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  • atomic writes to ehcache

    - by Jacques René Mesrine
    Context I am storing a java.util.List inside ehcache. Key(String) --> List<UserDetail> The ordered List contains a Top 10 ranking of my most active users. Problem Concurrent 3rd party clients might be requesting for this list. I have a requirement to be as current as possible with regards to the ranking. Thus if the ranking is changed due the activities of users, the ordered List in the cache must not be left stale for very long. Once I've recalculated a new List, I want to replace the one in cache immediately. Consider a busy scenario whereby multiple concurrent clients are requesting for the ranking; how can I replace the cache item in an fashion such that: Clients can continue to pull a possibly stale snapshot. They should never get a null value. There will only be 1 server thread that writes to the cache.

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  • What happens if two COM classes each without a threading model are implemented in one in-proc COM se

    - by sharptooth
    Consider a situation. I have an in-proc COM server that contains two COM classes. Both classes are marked as "no threading model" in the registry - the "ThreadingModel" value is just absent. Both classes read/write the same set of global variable without any synchronization. As far as I know "no threading model" will enforce COM to disallow concurrent access to the same or different instances of the same class by different threads. Will COM prevent concurrent access to instances of the two abovementioned different classes? Do I need synchronization when accessing the global variables from two different COM classes in this situation?

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  • Producer/consumer in Grails?

    - by Mulone
    Hi all, I'm trying to implement a Consumer/Producer app in Grails, after several unsuccessful attempts at implementing concurrent threads. Basically I want to store all the events coming from a clients (through separate AJAX calls) in a single queue and then process such a queue in a linear way as soon as new events are added. This looks like a Producer/Consumer problem: http://en.wikipedia.org/wiki/Producer-consumer_problem How can I implement this in Grails (maybe with a timer or even better by generating an event 'process queue')? Basically I'd like to a have a singleton service waiting for new events in the queue and processing them linearly (even if the queue is loaded by several concurrent processes). Any hints? Cheers!

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  • How to prevent column b containing the same value as any column a in Oracle?

    - by Janek Bogucki
    What is a good way to prevent a table with 2 columns, a and b, from having any record where column b is equal to any value in column a? This would be used for a table of corrections like this, MR -> Mr Prf. -> Prof. MRs -> Mrs I can see how it could be done with a trigger and a subquery assuming no concurrent activity but a more declarative approach would be preferable. This is an example of what should be prevented, Wing Commdr. -> Wing Cdr. Wing Cdr. -> Wing Commander Ideally the solution would work with concurrent inserts and updates.

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  • Push data to flex client

    - by KensoDev
    Howday, I want to push data to flex clients. I am talking about anywhere between 5000-15000 concurrent users, need to get data every time a currency is changed so that means lots of changes for lots of users. I have been looking into WebOrb.net, but the performance seem very poor (100 users concurrent) for a product so pricy (we purchased a license). So, I have to look into alternatives, I know there's fluorineFx but it seems no one is really using it for products and it lacks in examples and documentation. My question is: what products can answer my needs (.net backend) and what are the performance I can expect out of these products? Thanks

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  • spring web application context is not loaded from jar file in WEB-INF/lib when running tomcat in eclipse

    - by Remy J
    I am experimenting with spring, maven, and eclipse but stumbling on a weird issue. I am running Eclipse Helios SR1 with the STS (Spring tools suite) plugin which includes the Maven plugin also. What i want to achieve is a spring mvc webapp which uses an application context loaded from a local application context xml file, but also from other application contexts in jar files dependencies included in WEB-INF/lib. What i'd ultimately like to do is have my persistence layer separated in its own jar file but containing its own spring context files with persistence specific configuration (e.g a jpa entityManagerFactory for example). So to experiment with loading resources from jar dependencies, i created a simple maven project from eclipse, which defines an applicationContext.xml file in src/main/resources Inside, i define a bean <bean id="mybean" class="org.test.MyClass" /> and create the class in the org.test package I run mvn-install from eclipse, which generates me a jar file containing my class and the applicationContext.xml file: testproj.jar |_META-INF |_org |_test |_MyClass.class |_applicationContext.xml I then create a spring mvc project from the Spring template projects provided by STS. I have configured an instance of Tomcat 7.0.8 , and also an instance of springSource tc Server within eclipse. Deploying the newly created project on both servers works without problem. I then add my previous project as a maven dependency of the mvc project. the jar file is correctly added in the Maven Dependencies of the project. In the web.xml that is generated, i now want to load the applicationContext.xml from the jar file as well as the existing one generated for the project. My web.xml now looks like this: org.springframework.web.context.ContextLoaderListener <!-- Processes application requests --> <servlet> <servlet-name>appServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value> classpath*:applicationContext.xml, /WEB-INF/spring/appServlet/servlet-context.xml </param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>appServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> Also, in my servlet-context.xml, i have the following: <context:component-scan base-package="org.test" /> <context:component-scan base-package="org.remy.mvc" /> to load classes from the jar spring context (org.test) and to load controllers from the mvc app context. I also change one of my controllers in org.remy.mvc to autowire MyClass to verify that loading the context has worked as intended. public class MyController { @Autowired private MyClass myClass; public void setMyClass(MyClass myClass) { this.myClass = myClass; } public MyClass getMyClass() { return myClass; } [...] } Now this is the weird bit: If i deploy the spring mvc web on my tomcat instance inside eclipse (run on server...) I get the following error : org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0': Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/test/MyClass at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425) at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:442) at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:458) at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:339) at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:306) at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:127) at javax.servlet.GenericServlet.init(GenericServlet.java:160) at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1133) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1087) at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:996) at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4834) at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5155) at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5150) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.NoClassDefFoundError: org/test/MyClass at java.lang.Class.getDeclaredMethods0(Native Method) at java.lang.Class.privateGetDeclaredMethods(Class.java:2427) at java.lang.Class.getDeclaredMethods(Class.java:1791) at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:446) at org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping.determineUrlsForHandlerMethods(DefaultAnnotationHandlerMapping.java:172) at org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping.determineUrlsForHandler(DefaultAnnotationHandlerMapping.java:118) at org.springframework.web.servlet.handler.AbstractDetectingUrlHandlerMapping.detectHandlers(AbstractDetectingUrlHandlerMapping.java:79) at org.springframework.web.servlet.handler.AbstractDetectingUrlHandlerMapping.initApplicationContext(AbstractDetectingUrlHandlerMapping.java:58) at org.springframework.context.support.ApplicationObjectSupport.initApplicationContext(ApplicationObjectSupport.java:119) at org.springframework.web.context.support.WebApplicationObjectSupport.initApplicationContext(WebApplicationObjectSupport.java:72) at org.springframework.context.support.ApplicationObjectSupport.setApplicationContext(ApplicationObjectSupport.java:73) at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:106) at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:85) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:394) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1413) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) ... 25 more 20-Feb-2011 10:54:53 org.apache.catalina.core.ApplicationContext log SEVERE: StandardWrapper.Throwable org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0': Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/test/MyClass If i build the war file (using maven "install" goal), and then deploy that war file in the webapps directory of a standalone tomcat server (7.0.8 as well) it WORKS :-( What am i missing ? Thanks for the help.

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  • Do MyISAM holes get filled in automatically?

    - by NNN
    When you run a delete on a MyISAM table, it leaves a hole in the table until the table is optimized. This affects concurrent inserts. On the default setting, concurrent_inserts only work for tables without holes. However, in the documentation for MyISAM, under the concurrent_insert section it says: Enables concurrent inserts for all MyISAM tables, even those that have holes. For a table with a hole, new rows are inserted at the end of the table if it is in use by another thread. Otherwise, MySQL acquires a normal write lock and inserts the row into the hole. http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_concurrent_insert Does that mean MyISAM automatically fills in holes whenever a new row is insert into the table? Previously I thought the holes would not be fixed until you OPTIMIZE a table.

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  • How/is data shared between fastCGI processes?

    - by Josh the Goods
    I've written a simple perl script that I'm running via fastCGI on Apache. The application loads a set of XML data files which are used to lookup values based upon the the query parameters of an incoming request. As I understand it, if I want to increase the amount of concurrent requests my application can handle I need to allow fastCGI to spawn multiple processes. Will each of these processes have to hold duplicate copies of the XML data in memory? Is there a way to set things up so that I can have one copy of the XML data loaded in memory while increasing the capacity to handle concurrent requests?

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  • java.io.FileNotFoundException for valid URL

    - by Alexei
    Hello. I use library rome.dev.java.net to fetch RSS. Code is URL feedUrl = new URL("http://planet.rubyonrails.ru/xml/rss"); SyndFeedInput input = new SyndFeedInput(); SyndFeed feed = input.build(new XmlReader(feedUrl)); You can check that http://planet.rubyonrails.ru/xml/rss is valid URL and the page is shown in browser. But I get exception from my application java.io.FileNotFoundException: http://planet.rubyonrails.ru/xml/rss at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1311) at com.sun.syndication.io.XmlReader.<init>(XmlReader.java:237) at com.sun.syndication.io.XmlReader.<init>(XmlReader.java:213) at rssdaemonapp.ValidatorThread.run(ValidatorThread.java:32) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) I don't use any proxy. I get this exception on my PC and on the production server and only for this URL, other URLs are working.

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  • Recommendations for an in memory database vs thread safe data structures

    - by yx
    TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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  • How can I find file system concurrency issues ?

    - by krosenvold
    I have an application running on Linux, and I find myself wanting windows (!). The problem is that every 1000 times or so I run into concurrency problems that are consistent with concurrent reading/writing of files. I am fairly sure that this behavior would be prohibited by file locking under Windows, but I don't have any sufficiently fast windows box to check. There is simply too much file access (too much data) to expect strace to work reliably - the sheer volume of output is likely to change the problem too. It also happens on different files every time. Ideally I would like to change/reconfigure the linux file system to be more restrictive (as in fail-fast) wrt concurrent access. Are there any tools/settings I can use to achieve this ?

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  • Actors in Scala.net

    - by weijiajun
    I have recently completed some study of erlang, and was intrigued by scala for its feature set and the ease of interpolating with java (and possibly .net) applications. I am finally studying actors and was wondering if there is an actor mechanism that currently works in .net. I have looked at the libararies that come down with sbaz and have found that there is a scala.Concurrent but no scala.actors.Actor. I tried to use the scala.Concurrent.Channel but was unable to use the ! to send messages. I was just wondering if this is something that is currently available and if so how do you go about setting it up.

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  • Android UnknownHost in asyncTask - loading web page

    - by Sneha
    I followed this tutorial for AsyncTask and getting the following error log: 03-23 11:44:42.936: WARN/System.err(315): java.net.UnknownHostException: www.google.co.in 03-23 11:44:42.936: WARN/System.err(315): at java.net.InetAddress.lookupHostByName(InetAddress.java:513) 03-23 11:44:42.936: WARN/System.err(315): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:278) 03-23 11:44:42.936: WARN/System.err(315): at java.net.InetAddress.getAllByName(InetAddress.java:242) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:136) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:348) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 03-23 11:44:42.936: WARN/System.err(315): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 03-23 11:44:42.944: WARN/System.err(315): at org.apache.http.impl.client.AbstractHttpC lient.execute(AbstractHttpClient.java:465) 03-23 11:44:42.944: WARN/System.err(315): at com.test.async.AsyncTaskExampleActivity$DownloadWebPageTask.doInBackground (AsyncTaskExampleActivity.java:36) 03-23 11:44:42.944: WARN/System.err(315): at com.test.async.AsyncTaskExampleActivity$DownloadWebPageTask.doInBackground (AsyncTaskExampleActivity.java:1) 03-23 11:44:42.944: WARN/System.err(315): at android.os.AsyncTask$2.call(AsyncTask.java:185) 03-23 11:44:42.944: WARN/System.err(315): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 03-23 11:44:42.944: WARN/System.err(315): at java.util.concurrent.FutureTask.run (FutureTask.java:137) 03-23 11:44:42.944: WARN/System.err(315): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 03-23 11:44:42.944: WARN/System.err(315): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 03-23 11:44:42.944: WARN/System.err(315): at java.lang.Thread.run(Thread.java:1096) How do i fix it?? My Code: public class AsyncTaskExampleActivity extends Activity { private TextView textView; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); textView = (TextView) findViewById(R.id.TextView01); } private class DownloadWebPageTask extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... urls) { String response = ""; Log.i("", "in doInBackgroundddddddddd.........."); Log.i("", "in readWebpageeeeeeeeeeeee"); /* * try { InetAddress i = * InetAddress.getByName("http://google.co.in"); } catch * (UnknownHostException e1) { e1.printStackTrace(); } */ for (String url : urls) { Log.i("", "in for looooooop doInBackgroundddddddddd.........."); DefaultHttpClient client = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(url); try { Log .i("", "afetr for looooooop try doInBackgroundddddddddd.........."); HttpResponse execute = client.execute(httpGet); Log .i("", "afetr for looooooop try client ..execute doInBackgroundddddddddd.........."); InputStream content = execute.getEntity().getContent(); BufferedReader buffer = new BufferedReader( new InputStreamReader(content)); String s = ""; while ((s = buffer.readLine()) != null) { response += s; Log .i("", "afetr while looooooop try client ..execute doInBackgroundddddddddd.........."); } } catch (Exception e) { e.printStackTrace(); } } Log .i("", "afetr lasttttttttttttt b4 response doInBackgroundddddddddd.........."); return response; } @Override protected void onPostExecute(String result) { Log.i("", "in onPostExecuteeee.........."); textView.setText(result); } } public void readWebpage(View view) { /* * System.setProperty("http.proxyHost", "10.132.116.10"); * System.setProperty("http.proxyPort", "3128"); */ DownloadWebPageTask task = new DownloadWebPageTask(); task.execute(new String[] { "http://google.co.in" }); Log.i("", "in readWebpageeeeeeeeeeeee after execute.........."); } } main.xml: <Button android:id="@+id/readWebpage" android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="readWebpage" android:text="Load Webpage"> </Button> <TextView android:id="@+id/TextView01" android:layout_width="match_parent" android:layout_height="match_parent" android:text="Example Text"> </TextView> Manifest: <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.test.async" android:versionCode="1" android:versionName="1.0"> <uses-sdk android:minSdkVersion="8" /> <uses-permission android:name="android.permission.INTERNET"></uses-permission> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".AsyncTaskExampleActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> Thanks Sneha

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  • Best wrapper for simultaneous API requests?

    - by bluebit
    I am looking for the easiest, simplest way to access web APIs that return either JSON or XML, with concurrent requests. For example, I would like to call the twitter search API and return 5 pages of results at the same time (5 requests). The results should ideally be integrated and returned in one array of hashes. I have about 15 APIs that I will be using, and already have code to access them individually (using simple a NET HTTP request) and parse them, but I need to make these requests concurrent in the easiest way possible. Additionally, any error handling for JSON/XML parsing is a bonus.

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  • MS Access vs SQL Server and others ? Is it worth taking a db server when less than 2 Gb and only 20

    - by asksuperuser
    After my experiment with MSAccess vs MySQL which shows MS Access hugely overperforming Mysql odbc insert by a factor 1000% before I would do the same experiment with SQL Server I searched for some other's people and found this one: http://blog.nkadesign.com/2009/access-vs-sql-server-some-stats-part-1/ which says "As a side note, in this particular test, Access offers much better raw performance than SQL Server. In more complex scenarios it’s very likely that Access’ performance would degrade more than SQL Server, but it’s nice to see that Access isn’t a sloth." So is worth bother with some db server when data is less than 2 Gb and users are about 20 (knowing that MS Access theorically supports up to 255 concurrent users though practically it's around a dozen concurrent users only). Are there any real world studies that really compare MS Access with other db in these specific use case ? Because professionaly speaking I keep hearing people systematically recommend DB server from people who have never used Access just because they think DB Server can only perform better in every case which I used to think myself I confess.

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  • Handling file upload in a non-blocking manner

    - by Kaliyug Antagonist
    The background thread is here Just to make objective clear - the user will upload a large file and must be redirected immediately to another page for proceeding different operations. But the file being large, will take time to be read from the controller's InputStream. So I unwillingly decided to fork a new Thread to handle this I/O. The code is as follows : The controller servlet /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub System.out.println("In Controller.doPost(...)"); TempModel tempModel = new TempModel(); tempModel.uploadSegYFile(request, response); System.out.println("Forwarding to Accepted.jsp"); /*try { Thread.sleep(1000 * 60); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }*/ request.getRequestDispatcher("/jsp/Accepted.jsp").forward(request, response); } The model class package com.model; import java.io.IOException; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.utils.ProcessUtils; public class TempModel { public void uploadSegYFile(HttpServletRequest request, HttpServletResponse response) { // TODO Auto-generated method stub System.out.println("In TempModel.uploadSegYFile(...)"); /* * Trigger the upload/processing code in a thread, return immediately * and notify when the thread completes */ try { FileUploaderRunnable fileUploadRunnable = new FileUploaderRunnable( request.getInputStream()); /* * Future<FileUploaderRunnable> future = ProcessUtils.submitTask( * fileUploadRunnable, fileUploadRunnable); * * FileUploaderRunnable processed = future.get(); * * System.out.println("Is file uploaded : " + * processed.isFileUploaded()); */ Thread uploadThread = new Thread(fileUploadRunnable); uploadThread.start(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } /* * catch (InterruptedException e) { // TODO Auto-generated catch block * e.printStackTrace(); } catch (ExecutionException e) { // TODO * Auto-generated catch block e.printStackTrace(); } */ System.out.println("Returning from TempModel.uploadSegYFile(...)"); } } The Runnable package com.model; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; public class FileUploaderRunnable implements Runnable { private boolean isFileUploaded = false; private InputStream inputStream = null; public FileUploaderRunnable(InputStream inputStream) { // TODO Auto-generated constructor stub this.inputStream = inputStream; } public void run() { // TODO Auto-generated method stub /* Read from InputStream. If success, set isFileUploaded = true */ System.out.println("Starting upload in a thread"); File outputFile = new File("D:/06c01_output.seg");/* * This will be changed * later */ FileOutputStream fos; ReadableByteChannel readable = Channels.newChannel(inputStream); ByteBuffer buffer = ByteBuffer.allocate(1000000); try { fos = new FileOutputStream(outputFile); while (readable.read(buffer) != -1) { fos.write(buffer.array()); buffer.clear(); } fos.flush(); fos.close(); readable.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("File upload thread completed"); } public boolean isFileUploaded() { return isFileUploaded; } } My queries/doubts : Spawning threads manually from the Servlet makes sense to me logically but scares me coding wise - the container isn't aware of these threads after all(I think so!) The current code is giving an Exception which is quite obvious - the stream is inaccessible as the doPost(...) method returns before the run() method completes : In Controller.doPost(...) In TempModel.uploadSegYFile(...) Returning from TempModel.uploadSegYFile(...) Forwarding to Accepted.jsp Starting upload in a thread Exception in thread "Thread-4" java.lang.NullPointerException at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:512) at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:497) at org.apache.coyote.http11.InternalInputBuffer$InputStreamInputBuffer.doRead(InternalInputBuffer.java:559) at org.apache.coyote.http11.AbstractInputBuffer.doRead(AbstractInputBuffer.java:324) at org.apache.coyote.Request.doRead(Request.java:422) at org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:287) at org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:407) at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:310) at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:202) at java.nio.channels.Channels$ReadableByteChannelImpl.read(Unknown Source) at com.model.FileUploaderRunnable.run(FileUploaderRunnable.java:39) at java.lang.Thread.run(Unknown Source) Keeping in mind the point 1., does the use of Executor framework help me in anyway ? package com.utils; import java.util.concurrent.Future; import java.util.concurrent.ScheduledThreadPoolExecutor; public final class ProcessUtils { /* Ensure that no more than 2 uploads,processing req. are allowed */ private static final ScheduledThreadPoolExecutor threadPoolExec = new ScheduledThreadPoolExecutor( 2); public static <T> Future<T> submitTask(Runnable task, T result) { return threadPoolExec.submit(task, result); } } So how should I ensure that the user doesn't block and the stream remains accessible so that the (uploaded)file can be read from it?

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  • Java concurrency - Should block or yield?

    - by teto
    Hi, I have multiple threads each one with its own private concurrent queue and all they do is run an infinite loop retrieving messages from it. It could happen that one of the queues doesn't receive messages for a period of time (maybe a couple seconds), and also they could come in big bursts and fast processing is necessary. I would like to know what would be the most appropriate to do in the first case: use a blocking queue and block the thread until I have more input or do a Thread.yield()? I want to have as much CPU resources available as possible at a given time, as the number of concurrent threads may increase with time, but also I don't want the message processing to fall behind, as there is no guarantee of when the thread will be reescheduled for execution when doing a yield(). I know that hardware, operating system and other factors play an important role here, but setting that aside and looking at it from a Java (JVM?) point of view, what would be the most optimal?

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  • how to properly transfer user input from index to invoice?

    - by Romel
    I got a dillema, I'm trying to find a solution for my code. How do I make it so that when the user inputs a given quantity in the text box from the index.php it will transfer that input quantity to the invoice.php. I've tried doing the post method but it seems like it's not working :/ As always, any help or suggestions will be greatly appreciated! I hope it's something simple:( Here's my code: index.php <html> <style> body{ background-image: url('URL HERE'); font-family: "Helvetica"; font-size:15px; } h1{ color:black; text-align:center; } p{ font-size:15px; } </style> <h1> STORE TITLE HERE </h1> <body> <form action="login.php" method="post"> <?php //Include products info.inc (Which holds all our product arrays and info) //Credit: Tracy & Mark (THank you!) include 'products_info.inc'; /*The following code centers my table on the page, makes the table background white, makes the table 50% of the browser window, gives it a border of 1 px, gives a padding of 2 px between the cell border and content, and gives 1 px of spacing between cells. */ echo "<table align=center bgcolor='FFFFFF' width=50% border=1 cellpadding=1 cellspacing=2>"; //Credit: Tracy & Mark (THank you!) echo '<th>Product</th> <th>Description</th> <th>Price</th> <th>Quantity</th>'; //The following code loops through the whole table body and then prints each row. for($i=0; $i<count($allfood); $i++) { //Credit: Tracy & Mark (THank you!) echo "<tr align=center>"; echo "<td>{$allfood[$i]['Product']}</td>"; echo "<td>{$allfood[$i]['Description']}</td>"; echo "<td>{$allfood[$i]['Price']}</td>"; echo "<td>{$allfood[$i]['Quantity']}</td>"; echo "</tr>"; } //This code ends the table. echo "</table>"; echo "<br>"; ?> <br><center><input type='submit' name='purchase' value='Purchase'></center> </form> </body> </html> And here's my invoice.php <html> <style> body{ background-image: url('URL HERE'); font-family: "Helvetica"; font-size:15px; } h1{ color:black; text-align:center; } p{ font-size:15px; } </style> <h1> Invoice </h1> </html> <?php //Include products info.inc (Which holds all our product arrays and info) //Credit: Tracy & Mark (Thank you!) include 'products_info.inc'; //Display the invoice & 'WELCOME USER. THANK YOU FOR USING THIS DAMN THING msg' /*The following code centers my invoice table on the page, makes the table background white, makes the table 50% of the browser window, gives it a border of 1 px, gives a padding of 2 px between the cell border and content, and gives 1 px of spacing between cells. */ echo "<table align=center bgcolor='FFFFFF' width=50% border=1 cellpadding=1cellspacing=2>"; echo "<tr>"; echo "<td align=center><b>Product</b></td>"; echo "<td align=center><b>Quantity</b></td>"; echo "<td align=center><b>Price</></td>"; echo "<td align=center><b>Extended Price</b></td>"; echo "</tr>"; for($i=0; $i<count($allfood); $i++) { //Credit: Tracy & Mark (Thank you!) $qty= @$_POST['Quantity']['$i']; // This calculates the price if the user orders more than 1 item. $extendedprice = $qty*$allfood[$i]['Price']; echo "<tr>"; echo "<td align=center>{$allfood[$i]['Product']}</td>"; echo "<td align=center>$extendedprice</td>"; echo "<td align=center>{$allfood[$i]['Price']}</td>"; echo "</tr>"; } // The goal here was to make it so that if the user selected a certain quantity from index.php, it would carry over and display on the invoice.php if ($qty = 0) { echo "please choose 1"; } elseif ($qty > 0) { echo $qty; } /*echo "<tr>"; echo "<td align=center>Subtotal</b></td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; echo "<tr>"; echo "<td align=center>Tax at 5.75%</td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; echo "<tr>"; echo "<td align=center><b>Grand total</b></td>"; echo "<td align=center></td>"; echo "<td align=center></td>"; */ echo "</table>"; ?> <br> <center> <form action="index.php" method="post"> <input type="submit" name="home" value="Back to homepage"> </form> </center>

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  • Performance issues when using SSD for a developer notebook (WAMP/LAMP stack)?

    - by András Szepesházi
    I'm a web application developer using my notebook as a standalone development environment (WAMP stack). I just switched from a Core2-duo Vista 32 bit notebook with 2Gb RAM and SATA HDD, to an i5-2520M Win7 64 bit with 4Gb RAM and 128 GB SDD (Corsair P3 128). My initial experience was what I expected, fast boot, quick load of all the applications (Eclipse takes now 5 seconds as opposed to 30s on my old notebook), overall great experience. Then I started to build up my development stack, both as LAMP (using VirtualBox with a debian guest) and WAMP (windows native apache + mysql + php). I wanted to compare those two. This still all worked great out, then I started to pull in my projects to these stacks. And here came the nasty surprise, one of those projects produced a lot worse response times than on my old notebook (that was true for both the VirtualBox and WAMP stack). Apache, php and mysql configurations were practically identical in all environments. I started to do a lot of benchmarking and profiling, and here is what I've found: All general benchmarks (Performance Test 7.0, HDTune Pro, wPrime2 and some more) gave a big advantage to the new notebook. Nothing surprising here. Disc specific tests showed that read/write operations peaked around 380M/160M for the SSD, and all the different sized block operations also performed very well. Started apache performance benchmarking with Apache Benchmark for a small static html file (10 concurrent threads, 500 iterations). Old notebook: min 47ms, median 111ms, max 156ms New WAMP stack: min 71ms, median 135ms, max 296ms New LAMP stack (in VirtualBox): min 6ms, median 46ms, max 175ms Right here I don't get why the native WAMP stack performed so bad, but at least the LAMP environment brought the expected speed. Apache performance measurement for non-cached php content. The php runs a loop of 1000 and generates sha1(uniqid()) inisde. Again, 10 concurrent threads, 500 iterations were used for the benchmark. Old notebook: min 0ms, median 39ms, max 218ms New WAMP stack: min 20ms, median 61ms, max 186ms New LAMP stack (in VirtualBox): min 124ms, median 704ms, max 2463ms What the hell? The new LAMP performed miserably, and even the new native WAMP was outperformed by the old notebook. php + mysql test. The test consists of connecting to a database and reading a single record form a table using INNER JOIN on 3 more (indexed) tables, repeated 100 times within a loop. Databases were identical. 10 concurrent threads, 100 iterations were used for the benchmark. Old notebook: min 1201ms, median 1734ms, max 3728ms New WAMP stack: min 367ms, median 675ms, max 1893ms New LAMP stack (in VirtualBox): min 1410ms, median 3659ms, max 5045ms And the same test with concurrency set to 1 (instead of 10): Old notebook: min 1201ms, median 1261ms, max 1357ms New WAMP stack: min 399ms, median 483ms, max 539ms New LAMP stack (in VirtualBox): min 285ms, median 348ms, max 444ms Strictly for my purposes, as I'm using a self contained development environment (= low concurrency) I could be satisfied with the second test's result. Though I have no idea why the VirtualBox environment performed so bad with higher concurrency. Finally I performed a test of including many php files. The application that I mentioned at the beginning, the one that was performing so bad, has a heavy bootstrap, loads hundreds of small library and configuration files while initializing. So this test does nothing else just includes about 100 files. Concurrency set to 1, 100 iterations: Old notebook: min 140ms, median 168ms, max 406ms New WAMP stack: min 434ms, median 488ms, max 604ms New LAMP stack (in VirtualBox): min 413ms, median 1040ms, max 1921ms Even if I consider that VirtualBox reached those files via shared folders, and that slows things down a bit, I still don't see how could the old notebook outperform so heavily both new configurations. And I think this is the real root of the slow performance, as the application uses even more includes, and the whole bootstrap will occur several times within a page request (for each ajax call, for example). To sum it up, here I am with a brand new high-performance notebook that loads the same page in 20 seconds, that my old notebook can do in 5-7 seconds. Needless to say, I'm not a very happy person right now. Why do you think I experience these poor performance values? What are my options to remedy this situation?

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  • small & readable scheme interpreter in C++ ?

    - by anon
    Anyone know of a good / small scheme interpreter in C++? Perferably something < 2000 LOC, with a simple garbage collectro (either compacting or mark & sweep), no need to support all of R5RS, just basics of if/lambda/set!/cons/car/cdr and some basic operations. Thanks!

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  • Le projet MonoDroid apporte .NET sur Android, Novell veut construire une passerelle entre le framewo

    Le projet MonoDroid apporte .NET sur Android Novell veut construire une passerelle entre le framework de Microsoft et l'OS de Google Ce n'est pas un scoop, .NET tend à se généraliser. Aujourd'hui, le framework de Microsoft pourrait bien toucher Android, la plateforme Java de son grand concurrent Google, grâce à un projet de Novell, l'éditeur de Mono. Petit retour sur le projet Mono. Mono est l'implantation open-source et portable du framework .Net. Certains vont même jusqu'à dire qu...

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  • Oracle Enterprise Manager Cloud Control 12c: Contributing to emerging Cloud standards

    - by Anand Akela
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Contributed by Tony Di Cenzo, Director for Standards Strategy and Architecture, and Mark Carlson, Principal Cloud Architect, for Oracle's Systems Management and Storage Products Groups . As one would expect of an industry leader, Oracle's participation in industry standards bodies is extensive. We participate in dozens of organizations that produce open standards which apply to our products, and our commitment to the success of these organizations is manifest in several way - we support them financially through our memberships; our senior engineers are active participants, often serving in leadership positions on boards, technical working groups and committees; and when it makes good business sense we contribute our intellectual property. We believe supporting the development of open standards is fundamental to Oracle meeting customer demands for product choice, seamless interoperability, and lowering the cost of ownership. Nowhere is this truer than in the area of cloud standards, and for the most recent release of our flagship management product, Oracle Enterprise Manager Cloud Control 12c (EM Cloud Control 12c). There is a fundamental rule that standards follow architecture. This was true of distributed computing, it was true of service-oriented architecture (SOA), and it's true of cloud. If you are familiar with Enterprise Manager it is likely to be no surprise that EM Cloud Control 12c is a source of technology that can be considered for adoption within cloud management standards. The reason, quite simply, is that the Oracle integrated stack architecture aligns with the cloud architecture models being adopted by the industry, and EM Cloud Control 12c has been developed to manage this architecture. EM Cloud Control 12c has facilities for managing the various underlying capabilities of the integrated stack in IaaS, PaaS, and SaaS clouds, and enables essential characteristics such as on-demand self-service provisioning, centralized policy-based resource management, integrated chargeback, and capacity planning, and complete visibility of the physical and virtual environment from applications to disk. Our most recent contribution in support of cloud management standards to come out of the EM Cloud Control 12c work was the Oracle Cloud Elemental Resource Model API. Oracle contributed the Elemental Resource Model API to the Distributed Management Task Force (DMTF) in 2011 where it was assigned to DMTF's Cloud Management Working Group (CMWG). The CMWG is considering the Oracle specification and those of several other vendors in their effort to produce a best practices specification for managing IaaS clouds. DMTF's Cloud Infrastructure Management Interface specification, called CIMI for short, is currently out for public review and expected to be released by DMTF later this year. We are proud to be playing an important role in the development of what is expected to become a major cloud standard. You can find more information on DMTF CIMI at http://dmtf.org/standards/cloud. You can find the work-in-progress release of CIMI at http://dmtf.org/content/cimi-work-progress-specifications-now-available-public-comment . The Oracle Cloud API specification is available on the Oracle Technology Network. You can find more information about the Oracle Cloud Elemental Resource Model API on the Oracle Technical Network (OTN), including a webcast featuring the API engineering manager Jack Yu (see TechCast Live: Inside the Oracle Cloud Resource Model API). If you have not seen this video we recommend you take the time to view it. Simply hover your cursor over the webcast title and control+click to follow the embedded link. If you have a question about the Oracle Cloud API or want to learn more about Oracle's participation in cloud management standards efforts drop us a line. We'd love to hear from you. The Enterprise Manager Standards Blogs are written by Tony Di Cenzo, Director for Standards Strategy and Architecture, and Mark Carlson, Principal Cloud Architect, for Oracle's Systems Management and Storage Products Groups. They can be reached at Tony.DiCenzo at Oracle.com and Mark.Carlson at Oracle.com respectively. Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • Silverlight Cream for February 26, 2011 -- #1052

    - by Dave Campbell
    In this Issue: Mark Monster, Gill Cleeren, Pencho Popadiyn, Kevin Dockx, Joost van Schaik, Jesse Liberty, John Papa, Jeremy Likness, Arik Poznanski(-2-), Page Brooks, Deborah Kurata, Mike Snow, Alfred Astort, Samuel Jack, XAMLNinja, and Shawn Wildermuth. Above the Fold: Silverlight: "Asynchronous Callbacks with Rx" Jesse Liberty WP7: "Phoney Windows Phone 7 Project Now Available!" Shawn Wildermuth MVVM: "Validating our ViewModel" Mark Monster Shoutouts: Shawn Wildermuth has a video up of his FadingMessage class to show it off: Introducing Phoney's FadingMessage Class From SilverlightCream.com: Validating our ViewModel Mark Monster discusses Validation in his latest post... using INotifyDataErrorInfo and his own implementation of a ViewModel base that supports it and INPC. Getting ready for Microsoft Silverlight Exam 70-506 (Part 7) Gill Cleeren hits part 7 of his series at SilverlightShow on a great walk through Silverlight and getting ready for the exam. This is the final part and concentrates on deploying apps. Windows Phone 7–Creating Custom Keyboard Pencho Popadiyn has a post at SilverlightShow discussing problems with WP7 keyboards in his native Bulgaria, and his solution to the problem... create his own. 360 Degrees Feedback by Kevin Dockx Kevin Dockx produced a white paper for his company about an employee review solution they did in Silverlight. The white paper is available, and SilverlightShow interviewd Kevin to answer questions about the app. Extended Windows Phone 7 page for handling rotation, focused element updates and back key press Looks like Joost van Schaik has a few posts I've missed... and I'm not going to get to them all today! ... this one is about the base class he uses for WP7 apps... a bunch of utilities he uses... definitely worth a look (and a take). Asynchronous Callbacks with Rx Jesse Liberty has his 8th post in the Rx series up and this one's on Asynchronous Callbacks... if you haven't seen this before, you should definitely look into it... cool stuff, Jesse! Silverlight TV 63: Exploring National Instruments' App Using Data and Business Features John Papa has Silverlight TV number 63 up and is talking to Steve Lasker about National Instruments and their Lab View product. Great demo and discussion. Jounce Part 11: Debugging MEF Jeremy Likness's latest (number 11) in his series on his MVVM framework Jounce is out, and he's discussing how to debug MEF, which Jounce handles nicely through the logging he provides... and you can use it externally to Jounce. Get Twitter Trends on Windows Phone 7 Arik Poznanski has a couple Twitter for WP7 posts up... first is one for pulling Twitter trends from whatthetrend.com... plus the code to do it. Searching Twitter on Windows Phone 7 In his next post, Arik Poznanski shows how to search twitter from your WP7 ... again with code. Tiled Background Control in Silverlight Page Brooks shows how to get a tiled background control in Silverlight ... did you know there was one in the JetPack them? Silverlight Charting: Displaying Data Above the Column Deborah Kurata continues her charting posts with this one displaying the column value above the column. I like this... it has a clean look and all the data is available at a glance. Silverlight: Tasks on the Win7 Mobile Phone Mike Snow has a list of the WP7 tasks available and an example of using them... looks like a pretty good reference! 10 of 10 - Aesthetics and alignment matter Alfred Astort discusses aesthetics and WP7 dev... looks like it's the same as any app development, but if you're not doing it, you should be. Simon Squared – We have Multi-player: Days 4, 5 and (ahem!) 6 Samuel Jack details the completion of his multi-player game for WP7 utilizing Azure, in the hour-by-hour detail he's done the rest... plus a video of the final product! Who ate all the pies!! XAMLNinja has a very good discussion/link set of Charting posts all leading up to a portrait-only version of charting for WP7 with labels that looks looks great Phoney Windows Phone 7 Project Now Available! Shawn Wildermuth has a collection of classes he always uses with WP7 dev, and he's sharing them with all of us a "Phoney" Tools project on Codeplex... and now has a NuGet project also. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Google I/O 2011: Memory management for Android Apps

    Google I/O 2011: Memory management for Android Apps Patrick Dubroy Android apps have more memory available to them than ever before, but are you sure you're using it wisely? This talk will cover the memory management changes in Gingerbread and Honeycomb (concurrent GC, heap-allocated bitmaps, "largeHeap" option) and explore tools and techniques for profiling the memory usage of Android apps. From: GoogleDevelopers Views: 5698 45 ratings Time: 58:42 More in Science & Technology

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