IntelliJ: Regular expression to join multiple lines into single CSV line? - regex

Question

Occasionally I need to join multiple lines of data into a single line, and in this case, specifically as comma-separated values on a single line:
input: (lines pasted into some Android Studio editor tab)
Rush
IQ
Saga
Yes
desired output:
'Rush','IQ','Saga','Yes'
Edit > Find > Replace I got close with this regex pattern to match newline character (\n) with goal eliminate it:
search: ^(.*)$\n
replace: '$1',
[x] Regex
but produces this undesired output:
'Rush',IQ
'Saga',Yes
because after the a new line is eliminated the following line is already adjoining so it's skipped... so we get this "every other line" behavior.

Answer 1

The fastest and easiest way I could think of is to replace \n by ',' and then manually wrap the whole line in quotes:
The result of the first replacement would be:
Rush','IQ','Saga','Yes
And then just manually add first and last quote.

Answer 2

Step 1: Concatenate the lines, use
(.+)(?:\R|\z)
Replace with '$1',.
The (.+)(?:\R|\z) pattern matches any 1+ chars other than line break chars as many as possible (.+) and captures this into Group 1 and (?:\R|\z) matches either a line break sequence (\R) or (|) the very end of the string (\z).
Step 2: Post-process by repalcing ,$ with an empty string. This pattern matches , at the end of the line.

Answer 3

Occasionally I need to join multiple lines of data into a single line, and in this case, specifically as comma-separated values on a single line:
Regex may not be the best solution for this.
CSV library
There are several comma-separated values (CSV) libraries available to make quick work of this.
The libraries will handle a particular problem you may overlook in writing your own code: Some of your lines of input having the single-quote mark within their content. Such cases need to be escaped. Quoting RFC 4180 section 2.7:
If double-quotes are used to enclose fields, then a double-quote
appearing inside a field must be escaped by preceding it with
another double quote. For example:
"aaa","b""bb","ccc"
Here is an example of using Apache Commons CSV library.
We use lambda syntax with a Scanner to get an Iterable of the lines of text from your input.
We specify using a single-quote, as you desire, rather than default of double-quote in standard CSV.
We use try-with-resources syntax to automatically close the CSVPrinter object, whether our code runs successfully or throws an exception.
String input = "Rush\n" +
"IQ\n" +
"Saga\n" +
"Yes";
Iterable < String > iterable = ( ) -> new Scanner( input ).useDelimiter( "\n" ); // Lambda syntax to get a `Iterable` of lines from a `String`.
CSVFormat format =
CSVFormat
.RFC4180
.withQuoteMode( QuoteMode.ALL )
.withQuote( '\'' );
StringBuilder stringBuilder = new StringBuilder();
try (
CSVPrinter printer = new CSVPrinter( stringBuilder , format ) ;
)
{
printer.printRecord( iterable );
}
catch ( IOException e )
{
e.printStackTrace();
}
String output = stringBuilder.toString();
System.out.println( "output: " + output );
When run:
output: 'Rush','IQ','Saga','Yes'
We can shorten that code.
try (
CSVPrinter printer = new CSVPrinter( new StringBuilder() , CSVFormat.RFC4180.withQuoteMode( QuoteMode.ALL ).withQuote( '\'' ) ) ;
)
{
printer.printRecord( ( Iterable < String > ) ( ) -> new Scanner( input ).useDelimiter( "\n" ) );
System.out.println( printer.getOut().toString() ); // Or: `return printer.getOut()` returning an `Appendable` object.
}
catch ( IOException e )
{
e.printStackTrace();
}
Not that this is particularly better shortened. Personally, I would use the longer version wrapped in a method in a utility class. Like this:
public String enquoteLines( String input ) {
String output = "";
Iterable < String > iterable = ( ) -> new Scanner( input ).useDelimiter( "\n" ); // Lambda syntax to get a `Iterable` of lines from a `String`.
CSVFormat format =
CSVFormat
.RFC4180
.withQuoteMode( QuoteMode.ALL )
.withQuote( '\'' );
StringBuilder stringBuilder = new StringBuilder();
try (
CSVPrinter printer = new CSVPrinter( stringBuilder , format ) ;
)
{
printer.printRecord( iterable );
output = printer.getOut().toString();
}
catch ( IOException e )
{
e.printStackTrace();
}
return output;
}
Calling it:
String input = "Rush\n" +
"IQ\n" +
"Saga\n" +
"Oui";
String output = this.enquoteLines( input );