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  • Understanding java's native threads and the jvm

    - by Moev4
    I understand that the jvm is itself an application that turns the bytecode of the java executable into native machine code, but when using native threads I have some questions that I just cannot seem to answer. Does every thread create their own instance of the jvm to handle their particular execution? If not then does the jvm have to have some way to schedule which thread it will handle next, if so wouldn't this render the multi-threaded nature of java useless since only one thread can be ran at a time?

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  • Interface Casting vs. Class Casting

    - by Legatou
    I've been led to believe that casting can, in certain circumstances, become a measurable hindrance on performance. This may be moreso the case when we start dealing with incoherent webs of nasty exception throwing\catching. Given that I wish to create more correct heuristics when it comes to programming, I've been prompted to ask this question to the .NET gurus out there: Is interface casting faster than class casting? To give a code example, let's say this exists: public interface IEntity { IParent DaddyMommy { get; } } public interface IParent : IEntity { } public class Parent : Entity, IParent { } public class Entity : IEntity { public IParent DaddyMommy { get; protected set; } public IParent AdamEve_Interfaces { get { IEntity e = this; while (this.DaddyMommy != null) e = e.DaddyMommy as IEntity; return e as IParent; } } public Parent AdamEve_Classes { get { Entity e = this; while (this.DaddyMommy != null) e = e.DaddyMommy as Entity; return e as Parent; } } } So, is AdamEve_Interfaces faster than AdamEve_Classes? If so, by how much? And, if you know the answer, why?

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  • Newtonsoft JSON Interface Serialization error

    - by Ben
    I am using C# .NET 4.0, Newtonsoft JSON 4.5.0. public class Recipe { [JsonProperty(TypeNameHandling = TypeNameHandling.All)] public List<IFood> Foods{ get; set; } ... } I want to serialize and deserialize this Recipe object. If I serialize and deserialize the object during application lifetime this succeeds, but if I serialize the object, exit application and then deserialize it then it throws an exception, that it cannot instantiate IFood (since it is an interface). The problem is that it does not serialize the implementation of interface. "$type": "System.Collections.Generic.List`1[[NSM.Shared.Models.IFood, NSMShared]], mscorlib" I tried using TypeNameHandling.Object and Array and Auto, but it didn't help. Is there any way to serialize it properly? Or at least to define the class mapping before deserializing? EDIT: I am using JSON coupled with Hammock ( http://code.google.com/p/relax-net/ ), C# driver for CouchDB, which internally serializes and deserializes objects. As mentioned the problem is that it does not serialize the interface implementation.

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  • Delphi RTTI unable to find interface

    - by conciliator
    I'm trying to fetch an interface using D2010 RTTI. program rtti_sb_1; {$APPTYPE CONSOLE} {$M+} uses SysUtils, Rtti, mynamespace in 'mynamespace.pas'; var ctx: TRttiContext; RType: TRttiType; MyClass: TMyIntfClass; begin ctx := TRttiContext.Create; MyClass := TMyIntfClass.Create; // This prints a list of all known types, including some interfaces. // Unfortunately, IMyPrettyLittleInterface doesn't seem to be one of them. for RType in ctx.GetTypes do WriteLn(RType.Name); // Finding the class implementing the interface is easy. RType := ctx.FindType('mynamespace.TMyIntfClass'); // Finding the interface itself is not. RType := ctx.FindType('mynamespace.IMyPrettyLittleInterface'); MyClass.Free; ReadLn; end. Both IMyPrettyLittleInterface and TMyIntfClass = class(TInterfacedObject, IMyPrettyLittleInterface) are declared in mynamespace.pas. Do anyone know why this doesn't work? Is there a way to solve my problem? Thanks in advance!

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  • Cannot inherit from generic base class and specific interface using same type with generic constrain

    - by simendsjo
    Sorry about the strange title. I really have no idea how to express it any better... I get an error on the following snippet. I use the class Dummy everywhere. Doesn't the compiler understand the constraint I've added on DummyImplBase? Is this a compiler bug as it works if I use Dummy directly instead of setting it as a constraint? Error 1 'ConsoleApplication53.DummyImplBase' does not implement interface member 'ConsoleApplication53.IRequired.RequiredMethod()'. 'ConsoleApplication53.RequiredBase.RequiredMethod()' cannot implement 'ConsoleApplication53.IRequired.RequiredMethod()' because it does not have the matching return type of 'ConsoleApplication53.Dummy'. C:\Documents and Settings\simen\My Documents\Visual Studio 2008\Projects\ConsoleApplication53\ConsoleApplication53\Program.cs 37 27 ConsoleApplication53 public class Dummy { } public interface IRequired<T> { T RequiredMethod(); } public interface IDummyRequired : IRequired<Dummy> { void OtherMethod(); } public class RequiredBase<T> : IRequired<T> { public T RequiredMethod() { return default(T); } } public abstract class DummyImplBase<T> : RequiredBase<T>, IDummyRequired where T: Dummy { public void OtherMethod() { } }

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  • How to solve this nullPointer Exception in jasper report?

    - by Kumar
    Hi, I am new to jasper report, I need to create pdf document with BeanDatasource and subreport. I refer the following blog " http://knol.google.com/k/jasper-reports-working-with-beans-and-sub-report# " . I followed all the steps perfectly. While i am running the report using IReport i can get the pdf document with the content. But when we try to create from java program i m getting exception in the following line Line number 110: " JasperFillManager.fillReportToFile("C:/JasperReports/contacts.jasper", parameters, new JRBeanCollectionDataSource(TestPerson.getBeanCollection())); " and this is the following error i am getting in my Eclipse Console window . java.lang.NullPointerException at net.sf.jasperreports.engine.JRPropertiesMap.readObject(JRPropertiesMap.java:185) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at java.io.ObjectStreamClass.invokeReadObject(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readArray(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:88) at net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation(JRLoader.java:257) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:308) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257) at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275) at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:891) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:814) at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:89) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:601) at test.TestJasperReport.main(TestJasperReport.java:110)

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  • Java update/install via group policy

    - by Maximus
    I trying to deploy the latest Java RE version via GP, Java 7 update 9. I want to update computers that are currently running an older version of Java, a mixture of 7.6 and 7.7, some computers are running versions as old as 6.31. Some are running a mixture of both. I would also like this GP to install Java if it's not installed. Previously I used push out Java updates to users machines as Java didn't remove the old version. So when it was done the user would restart their browser or pc to start using the latest version. Not the best way to manage it as it leaves the old version installed but it worked. I've created group policies before for printer deployment, log on drive mapping scripts, but never software deployment. I've extracted the Java MSI and created a transform file to suppress reboot etc using orca. As described on this site http://ivan.dretvic.com/2011/06/how-to-package-and-deploy-java-jre-1-6-0_26-via-group-policy/. I have also tried saving the edited MSI directly and that didn't work either. But it just won't deploy. I have tried to enable logging as suggested on this site http://openofficetechnology.com/node/32, GPO logging via UserEnvDebugLevel, Software deployment logging via AppmgmtDebugLevel and MSI logging, but there is no log C:\Windows\Debug\UserMode\userenv.log being created. The windows event viewer has the following errors: Error 24/10/2012 11:44:04 AM - "Failed to apply changes to software installation settings. Software changes could not be applied. A previous log entry with details should exist. The error was : %%1612" Information 24/10/2012 11:44:04 AM - "The removal of the assignment of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy succeeded." Error 24/10/2012 11:44:04 AM - "The install of application Java 7 Update 9 - FB Java Transform from policy JavaDeploy failed. The error was : %%1612" There is a log created for MSI logging and it's as below. It says the source is invalid but it exists on the share and the PC that I'm testing has permissions and I've included the recommendation here Group Policy installation failed error 1274 to enable "Always wait for the network at computer startup and logon" === Verbose logging started: 24/10/2012 11:43:59 Build type: SHIP UNICODE 5.00.7601.00 Calling process: C:\Windows\system32\svchost.exe === MSI (c) (9C:EC) [11:43:59:898]: Resetting cached policy values MSI (c) (9C:EC) [11:43:59:898]: Machine policy value 'Debug' is 3 MSI (c) (9C:EC) [11:43:59:898]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (c) (9C:EC) [11:43:59:898]: Client-side and UI is none or basic: Running entire install on the server. MSI (c) (9C:EC) [11:43:59:898]: Grabbed execution mutex. MSI (c) (9C:EC) [11:44:03:431]: Cloaking enabled. MSI (c) (9C:EC) [11:44:03:431]: Attempting to enable all disabled privileges before calling Install on Server MSI (c) (9C:EC) [11:44:03:439]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:03:574]: Running installation inside multi-package transaction {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:70) [11:44:03:574]: Grabbed execution mutex. MSI (s) (2C:7C) [11:44:03:607]: Resetting cached policy values MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'Debug' is 3 MSI (s) (2C:7C) [11:44:03:607]: ******* RunEngine: ******* Product: {26a24ae4-039d-4ca4-87b4-2f83217009ff} ******* Action: ******* CommandLine: ********** MSI (s) (2C:7C) [11:44:03:607]: Machine policy value 'DisableUserInstalls' is 0 MSI (s) (2C:7C) [11:44:03:623]: User policy value 'SearchOrder' is 'nmu' MSI (s) (2C:7C) [11:44:03:624]: User policy value 'DisableMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: Machine policy value 'AllowLockdownMedia' is 0 MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media enabled only if package is safe. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Looking for sourcelist for product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Adding {26a24ae4-039d-4ca4-87b4-2f83217009ff}; to potential sourcelist list (pcode;disk;relpath). MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Now checking product {26a24ae4-039d-4ca4-87b4-2f83217009ff} MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Media is enabled for product. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Attempting to use LastUsedSource from source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Processing net source list. MSI (s) (2C:7C) [11:44:03:624]: SOURCEMGMT: Trying source \\server\share\deployment\Java\stable\x32\. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 2303 2: 5 3: \\server\share\ MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1325 2: deployment MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource: CreatePath/CreateFilePath failed with: -2147483648 1325 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: ConnectToSource (con't): CreatePath/CreateFilePath failed with: -2147483648 -2147483648 MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: net source '\\server\share\deployment\Java\stable\x32\' is invalid. MSI (s) (2C:7C) [11:44:03:650]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:03:650]: SOURCEMGMT: Processing media source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 2203 2: 3: -2147287037 MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Source is invalid due to missing/inaccessible package. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Processing URL source list. MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1402 2: UNKNOWN\URL 3: 2 MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: -2147483647 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: Note: 1: 1706 2: 3: jre1.7.0_09.msi MSI (s) (2C:7C) [11:44:04:668]: SOURCEMGMT: Failed to resolve source MSI (s) (2C:7C) [11:44:04:668]: MainEngineThread is returning 1612 MSI (s) (2C:70) [11:44:04:670]: User policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Machine policy value 'DisableRollback' is 0 MSI (s) (2C:70) [11:44:04:670]: Incrementing counter to disable shutdown. Counter after increment: 0 MSI (s) (2C:70) [11:44:04:670]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\Rollback\Scripts 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Note: 1: 1402 2: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer\InProgress 3: 2 MSI (s) (2C:70) [11:44:04:671]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (s) (2C:70) [11:44:04:671]: Restoring environment variables MSI (c) (9C:EC) [11:44:04:675]: Decrementing counter to disable shutdown. If counter >= 0, shutdown will be denied. Counter after decrement: -1 MSI (c) (9C:EC) [11:44:04:675]: MainEngineThread is returning 1612 === Verbose logging stopped: 24/10/2012 11:44:04 === I'm not sure what my next approach should be. Any help would be much appreciated. Thanks.

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  • NoSuchPortException using RXTX Java library on Windows?

    - by Steve
    I have followed the instructions to setup rxtx on windows from http://www.jcontrol.org/download/readme_rxtx_en.html. What I did exactly was copy rxtxSerial.dll to "C:\Program Files\Java\jdk1.6.0_07\jre\bin" and copied RXTXcomm.jar to "C:\Program Files\Java\jdk1.6.0_07\jre\lib\ext" (my JAVA_HOME variable is set to C:\Program Files\Java\jdk1.6.0_07\jre) I also added RXTXcomm.jar to my eclipse project. But when I run it, it still says "NoSuchPortException" Devel Library ========================================= Native lib Version = RXTX-2.0-7pre1 Java lib Version = RXTX-2.0-7pre1 java.lang.ClassCastException: gnu.io.RXTXCommDriver cannot be cast to gnu.io.CommDriver thrown while loading gnu.io.RXTXCommDriver gnu.io.NoSuchPortException at gnu.io.CommPortIdentifier.getPortIdentifier(CommPortIdentifier.java:218) at TwoWaySerialComm.connect(TwoWaySerialComm.java:20) at TwoWaySerialComm.main(TwoWaySerialComm.java:107) In my java file, I tell it: try { (new TwoWaySerialComm()).connect("COM4"); } and I've also tried the Java Comm API. Both cannot recognize my serial port but I am sure I followed the instruction correctly. There files are there. Does anybody have any idea what it could be?

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  • bash - how to filter java exception info

    - by Michael Mao
    Hi all: We've got a multi-agent Java environment where different agent would most likely produce all sorts of exceptions thrown to stderr. Here is a sample taken from the huge exception log **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at MySmarterAgent.hotelRoomBookings(MySmarterAgent.java:108) fortunately all top-tier exceptions are denoted by no leading spaces, as wrapped by ** above. My concern is to get all of the top-tier exception name (delimited by colon :), together with the first line below which contains something like at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) Basically, something with padded style, starts with "at" and ends with ".java:108" So this info can be forwarded to the owner of that error-prone agent and let him/her fix it. My code in ~/.bashrc is incompleted now : alias startmatch='java -jar "emarket.jar" ../tournament 100'; function geterrors() { startmatch 2>"$1"; a=0; while read line do if true; then a=$(($a+1)); echo $a; fi; done } What it does now is to redirect all stderr to a text file specified by the first argument passed in, and after that, parse that text file line by line, if certain conditions returns true, echo only that line. And I am stuck with what to do inside the loop. Any suggestion is much appreciates, any hint is welcomed.

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  • What is the difference between Java RMI and JMS?

    - by Sanoj
    When designing an distributed application in Java there seams to be a few technologies that address the same kind of problem. I have briefly read about Java Remote Method Invocation and Java Message Service, but it is hard to really see the difference. Java RMI seams to be more tightly coupled than JMS because JMS use asynchronous communication, but otherwise I don't see any big differences. What is the difference between them? Is one of them newer than the other one? Which one is more common/popular in enterprises? What advantages do they have over eachother? When is one preferred over the other? Do they differ much in how difficult they are to implement? I also think that Web Services and CORBA address the same problem.

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  • Is there a java library / package analogous to <stdio.h>?

    - by Roboprog
    I have been doing Java on and off for about 14 years, and almost nothing else the last 6 years or so. I really hate the java.io package -- its legion of subclasses and adapters. I do like exceptions, rather than having to always poll "errno" and the like, but I could surely live without declared exceptions. Is there anything that functions like the Unix/ANSI stdio.h routines in C? I know we will never be rid of java.io and its conventions until java itself is retired, as they have metastasized throughout the many frameworks that have accreted to java. That said, I would like something that works kind of like this (let's call it package javax.stdio): Have a main utility class, perhaps FileStar, that can read and write files (or pipes), either text or binary, either sequentially or random access, with constructors that mimic fopen() and popen(). This class should have a load of useful methods that do things like fread(), fwrite(), fgets(), fputs(), fseek(), and whatever else (fprintf()?). Methods that are incompatible with the open/construct mode simply throw up (just like some of the collections classes/methods do when restricted). Then, have a bunch of interfaces that suggest how you intend to use the stream once you have created it: Sequential, RandomAccess, ReadOnly, WriteOnly, Text, Binary, plus combinations of these that make sense. Perhaps even have methods to return the appropriate type-cast (interface), throwing up if you have asked for something incompatible. For extra flavor, skip the declared exceptions -- e.g. - javax.stdio.IOException extends RuntimeException. Is there an open source project like this floating around?

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  • IIS7 Modules - managed or native?

    - by Simon Linder
    Hi all, as the old ISAPI filters are going to die sooner or later, I want to rewrite an old ISAPI filter that was used in IIS 6 into a module for use in IIS 7. The module will be used globally, meaning it will be used within each site, on a Windows Server 2008 R2 with IIS 7.5 installed, that will host several thousand web sites and managing about 50 application pools. My question now is if I should write that module in managed or unmanaged code? One of my concerns regarding managed code is the massive memory consumption due to the .NET framework overhead. I don't know how this would effect the server's performance. I already wrote modules in managed as well as in unmanaged code. So this is not the bothering my decision. But I would prefer to write the module in C# if there are no huge drawbacks. Any suggestions about that issue?

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  • Problem with relative file path

    - by Richard Knop
    So here is my program, which works ok: import java.io.FileReader; import java.io.BufferedReader; import java.io.IOException; import java.util.Scanner; import java.util.Locale; public class ScanSum { public static void main(String[] args) throws IOException { Scanner s = null; double sum = 0; try { s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); s.useLocale(Locale.US); while (s.hasNext()) { if (s.hasNextDouble()) { sum += s.nextDouble(); } else { s.next(); } } } finally { s.close(); } System.out.println(sum); } } As you can see, I am using absolute path to the file I am reading from: s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); The problem arises when I try to use the relative path: s = new Scanner(new BufferedReader(new FileReader("usnumbers.txt"))); I get an error: Exception in thread "main" java.lang.NullPointerException at ScanSum.main(ScanSum.java:24) The file usnumbers.txt is in the same directory as the ScanSum.class file: D:/java-projects/HelloWorld/bin/ScanSum.class D:/java-projects/HelloWorld/bin/usnumbers.txt How could I solve this?

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  • simulate what native object is not exist

    - by Naitro
    Here is the situation: I have checking on existing class like: ('Promise' in window) // true/false` And I wanna force return false or true on it, can I do it? Yes, I can check it by some other way, like ` window.Promise = undefined; window.Promise === undefined; Or something like this, but can I somehow delete this object or simulate something for 'in' operator? I check specification and v8 code, there is 'in' operator just call 'HasProperty' operator, which realization on c++.. I know 'hack' with faking toString/valueOf methods: obj = { toString: function(){ return 'myName'; } }, obj2 = {}; obj2[obj] = 1; // Object {myName: 1} May be I can use it in some way? But, as I send string 'Promise' I can't just fake it like this way.. may be exist some way to fake 'HasProperty'?

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  • google calendar api (java) authentication error in dynamic web project

    - by HazProblem
    org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: com/google/gdata/util/AuthenticationException org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:823) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) javax.servlet.http.HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) The class i have written works fine as a normal java application, but when i try to use the code in an dynamic web project i get this authentication failure. Where´s the difference?

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  • class hierarchy design for small java project

    - by user523956
    I have written a java code which does following:- Main goal is to fetch emails from (inbox, spam) folders and store them in database. It fetches emails from gmail,gmx,web.de,yahoo and Hotmail. Following attributes are stored in mysql database. Slno, messagedigest, messageid, foldername, dateandtime, receiver, sender, subject, cc, size and emlfile. For gmail,gmy and web.de, I have used javamail API, because email form it can be fetched with IMAP. For yahoo and hotmail, I have used html parser and httpclient to fetch emails form spam folder and for inbox folder, I have used pop3 javamail API. I want to have proper class hierarchy which makes my code efficient and easily reusable. As of now I have designed class hierarchy as below: I am sure it can still be improved. So I would like to have different opinions on it. I have following classes and methods as of now. MainController:- Here I pass emailid, password and foldername from which emails have to be fetched. Abstract Class :-EmailProtocol Abstract Methods of it (All methods except executeParser contains method definition):- connectImap() // used by gmx,gmail and web.de email ids connectPop3() // used by hotmail and yahoo to fetch emails of inbox folder createMessageDigest // used by every email provider(gmx, gmail,web.de,yahoo,hotmail) establishDBConnection // used by every email emailAlreadyExists // used by every email which checks whether email already exists in db or not, if not then store it. storeemailproperties // used by every email to store emails properties to mysql database executeParser // nothing written in it. Overwridden and used by just hotmail and yahoo to fetch emails form spam folder. Imap extends EmailProtocol (nothing in it. But I have to have it to access methods of EmailProtocol. This is used to fetch emails from gmail,gmx and web.de) I know this is really a bad way but don't know how to do it other way. Hotmsil extends EmailProtocol Methods:- executeParser() :- This is used by just hotmail email id. fetchjunkemails() :- This is also very specific for only hotmail email id. Yahoo extends EmailProtocol Methods:- executeParser() storeEmailtotemptable() MoveEmailtoInbox() getFoldername() nullorEquals() All above methods are specific for yahoo email id. public DateTimeFormat(class) format() //this formats datetime of gmax,gmail and web.de emails. formatYahoodate //this formats datetime of yahoo email. formatHotmaildate // this formats datetime of hotmail email. public StringFormat ConvertStreamToString() // Accessed by every class except DateTimeFormat class. formatFromTo() // Accessed by every class except DateTimeFormat class. public Class CheckDatabaseExistance public static void checkForDatabaseTablesAvailability() (This method checks at the beginnning whether database and required tables exist in mysql or not. if not it creates them) Please see code of my MainController class so that You can have an idea about how I use different classes. public class MainController { public static void main(String[] args) throws Exception { ArrayList<String> web_de_folders = new ArrayList<String>(); web_de_folders.add("INBOX"); web_de_folders.add("Unbekannt"); web_de_folders.add("Spam"); web_de_folders.add("OUTBOX"); web_de_folders.add("SENT"); web_de_folders.add("DRAFTS"); web_de_folders.add("TRASH"); web_de_folders.add("Trash"); ArrayList<String> gmx_folders = new ArrayList<String>(); gmx_folders.add("INBOX"); gmx_folders.add("Archiv"); gmx_folders.add("Entwürfe"); gmx_folders.add("Gelöscht"); gmx_folders.add("Gesendet"); gmx_folders.add("Spamverdacht"); gmx_folders.add("Trash"); ArrayList<String> gmail_folders = new ArrayList<String>(); gmail_folders.add("Inbox"); gmail_folders.add("[Google Mail]/Spam"); gmail_folders.add("[Google Mail]/Trash"); gmail_folders.add("[Google Mail]/Sent Mail"); ArrayList<String> pop3_folders = new ArrayList<String>(); pop3_folders.add("INBOX"); CheckDatabaseExistance.checkForDatabaseTablesAvailability(); EmailProtocol imap = new Imap(); System.out.println("CHECKING FOR NEW EMAILS IN WEB.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", web_de_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMX.DE...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmx_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN GMAIL...(IMAP)"); System.out.println("*********************************************************************************"); imap.connectImap("[email protected]", "pwd", gmail_folders); EmailProtocol yahoo = new Yahoo(); Yahoo y=new Yahoo(); System.out.println("\nEXECUTING YAHOO PARSER"); System.out.println("*********************************************************************************"); y.executeParser("http://de.mc1321.mail.yahoo.com/mc/welcome?ymv=0","[email protected]","pwd"); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF YAHOO (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); System.out.println("\nCHECKING FOR NEW EMAILS IN INBOX OF HOTMAIL (POP3)"); System.out.println("*********************************************************************************"); yahoo.connectPop3("[email protected]","pwd",pop3_folders); EmailProtocol hotmail = new Hotmail(); Hotmail h=new Hotmail(); System.out.println("\nEXECUTING HOTMAIL PARSER"); System.out.println("*********************************************************************************"); h.executeParser("https://login.live.com/ppsecure/post.srf","[email protected]","pwd"); } } I have kept DatetimeFormat and StringFormat class public so that I can access its public methods by just (DatetimeFormat.formatYahoodate for e.g. from different methods). This is the first time I have developed something in java. It serves its purpose but of course code is still not so efficient I think. I need your suggestions on this project.

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  • Java collision detection and player movement: tips

    - by Loris
    I have read a short guide for game develompent (java, without external libraries). I'm facing with collision detection and player (and bullets) movements. Now i put the code. Most of it is taken from the guide (should i link this guide?). I'm just trying to expand and complete it. This is the class that take care of updates movements and firing mechanism (and collision detection): public class ArenaController { private Arena arena; /** selected cell for movement */ private float targetX, targetY; /** true if droid is moving */ private boolean moving = false; /** true if droid is shooting to enemy */ private boolean shooting = false; private DroidController droidController; public ArenaController(Arena arena) { this.arena = arena; this.droidController = new DroidController(arena); } public void update(float delta) { Droid droid = arena.getDroid(); //droid movements if (moving) { droidController.moveDroid(delta, targetX, targetY); //check if arrived if (droid.getX() == targetX && droid.getY() == targetY) moving = false; } //firing mechanism if(shooting) { //stop shot if there aren't bullets if(arena.getBullets().isEmpty()) { shooting = false; } for(int i = 0; i < arena.getBullets().size(); i++) { //current bullet Bullet bullet = arena.getBullets().get(i); System.out.println(bullet.getBounds()); //angle calculation double angle = Math.atan2(bullet.getEnemyY() - bullet.getY(), bullet.getEnemyX() - bullet.getX()); //increments x and y bullet.setX((float) (bullet.getX() + (Math.cos(angle) * bullet.getSpeed() * delta))); bullet.setY((float) (bullet.getY() + (Math.sin(angle) * bullet.getSpeed() * delta))); //collision with obstacles for(int j = 0; j < arena.getObstacles().size(); j++) { Obstacle obs = arena.getObstacles().get(j); if(bullet.getBounds().intersects(obs.getBounds())) { System.out.println("Collision detect!"); arena.removeBullet(bullet); } } //collisions with enemies for(int j = 0; j < arena.getEnemies().size(); j++) { Enemy ene = arena.getEnemies().get(j); if(bullet.getBounds().intersects(ene.getBounds())) { System.out.println("Collision detect!"); arena.removeBullet(bullet); } } } } } public boolean onClick(int x, int y) { //click on empty cell if(arena.getGrid()[(int)(y / Arena.TILE)][(int)(x / Arena.TILE)] == null) { //coordinates targetX = x / Arena.TILE; targetY = y / Arena.TILE; //enables movement moving = true; return true; } //click on enemy: fire if(arena.getGrid()[(int)(y / Arena.TILE)][(int)(x / Arena.TILE)] instanceof Enemy) { //coordinates float enemyX = x / Arena.TILE; float enemyY = y / Arena.TILE; //new bullet Bullet bullet = new Bullet(); //start coordinates bullet.setX(arena.getDroid().getX()); bullet.setY(arena.getDroid().getY()); //end coordinates (enemie) bullet.setEnemyX(enemyX); bullet.setEnemyY(enemyY); //adds bullet to arena arena.addBullet(bullet); //enables shooting shooting = true; return true; } return false; } As you can see for collision detection i'm trying to use Rectangle object. Droid example: import java.awt.geom.Rectangle2D; public class Droid { private float x; private float y; private float speed = 20f; private float rotation = 0f; private float damage = 2f; public static final int DIAMETER = 32; private Rectangle2D rectangle; public Droid() { rectangle = new Rectangle2D.Float(x, y, DIAMETER, DIAMETER); } public float getX() { return x; } public void setX(float x) { this.x = x; //rectangle update rectangle.setRect(x, y, DIAMETER, DIAMETER); } public float getY() { return y; } public void setY(float y) { this.y = y; //rectangle update rectangle.setRect(x, y, DIAMETER, DIAMETER); } public float getSpeed() { return speed; } public void setSpeed(float speed) { this.speed = speed; } public float getRotation() { return rotation; } public void setRotation(float rotation) { this.rotation = rotation; } public float getDamage() { return damage; } public void setDamage(float damage) { this.damage = damage; } public Rectangle2D getRectangle() { return rectangle; } } For now, if i start the application and i try to shot to an enemy, is immediately detected a collision and the bullet is removed! Can you help me with this? If the bullet hit an enemy or an obstacle in his way, it must disappear. Ps: i know that the movements of the bullets should be managed in another class. This code is temporary. update I realized what happens, but not why. With those for loops (which checks collisions) the movements of the bullets are instantaneous instead of gradual. In addition to this, if i add the collision detection to the Droid, the method intersects returns true ALWAYS while the droid is moving! public void moveDroid(float delta, float x, float y) { Droid droid = arena.getDroid(); int bearing = 1; if (droid.getX() > x) { bearing = -1; } if (droid.getX() != x) { droid.setX(droid.getX() + bearing * droid.getSpeed() * delta); //obstacles collision detection for(Obstacle obs : arena.getObstacles()) { if(obs.getRectangle().intersects(droid.getRectangle())) { System.out.println("Collision detected"); //ALWAYS HERE } } //controlla se è arrivato if ((droid.getX() < x && bearing == -1) || (droid.getX() > x && bearing == 1)) droid.setX(x); } bearing = 1; if (droid.getY() > y) { bearing = -1; } if (droid.getY() != y) { droid.setY(droid.getY() + bearing * droid.getSpeed() * delta); if ((droid.getY() < y && bearing == -1) || (droid.getY() > y && bearing == 1)) droid.setY(y); } }

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  • JMS MQ Connection closed in JSF 2 SessionBean

    - by veote
    I use Websphere Application Server 8 with MQ Series as Messaging Queue. When I open close the connection in sessionbean in a "postConstruct" method and I use it in another method then its closed. My Code is: import java.io.Serializable; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.annotation.Resource; import javax.faces.application.FacesMessage; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; import javax.faces.context.FacesContext; import javax.jms.JMSException; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.Session; import javax.jms.TextMessage; @ManagedBean @SessionScoped public class MQRequest implements Serializable { private static final long serialVersionUID = 1L; @Resource(name = "jms/wasmqtest/wasmqtest_QCF") private QueueConnectionFactory connectionFactory; @Resource(name = "jms/wasmqtest/Request_Q") private Queue requestQueue; private QueueConnection connection; private String text = ""; public void sendMessage() { System.out.println("Connection in sendMessage: \n" + connection); TextMessage msg; try { QueueSession queueSession = connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); QueueSender sender = queueSession.createSender(requestQueue); msg = queueSession.createTextMessage(text); sender.send(msg); queueSession.close(); sender.close(); } catch (JMSException e) { // TODO Auto-generated catch block e.printStackTrace(); } text = ""; } @PostConstruct public void openConenction() { System.out.println("Open Connection"); try { connection = connectionFactory.createQueueConnection(); connection.start(); System.out.println("Connection in OpenConnectioN: \n" + connection); } catch (JMSException e) { e.printStackTrace(); } } @PreDestroy public void closeConnection() { try { System.out.println("Closing Connection"); connection.close(); } catch (JMSException e) { e.printStackTrace(); } } public void setText(String text) { this.text = text; } public String getText() { return text; } } In PostConstruct method the connection is initialized: [21.10.13 07:36:05:574 CEST] 00000025 SystemOut O Connection in OpenConnectioN: com.ibm.ejs.jms.JMSQueueConnectionHandle@36c9b1a managed connection = com.ibm.ejs.jms.JMSManagedQueueConnection@3657e8b physical connection = com.ibm.mq.jms.MQXAQueueConnection@36618b6 closed = false invalid = false restricted methods enabled = false open session handles = [] temporary queues = [] But in sendMessage() method it isnt and I get a ConnectionClosed Problem: [21.10.13 07:36:12:493 CEST] 00000025 SystemOut O Connection in sendMessage: com.ibm.ejs.jms.JMSQueueConnectionHandle@36c9b1a managed connection = null physical connection = null closed = true invalid = false restricted methods enabled = false open session handles = [] temporary queues = [] 21.10.13 07:36:12:461 CEST] 00000025 SystemErr R 15 [WebContainer : 3] INFO org.apache.bval.jsr303.ConfigurationImpl - ignoreXmlConfiguration == true [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R javax.jms.IllegalStateException: Connection closed [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at com.ibm.ejs.jms.JMSConnectionHandle.checkOpen(JMSConnectionHandle.java:821) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at com.ibm.ejs.jms.JMSQueueConnectionHandle.createQueueSession(JMSQueueConnectionHandle.java:206) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at de.volkswagen.wasmqtest.queue.MQRequest.sendMessage(MQRequest.java:51) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60) [21.10.13 07:36:12:601 CEST] 00000025 SystemErr R at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at java.lang.reflect.Method.invoke(Method.java:611) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.el.parser.AstValue.invoke(AstValue.java:262) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.view.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:83) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component._MethodExpressionToMethodBinding.invoke(_MethodExpressionToMethodBinding.java:88) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:100) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UICommand.broadcast(UICommand.java:120) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot._broadcastAll(UIViewRoot.java:973) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:275) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot._process(UIViewRoot.java:1285) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:711) [21.10.13 07:36:12:602 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.InvokeApplicationExecutor.execute(InvokeApplicationExecutor.java:34) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:171) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at javax.faces.webapp.FacesServlet.service(FacesServlet.java:189) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1147) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:722) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:449) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1020) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3703) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:953) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1655) [21.10.13 07:36:12:603 CEST] 00000025 SystemErr R at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:452) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:511) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:305) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775) [21.10.13 07:36:12:604 CEST] 00000025 SystemErr R at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905) [21.10.13 07:36:12:605 CEST] 00000025 SystemErr R at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1650) Do you have an idea why the connection is closed?

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  • Design pattern for window management in a Java Swing app

    - by Lord Torgamus
    I've just started creating my very first little Java Swing app. When the program opens, it brings up a single, simple window with a label and a couple buttons. Clicking one of those buttons is supposed to wipe out the welcome screen and replace it with a totally different panel. I'm not sure what the best way to create that functionality is. One method would be to pass my JFrame as an argument into... just about every other component, but that feels hacky to me. Or, there's making each panel double as an action listener, but that doesn't seem right, either. Is there a design pattern I should be applying here? "Replace the contents of the main — and only — window" must be a reasonably common operation. A name for the pattern would be enough; I can use Google on my own from there. (I wouldn't say no to a longer explanation, though.)

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  • Why do you hate Java? Is it the language or the framework? [closed]

    - by zneak
    According to you all, Java is the third most-hated language here. The two other most hated languages are PHP and VBScript. (It's quite funny how they stand together on the podium.) I'd like to make it known that the question mostly addresses people who don't like Java. I assume here a number of subjective opinions as facts because they're usually considered true among people who don't like Java, and I don't want to be convinced otherwise here. If you're a Java enthusiast, you might find this question frustrating. It's never been made clear if people hate Java itself, or if they hate it because of the framework, or if it's a mixture of the two. On a side you have the language, where you have: the "everything should be an object" philosophy, even in instances where it should obviously be something else (event handlers I'm pointing you); checked exceptions; the idea that all logic should be presented as methods and properties is a big no-no; the fact that "closures" created by anonymous types only include final variables and arguments, but will allow write access to any member of the parent class; a few more. On the other side, you have the JDK, with... its load of inconsistencies and overengineering; monolithic class hierarchies; meaningless base exceptions like IOException (though other frameworks have similar exception hierarchies); sluggish responsiveness even with Swing; a few more. My question is, do you think that, if either one (Java or the JDK) was taken alone, and the other was dropped in favor of something else, the new combination would be better? For instance, if you could use the C# syntax with the JDK (adapting get*/set* methods into properties, and interfaces with only one method into delegates), or the Java syntax with the .NET Framework (doing the inverse transformations), would things get better in your opinion?

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  • how to think like a computer scientist java edition exercise 7.2 [on hold]

    - by James Canfield
    I cannot figure out how to write this program, can someone please help me?! The purpose of this method is to practice manipulating St rings. Create a new program called Name.java. This program will take a name string consisting of EITHER a first name followed by a last name (nonstandar d format) or a last name followed by a comma then a first name (standard format). Ie . “Joe Smith” vs. “Smith, Joe”. This program will convert the string to standard format if it is not already in standard format. Write a method called hasComma that takes a name as an argument and that returns a boolean indicating whether it contains a comma. If i t does, you can assume that it is in last name first format. You can use the indexOf String m ethod to help you. Write a method called convertName that takes a name as an argument. It should check whether it contains a comma by calling your hasComma method. If it does, it should just return the string. If not, then it should assume th at the name is in first name first format, and it should return a new string that contains the name converted to last name comma first format. Uses charAt, length, substring, and indexOf methods. In your main program, loop, asking the user for a n ame string. If the string is not blank, call convertName and print the results. The loop terminat es when the string is blank. HINTS/SUGGESTIONS: Use the charAt, length, substring, and indexOf Str ing methods. Use scanner for your input. To get the full line, complete with spaces, use reader.nextLine()

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  • Is there a canonical book for learning Java as an experienced developer?

    - by Steven Elliott Jr
    I have been a .NET developer now for about the past 5/6 years give or take. I have never done any professional Java development and the last time I really touched it was probably back in college. I have been toying with the Scala language a little bit but nothing serious. Recently, I've been offered an opportunity to do some pretty cool work, but using Java instead of .NET. I think I can get by alright with my current skill set, meaning I already know how to program well and am familiar with languages such as C# and C++, etc. So, the syntax and all that language stuff are really not a problem. What I need is a really good reference book and a book about how to think in Java. Each language/Framework/Stack tries to address things a certain way and I'm sure Java is no different. What are some great Java books that you simply can't live without? Are there any books that talk about the most important parts of Java that must be understood before all else? As a side note, I will be doing mostly Java web development. Not really 100% on what types of stuff they are using for persistence, framework, server, etc.

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