DateFormat 类的parse()方法问题

[anqini]

我调用的是单个参数的方法，怎么我给它传"2008121a"，我把这个转化成yyyy/mm/dd格式，我想应该报错，怎么输出的结果是2008/12/01???

[jmslyz]

toLocaleString已经不被推荐。 JDK 版本 1.1以后，
被DateFormat.format(Date date)调换了。

[hudingchen]

为什么不抱错，只能看看源码了

public Date parse(String text, ParsePosition pos)
{
        int start = pos.index;
        int oldStart = start;
        int textLength = text.length();

        boolean[] ambiguousYear = {false};

        calendar.clear(); // Clears all the time fields

        for (int i = 0; i < compiledPattern.length; ) {
            int tag = compiledPattern[i] >>> 8;
		    int count = compiledPattern[i++] & 0xff;
		    if (count == 255) {
				count = compiledPattern[i++] << 16;
				count |= compiledPattern[i++];
	    	}

	    switch (tag) {
		    case TAG_QUOTE_ASCII_CHAR:
			if (start >= textLength || text.charAt(start) != (char)count) {
			    pos.index = oldStart;
			    pos.errorIndex = start;
			    return null;
			}
			start++;
			break;

		    case TAG_QUOTE_CHARS:
			while (count-- > 0) {
			    if (start >= textLength || text.charAt(start) != compiledPattern[i++]) {
					pos.index = oldStart;
					pos.errorIndex = start;
					return null;
			    }
			    start++;
			}
			break;

		    default:
			// Peek the next pattern to determine if we need to
			// obey the number of pattern letters for
			// parsing. It's required when parsing contiguous
			// digit text (e.g., "20010704") with a pattern which
			// has no delimiters between fields, like "yyyyMMdd".
			boolean obeyCount = false;
			if (i < compiledPattern.length) {
			    int nextTag = compiledPattern[i] >>> 8;
			    if (!(nextTag == TAG_QUOTE_ASCII_CHAR || nextTag == TAG_QUOTE_CHARS)) {
					obeyCount = true;
			    }
			}
			start = subParse(text, start, tag, count, obeyCount,
					 ambiguousYear, pos);
			if (start < 0) {
			    pos.index = oldStart;
			    return null;
			}
	    }
	}

	// If only AM_PM has been set without any hour value, then
	// HOUR is set to 0 to force calendar to take the HOUR and
	// AM_PM fields. (bugid: 4736959) (Changing GregorianCalendar
	// to take a look at both the HOUR and AM_PM stamp values
	// breaks JCK GregorianCalendar2057.)
	if (calendar.isSet(Calendar.AM_PM) && !calendar.isSet(Calendar.HOUR) &&
	    !calendar.isSet(Calendar.HOUR_OF_DAY)) {
	    calendar.set(Calendar.HOUR, 0); // force to update the stamp value
	}

        // At this point the fields of Calendar have been set.  Calendar
        // will fill in default values for missing fields when the time
        // is computed.

        pos.index = start;

        // This part is a problem:  When we call parsedDate.after, we compute the time.
        // Take the date April 3 2004 at 2:30 am.  When this is first set up, the year
        // will be wrong if we're parsing a 2-digit year pattern.  It will be 1904.
        // April 3 1904 is a Sunday (unlike 2004) so it is the DST onset day.  2:30 am
        // is therefore an "impossible" time, since the time goes from 1:59 to 3:00 am
        // on that day.  It is therefore parsed out to fields as 3:30 am.  Then we
        // add 100 years, and get April 3 2004 at 3:30 am.  Note that April 3 2004 is
        // a Saturday, so it can have a 2:30 am -- and it should. [LIU]
        /*
        Date parsedDate = calendar.getTime();
        if( ambiguousYear[0] && !parsedDate.after(defaultCenturyStart) ) {
            calendar.add(Calendar.YEAR, 100);
            parsedDate = calendar.getTime();
        }
        */
        // Because of the above condition, save off the fields in case we need to readjust.
        // The procedure we use here is not particularly efficient, but there is no other
        // way to do this given the API restrictions present in Calendar.  We minimize
        // inefficiency by only performing this computation when it might apply, that is,
        // when the two-digit year is equal to the start year, and thus might fall at the
        // front or the back of the default century.  This only works because we adjust
        // the year correctly to start with in other cases -- see subParse().
        Date parsedDate;
        try {
            if (ambiguousYear[0]) // If this is true then the two-digit year == the default start year
            {
                // We need a copy of the fields, and we need to avoid triggering a call to
                // complete(), which will recalculate the fields.  Since we can't access
                // the fields[] array in Calendar, we clone the entire object.  This will
                // stop working if Calendar.clone() is ever rewritten to call complete().
                Calendar savedCalendar = (Calendar)calendar.clone();
                parsedDate = calendar.getTime();
                if (parsedDate.before(defaultCenturyStart))
                {
                    // We can't use add here because that does a complete() first.
                    savedCalendar.set(Calendar.YEAR, defaultCenturyStartYear + 100);
                    parsedDate = savedCalendar.getTime();
                }
            }
            else parsedDate = calendar.getTime();
        }
        // An IllegalArgumentException will be thrown by Calendar.getTime()
        // if any fields are out of range, e.g., MONTH == 17.
        catch (IllegalArgumentException e) {
            pos.errorIndex = start;
            pos.index = oldStart;
            return null;
        }

        return parsedDate;
    }

[胡矣]

public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {

        SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd");
        Date date = null;
        try {
            date = format.parse("2008/12/1a");
            //改成date = format.parse("2008121a");就报错了.
            System.out.println(date.toLocaleString());
        } catch (ParseException e) {
            // TODO 自動生成された catch ブロック
            e.printStackTrace();
            System.out.println("error");
        }
    }

}

[nihuajie05]

[Quote=引用 7 楼 anqini 的回复:]
引用 6 楼 nihuajie05 的回复:
// TODO 自動生成された catch ブロック
日文版本的 EClipse吧.....楼上的强人在强奸他钱掠来的新娘----这话是徐志摩说的,不是我


不管是你说的还是xxx说的我不介意！！！下一楼开始不想回答就别留言了，想找6楼这样的话题就谢绝了
[/Quote]
偶尔说了点恶心东西就给鄙视了
好吧,我回点像样的吧
DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date d = sdf.parse("2008121");
System.out.println(d);
也会报错的
为什么,你从一开始就没有满足你自己定义的pattern
而
Date d = sdf.parse("2008-12=-1a");之所以能够通过,并得到结果是因为在两个/d+[-]/d+-/d+ 以后末尾的非数字的字符被屏弃掉了
这样你就能满足来完成,当然了,你也可以认为这是一个不对的,但是JAVA就是这样去做,来提高format的匹配能力的
好了,就是这样了....
还有被人鄙视真的很不爽撒!!!

[火龙果被占用了]

为什么我运行会报错啊？

parse 转成的是一个 Date，怎么会输出呢？

[anqini]

[Quote=引用 1 楼 bao110908 的回复:]
为什么我运行会报错啊？

parse 转成的是一个 Date，怎么会输出呢？
[/Quote]

我是这么想的，因为参数是"2008121a"，但是这个字符串里有不是数字的字母，所以我认为是会报错~

[火龙果被占用了]

DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date d = sdf.parse("2008121a");
System.out.println(d);

我这样就会报错啊，你是怎么弄的？

[hudingchen]

lz 把代码贴上来看看阿，我也抱错

[anqini]

public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {

        SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd");
        Date date = null;
        try {
            date = format.parse("2008/12/1a");
            System.out.println(date.toLocaleString());
        } catch (ParseException e) {
            // TODO 自動生成された catch ブロック
            e.printStackTrace();
            System.out.println("error");
        }
    }

}

[nihuajie05]

// TODO 自動生成された catch ブロック
日文版本的 EClipse吧.....楼上的强人在强奸他钱掠来的新娘----这话是徐志摩说的,不是我

[anqini]

[Quote=引用 6 楼 nihuajie05 的回复:]
// TODO 自動生成された catch ブロック
日文版本的 EClipse吧.....楼上的强人在强奸他钱掠来的新娘----这话是徐志摩说的,不是我
[/Quote]

不管是你说的还是xxx说的我不介意！！！下一楼开始不想回答就别留言了，想找6楼这样的话题就谢绝了