Java中的Java Clock withZone()方法和示例

Java.time.Clock.withZone(ZoneId zone)方法是 Clock 类的方法，它返回应用此方法的时钟对象的时钟副本，具有不同的时区。如果有时钟并且需要更改时钟的区域而不是其他属性，则使用 withZone() 方法。此方法以 zone 作为参数，即需要更改的时区。它返回带区域的时钟，与参数中传递的区域相同。

句法：

public abstract Clock withZone(ZoneId zone)

参数：该方法需要一个ZoneId类型的强制参数zone ，其中需要更改时区。

返回：此方法返回应用此方法的时钟对象的时钟副本，不同的时区作为参数传递。

例子：

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".

下面的程序说明了Java.time.Clock 类的 withZone() 方法：

程序 1：在 withZone() 的帮助下创建一个与 First Clock 具有相似属性但 zoneId 等于“Asia/Calcutta”的时钟。

// 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());
    }
}

输出：

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() 为 withZone() 创建的时钟打印 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());
    }
}

输出：

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

参考：
https://docs.oracle.com/javase/8/docs/api/java Java