如何使用Java更改日期中的天数？

2024 年 9 月 10 日 | 阅读 3 分钟

Java的Calendar类（java.util.Calendar）是Java中一个非常有用且实用的日期和时间操作类。在这里，我将向您展示如何使用Calendar类来更改日期和时间。

使用calendar()类方法获取今天的日期和时间。

DateFormat dF = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Calendar c = Calendar.getInstance();
System.out.println(" Present Date Time is : " + dF.format(c.getTime()));

更改日历上的日期或时间。

// Date and time are current plus one day.
cal.add(Calendar.DATE, 1);
// Date and time are current plus one month.
c.add(Calendar.MONTH, 1);
// Date and time are current plus one year.
c.add(Calendar.YEAR, 1);
// Date and time are current plus one hour.
c.add(Calendar.HOUR, 1);
// Date and time are current plus one minute.
c.add(Calendar.MINUTE, 1);
// Date and time are current plus one second.
c.add(Calendar.SECOND, 1);
// Take a day out of the current date.
c.add(Calendar.DATE, -1);
// Take a month out of the current date.
c.add(Calendar.MONTH, -1);
// Take a year out of the current date.
c.add(Calendar.YEAR, -1);
// Take an hour out of the current date.
c.add(Calendar.HOUR, -1);

// Take a minute out of the current date.
c.add(Calendar.MINUTE, -1);

// Take a second out of the current date.
c.add(Calendar.SECOND, -1);

这段完整的源代码演示了如何在Java中更改日期和时间。

// 文件名: DateTimeChanging.java

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class DateTimeChanging {
  public static void main(String args[]) {
 
	   DateFormat dF = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
	   // retrieve the current time and date with a calendar ()
	   Calendar c = Calendar.getInstance();
	   System.out.println(" Present Date Time is : " + dF.format(c.getTime()));
	   // Date and time are current plus one day.
	   c.add(Calendar.DATE, 1);
	   System.out.println(" Adding one day to the present date : " + dF.format(c.getTime()));
	   // Date and time are current plus one month.
	   c = Calendar.getInstance();
	   c.add(Calendar.MONTH, 1);
	   System.out.println(" Adding one month to the present date : " + dF.format(c.getTime()));
	   // Date and time are current plus one year.
	   c = Calendar.getInstance();
	   c.add(Calendar.YEAR, 1);
	   System.out.println(" Adding one year to the present date : " + dF.format(c.getTime()));
	   // Date and time are current plus one hour.
	   c = Calendar.getInstance();
	   c.add(Calendar.HOUR, 1);
	   System.out.println(" Adding one hour to the present date : " + dF.format(c.getTime()));
	   // Date and time are current plus one minute.
	   c = Calendar.getInstance();
	   c.add(Calendar.MINUTE, 1);
	   System.out.println(" Adding one minute to the present date : " + dF.format(c.getTime()));
	   // Date and time are current plus one second.
	   c = Calendar.getInstance();
	   c.add(Calendar.SECOND, 1);
	   System.out.println(" Adding one second to the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current date.
	   c = Calendar.getInstance();
	   c.add(Calendar.DATE, -1);
	   System.out.println(" Subtracting one day from the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current month.
	   c = Calendar.getInstance();
	   c.add(Calendar.MONTH, -1);
	   System.out.println(" Subtracting one month from the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current year.
	   c = Calendar.getInstance();
	   c.add(Calendar.YEAR, -1);
	   System.out.println(" Subtracting one year from the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current hour.
	   c = Calendar.getInstance();
	   c.add(Calendar.HOUR, -1);
	   System.out.println(" Subtracting one hour from the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current minute.
	   c = Calendar.getInstance();
	   c.add(Calendar.MINUTE, -1);
	   System.out.println(" Subtracting one minute from the present date : " + dF.format(c.getTime()));
	   // Take a day out of the current second.
	   c = Calendar.getInstance();
	   c.add(Calendar.SECOND, -1);
	   System.out.println(" Subtracting one second from the present date : " + dF.format(c.getTime()));	   
 
  }
}

输出

Present Date Time is : 2023/01/14 18:15:26
 Adding one day to the present date : 2023/01/15 18:15:26
 Adding one month to the present date : 2023/02/14 18:15:26
 Adding one year to the present date : 2024/01/14 18:15:26
 Adding one hour to the present date : 2023/01/14 19:15:26
 Adding one minute to the present date : 2023/01/14 18:16:26
 Adding one second to the present date : 2023/01/14 18:15:27
 Subtracting one day from the present date : 2023/01/13 18:15:26
 Subtracting one month from the present date : 2022/12/14 18:15:26
 Subtracting one year from the present date : 2022/01/14 18:15:26
 Subtracting one hour from present date : 2023/01/14 17:15:26
 Subtracting one minute from the present date : 2023/01/14 18:14:26
 Subtracting one second from the present date : 2023/01/14 18:15:25

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