, 2023

3. 完整示例

importjava.text.ParseException;importjava.text.SimpleDateFormat;importjava.util.Date;importjava.util.Locale;publicclassSimpleDateFormatDemo{publicstaticvoidmain(String[]args){try{// 1. 日期转字符串Datenow=newDate();SimpleDateFormatsdf1=newSimpleDateFormat("yyyy-MM-dd");System.out.println("日期: "+sdf1.format(now));SimpleDateFormatsdf2=newSimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");System.out.println("详细时间: "+sdf2.format(now));SimpleDateFormatsdf3=newSimpleDateFormat("EEEE",Locale.CHINA);System.out.println("星期: "+sdf3.format(now));// 2. 字符串转日期StringdateStr="2023-12-15 14:30:00";SimpleDateFormatsdf4=newSimpleDateFormat("yyyy-MM-dd HH:mm:ss");DateparsedDate=sdf4.parse(dateStr);System.out.println("解析后的日期: "+parsedDate);// 3. 带时区的格式化SimpleDateFormatsdf5=newSimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");System.out.println("ISO格式: "+sdf5.format(now));}catch(ParseExceptione){e.printStackTrace();}}}

4. 线程安全问题及解决方案

importjava.text.SimpleDateFormat;importjava.util.Date;importjava.util.concurrent.ExecutorService;importjava.util.concurrent.Executors;publicclassThreadSafeDateFormat{// 方案1: 每次创建新的实例（开销大但安全）publicStringformatDate1(Datedate){SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-dd");returnsdf.format(date);}// 方案2: 使用ThreadLocal（推荐用于多线程）privatestaticfinalThreadLocal<SimpleDateFormat>threadLocalSdf=ThreadLocal.withInitial(()->newSimpleDateFormat("yyyy-MM-dd HH:mm:ss"));publicStringformatDate2(Datedate){returnthreadLocalSdf.get().format(date);}// 方案3: 同步代码块privatestaticfinalSimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-dd");publicsynchronizedStringformatDate3(Datedate){returnsdf.format(date);}}

二、DateTimeFormatter（Java 8+ 推荐）

1. 基本用法

importjava.time.LocalDateTime;importjava.time.format.DateTimeFormatter;publicclassDateTimeFormatterDemo{publicstaticvoidmain(String[]args){// 获取当前时间LocalDateTimenow=LocalDateTime.now();// 预定义格式器DateTimeFormatterisoFormatter=DateTimeFormatter.ISO_DATE_TIME;System.out.println("ISO格式: "+now.format(isoFormatter));// 自定义格式器DateTimeFormattercustomFormatter=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");System.out.println("自定义格式: "+now.format(customFormatter));DateTimeFormatterchineseFormatter=DateTimeFormatter.ofPattern("yyyy年M月d日 EEEE HH:mm");System.out.println("中文格式: "+now.format(chineseFormatter));}}

2. 完整示例

importjava.time.*;importjava.time.format.DateTimeFormatter;importjava.time.format.FormatStyle;importjava.util.Locale;publicclassJava8DateFormatExample{publicstaticvoidmain(String[]args){// 1. 各种日期时间类型的格式化LocalDatedate=LocalDate.now();LocalTimetime=LocalTime.now();LocalDateTimedateTime=LocalDateTime.now();ZonedDateTimezonedDateTime=ZonedDateTime.now();// 2. 使用预定义格式System.out.println("基本ISO日期: "+date.format(DateTimeFormatter.BASIC_ISO_DATE));System.out.println("ISO日期时间: "+dateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));System.out.println("ISO时区时间: "+zonedDateTime.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));// 3. 本地化格式化DateTimeFormattershortFormatter=DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT);DateTimeFormattermediumFormatter=DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM);DateTimeFormatterlongFormatter=DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG);DateTimeFormatterfullFormatter=DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withLocale(Locale.CHINA);System.out.println("短格式: "+dateTime.format(shortFormatter));System.out.println("中格式: "+dateTime.format(mediumFormatter));System.out.println("长格式: "+dateTime.format(longFormatter));System.out.println("完整格式: "+dateTime.format(fullFormatter));// 4. 自定义格式DateTimeFormattercustomFormatter1=DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm");DateTimeFormattercustomFormatter2=DateTimeFormatter.ofPattern("dd-MMM-yyyy",Locale.US);DateTimeFormattercustomFormatter3=DateTimeFormatter.ofPattern("'日期:' yyyy年MM月dd日 '时间:' HH时mm分");System.out.println("斜杠格式: "+dateTime.format(customFormatter1));System.out.println("英文月份: "+date.format(customFormatter2));System.out.println("带文字格式: "+dateTime.format(customFormatter3));// 5. 解析字符串为日期StringdateStr="2023-12-15 14:30:00";DateTimeFormatterparser=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");LocalDateTimeparsedDateTime=LocalDateTime.parse(dateStr,parser);System.out.println("解析后的时间: "+parsedDateTime);// 6. 带时区的格式化DateTimeFormatterzonedFormatter=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss z").withZone(ZoneId.systemDefault());System.out.println("带时区: "+zonedFormatter.format(zonedDateTime));}}

3. 实用工具类

importjava.time.*;importjava.time.format.DateTimeFormatter;importjava.time.temporal.TemporalAccessor;importjava.util.Date;publicclassDateUtil{// 预定义的格式化器（线程安全，可以全局使用）publicstaticfinalDateTimeFormatterDATE_FORMATTER=DateTimeFormatter.ofPattern("yyyy-MM-dd");publicstaticfinalDateTimeFormatterTIME_FORMATTER=DateTimeFormatter.ofPattern("HH:mm:ss");publicstaticfinalDateTimeFormatterDATETIME_FORMATTER=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");publicstaticfinalDateTimeFormatterTIMESTAMP_FORMATTER=DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");/** * 格式化 LocalDateTime */publicstaticStringformat(LocalDateTimedateTime,Stringpattern){returndateTime.format(DateTimeFormatter.ofPattern(pattern));}/** * 格式化 LocalDate */publicstaticStringformat(LocalDatedate,Stringpattern){returndate.format(DateTimeFormatter.ofPattern(pattern));}/** * 解析字符串为 LocalDateTime */publicstaticLocalDateTimeparseDateTime(StringdateStr,Stringpattern){returnLocalDateTime.parse(dateStr,DateTimeFormatter.ofPattern(pattern));}/** * Date 转 LocalDateTime */publicstaticLocalDateTimetoLocalDateTime(Datedate){returnLocalDateTime.ofInstant(date.toInstant(),ZoneId.systemDefault());}/** * LocalDateTime 转 Date */publicstaticDatetoDate(LocalDateTimedateTime){returnDate.from(dateTime.atZone(ZoneId.systemDefault()).toInstant());}/** * 生成时间戳字符串 */publicstaticStringgenerateTimestamp(){returnLocalDateTime.now().format(TIMESTAMP_FORMATTER);}/** * 获取中文日期格式 */publicstaticStringgetChineseDate(LocalDatedate){returndate.format(DateTimeFormatter.ofPattern("yyyy年M月d日 E").withLocale(Locale.CHINA));}/** * 格式化持续时间（如：01:23:45） */publicstaticStringformatDuration(Durationduration){longhours=duration.toHours();longminutes=duration.toMinutesPart();longseconds=duration.toSecondsPart();returnString.format("%02d:%02d:%02d",hours,minutes,seconds);}/** * 获取日期范围 */publicstaticStringgetDateRange(LocalDatestart,LocalDateend,Stringpattern){DateTimeFormatterformatter=DateTimeFormatter.ofPattern(pattern);returnstart.format(formatter)+" 至 "+end.format(formatter);}publicstaticvoidmain(String[]args){// 使用示例LocalDateTimenow=LocalDateTime.now();System.out.println("标准格式: "+format(now,"yyyy-MM-dd HH:mm:ss"));System.out.println("中文格式: "+getChineseDate(now.toLocalDate()));System.out.println("时间戳: "+generateTimestamp());System.out.println("使用预定义格式器: "+now.format(DATETIME_FORMATTER));// 解析示例LocalDateTimeparsed=parseDateTime("2023-12-15 14:30:00","yyyy-MM-dd HH:mm:ss");System.out.println("解析结果: "+parsed);}}

三、对比与选择建议

四、常见问题解决

1. 时区处理

// SimpleDateFormat 时区设置SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-dd HH:mm:ss");sdf.setTimeZone(TimeZone.getTimeZone("GMT+8"));// DateTimeFormatter 时区设置DateTimeFormatterformatter=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").withZone(ZoneId.of("Asia/Shanghai"));

2. 语言环境（Locale）

// 中文环境SimpleDateFormatsdfCN=newSimpleDateFormat("yyyy年MM月dd日 EEEE",Locale.CHINA);// 英文环境DateTimeFormatterformatterEN=DateTimeFormatter.ofPattern("EEEE, MMMM dd, yyyy",Locale.US);

3. 性能优化建议

// 缓存 DateTimeFormatter 实例publicclassFormatterCache{privatestaticfinalMap<String,DateTimeFormatter>FORMATTER_CACHE=newConcurrentHashMap<>();publicstaticDateTimeFormattergetFormatter(Stringpattern){returnFORMATTER_CACHE.computeIfAbsent(pattern,DateTimeFormatter::ofPattern);}publicstaticStringformat(LocalDateTimedateTime,Stringpattern){returndateTime.format(getFormatter(pattern));}}

4. 错误处理

publicclassSafeDateParser{publicstaticDatesafeParse(StringdateStr,Stringpattern){try{SimpleDateFormatsdf=newSimpleDateFormat(pattern);sdf.setLenient(false);// 严格模式，防止"2023-02-30"被接受returnsdf.parse(dateStr);}catch(ParseExceptione){// 记录日志，返回默认值或抛出业务异常returnnull;}}publicstaticLocalDateTimesafeParseDateTime(StringdateStr,Stringpattern){try{DateTimeFormatterformatter=DateTimeFormatter.ofPattern(pattern);returnLocalDateTime.parse(dateStr,formatter);}catch(DateTimeParseExceptione){// 处理解析失败returnnull;}}}

总结建议

1. 新项目：优先使用DateTimeFormatter（Java 8+）
2. 旧项目维护：继续使用SimpleDateFormat，注意线程安全
3. 多线程环境：使用ThreadLocal<SimpleDateFormat>或DateTimeFormatter
4. 复杂日期操作：使用java.time包（Java 8+）