See
java.util.Formatter:
'b', 'B' - If the argument arg is null, then the result is "false". If arg is a boolean or Boolean, then the result is the string returned by String.valueOf(). Otherwise, the result is "true".
's', 'S' - If the argument arg is null, then the result is "null". If arg implements Formattable, then arg.formatTo is invoked. Otherwise, the result is obtained by invoking arg.toString().
The A is a little bit confusing as a Boolean(
String) constructor will return true only for a string "true" (ingnoring case). At least they agree on null.
[ April 13, 2008: Message edited by: Irina Goble ]