Java String format issue

Question

I have a problem using the String.format() method.

So I want to create a String with a line feed, for which I use %n .

I create the string like this:

for (int i = 0; i < authorNames.size(); i++) {
  tmpReturnString += authorNames.get(i) + "%n";
}

with authorNames beeing a ArrayList. Next I want to return the formatted String:

returnResult.setAttributes(0, String.format(tmpReturnString.substring(0, tmpReturnString.length() - 1)))

returnResult is going to be my return.

But here I get a java.util.UnknownFormatConversionException: Conversion = '%' .

Unfortunatly I have no clue how to fix this issue. Also, non of the other questions helped me.

Thanks in advance!

Answer 1

I guess you want to remove the last new line, but by removing only one character you end up with your string ending with % .

Do this instead:

String.format(tmpReturnString.substring(0, tmpReturnString.length() - 2))

(remove 2 characters instead of just 1)

Or, even better, if you use apache commons:

String.format(StringUtils.join(authorNames, "%n"));

Answer 2

for (int i = 0; i < authorNames.size(); i++) {
  tmpReturnString += authorNames.get(i) + "%n";
}

alway return the string with two last character is "%n". So when you use

substring(0, tmpReturnString.length() - 1)

Now the last character is '%'. The '%' is not a valid format specifier.