Java中时间戳和时间的转换方法代码

//使用系统时间戳
long timestamp = System.currentTimeMillis();
System.out.println("timestamp:" + timestamp);
//>>timestamp:1733907943319

Long timestamp1 = Instant.now().toEpochMilli();
System.out.println("timestamp1:"+timestamp1);
//>>1733908000856

//获取秒级时间戳
long timestamp2 = System.currentTimeMillis() / 1000;
System.out.println("timestamp2:"+timestamp2);
//>>1733908113

long timestamp3 = Instant.now().getEpochSecond();
System.out.println("timestamp3:"+timestamp3);
//>>1733908113

LocalDateTime localDateTime = LocalDateTime.now();
System.out.println("localDateTime:"+localDateTime);
//>>localDateTime:2024-12-11T17:10:45.800
//获取我们常见的时间格式
String dateTime = localDateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
System.out.println("dateTime:"+dateTime);
//>>dateTime:2023-04-07 14:06:53
//localDateTime获取时间戳
long timestamp4 = localDateTime.toInstant(ZoneOffset.of("+8")).toEpochMilli();
System.out.println("timestamp4:"+timestamp4);
//>>1733908245800
long timestamp5 = localDateTime.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
System.out.println("timestamp5:"+timestamp5);
//>> 1733908324740
long timestamp6 = ZonedDateTime.now().toInstant().toEpochMilli();
System.out.println("timestamp6:"+timestamp6);
//>>1733908374866
long timestamp7 = ZonedDateTime.now().toEpochSecond();
System.out.println("timestamp7:"+timestamp7);
//>>1733908374
long timestamp8 = ZonedDateTime.now().toLocalDateTime().toEpochSecond(ZoneOffset.of("+8"));
System.out.println("timestamp8:"+timestamp8);

long time = System.currentTimeMillis();
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
 System.out.println("time:"+time);
 // 将毫秒时间戳转换为 Instant 对象
Instant instant=Instant.ofEpochMilli(time);
System.out.println("instant:"+instant);
 // 将 Instant 对象转换为 LocalDateTime 对象，使用系统默认时区
LocalDateTime localDateTime=LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
System.out.println("localDateTime:"+localDateTime.format(formatter));
LocalDateTime localDateTime1 =LocalDateTime.ofEpochSecond(instant.getEpochSecond(),0, ZoneOffset.of("+8"));
System.out.println("localDateTime1:"+localDateTime1.format(formatter));

String dt = "2024-12-11";
String dtt = "2024-12-11 17:44:28";
String format_DateTime = "yyyy-MM-dd HH:mm:ss";
DateTimeFormatter df = DateTimeFormatter.ofPattern(format_DateTime);
LocalDateTime localDateTime = LocalDateTime.parse(dtt, df);
System.out.println("localDateTime:"+localDateTime);
//转为Instant
Instant instant = localDateTime.toInstant(ZoneOffset.of("+8"));
System.out.println("instant:"+instant);
System.out.println("毫秒级时间戳:"+instant.toEpochMilli());
System.out.println("秒级时间戳:"+instant.getEpochSecond());
LocalDate localDate = LocalDate.parse(dt);
System.out.println("localDate:"+localDate);
System.out.println("localDate.atStartOfDay():"+localDate.atStartOfDay().format(df));
//转为Instant
Instant instant1 = localDate.atStartOfDay().toInstant(ZoneOffset.of("+8"));
System.out.println("毫秒级时间戳:"+instant.toEpochMilli());
System.out.println("秒级时间戳:"+instant.getEpochSecond());