SimpleDateFormat解析函数更改格式

Question

I have a String with several dates:

[20-Jul-2012 5:11:36,670 UTC PM, 20-Jul-2012 5:11:36,683 UTC PM]

ParsePosition parsePos = new ParsePosition(1);
SimpleDateFormat format2 = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss,SSS z a");
System.out.println(format2.parse(entry.getValue().toString(), parsePos)) ;

Output : Fri Jul 20 06:11:36 BST 2012

I need the output to be 20-Jul-2012 5:11:36,670 UTC PM .

Do I need to set a LOCALE in the SimpleDateFormat to not have a different output?

Answer 1

You need to set the time zone, but more importantly, you simply need to actually use the format to format the date:

Date date = format2.parse(...);
String formattedDate = format2.format(date);
System.out.println(formattedDate);

What your code does is:

Date date = format2.parse(...);
System.out.println(date.toString());

I don't really understand the point in parsing a string to a date, and then displaying the date using the exact same format, though (except to validate that the String is indeed a valid date, but then you could simply reuse the original string).

Answer 2

You've got two small problems:

1. Use hh for the hour, not HH . H is "Hour in day (0-23), and so will not work correctly with a , the AM/PM marker. Your two example date strings will parse to AM, not PM.
2. You're using SimpleDateFormat to parse the string, but not format it. Use format2.format(format2.parse(entry.getValue().toString()) .

Here's a complete example:

SimpleDateFormat format = new SimpleDateFormat("dd-MMM-yyyy hh:mm:ss,SSS z a");
String input = "20-Jul-2012 5:11:36,670 UTC PM";
Date date = format.parse(input);
String output = format.format(date);
System.out.println(output);

Result:

20-Jul-2012 05:11:36,670 UTC PM