如何使用正则表达式替换字符？

Question

How to replace characters '-' using regular expressions?

There some date or datetime fields in my json string and they all use character '/' as separator, such as '2016/10/10 10:10:10' .
now i need the date or datetime fields with this form '2016-10-10 10:10:10' .

For example:

{
 "code": "200",
 "error": "",
 "total": "10",
 "page": "1",
 "result": [
   {
     "CustomerNo": "0432215",
     "Name": "ACE-Dick/USA",
     "LastUpdatedDate": "2015/08/07 13:25:32",
     "LastUpdatedBy": "System"
   }
 ]
}

The text below is correct json what i want.

{
 "code": "200",
 "error": "",
 "total": "10",
 "page": "1",
 "result": [
   {
     "CustomerNo": "0432215",
     "Name": "ACE-Dick/USA",
     "LastUpdatedDate": "2015-08-07 13:25:32",
     "LastUpdatedBy": "System"
   }
 ]
}

I can find the date string using regular expresion as follow,but how can replace it?

\\d{4}/\\d{2}/\\d{2} \\d{2}:\\d{2}:\\d{2}

Answer 1

Use capturing groups around the values you need to keep, and just match what you need to replace:

(\d{4})/(\d{2})/(\d{2} \d{2}:\d{2}:\d{2})
^ -1- ^ ^ -2- ^ ^ --------- 3---------- ^

and replace with $1-$2-$3 where $1 is a backreference to the value captured with Group 1, $2 references Group 2 value, etc.

See the regex demo

Java demo :

String s = "2016/10/10 10:10:10"; 
String rx = "(\\d{4})/(\\d{2})/(\\d{2} \\d{2}:\\d{2}:\\d{2})";
System.out.println(s.replaceAll(rx, "$1-$2-$3")); 

See more on capturing groups and backreferences here .

Answer 2

You can do grouping and substitution, the syntax will vary according to the language you are using. For grouping you can use (\\d{4})/(\\d{2})/(\\d{2} \\d{2}:\\d{2}:\\d{2}) for substitution just use $1,$2,$3 to reference these groups while substituting.

Answer 3

If you have your date as a String, you can use replaceAll()

Example

yourString.replaceAll("/", "-")