java关于日期的计算

Java中提供了丰富的日期表示方式。其中包括Date、Timestamp、Calendar、GregorianCalendar类。GregorianCalendar类中提供了用于计算日期的add()方法，可以很方便地计算若干年、月、日后的日期。

给个例子看看：

Java代码 :

package testjava;   
    
import java.sql.Timestamp;   
import java.text.SimpleDateFormat;   
import java.util.Date;   
import java.util.GregorianCalendar;   
    
public class DateTest {   
    
public static void main(String[] args) {   
    
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");   
DateTest test = new DateTest();   
//Date   
Date currentDate = new Date();   
System.out.println("当前日期是：" + df.format(currentDate));   
System.out.println("一周后的日期是：" + df.format(test.nextWeek(currentDate)));   
System.out.println("一月后的日期是：" + df.format(test.nextMonth(currentDate)));   
System.out.println("一年后的日期是：" + df.format(test.nextYear(currentDate)));   
//Timestamp   
Timestamp currentTime = new Timestamp(System.currentTimeMillis());   
System.out.println("当前日期是：" + df.format(currentTime));   
System.out.println("一周后的日期是：" + df.format(test.nextWeek(currentTime)));   
System.out.println("一月后的日期是：" + df.format(test.nextMonth(currentTime)));   
System.out.println("一年后的日期是：" + df.format(test.nextYear(currentTime)));   
    
//另一种计算方式，这种方式计算月和年的日期比较困难   
Timestamp nextTime = new Timestamp(currentTime.getTime() + 7 * 24 * 60 * 60 * 1000);   
System.out.println("当前日期是：" + df.format(currentTime));   
System.out.println("一周后的日期是：" + df.format(nextTime));   
    
}   
    
//获取下一周的日期   
public Date nextWeek(Date currentDate) {   
GregorianCalendar cal = new GregorianCalendar();   
cal.setTime(currentDate);   
cal.add(GregorianCalendar.DATE, 7);//在日期上加7天   
return cal.getTime();   
}   
    
//获取本周日的日期   
public Date getSunday(Date monday) {   
GregorianCalendar cal = new GregorianCalendar();   
cal.setTime(monday);   
cal.add(GregorianCalendar.DATE, 6);//在日期上加6天   
return cal.getTime();   
}   
    
//获取下一月的日期   
public Date nextMonth(Date currentDate) {   
GregorianCalendar cal = new GregorianCalendar();   
cal.setTime(currentDate);   
cal.add(GregorianCalendar.MONTH, 1);//在月份上加1   
return cal.getTime();   
}   
    
//获取下一年的日期   
public Date nextYear(Date currentDate) {   
GregorianCalendar cal = new GregorianCalendar();   
cal.setTime(currentDate);   
cal.add(GregorianCalendar.YEAR, 1);//在年上加1   
return cal.getTime();   
}   
}