java - Android: javac vs Dalvik -


my understanding google didn't oracle's licensing policy using jre in java me rewrote using own jvm specification mimics jre behaves little bit differently, when comes making things more efficient , more secure.

so, if understanding correct, means when javac ran on java source code , compiled "binary" byetcode, compliant jvm interpret bytecode different dalvik (in cases). inherent difference between dalvik , other (compliant) jvms.

if have said far incorrect, please begin correcting me!

now, if android came own compiler (which might), , compiled java source in different (dalvik-compliant) manner javac, understand how code (not compiled android sdk) not run on android device:

mysource.java --> javac --> mysource.class (jre-compliant) --> jvm --> running java app mysource.java --> android-compiler --> mysource.class (dalvik-compliant) --> dalvik jvm --> running android app

however, looks use javac compile android apps!?!? looks have this:

mysource.java --> javac --> mysource.class (jre-compliant) --> jvm --> running java app mysource.java --> javac --> mysource.class (jre-compliant) --> dalvik jvm --> running android app (???)

if javac used compile sources bytecode, why dalvik can't run types of java code?

i asked similar question yesterday , although technically answered (after re-reading question see not specific enough) no 1 able explain that's inherent dalvik makes impossible run java code projects google guice or apache camel. told in order camel run on dalvik, have camel's source , have "built android sdk", couldn't clarity on meant or implied.

with camel, instance, have (simplified):

routebuilder.java --> javac --> routebuilder.class --> jartool --> camel-context-2.9.jar --> jvm --> running camel esb routebuilder.java --> javac --> routebuilder.class --> jartool --> camel-context-2.9.jar --> dalvik jvm --> doesn't work !!! (???)

clearly, happening inside dalvik jvm prevents running types of java code. i'm trying understand types of java code not run when "fed" dalvik jvm.

edit: in before "but camel 3.0 run on android!" know - not question!

i'm trying understand types of java code not run when "fed" dalvik jvm.

dalvik jvm differs other jvms in following aspects:

  • it uses special dex format storing applications binaries vs. jar , pack200 formats used standard java virtual machines. google claims dex results in smaller binaries jar. think use pack200 same success, decided go own way in aspect

  • dalvik jvm optimized running multiple jvm processes simultaneously

  • dalvik jvm uses register-based architecture vs. stack based architecture of other jvms intent speed execution , reduce binary sizes

  • it uses own instructions set (not standard jvm bytecode)

  • one can run (if needed) several independent android applications within single jvm process

  • application execution can span across several dalvik jvm processes “naturally”. support adds:

    • special object serialization mechanism based on parcel , parcelable classes. functionally serves same purpose standard java serializable, results in smaller data footprint , potentially more lenient towards differences in versions of classes

    • special android way execute inter process calls (ipc) based on android interface definition language (aidl)

  • until android 2.2 dalvik jvm did not support jit compilation adversely impacted android application performance. adding in 2.2 improves markedly execution speed used applications


Comments

Post a Comment

Popular posts from this blog

javascript - backbone.js Collection.add() doesn't `construct` (`initialize`) an object -

<!doctype html public "-//w3c//dtd xhtml 1.0 strict//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-strict.dtd"> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script> <script src="http://documentcloud.github.com/underscore/underscore-min.js"></script> <script src="http://documentcloud.github.com/backbone/backbone-min.js"></script> </head> <body> <button id="cmd_create_event" name="cmd_create_event" type="button">create new `event`</button> <script type="text/javascript"> var eventmodel = backbone.model.extend({ initialize : function() { console.log("`event` initialized. id: " + this.cid); this.bind("change:status", function() { console.log(this.get("status") + " value `status`"); }); this.bind("error", function(model, e...
Read more

php - Get uncommon values from two or more arrays -

is there function in php give array of uncommon values 2 or more arrays? for example: $array1 = array( "green", "red", "blue"); $array2 = array( "green", "yellow", "red"); .... $result = function_needed($array1, $array2,...); print_r($result); should give output: array("blue", "yellow", ...); use array_diff , array_merge : $result = array_merge(array_diff($array1, $array2), array_diff($array2, $array1)); here's demo. for multiple arrays, combine callback , array_reduce : function unique(&$a, $b) { return $a ? array_merge(array_diff($a, $b), array_diff($b, $a)) : $b; } $arrays = array( array('green', 'red', 'blue'), array('green', 'yellow', 'red') ); $result = array_reduce($arrays, 'unique'); and here's demo of that.
Read more

Adding duplicate array rows in Php -

i create function in php adds rows of array shared column value. so input. $test = array( array("c", 5, 6), array("c", 2, 3), array("test", 5, 6) ); and output. $testduplicatefree = array( array("c", 7, 9), array("test", 5, 6) ) ); i'm thinking function combine_duplicates($array,$col){ ... ... return $duplicatefreearray; } where $col duplicate free array. so, in case, combine_duplicates($test,0); would me desired output. this. <?php function combine_duplicates($array,$col) { $index = array(); foreach ($array $row) { $key = $row[$col]; if (!isset($index[$key])) { $index[$key] = $row; } else { ($i = 0; $i < count($row); ++$i) { if ($i != $col) { $index[$key][$i] += $row[$i]; } } } } return array_values($index); } $array = array( array("c", 5, 6), array("c", 2, 3), array("test", 5, 6) ); print_r(combine_duplicates($array, 0)); try here: http://codepad.org/mdhesqhi
Read more