Question

When I kick off my maven build, it fails with this error

“Conversion = s, Flags = #”

on the below test.

public class Test {

    public static void main(String[] argv) {
        String a = String.format("%1$#" + (250 + 1) + "s", "");
        System.out.println("a = " + a);
    }
}

Please advise.

Thanks.

Answer 1

So this is really all down to a call which looks like this:

String.format("%1$#251s", "");

If you look at the Formatter docs, this format string is requesting a string conversion (s) with a width of 251 and a flag of #.

The docs for string conversions state:

If the ‘#’ flag is given and the argument is not a Formattable , then a FormatFlagsConversionMismatchException will be thrown.

Now java.lang.String doesn’t implement Formattable – so the exception is thrown, exactly as documented.

What did you expect this to do?