String.format () throws FormatFlagsConversionMismatchException

Question

This code works fine in Java 1.6:

public static String padLeft(String s, int n) { if (n <= 0) return s; int noOfSpaces = n * 2; String output; noOfSpaces = s.length() + noOfSpaces; output = String.format("%1$#" + noOfSpaces + "s", s); return output; } 

But newer versions (and some other VM implementations) throw this Exception :

 java.util.FormatFlagsConversionMismatchException: Mismatched Convertor =s, Flags= # at java.util.Formatter$Transformer.transformFromString(Formatter.java:1020) at java.util.Formatter$Transformer.transform(Formatter.java:861) at java.util.Formatter.format(Formatter.java:565) at java.util.Formatter.format(Formatter.java:509) at java.lang.String.format(String.java:1961) 

Any workarounds?

Answer 1

You asked for a workaround; just use StringBuilder :

 public static String padLeft(String s, int n) { if (n <= 0) return s; int noOfSpaces = n * 2; StringBuilder output = new StringBuilder(s.length() + noOfSpaces); while (noOfSpaces > 0) { output.append(" "); noOfSpaces--; } output.append(s); return output.toString(); } 

Answer 2

Since you use the # flag in the format string, you must pass Formattable as an argument ( doc ).

Any work around?

Do not use # in format string?