[英]Format a Date object with DateFormat in Java
我正在嘗試了解Date對象和DateFormat類,並且在嘗試執行的示例中不斷出現錯誤。 目的是通過在假發票日期上增加30天來獲得到期日期,然后格式化該到期日期。 我相信dueDate方法是正確的,但是我在正確格式化它時遇到了麻煩。
這是我要發票日期並加上30天的第一件事。
public Date getDueDate()
{
Calendar cal = new GregorianCalendar();
cal.setTime(getInvoiceDate());
cal.add(Calendar.DATE, 30);
Date dueDate = cal.getTime();
return dueDate;
}
下一部分是我遇到麻煩的地方,因為它一直告訴我它期望使用Date對象,但是正在接收String,並且我不確定為什么,因為我正在提供Date對象。
public Date getFormattedDueDate()
{
Date dueDate = getDueDate();
DateFormat shortDate = DateFormat.getDateInstance(DateFormat.SHORT);
return shortDate.format(dueDate);
}
誰能幫我弄清楚為什么當我將提供的變量(dueDate)編碼為Date對象時,它告訴我的是String嗎?
format(Date date)
將Date
格式化為日期/時間String
。
假的是對的
shortDate.format(dueDate);
返回一個字符串,您可以輕松地解決此問題,更改返回類型
public String getFormattedDueDate()
{
Date dueDate = getDueDate();
DateFormat shortDate = DateFormat.getDateInstance(DateFormat.SHORT);
return shortDate.format(dueDate);
}
Shamse的答案是正確的。
對於此問題,這里是相同類型的代碼,但:
// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
java.util.Date date = new Date(); // = getInvoiceDate();
org.joda.time.DateTime invoiceStoredDateTime = new org.joda.time.DateTime( date );
// Set to desired time zone. Ideally that invoice date was stored in UTC.
// Time Zone list: http://joda-time.sourceforge.net/timezones.html
org.joda.time.DateTimeZone denverTimeZone = org.joda.time.DateTimeZone.forID( "America/Denver" );
org.joda.time.DateTime invoiceZonedDateTime = invoiceStoredDateTime.toDateTime( denverTimeZone );
// Call method .withTimeAtStartOfDay() to set the time component to first moment of the day.
org.joda.time.DateTime dueDateInThirtyDays = invoiceZonedDateTime.plusDays( 30 ).withTimeAtStartOfDay();
org.joda.time.DateTime dueDateInOneMonth = invoiceZonedDateTime.plusMonths( 1 ).withTimeAtStartOfDay(); // Smart month calculation, aiming at same day number of month.
// Style – Specify a character of 'S' for short style, 'M' for medium, 'L' for long, and 'F' for full. First for date, second for time.
// A date or time may be omitted by specifying a style character '-'.
String dueDateAsString = org.joda.time.format.DateTimeFormat.forStyle("S-").withLocale( Locale.US ).print( dueDateInThirtyDays );
org.joda.time.DateTime dueDateInUtcForStorage = dueDateInThirtyDays.toDateTime( org.joda.time.DateTimeZone.UTC );
在控制台上顯示值:
System.out.println( "date: " + date );
System.out.println( "invoiceZonedDateTime: " + invoiceZonedDateTime );
System.out.println( "dueDateInThirtyDays: " + dueDateInThirtyDays );
System.out.println( "dueDateInOneMonth: " + dueDateInOneMonth );
System.out.println( "dueDateAsString: " + dueDateAsString );
System.out.println( "dueDateInUtcForStorage: " + dueDateInUtcForStorage );
運行時...
date: Thu Nov 28 13:39:05 PST 2013
invoiceZonedDateTime: 2013-11-28T14:39:05.125-07:00
dueDateInThirtyDays: 2013-12-28T00:00:00.000-07:00
dueDateInOneMonth: 2013-12-28T00:00:00.000-07:00
dueDateAsString: 12/28/13
dueDateInUtcForStorage: 2013-12-28T07:00:00.000Z
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