Array question - enthuware

[Daniel Martins]

Hi

I do not understand this syntax...

  int[] a = { 1, 2, 3, 4 };
    int[] b = { 2, 3, 1, 0 };
    System.out.println( a [ (a = b)[3] ] );

[Punit Singh]

Daniel Martins wrote:Hi

I do not understand this syntax...

  int[] a = { 1, 2, 3, 4 };
    int[] b = { 2, 3, 1, 0 };
    System.out.println( a [ (a = b)[3] ] );

why ?

   

a [ (a = b)[3] ]
{1,2,3,4}[{2,3,1,0}[3]] ==> {1,2,3,4}[0]=1
 

[Ankur kothari]

hey here doesnt assigning b to a will change the value of a...i mean
a=b will be evaluated thus a will be {2,3,1,0}

thus the expression would be {2,3,1,0}[{2,3,1,0}[3]]...isnt it.

i know there is something wrong

please correct me

[Punit Singh]

Ankur kothari wrote:hey here doesnt assigning b to a will change the value of a...i mean
a=b will be evaluated thus a will be {2,3,1,0}

thus the expression would be {2,3,1,0}[{2,3,1,0}[3]]...isnt it.

i know there is something wrong

please correct me

That was the main funda in this question, everybody in starting thinks like you think, even I thought that way, but after running the example I got it that it is evaluating in different way, means left a evaluated before a=b is evaluated. It has some relationship with array expression evaluation. We need to discuss it further.

[Ankur kothari]

  int x=9;int y=10;
		System.out.println(x*(x=y));  

what do you think will be the answer?

100 or 90?

[Ankit Garg]

See this part of the JLS...

[Punit Singh]

Ankur kothari wrote:

  int x=9;int y=10;
		System.out.println(x*(x=y));  

what do you think will be the answer?

100 or 90?

90

[Ankur kothari]

yes the answer is 90...what i meant is that this works not only for arrays.....gotto look at the jls link ankit gave

[Punit Singh]

Ankur kothari wrote:yes the answer is 90...what i meant is that this works not only for arrays.....gotto look at the jls link ankit gave

But the JLS topic itself is saying

15.13.1 Runtime Evaluation of Array Access

And I had also said the it has relation with Array expression evaluation.

[Ankur kothari]

yes punit you were right but what explains x*(x=y) expression?

[Punit Singh]

Ankur kothari wrote:yes punit you were right but what explains x*(x=y) expression?

That is a simple expression that follows left to right evaluation. Array expression are bit complex.
But why did you say this?

hey here doesnt assigning b to a will change the value of a...i mean
a=b will be evaluated thus a will be {2,3,1,0}

thus the expression would be {2,3,1,0}[{2,3,1,0}[3]]...isnt it.

i know there is something wrong

please correct me

[Ankur kothari]

oh yes left to write....i remember it said first all the operands are calculated from left to right and then operations are done.....thanks a lot....

hey when i wrote that i had not read the jls document

[Punit Singh]

Great healthy discussion of topic is good thing to remember the concepts for long terms.

[Ankur kothari]

if we have to learn a language we have to speak it....that is why i love javaranch

[Ankit Garg]

Ankur kothari wrote:oh yes left to write....

Left to Right

(I hope you don't think I'm trying to piss you off, I try to find any opportunity to make a joke )...

[Ankur kothari]

hahaha.....

[Punit Singh]

Ankur kothari wrote:if we have to learn a language we have to speak it....that is why i love javaranch

Good you are getting enough time to discuss it, in between from March to October I did not get time to discuss anything on javaranch due to my cumbersome job, now after changing my job I am getting enough time.

[Chintan B Shah]

  int x=9;int y=10;
	   System.out.println(x*(x=y));  
  

Why would this print 90? Wouldn't expression within brackets(x=y) have precedence over *?

Thanks
Chintan.

[rohan yadav]

Chintan writes:
Why would this print 90? Wouldn't expression within brackets(x=y) have precedence over *?

Hi chintan, printf statement evaluates from left to right, hence first value of x is 9 and after assignment x is 10 hence answer is 90.

[harish gowda Java green]

Punit Singh wrote:

Ankur kothari wrote:hey here doesnt assigning b to a will change the value of a...i mean
a=b will be evaluated thus a will be {2,3,1,0}

thus the expression would be {2,3,1,0}[{2,3,1,0}[3]]...isnt it.

i know there is something wrong

please correct me

That was the main funda in this question, everybody in starting thinks like you think, even I thought that way, but after running the example I got it that it is evaluating in different way, means left a evaluated before a=b is evaluated. It has some relationship with array expression evaluation. We need to discuss it further.

" a [ (a = b)[3] ]
a [ b[3] ]
since b[3]=0
hence a[0] i.e 1 will be the answer
"

[Ankit Garg]

"harish gowda Java green" please check your private messages for some administrative matter.

[Chintan B Shah]

Thanks Rohan.

Regards,
Chintan

[jeetendra Choudhary]

rohan yadav wrote:

Chintan writes:
Why would this print 90? Wouldn't expression within brackets(x=y) have precedence over *?

Hi chintan, printf statement evaluates from left to right, hence first value of x is 9 and after assignment x is 10 hence answer is 90.

Hey From Where this printf came here..?? I think It was println().