Java TemporalAdjusters firstDayOfYear()用法及代碼示例

TemporalAdjusters類的firstDayOfYear()方法用於返回“一年的第一天” TemporalAdjuster對象，該對象返回設置為該年第一天的新的Date對象。

用法:

public static TemporalAdjuster firstDayOfYear()

參數：此方法不接受任何內容。

返回值：此方法返回年份調節器的第一天，而不是null。

以下示例程序旨在說明TemporalAdjusters.firstDayOfYear()方法：
程序1:

// Java program to demonstrate 
// TemporalAdjusters.firstDayOfYear() 
  
import java.time.LocalDate; 
import java.time.temporal.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // get TemporalAdjuster with first day 
        // of the year adjuster 
        TemporalAdjuster temporalAdjuster 
            = TemporalAdjusters.firstDayOfYear(); 
  
        // using adjuster for local date-time 
        LocalDate localDate 
            = LocalDate.of(2012, 05, 31); 
        LocalDate firstDayOfYear 
            = localDate.with(temporalAdjuster); 
  
        // print 
        System.out.println("First day of the "
                           + "year for localdate "
                           + localDate + ":"
                           + firstDayOfYear); 
    } 
}

輸出：

First day of the year for localdate 2012-05-31:2012-01-01

程序2:

// Java program to demonstrate 
// TemporalAdjusters.firstDayOfYear() method 
  
import java.time.LocalDate; 
import java.time.temporal.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // get TemporalAdjuster with first day 
        // of the year adjuster 
        TemporalAdjuster temporalAdjuster 
            = TemporalAdjusters.firstDayOfYear(); 
  
        // using adjuster for local date time 
        LocalDate localDate 
            = LocalDate.of(2000, 12, 21); 
        LocalDate firstDayOfYear 
            = localDate.with(temporalAdjuster); 
  
        // print 
        System.out.println("First day of the "
                           + "year for localdate "
                           + localDate + ":"
                           + firstDayOfYear); 
    } 
}

輸出：

First day of the year for localdate 2000-12-21:2000-01-01

參考文獻：https://docs.oracle.com/javase/10/docs/api/java/time/format/TemporalAdjusters.html

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