Doubt in K&B concerning topic :Operators

[Najmunnisa Sageer]

Hi,

I am new to this forum.I am preparing for scjp5.The following question is from K&B chapter 4 Question no.5.

class Foozit{
public static void main(String args[]){

Integer x = 0;
Integer y = 0;

for(Short z =0; z < 5; z++)

if((++x > 2) || (++y > 2));
x++;
System.out.println(x + " " + y);

}
}

What is the result?

A. 5 1
B. 5 2
C. 5 3
D. 8 1
E. 8 2
F. 8 3
G. 10 2
H. 10 3


The answer marked in the K&B is E.But when I compiled and run this program I got the result as 6 2.

Here,after the if statement the x is not an expression just a postincrement of x.(Is it because of that?)

Please correct me if I am wrong?

Thanks
Neju.

[marc weber]

Welcome to JavaRanch!

I don't have the book with me, but I think I see your problem. You have a semicolon at the end of your "if" condition. And because of this "empty" statement, your code is doing this...

if((++x > 2) || (++y > 2)) {
    //nothing!
}
x++;

...when it should be doing this...

if((++x > 2) || (++y > 2)) {
    x++;
}

Please check the book and let us know if that solves it.

(I'm not sure what you're asking about the line x++. Yes, it is a postincrement operation on x, but it is also an expression that evaluates to the value of x before being incremented.)

[Najmunnisa Sageer]

Hi Marc,

You are right,In the book there is no semicolon.(I added by mistake that semicolon).Its working perfectly and understood the concept also.


Thanks
Neju.

[Ahlem Ouertani]

hello everybody,

I have the same exercise to do, but i do not understand how can we get the result 8 2
Could someone explain? txs

[Krishnamoorthy Vuyala Muralidharan]

Hi

for (Short z = 0; z < 5; z++){ // line1
if ((++x > 2) || (++y > 2)){ // line2
x++; // line3
}
}
System.out.println(x + " " + y);

Here there are three conceptual things to be noted. One thing is, short-circuit ||, pre increment ++x and post-increment x++

line1 - for loop which iterates for 5 times that is 0 to 4
line2 - checks if x is greater than 2 with a short-circuit || and if its false then only the other operand on the right hand will get executed
line 3 - if line2 evalutes to true then this line will be executed (post-increment x++)


The below shows the values for ++x,++y,z and x++ at every iteration of the for loop.
z|x++|++x|++y
0|- |1 |1
1|- |2 |2
2|4 |3
3|6 |5
4|8 |7


Hope this helps.

Kris

[Ninad Kulkarni]

only because of semicolon at end of if statement
output are different
when semicolon is present at end of if then output is 6 2
when semicolon is not present at end of if then output is 8 2

I think every one should note it


Regards
Ninad