Enthuware

K&B book states that "if you have a mismatch between the type specified in your conversion character and your argument, you will get a runtime exception"

I do not understand

%b implies you are trying to print a value as a boolean. The rule for conversion to a boolean is as follows: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".

The given explanation is correct as per the API JavaDoc at: http://download.oracle.com/javase/6/doc ... tml#syntax

ETS User wrote:K&B book states that "if you have a mismatch between the type specified in your conversion character and your argument, you will get a runtime exception"

I do not understand

%b implies you are trying to print a value as a boolean. The rule for conversion to a boolean is as follows: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".

I remembered the same thing in K&B, but he is right. I just tested it.

%b and %s have some slightly different rules.

I think the others follow what K&B said and I think the K&B example was using one of the ones that would cause an exception, but they made it sound like it applied to all format codes.

Any logical reason why the compiler does not see that boolean is not convertible to decimal, when using Format String Syntax?

It does see it in this case:

boolean flag = false;
float f = (float) flag; //obviously does not compile
System.out.print(f);

Because the compiler does not know that you are trying to convert a boolean to float.You are basically passing a boolean to a method that accepts a boolean. What that method does at run time to that boolean is not really known to the compiler.

Thanks.