Java Clock withZone()用法及代碼示例

java.time.Clock.withZone(ZoneId zone)方法是Clock類的一種方法，該方法返回應用了該方法的時鍾對象的時鍾副本，並帶有不同的時區。如果有時鍾，並且需要更改時鍾區域，但沒有其他屬性，則使用withZone()方法。此方法將zone作為參數，這是需要更改的時區。它返回帶區域的時鍾，與參數中傳遞的區域相同。

用法:

public abstract Clock withZone(ZoneId zone)

參數：此方法采用ZoneId類型的強製性參數區域，在其中需要更改時區。

返回：此方法返回應用了此方法的時鍾對象的時鍾副本，並以不同的時區作為參數傳遞。

例：

Code:
//Clock with default zone
Clock clock1=Clock.systemUTC();
ZoneId zone = ZoneId.of("Asia/Calcutta");
Clock clock2 = clock1.withZone(zone);
System.out.println(clock2.toString());

Output::
SystemClock[Asia/Calcutta]

Explanation::
when withZone() is called for Clock object clock1 with zoneId "Asia/Calcutta",
then the withZone() method will return a Clock whose Zone is "Asia/Calcutta".

下麵的程序演示了java.time.Clock類的withZone()方法：

程序1:在withZone()的幫助下，創建具有與“第一時鍾”相似的屬性但zoneId等於“Asia/Calcutta”的時鍾。

// Java program to demonstrate 
// withZone() method of Clock class 
  
import java.time.*; 
  
// create class 
public class withZoneMethodDemo { 
  
    // Main method 
    public static void main(String[] args) 
    { 
        // create a base Clock with systemUTC() method 
        Clock baseclock = Clock.systemUTC(); 
  
        // get ZonedDateTime object from baseclock 
        // clock instant to get date time 
        ZonedDateTime baseTime = baseclock 
                                     .instant() 
                                     .atZone(baseclock.getZone()); 
  
        // print details of ZonedDateTime 
        System.out.println("ZonedDateTime of baseclock "
                           + baseTime.toString()); 
  
        // create ZoneId object with Zone Asia/Calcutta 
        ZoneId zone = ZoneId.of("Asia/Calcutta"); 
  
        // apply withZone() to change zone from utc to Asia/Calcutta 
        Clock clockWithOtherZone = baseclock.withZone(zone); 
  
        // get ZonedDateTime object from clockWithOtherZone 
        // clock instant to get date time 
        ZonedDateTime calcuttaTime = clockWithOtherZone 
                                         .instant() 
                                         .atZone(clockWithOtherZone.getZone()); 
  
        // print details of ZonedDateTime 
        System.out.println("ZonedDateTime of clockWithOtherZone "
                           + calcuttaTime.toString()); 
    } 
}

輸出：

ZonedDateTime of baseclock 2018-08-24T08:09:17.354Z
ZonedDateTime of clockWithOtherZone 2018-08-24T13:39:17.539+05:30[Asia/Calcutta]

程序2:使用getZone()為withZone()創建的時鍾打印zoneId。

// Java program to demonstrate 
// withZone() method of Clock class 
  
import java.time.*; 
  
// create class 
public class withZoneMethodDemo { 
  
    // Main method 
    public static void main(String[] args) 
    { 
        // create a base Clock with systemDefaultZone() method 
        Clock baseclock = Clock.systemDefaultZone(); 
  
        // print details of ZonedDateTime 
        System.out.println("baseclock Zone:"
                           + baseclock.getZone()); 
  
        // create ZoneId object with Zone Asia/Calcutta 
        ZoneId zone = ZoneId.of("Asia/Calcutta"); 
  
        // apply withZone() to change zone 
        // of baseclock to Asia/Calcutta 
        Clock clockWithOtherZone = baseclock.withZone(zone); 
  
        // print details of ZonedDateTime 
        System.out.println("clockWithOtherZone Zone:"
                           + clockWithOtherZone.getZone()); 
    } 
}

輸出：

baseclock Zone:Etc/UTC
clockWithOtherZone Zone:Asia/Calcutta

參考：
https://docs.oracle.com/javase/8/docs/api/java/time/Clock.html#withZone-java.time.ZoneId-

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注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 Java Clock withZone() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。