問題描述

所以我從表單中的傳入對象中獲取日期屬性:

So I get a date attribute from an incoming object in the form:

Tue May 24 05:05:16 EDT 2011

我正在編寫一個簡單的輔助方法來將其轉換為日歷方法，我使用的是以下代碼:

I am writing a simple helper method to convert it to a calendar method, I was using the following code:

    public static Calendar DateToCalendar(Date date ) 
{ 
 Calendar cal = null;
 try {   
  DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
  date = (Date)formatter.parse(date.toString()); 
  cal=Calendar.getInstance();
  cal.setTime(date);
  }
  catch (ParseException e)
  {
      System.out.println("Exception :"+e);  
  }  
  return cal;
 }

為了模擬傳入的對象，我只是在當前使用的代碼中分配值:

To simulate the incoming object I am just assigning the values within the code currently using:

private Date m_lastActivityDate = new Date();

但是，一旦方法到達，這會給我一個空指針:

However this is givin me a null pointer once the method reaches:

date = (Date)formatter.parse(date.toString()); 

推薦答案

這是你的方法:

public static Calendar toCalendar(Date date){ 
  Calendar cal = Calendar.getInstance();
  cal.setTime(date);
  return cal;
}

你所做的一切都是錯誤和不必要的.

Everything else you are doing is both wrong and unnecessary.

順便說一句，Java 命名約定建議方法名稱以小寫字母開頭，因此應該是:dateToCalendar 或 toCalendar(如圖所示).

BTW, Java Naming conventions suggest that method names start with a lower case letter, so it should be: dateToCalendar or toCalendar (as shown).

好的，讓我們擠一下你的代碼，好嗎?

OK, let's milk your code, shall we?

DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
date = (Date)formatter.parse(date.toString()); 

DateFormat 用于將字符串轉換為日期(parse())或將日期轉換為字符串(format()).您正在使用它將日期的字符串表示解析回日期.這不可能吧?

DateFormat is used to convert Strings to Dates (parse()) or Dates to Strings (format()). You are using it to parse the String representation of a Date back to a Date. This can't be right, can it?

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