java - Unary Operations fused with assignment -


doubtful result in following code:

public static void main (string[] args) {  int = 2; = i+=2 + i++; system.out.println(i); }

was expecting 8 output, 'i+=2' should update i, not behaving so.

output: 6

i infer short-hand assignment operator returning 4 expected not updating same in variable i. explanation appreciated.

i++ postfix increment - increments i, returns old value of i. equivalent prefix operator, ++i, return "updated" value, that's not what's being used here.

i+=2 works differently however, it's equivalent i+2, since does return updated value.

however, think confusion arises you're looking @ this:

i = (i += 2) + i++;

...which does give expected result. i+=2 gives 4, , updates i 4, i++ returns 4 (instead of 5 since it's post increment.) however, when take operator precedence equation, java "brackets" default:

i = += (2 + i++);

just clear confusion, java evaluates way because += operator has least precedence in example, , therefore addition expression (+) calculated first.

this bracketed statement equivalent to:

i = (i = + (2 + i++));

which in turn simplifies to:

i = + (2 + i++);

so given above statement, , evaluating left right, first take value of (2), , add value of 2+i++; latter giving 4 (because of postfix increment). our final result 2+4, 6.


Comments

Post a Comment

Popular posts from this blog

php - Why I am getting the Error "Commands out of sync; you can't run this command now" -

the documentation of error mentioned in title says if commands out of sync; can't run command now in client code, calling client functions in wrong order. this can happen, example, if using mysql_use_result() , try execute new query before have called mysql_free_result(). can happen if try execute 2 queries return data without calling mysql_use_result() or mysql_store_result() in between. from here: http://dev.mysql.com/doc/refman/5.0/en/commands-out-of-sync.html but in first query not fetching data mysql database, inserting. , in second query getting data database. here code $connection = mysqli_connect("localhost","username","password","tbl_msgs"); if(mysqli_connect_errno($connection)) { die("failed connect mysql: " . mysqli_connect_error()); } $query = "insert users (total_comments, total_views) values ({$total_comments}, {$total_views});"; $query .= "insert msgs (no...
Read more

linux - Does gcc have any options to add version info in ELF binary file? -

i mean whether gcc can insert source code version infor elf binary section or similar. not want change source file, add info gcc option in makefile. you can emit version info text file, turn text file object file statically link executable. the first step simple have write code: script or write version info in format plain text file. write makefile rule produce version.o version.txt, using objcopy . you'll have object file 2 useful symbols defined in it: beginning , end of textual version info. add generated object executable, , you'll able access version 2 ways: running strings on binary, or writing code in application print version string (you'll need declare start , end symbols variables in header file).
Read more

java - Are there any classes that implement javax.persistence.Parameter<T>? -

i'm using named queries fetch entities database using jpa , hibernate , came across puzzling me: how come there no default implementations of javax.persistence.parameter interface? i rather impressed how @staticmetamodel used criteriabuilder in jpa2 meaning type safety , don't have mess around setting string names. wanted apply similar of jpa1 ejb's i'm working on: dealergroup_.class: public dealergroup_ { public parameter<integer> id = new parameterimpl<integer>("id"); /// etc... } dealergroupfacade.class: // ... public dealergroup fetch(integer id) { typedquery<dealergroup> query = em.createnamedquery("dealergroup.fetchbyid", dealergroup.class); query.setparameter(dealergroup_.id, query); return query.getsingleresult(); } // ... i surprised find there no implementations of parameter interface - of course, implement myself absence makes me suspicious may mistake using in way? should implementing parameter...
Read more