Change date format in a Java string

Question

I've a String representing a date.

String date_s = "2011-01-18 00:00:00.0";

I'd like to convert it to a Date and output it in YYYY-MM-DD format.

2011-01-18

How can I achieve this?

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Okay, based on the answers I retrieved below, here's something I've tried:

String date_s = " 2011-01-18 00:00:00.0"; 
SimpleDateFormat dt = new SimpleDateFormat("yyyyy-mm-dd hh:mm:ss"); 
Date date = dt.parse(date_s); 
SimpleDateFormat dt1 = new SimpleDateFormat("yyyyy-mm-dd");
System.out.println(dt1.format(date));

But it outputs 02011-00-1 instead of the desired 2011-01-18. What am I doing wrong?

Answer 1

Use LocalDateTime#parse() (or ZonedDateTime#parse() if the string happens to contain a time zone part) to parse a String in a certain pattern into a LocalDateTime.

String oldstring = "2011-01-18 00:00:00.0";
LocalDateTime datetime = LocalDateTime.parse(oldstring, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.S"));

Use LocalDateTime#format() (or ZonedDateTime#format()) to format a LocalDateTime into a String in a certain pattern.

String newstring = datetime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
System.out.println(newstring); // 2011-01-18

Or, when you're not on Java 8 yet, use SimpleDateFormat#parse() to parse a String in a certain pattern into a Date.

String oldstring = "2011-01-18 00:00:00.0";
Date date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S").parse(oldstring);

Use SimpleDateFormat#format() to format a Date into a String in a certain pattern.

String newstring = new SimpleDateFormat("yyyy-MM-dd").format(date);
System.out.println(newstring); // 2011-01-18

See also:

• Java string to date conversion

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Update: as per your failed attempt: the patterns are case sensitive. Read the java.text.SimpleDateFormat javadoc what the individual parts stands for. So stands for example M for months and m for minutes. Also, years exist of four digits yyyy, not five yyyyy. Look closer at the code snippets I posted here above.