String Joiner help needed in Java

Question

I need a help in String Joiners and i want to append To_date to before string and the format after string..

public static StringJoiner inputDatesToQuery(
        List<FileSubmtRetrlStatus> fileSubmtRetrlStatus) {
    StringJoiner joinNames = new StringJoiner(",", "TO_DATE('", "','YYYY-MM-DD HH24:MI:SS')");   // passing comma(,) and square-brackets as delimiter   
    for (FileSubmtRetrlStatus status : fileSubmtRetrlStatus) {
        joinNames.add(status.getFileSubRetDateTime());
        }
    return joinNames;

But the out put is coming like as below..

TO_DATE('2017-04-13 11:18:16,2017-04-13 11:17:44,2017-04-13 10:16:07',
'YYYY-MM-DD HH24:MI:SS')

But it should be like below...

TO_DATE('2017-04-13 11:18:16,'YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2017-04-13 11:17:44,'YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2017-04-13 10:16:07,'YYYY-MM-DD HH24:MI:SS')

Answer 1

StringJoiner only produces one output string. The example code in its documentation is:

The String "[George:Sally:Fred]" may be constructed as follows:

StringJoiner sj = new StringJoiner(":", "[", "]");
sj.add("George").add("Sally").add("Fred");
String desiredString = sj.toString();

Ie it takes all the items you add() , separates them by the delimiter (in your case, a comma), and when you call toString() puts the prefix at the beginning of the full string, and the suffix at the end.

If you want to use StringJoiner, you need a separate one for each entry you want to output. You might want to look at Formatter or StringBuilder instead.

Answer 2

If you want that output, you just need to setup the StringJoiner correctly:

String[] input = { "2017-04-13 11:18:16", "2017-04-13 11:17:44", "2017-04-13 10:16:07" };

StringJoiner joiner = new StringJoiner(",'YYYY-MM-DD HH24:MI:SS'),\nTO_DATE('",
                                       "TO_DATE('",
                                       ",'YYYY-MM-DD HH24:MI:SS')");
for (String s : input)
    joiner.add(s);
System.out.println(joiner.toString());

Output

TO_DATE('2017-04-13 11:18:16,'YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2017-04-13 11:17:44,'YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2017-04-13 10:16:07,'YYYY-MM-DD HH24:MI:SS')

Or to use Streams, like @LouisWasserman thinks you should :

String[] input = { "2017-04-13 11:18:16", "2017-04-13 11:17:44", "2017-04-13 10:16:07" };

String joined = Arrays.stream(input)
                      .collect(Collectors.joining(",'YYYY-MM-DD HH24:MI:SS'),\nTO_DATE('",
                                                  "TO_DATE('",
                                                  ",'YYYY-MM-DD HH24:MI:SS')"));

System.out.println(joined);

Remember, the prefix only goes before the first item , the suffix only goes after the last item , and the delimiter should be the entire text you want between items .

↓ prefix
TO_DATE(' ​2017-04-13 11:18:16​ ,'YYYY-MM-DD HH24:MI:SS'), ← delimiter
TO_DATE(' ​2017-04-13 11:17:44,'YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2017-04-13 10:16:07​ ,'YYYY-MM-DD HH24:MI:SS') ← suffix

---

UPDATE

For the people who don't like repetition or string with newlines, do this:

String prefix = "TO_DATE('";
String suffix = ",'YYYY-MM-DD HH24:MI:SS')";
StringJoiner joiner = new StringJoiner(suffix + ", " + prefix, prefix, suffix);