what is this??? I m confused

[atif aslam]

This is actually my first post, so hello to all
I m preparing for SCJP 1.6, and i was going all fine until i tried this question
can sumbody explain me the solution
code 1:


public class prac1 {
public static void main(String [] args){
if(a()|b()&c())
System.out.println("pass");
else System.out.println("fail");
}
static boolean b(){
System.out.println("b");
return true;
}
static boolean a(){
System.out.println("a");
return true;
}
static boolean c(){
System.out.println("c");
return false;
}

}

output:
a
b
c
pass

[atif aslam]

But when i changed the condition to a|b&&c it gave me a different answer, which actually makes sense
code 2:
public class prac1 {
public static void main(String [] args){
if(a()|b()&&c())
System.out.println("pass");
else System.out.println("fail");
}
static boolean b(){
System.out.println("b");
return true;
}
static boolean a(){
System.out.println("a");
return true;
}
static boolean c(){
System.out.println("c");
return false;
}

}

output:
a
b
c
fail

But what happended in code 1? can sumbody exlain?

[Ankit Garg]

Hi Ankush! Welcome to javaranch.

Ankush we have a rule here that when you post a question, you have to QuoteYourSources. So please tell us from where did you get this question so that we can help you...

[atif aslam]

Ankit Garg wrote:Hi Ankush! Welcome to javaranch.

Ankush we have a rule here that when you post a question, you have to QuoteYourSources. So please tell us from where did you get this question so that we can help you...

I tried it myself.
If somebody had posted this question elsewhere then i dont know.
If not then source is mine

[Ninad Kulkarni]

In First case if statement evaluates to following order:
if( true | (true&false) )
In Second case if statement evaluates to following order:
if( (true|true) && (false) )

I hope this clears
and see what other will say about it

[Reason for Editing of text : extra "|" in second if at the end of true keyword deleted]

[atif aslam]

Ninad Kulkarni wrote:
In First case if statement evaluates to following order:
if( true | (true&false) )
In Second case if statement evaluates to following order:
if( (true|true|) && (false) )

I hope this clears
and see what other will say about it

when it evaluates the condition (a|b&c)
it gives the output a,b,c so it follows left-right associativity
and no precedence

[atif aslam]

Ankush Baveja wrote:This is actually my first post, so hello to all

output:
a
b
c
pass

output shows what m talking about

[Ninad Kulkarni]

As per my knowledge in java expression evaluates from left to right and also operator precedence matters a lot
so don't think "no operator precedence"

[atif aslam]

Ninad Kulkarni wrote:As per my knowledge in java expression evaluates from left to right and also operator precedence matters a lot
so don't think "no operator precedence"

yeah i know it matters
i was just reffering to the problem in hand

[atif aslam]

Ninad Kulkarni wrote:
In First case if statement evaluates to following order:
if( true | (true&false) )
In Second case if statement evaluates to following order:
if( (true|true) && (false) )

I hope this clears
and see what other will say about it

[Reason for Editing of text : extra "|" in second if at the end of true keyword deleted]

I think you are right. i was confused a bit on the order of execution of the functions
i thought operands with high precendence operators are evaluated first .

[Ninad Kulkarni]

Yes Ankush

[Rohan Amin]

Use a debugger and you will see that the functions are evaluated first. So it prints out a,b,c and then it evaluates the if condition which by the way has
(true|true&false). Referring to operator precedence true & false is false and true | false is true so it prints out pass.
http://java.sun.com/docs/books/tutorial/java/nutsandbolts/operators.html

[Balaji Bang]

This is a similar kind of example from Devaka's Exam....

public class Greek{

     int i=1;

     public int getI(){
          System.out.print("Super");
          return i;
     }

     public static void main(String arhs[]){
          Greek ga=new Arabik();
          
          System.out.println(ga.i+" "+ga.getI()); //getI() will be evaluated first and then prints the values
     }
}


class Arabik extends Greek{

     int i=2;

     public int getI(){
          System.out.print("Sub");
          return i;
     }

}    

OUTPUT : Sub1 2

[Treimin Clark]

Ankush,

Please use code tags and indent your code properly.

[Bert Bates]

on the SCJP 6 exam you will need to understand logical operators (short circuit and not), but you will NOT have to remember the kinds of precedence rules being discussed in this thread. In the older exams there were precedence questions like this, but these have been removed.

hth,

Bert

[teja dharma]

Ankush Baveja wrote:This is actually my first post, so hello to all
I m preparing for SCJP 1.6, and i was going all fine until i tried this question
can sumbody explain me the solution
code 1:


public class prac1 {
public static void main(String [] args){
if(a()|b()&c())
System.out.println("pass");
else System.out.println("fail");
}
static boolean b(){
System.out.println("b");
return true;
}
static boolean a(){
System.out.println("a");
return true;
}
static boolean c(){
System.out.println("c");
return false;
}

}

output:
a
b
c
pass

hi ankush this is teja in boolean conditional expression evaluation the com[iler treats the above a()|b()&c() expression
aV(b^c)=(aVb)^(aVc)=(t)^(t)=t
the other expression a()|b()&&c() can be treated as (aVb)^c=(a^c)V(b^c)=(f)V(f)=f

[atif aslam]

Rohan Amin wrote:Use a debugger and you will see that the functions are evaluated first. So it prints out a,b,c and then it evaluates the if condition which by the way has
(true|true&false). Referring to operator precedence true & false is false and true | false is true so it prints out pass.
http://java.sun.com/docs/books/tutorial/java/nutsandbolts/operators.html

Thanks for the usefull suggestion, i dont have a debugger can you suggest one. M using eclipse

[atif aslam]

Treimin Clark wrote:Ankush,

Please use code tags and indent your code properly.

sure i will

System.out.println("Thanks 4 the info");