Meena R. Krishnan
posted 9 years ago
The JavaDoc that describes the conversion fields describes what is happening. Here is an excerpt of the relevant parts...
'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', 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().