添加日期到日期 [英] adding days to a date

问题描述

我有一个程序需要从1/1/09开始，当我开始新的一天，我的程序将显示第二天。
这是我到目前为止：

  GregorianCalendar startDate = new GregorianCalendar（2009，Calendar.JANUARY，1） ; 
 SimpleDateFormat sdf = new SimpleDateFormat（d / M / yyyy）; 
 public void setStart（）
 {
 startDate.setLenient（false）; 
 System.out.println（sdf.format（startDate.getTime（）））; 
} 
 
 public void today（）
 {
 newDay = startDate.add（5，1）; 
 System.out.println（newDay）; 
 //我想添加一天到开始的一天，当我开始另一个新的一天，我想添加另一天。 
} 
  

我发现错误void but expected int，in'newDay = startDate

解决方案

日历 对象有一个 add 方法，允许添加或减少指定字段的值。

例如，

  
 c.add（Calendar.DAY_OF_MONTH，1）; 
  

用于指定字段的常量可以在 日历 class。

仅供将来参考， Java API规范包含有关如何使用Java API一部分的许多有用的信息。

---

更新：

我收到错误，但
预期的int，在'newDay =
startDate.add（5，1）;'我该怎么
做？

添加方法不返回任何内容，因此，尝试分配调用 Calendar.add 的结果无效。

编译器错误表示一个人试图将一个 void 分配给一个变量h的类型 int 。这是无效的，因为不能将无分配给 int 变量。

只是一个猜测，但是也许这可能是想要实现的：

  //获取设置为指定日期的日历。 
日历calendar = new GregorianCalendar（2009，Calendar.JANUARY，1）; 
 
 //获取日历的当前日期表示。 
 Date startDate = calendar.getTime（）; 
 
 //将日历的日期增加1天。 
 calendar.add（Calendar.DAY_OF_MONTH，1）; 
 
 //获取日历的当前日期表示。 
 Date endDate = calendar.getTime（）; 
 
 System.out.println（startDate）; 
 System.out.println（endDate）; 
  

输出：

 code> Thu Jan 01 00:00:00 PST 2009 
 Fri Jan 02 00:00:00 PST 2009 
  

需要考虑的是日历实际上是

A 日历不是日期的表示。它是一个日历的表示，它正在指向哪里。为了获取当前日历指向的位置，应该获得一个 日期 从日历使用 getTime 方法。

I have a program that needs to start on 1/1/09 and when I start a new day, my program will show the next day. This is what I have so far:

GregorianCalendar startDate = new GregorianCalendar(2009, Calendar.JANUARY, 1);
SimpleDateFormat sdf = new SimpleDateFormat("d/M/yyyy"); 
public void setStart()
{
    startDate.setLenient(false);
    System.out.println(sdf.format(startDate.getTime()));
}

public void today()
{
    newDay = startDate.add(5, 1);
    System.out.println(newDay);
//I want to add a day to the start day and when I start another new day, I want to add another day to that.
}

I am getting the error found void but expected int, in 'newDay = startDate.add(5, 1);' What should I do?

解决方案

The Calendar object has an add method which allows one to add or subtract values of a specified field.

For example,

Calendar c = new GregorianCalendar(2009, Calendar.JANUARY, 1);
c.add(Calendar.DAY_OF_MONTH, 1);

The constants for specifying the field can be found in the "Field Summary" of the Calendar class.

Just for future reference, The Java API Specification contains a lot of helpful information about how to use the classes which are part of the Java API.

---

Update:

I am getting the error found void but expected int, in 'newDay = startDate.add(5, 1);' What should I do?

The add method does not return anything, therefore, trying to assign the result of calling Calendar.add is not valid.

The compiler error indicates that one is trying to assign a void to a variable with the type of int. This is not valid, as one cannot assign "nothing" to an int variable.

Just a guess, but perhaps this may be what is trying to be achieved:

// Get a calendar which is set to a specified date.
Calendar calendar = new GregorianCalendar(2009, Calendar.JANUARY, 1);

// Get the current date representation of the calendar.
Date startDate = calendar.getTime();

// Increment the calendar's date by 1 day.
calendar.add(Calendar.DAY_OF_MONTH, 1);

// Get the current date representation of the calendar.
Date endDate = calendar.getTime();

System.out.println(startDate);
System.out.println(endDate);

Output:

Thu Jan 01 00:00:00 PST 2009
Fri Jan 02 00:00:00 PST 2009

What needs to be considered is what Calendar actually is.

A Calendar is not a representation of a date. It is a representation of a calendar, and where it is currently pointing at. In order to get a representation of where the calendar is pointing at at the moment, one should obtain a Date from the Calendar using the getTime method.

这篇关于添加日期到日期的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！