I just downloaded J2SE 1.5/5.0 "Tiger" Beta and started playing with it. First, I could not get the Cheetah and the Tiger to play together.

For those who joined the game late (like me), Cheetah is the early preview of Eclipse's future support for J2SE 1.5. It is is not part of the Eclipse 3.0 release. If anyone got these two cubs in a cage and under control, please leave a comment or at least a link to how to make these two get along. Thanks in advance.

After a usual, HelloWorld program, I wanted to explore the new printf feature of the java.io.PrintStream. Given that this is advertised as the close cousin of C language's printf function, I thought I would put it to test and see how it is and is not similar to its C counterpart. This revealed some interesting observations that refreshed my Java fundamentals.

Let's start with a simple C code snippet. For those who attended some junior level C programmer interview, this is a familiar question. What is the output when the following code is executed?

int i = 0;
printf("%d %d %d", ++i, ++i, ++i);

If you were the interviewee and I am the interviewer and if you said "0 0 0" or "1 1 1" as the answer, I would let you go without wasting any more time. If you said the answer was "1 2 3", then I would have asked you to take another look at it. If you still didn't change the answer, I would have asked a fundamental question about how the parameters are passed between functions in C and in Pascal. That should ring bells somewhere and in order to proceed to my next question, you should change your answer to "3 2 1". Because in C the parameters are passed from right-to-left (commonly referred to as C calling sequence). If it were similar code in Pascal where the parameters are passed from right-to-left, the answer would be "1 2 3".

Okay. So much for the obsolete technologies. Now, in the latest bleeding edge Java 5.0, what would the following code print?

int i = 0;
System.out.printf("%d %d %d", ++i, ++i, ++i);

Is it "3 2 1"? or "1 2 3"? How are parameters passed to methods? We all know Java is strictly pass-by-value. But does it evaluate from right-to-left like C or left-to-right like Pascal?

The output of Tiger is "1 2 3". Trivial observation... given that Java is supposed NOT to be difficult and Sun is bent on "vbfication" of Java. As I was in the C++ mindset (thinking about Templates/Generics etc), for a second, I thought it would print "3 2 1".

Actually compiling the C code with -S option (if I remember it right) would generate the machine code that gives the appropriate mnemonics of the assembly. If you compare the outputs of differnt compilers on different platforms, these "++i" statements may get translated to three "INCR i" or three "ADD i 1" or if the compiler has a smart-ass optimizer, it may even do "ADD i 3" thinking that the programmer is a half-brain. Thus, I say that writing this type of code is a big no no. However, this sort of knowledge is useful in debugging/fixing/identifiying problems with the old C code.

If the compiler replaces all the ++i expressions with the result of "ADD i 3", the output would be "3 3 3".