Question

I am trying to use a .format method of a string. But if I place %1, %2, etc. in the string, java.util.UnknownFormatConversionException is thrown pointing to a confusing Java source code piece:

private void checkText(String s) {

    int idx;

    // If there are any '%' in the given string, we got a bad format
    // specifier.
    if ((idx = s.indexOf('%')) != -1) {
        char c = (idx > s.length() - 2 ? '%' : s.charAt(idx + 1));
        throw new UnknownFormatConversionException(String.valueOf(c));
    }
}

From this I understand that % char is forbidden. If so, then what should I use for argument placeholders?

I use Scala 2.8.

Answer 1

While all the previous responses are correct, they’re all in Java. Here’s a Scala example:

val placeholder = "Hello %s, isn't %s cool?"
val formatted = placeholder.format("Ivan", "Scala")

I also have a blog post about making format like Python’s % operator that might be useful.