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  • CLR via C# 3rd Edition is out

    - by Abhijeet Patel
    Time for some book news update. CLR via C#, 3rd Edition seems to have been out for a little while now. The book was released in early Feb this year, and needless to say my copy is on it’s way. I can barely wait to dig in and chew on the goodies that one of the best technical authors and software professionals I respect has in store. The 2nd edition of the book was an absolute treat and this edition promises to be no less. Here is a brief description of what’s new and updated from the 2nd edition. Part I – CLR Basics Chapter 1-The CLR’s Execution Model Added about discussion about C#’s /optimize and /debug switches and how they relate to each other. Chapter 2-Building, Packaging, Deploying, and Administering Applications and Types Improved discussion about Win32 manifest information and version resource information. Chapter 3-Shared Assemblies and Strongly Named Assemblies Added discussion of TypeForwardedToAttribute and TypeForwardedFromAttribute. Part II – Designing Types Chapter 4-Type Fundamentals No new topics. Chapter 5-Primitive, Reference, and Value Types Enhanced discussion of checked and unchecked code and added discussion of new BigInteger type. Also added discussion of C# 4.0’s dynamic primitive type. Chapter 6-Type and Member Basics No new topics. Chapter 7-Constants and Fields No new topics. Chapter 8-Methods Added discussion of extension methods and partial methods. Chapter 9-Parameters Added discussion of optional/named parameters and implicitly-typed local variables. Chapter 10-Properties Added discussion of automatically-implemented properties, properties and the Visual Studio debugger, object and collection initializers, anonymous types, the System.Tuple type and the ExpandoObject type. Chapter 11-Events Added discussion of events and thread-safety as well as showing a cool extension method to simplify the raising of an event. Chapter 12-Generics Added discussion of delegate and interface generic type argument variance. Chapter 13-Interfaces No new topics. Part III – Essential Types Chapter 14-Chars, Strings, and Working with Text No new topics. Chapter 15-Enums Added coverage of new Enum and Type methods to access enumerated type instances. Chapter 16-Arrays Added new section on initializing array elements. Chapter 17-Delegates Added discussion of using generic delegates to avoid defining new delegate types. Also added discussion of lambda expressions. Chapter 18-Attributes No new topics. Chapter 19-Nullable Value Types Added discussion on performance. Part IV – CLR Facilities Chapter 20-Exception Handling and State Management This chapter has been completely rewritten. It is now about exception handling and state management. It includes discussions of code contracts and constrained execution regions (CERs). It also includes a new section on trade-offs between writing productive code and reliable code. Chapter 21-Automatic Memory Management Added discussion of C#’s fixed state and how it works to pin objects in the heap. Rewrote the code for weak delegates so you can use them with any class that exposes an event (the class doesn’t have to support weak delegates itself). Added discussion on the new ConditionalWeakTable class, GC Collection modes, Full GC notifications, garbage collection modes and latency modes. I also include a new sample showing how your application can receive notifications whenever Generation 0 or 2 collections occur. Chapter 22-CLR Hosting and AppDomains Added discussion of side-by-side support allowing multiple CLRs to be loaded in a single process. Added section on the performance of using MarshalByRefObject-derived types. Substantially rewrote the section on cross-AppDomain communication. Added section on AppDomain Monitoring and first chance exception notifications. Updated the section on the AppDomainManager class. Chapter 23-Assembly Loading and Reflection Added section on how to deploy a single file with dependent assemblies embedded inside it. Added section comparing reflection invoke vs bind/invoke vs bind/create delegate/invoke vs C#’s dynamic type. Chapter 24-Runtime Serialization This is a whole new chapter that was not in the 2nd Edition. Part V – Threading Chapter 25-Threading Basics Whole new chapter motivating why Windows supports threads, thread overhead, CPU trends, NUMA Architectures, the relationship between CLR threads and Windows threads, the Thread class, reasons to use threads, thread scheduling and priorities, foreground thread vs background threads. Chapter 26-Performing Compute-Bound Asynchronous Operations Whole new chapter explaining the CLR’s thread pool. This chapter covers all the new .NET 4.0 constructs including cooperative cancelation, Tasks, the aralle class, parallel language integrated query, timers, how the thread pool manages its threads, cache lines and false sharing. Chapter 27-Performing I/O-Bound Asynchronous Operations Whole new chapter explaining how Windows performs synchronous and asynchronous I/O operations. Then, I go into the CLR’s Asynchronous Programming Model, my AsyncEnumerator class, the APM and exceptions, Applications and their threading models, implementing a service asynchronously, the APM and Compute-bound operations, APM considerations, I/O request priorities, converting the APM to a Task, the event-based Asynchronous Pattern, programming model soup. Chapter 28-Primitive Thread Synchronization Constructs Whole new chapter discusses class libraries and thread safety, primitive user-mode, kernel-mode constructs, and data alignment. Chapter 29-Hybrid Thread Synchronization Constructs Whole new chapter discussion various hybrid constructs such as ManualResetEventSlim, SemaphoreSlim, CountdownEvent, Barrier, ReaderWriterLock(Slim), OneManyResourceLock, Monitor, 3 ways to solve the double-check locking technique, .NET 4.0’s Lazy and LazyInitializer classes, the condition variable pattern, .NET 4.0’s concurrent collection classes, the ReaderWriterGate and SyncGate classes.

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  • JDK bug migration: components and subcomponents

    - by darcy
    One subtask of the JDK migration from the legacy bug tracking system to JIRA was reclassifying bugs from a three-level taxonomy in the legacy system, (product, category, subcategory), to a fundamentally two-level scheme in our customized JIRA instance, (component, subcomponent). In the JDK JIRA system, there is technically a third project-level classification, but by design a large majority of JDK-related bugs were migrated into a single "JDK" project. In the end, over 450 legacy subcategories were simplified into about 120 subcomponents in JIRA. The 120 subcomponents are distributed among 17 components. A rule of thumb used was that a subcategory had to have at least 50 bugs in it for it to be retained. Below is a listing the component / subcomponent classification of the JDK JIRA project along with some notes and guidance on which OpenJDK email addresses cover different areas. Eventually, a separate incidents project to host new issues filed at bugs.sun.com will use a slightly simplified version of this scheme. The preponderance of bugs and subcomponents for the JDK are in library-related areas, with components named foo-libs and subcomponents primarily named after packages. While there was an overall condensation of subcomponents in the migration, in some cases long-standing informal divisions in core libraries based on naming conventions in the description were promoted to formal subcomponents. For example, hundreds of bugs in the java.util subcomponent whose descriptions started with "(coll)" were moved into java.util:collections. Likewise, java.lang bugs starting with "(reflect)" and "(proxy)" were moved into java.lang:reflect. client-libs (Predominantly discussed on 2d-dev and awt-dev and swing-dev.) 2d demo java.awt java.awt:i18n java.beans (See beans-dev.) javax.accessibility javax.imageio javax.sound (See sound-dev.) javax.swing core-libs (See core-libs-dev.) java.io java.io:serialization java.lang java.lang.invoke java.lang:class_loading java.lang:reflect java.math java.net java.nio (Discussed on nio-dev.) java.nio.charsets java.rmi java.sql java.sql:bridge java.text java.util java.util.concurrent java.util.jar java.util.logging java.util.regex java.util:collections java.util:i18n javax.annotation.processing javax.lang.model javax.naming (JNDI) javax.script javax.script:javascript javax.sql org.openjdk.jigsaw (See jigsaw-dev.) security-libs (See security-dev.) java.security javax.crypto (JCE: includes SunJCE/MSCAPI/UCRYPTO/ECC) javax.crypto:pkcs11 (JCE: PKCS11 only) javax.net.ssl (JSSE, includes javax.security.cert) javax.security javax.smartcardio javax.xml.crypto org.ietf.jgss org.ietf.jgss:krb5 other-libs corba corba:idl corba:orb corba:rmi-iiop javadb other (When no other subcomponent is more appropriate; use judiciously.) Most of the subcomponents in the xml component are related to jaxp. xml jax-ws jaxb javax.xml.parsers (JAXP) javax.xml.stream (JAXP) javax.xml.transform (JAXP) javax.xml.validation (JAXP) javax.xml.xpath (JAXP) jaxp (JAXP) org.w3c.dom (JAXP) org.xml.sax (JAXP) For OpenJDK, most JVM-related bugs are connected to the HotSpot Java virtual machine. hotspot (See hotspot-dev.) build compiler (See hotspot-compiler-dev.) gc (garbage collection, see hotspot-gc-dev.) jfr (Java Flight Recorder) jni (Java Native Interface) jvmti (JVM Tool Interface) mvm (Multi-Tasking Virtual Machine) runtime (See hotspot-runtime-dev.) svc (Servicability) test core-svc (See serviceability-dev.) debugger java.lang.instrument java.lang.management javax.management tools The full JDK bug database contains entries related to legacy virtual machines that predate HotSpot as well as retired APIs. vm-legacy jit (Sun Exact VM) jit_symantec (Symantec VM, before Exact VM) jvmdi (JVM Debug Interface ) jvmpi (JVM Profiler Interface ) runtime (Exact VM Runtime) Notable command line tools in the $JDK/bin directory have corresponding subcomponents. tools appletviewer apt (See compiler-dev.) hprof jar javac (See compiler-dev.) javadoc(tool) (See compiler-dev.) javah (See compiler-dev.) javap (See compiler-dev.) jconsole launcher updaters (Timezone updaters, etc.) visualvm Some aspects of JDK infrastructure directly affect JDK Hg repositories, but other do not. infrastructure build (See build-dev and build-infra-dev.) licensing (Covers updates to the third party readme, licenses, and similar files.) release_eng (Release engineering) staging (Staging of web pages related to JDK releases.) The specification subcomponent encompasses the formal language and virtual machine specifications. specification language (The Java Language Specification) vm (The Java Virtual Machine Specification) The code for the deploy and install areas is not currently included in OpenJDK. deploy deployment_toolkit plugin webstart install auto_update install servicetags In the JDK, there are a number of cross-cutting concerns whose organization is essentially orthogonal to other areas. Since these areas generally have dedicated teams working on them, it is easier to find bugs of interest if these bugs are grouped first by their cross-cutting component rather than by the affected technology. docs doclet guides hotspot release_notes tools tutorial embedded build hotspot libraries globalization locale-data translation performance hotspot libraries The list of subcomponents will no doubt grow over time, but my inclination is to resist that growth since the addition of each subcomponent makes the system as a whole more complicated and harder to use. When the system gets closer to being externalized, I plan to post more blog entries describing recommended use of various custom fields in the JDK project.

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  • Parallelism implies concurrency but not the other way round right?

    - by Cedric Martin
    I often read that parallelism and concurrency are different things. Very often the answerers/commenters go as far as writing that they're two entirely different things. Yet in my view they're related but I'd like some clarification on that. For example if I'm on a multi-core CPU and manage to divide the computation into x smaller computation (say using fork/join) each running in its own thread, I'll have a program that is both doing parallel computation (because supposedly at any point in time several threads are going to run on several cores) and being concurrent right? While if I'm simply using, say, Java and dealing with UI events and repaints on the Event Dispatch Thread plus running the only thread I created myself, I'll have a program that is concurrent (EDT + GC thread + my main thread etc.) but not parallel. I'd like to know if I'm getting this right and if parallelism (on a "single but multi-cores" system) always implies concurrency or not? Also, are multi-threaded programs running on multi-cores CPU but where the different threads are doing totally different computation considered to be using "parallelism"?

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  • Java regex patterns - compile time constants or instance members?

    - by KepaniHaole
    Currently, I have a couple of singleton objects where I'm doing matching on regular expressions, and my Patterns are defined like so: class Foobar { private final Pattern firstPattern = Pattern.compile("some regex"); private final Pattern secondPattern = Pattern.compile("some other regex"); // more Patterns, etc. private Foobar() {} public static Foobar create() { /* singleton stuff */ } } But I was told by someone the other day that this is bad style, and Patterns should always be defined at the class level, and look something like this instead: class Foobar { private static final Pattern FIRST_PATTERN = Pattern.compile("some regex"); private static final Pattern SECOND_PATTERN = Pattern.compile("some other regex"); // more Patterns, etc. private Foobar() {} public static Foobar create() { /* singleton stuff */ } } The lifetime of this particular object isn't that long, and my main reason for using the first approach is because it doesn't make sense to me to hold on to the Patterns once the object gets GC'd. Any suggestions / thoughts?

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  • Get coordinates of arraylist

    - by opiop65
    Here's my map class: public class map{ public static final int CLEAR = 0; public static final ArrayList<Integer> STONE = new ArrayList<Integer>(); public static final int GRASS = 2; public static final int DIRT = 3; public static final int WIDTH = 32; public static final int HEIGHT = 24; public static final int TILE_SIZE = 25; // static int[][] map = new int[WIDTH][HEIGHT]; ArrayList<ArrayList<Integer>> map = new ArrayList<ArrayList<Integer>>(WIDTH * HEIGHT); enum tiles { air, grass, stone, dirt } Image air, grass, stone, dirt; Random rand = new Random(); public Map() { /* default map */ /*for(int y = 0; y < WIDTH; y++){ map[y][y] = (rand.nextInt(2)); System.out.println(map[y][y]); }*/ /*for (int y = 18; y < HEIGHT; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = STONE; } } for (int y = 18; y < 19; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = GRASS; } } for (int y = 19; y < 20; y++) { for (int x = 0; x < WIDTH; x++) { map[x][y] = DIRT; } }*/ for (int y = 0; y < HEIGHT; y++) { for(int x = 0; x < WIDTH; x++){ map.set(x * WIDTH + y, STONE); } } try { init(null, null); } catch (SlickException e) { e.printStackTrace(); } render(null, null, null); } public void init(GameContainer gc, StateBasedGame sbg) throws SlickException { air = new Image("res/air.png"); grass = new Image("res/grass.png"); stone = new Image("res/stone.png"); dirt = new Image("res/dirt.png"); } public void render(GameContainer gc, StateBasedGame sbg, Graphics g) { for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y)) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } } public static boolean blocked(float x, float y) { return map[(int) x][(int) y] == STONE; } public static Rectangle blockBounds(int x, int y) { return (new Rectangle(x, y, TILE_SIZE, TILE_SIZE)); } } Specifically I am looking at this: for (int x = 0; x < WIDTH; x++) { for (int y = 0; y < HEIGHT; y++) { switch (map.get(x * WIDTH + y).intValue()) { case CLEAR: air.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case STONE: stone.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case GRASS: grass.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; case DIRT: dirt.draw(x * TILE_SIZE, y * TILE_SIZE, TILE_SIZE, TILE_SIZE); break; } } } How can I access the coordinates of my arraylist map and then draw the tiles to the screen? Thanks!

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  • JavaOne 2012 LAD Session: The Future of JVM Performance Tuning

    - by Ricardo Ferreira
    Hi folks. This year, together with the Oracle Open World Latin America, happened another edition of the JavaOne Latin America, the more important event of Java for the developers community. I would like to share with you the slides that I've used in my session. The session was "The Future of JVM Performance Tuning" and the idea was to share some knowledge about JVM enhancements that Oracle implemented in Hotspot about performance, specially those ones related with GC ("Garbage Collection") and SDP ("Sockets Direct Protocol"). I hope you enjoy the content :)

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  • fglrx installation without success - gl_conf issue

    - by Lucio
    I followed the steps of this guide. I've installed the drivers without any problems with sudo dpkg -i fglrx*.deb. The next step is Generate a new /etc/X11/xorg.conf file, but I can't do this due to the following reason: When I enter sudo aticonfig --initial -f the terminal show me this output: sudo: aticonfig: command not found This problem is caused by an error with the symbolics links into the fglrx directory. Look at this section, where you can see -how to fix it- but it doesn't work for me. Why it doesn't? Because after I enter sudo update-alternatives --auto gl_conf the terminal show me this: update-alternatives: error: no alternatives for gl_conf. What I have to do to fix this problem? GC: ATI RadeonHD 6670

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  • Fixing a collision detection bug in Slick2D

    - by Jesse Prescott
    My game has a bug with collision detection. If you go against the wall and tap forward/back sometimes the game thinks the speed you travelled at is 0 and the game doesn't know how to get you out of the wall. My collision detection works by getting the speed you hit the wall at and if it is positive it moves you back, if it is negative it moves you forward. It might help if you download it: https://rapidshare.com/files/1550046269/game.zip Sorry if I explained badly, it's hard to explain. float maxSpeed = 0.3f; float minSpeed = -0.2f; float acceleration = 0.002f; float deacceleration = 0.001f; float slowdownSpeed = 0.002f; float rotateSpeed = 0.08f; static float currentSpeed = 0; boolean up = false; boolean down = false; boolean noKey = false; static float rotate = 0; //Image effect system static String locationCarNormal; static String locationCarFront; static String locationCarBack; static String locationCarBoth; static boolean carFront = false; static boolean carBack = false; static String imageRef; boolean collision = false; public ComponentPlayerMovement(String id, String ScarNormal, String ScarFront, String ScarBack, String ScarBoth) { this.id = id; playerBody = new Rectangle(900/2-16, 700/2-16, 32, 32); locationCarNormal = ScarNormal; locationCarFront = ScarFront; locationCarBack = ScarBack; locationCarBoth = ScarBoth; imageRef = locationCarNormal; } @Override public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { Input input = gc.getInput(); playerBody.transform(Transform.createRotateTransform(2)); float hip = currentSpeed * delta; float unstuckspeed = 0.05f * delta; if(carBack && !carFront) { imageRef = locationCarBack; ComponentImageRender.updateImage(); } else if(carFront && !carBack) { imageRef = locationCarFront; ComponentImageRender.updateImage(); } else if(carFront && carBack) { imageRef = locationCarBoth; ComponentImageRender.updateImage(); } if(input.isKeyDown(Input.KEY_RIGHT)) { rotate += rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_LEFT)) { rotate -= rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_UP)) { if(!collision) { up = true; noKey = false; if(currentSpeed < maxSpeed) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 1; } } else if(input.isKeyDown(Input.KEY_DOWN) && !collision) { down = true; noKey = false; if(currentSpeed > minSpeed) { currentSpeed -= slowdownSpeed; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { noKey = true; if(currentSpeed > 0) { currentSpeed -= deacceleration; } else if(currentSpeed < 0) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } if(entityCollisionWith()) { collision = true; if(currentSpeed > 0 || up) { up = true; currentSpeed = 0; carFront = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate-180)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate-180)); } else if(currentSpeed < 0 || down) { down = true; currentSpeed = 0; carBack = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 0; } } else { collision = false; up = false; down = false; } if(currentSpeed >= -0.01f && currentSpeed <= 0.01f && noKey && !collision) { currentSpeed = 0; } } public static boolean entityCollisionWith() throws SlickException { for (int i = 0; i < BlockMap.entities.size(); i++) { Block entity1 = (Block) BlockMap.entities.get(i); if (playerBody.intersects(entity1.poly)) { return true; } } return false; } }

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  • Coherence Query Performance in Large Clusters

    - by jpurdy
    Large clusters (measured in terms of the number of storage-enabled members participating in the largest cache services) may introduce challenges when issuing queries. There is no particular cluster size threshold for this, rather a gradually increasing tendency for issues to arise. The most obvious challenges are that a client's perceived query latency will be determined by the slowest responder (more likely to be a factor in larger clusters) as well as the fact that adding additional cache servers will not increase query throughput if the query processing is not compute-bound (which would generally be the case for most indexed queries). If the data set can take advantage of the partition affinity features of Coherence, then the application can use a PartitionedFilter to target a query to a single server (using partition affinity to ensure that all data is in a single partition). If this can not be done, then avoiding an excessive number of cache server JVMs will help, as will ensuring that each cache server has sufficient CPU resources available and is also properly configured to minimize GC pauses (the most common cause of a slow-responding cache server).

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  • Languages with C/C++ output [closed]

    - by Vag
    Which languages have compilers able to emit plain standard C/C++ code? For a start: Haxe // uses Boehm GC Haskell (JHC) Haskell (old GHC) // -fvia-c, removed recently (emitted code is super ugly) Clay ATS Cython RPython (Shed Skin) // experimental RPython (PyPy) Python (Nuitka) // although author claims there are no speedups Common Lisp (ECL) COBOL (OpenCobol) Scheme (Chicken) APL // So far I've not found working implementation available for free download Ur/Web // GCC-specific output, and intended to be used only for web developments (included for completeness only) I'd like to build comprehensive up-to-date list but found only these ones so far. I've tested only Haxe and it works pretty well and quite fast. What about other ones? What is your expirience? How much ugly is generated code? Update. Any language chains (e.g. X - Scheme - C) will be perfectly OK as answer if its use is practical enough and suited for production use.

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  • Adding a short delay between bullets

    - by Sun
    I'm having some trouble simulating bullets in my 2D shooter. I want similar mechanics to Megaman, where the user can hold down the shoot button and a continues stream of bullets are fired but with a slight delay. Currently, when the user fires a bullet in my game a get an almost laser like effect. Below is a screen shot of some bullets being fired while running and jumping. In my update method I have the following: if(gc.getInput().isKeyDown(Input.KEY_SPACE) ){ bullets.add(new Bullet(player.getPos().getX() + 30,player.getPos().getY() + 17)); } Then I simply iterate through the array list increasing its x value on each update. Moreover, pressing the shoot button (Space bar) creates multiple bullets instead of just creating one even though I am adding only one new bullet to my array list. What would be the best way to solve this problem?

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  • New Development Snapshot

    I finished all the .NET 4.0 security model changes. If you build from source, you can now (optionally) build on .NET 4.0 and get native .NET 4.0 assemblies that use the new .NET 4.0 security model (and also experimental class gc support). The .NET 2.0 binaries also work on .NET 4.0. This is probably the final development snapshot before the first 0.44 release candidate and it has been tested more than a typical development snapshot. Please start testing ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • What parts of Java I should know by now?

    - by WinstonChurchill
    I have been working in the enterprise Java field, mostly for financial institutions, for about seven years. Beyond core Java, what are "parts" of Java I should know by now? Should as in it will be useful either to nail the interview, or in an actual job. For example, I have never used JSP beyond "hello, world", but I don't suppose that it's something I need to go learn. But I have got core Spring pretty well done. I've read up on GC but that was a while back and need to re-visit it. I'm looking for one suggestion per post please.

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  • How do you set the movement speed of a sprite?

    - by rphello101
    I'm using Slick 2D/Java to play around with graphics. Getting an image to move is easy: Input input = gc.getInput(); if(input.isKeyDown(sprite.up)){ sprite.y--; }else if (input.isKeyDown(sprite.down)){ sprite.y++; }else if (input.isKeyDown(sprite.left)){ sprite.x--; }else if (input.isKeyDown(sprite.right)){ sprite.x++; } However, this is called on every update, so if you hold up, the sprite moves to the edge of the screen in a few hundred milliseconds. Since coordinates are integers, I can't add less than 1 to slow the sprite down. I'm assuming I must have to implement a timer of some sort or something. Any advice?

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  • Python Memory leak - Solved, but still puzzled

    - by disappearedng
    Dear everyone, I have successfully debugged my own memory leak problems. However, I have noticed some very strange occurence. for fid, fv in freqDic.iteritems(): outf.write(fid+"\t") #ID for i, term in enumerate(domain): #Vector tfidf = self.tf(term, fv) * self.idf( term, docFreqDic) if i == len(domain) - 1: outf.write("%f\n" % tfidf) else: outf.write("%f\t" % tfidf) outf.flush() print "Memory increased by", int(self.memory_mon.usage()) - startMemory outf.close() def tf(self, term, freqVector): total = freqVector[TOTAL] if total == 0: return 0 if term not in freqVector: ## When you don't have these lines memory leaks occurs return 0 ## return float(freqVector[term]) / freqVector[TOTAL] def idf(self, term, docFrequencyPerTerm): if term not in docFrequencyPerTerm: return 0 return math.log( float(docFrequencyPerTerm[TOTAL])/docFrequencyPerTerm[term]) Basically let me describe my problem: 1) I am doing tfidf calculations 2) I traced that the source of memory leaks is coming from defaultdict. 3) I am using the memory_mon from http://stackoverflow.com/questions/276052/how-to-get-current-cpu-and-ram-usage-in-python 4) The reason for my memory leaks is as follows: a) in self.tf, if the lines: if term not in freqVector: return 0 are not added that will cause the memory leak. (I verified this myself using memory_mon and noticed a sharp increase in memory that kept on increasing) The solution to my problem was 1) since fv is a defaultdict, any reference to it that are not found in fv will create an entry. Over a very large domain, this will cause memory leaks. I decided to use dict instead of default dict and the memory problem did go away. My only puzzle is: since fv is created in "for fid, fv in freqDic.iteritems():" shouldn't fv be destroyed at the end of every for loop? I tried putting gc.collect() at the end of the for loop but gc was not able to collect everything (returns 0). Yes, the hypothesis is right, but the memory should stay fairly consistent with ever for loop if for loops do destroy all temp variables. This is what it looks like with that two line in self.tf: Memory increased by 12 Memory increased by 948 Memory increased by 28 Memory increased by 36 Memory increased by 36 Memory increased by 32 Memory increased by 28 Memory increased by 32 Memory increased by 32 Memory increased by 32 Memory increased by 40 Memory increased by 32 Memory increased by 32 Memory increased by 28 and without the the two line: Memory increased by 1652 Memory increased by 3576 Memory increased by 4220 Memory increased by 5760 Memory increased by 7296 Memory increased by 8840 Memory increased by 10456 Memory increased by 12824 Memory increased by 13460 Memory increased by 15000 Memory increased by 17448 Memory increased by 18084 Memory increased by 19628 Memory increased by 22080 Memory increased by 22708 Memory increased by 24248 Memory increased by 26704 Memory increased by 27332 Memory increased by 28864 Memory increased by 30404 Memory increased by 32856 Memory increased by 33552 Memory increased by 35024 Memory increased by 36564 Memory increased by 39016 Memory increased by 39924 Memory increased by 42104 Memory increased by 42724 Memory increased by 44268 Memory increased by 46720 Memory increased by 47352 Memory increased by 48952 Memory increased by 50428 Memory increased by 51964 Memory increased by 53508 Memory increased by 55960 Memory increased by 56584 Memory increased by 58404 Memory increased by 59668 Memory increased by 61208 Memory increased by 62744 Memory increased by 64400 I look forward to your answer

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  • MonoTouch App Crashes When Returning From MFMailComposeViewController

    - by Richard Khan
    My MonoTouch Version Info: Release ID: 20401003 Git revision: 2f1746af36f421d262dcd2b0542ce86b12158f02 Build date: 2010-12-23 23:13:38+0000 The MFMailComposeViewController is displayed and works correctly as a dialog using the following code: if (MFMailComposeViewController.CanSendMail) { MFMailComposeViewController mail; mail = new MFMailComposeViewController (); mail.SetSubject ("Subject Test"); mail.SetMessageBody ("Body Test", false); mail.Finished += HandleMailFinished; this.navigationController.PresentModalViewController (mail, true); } else { new UIAlertView ("Mail Failed", "Mail Failed", null, "OK", null).Show (); } However, once the user selects Cancel | Delete Draft or Cancel | Save Draft or Send, the App throws a run-time error like the following: Stacktrace: at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004 at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004 at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26 at MonoTouch.UIKit.UIApplication.Main (string[]) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31 at MailDialog.Application.Main (string[]) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15 at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr) Native stacktrace: 0 MailDialog 0x000be66f mono_handle_native_sigsegv + 343 1 MailDialog 0x0000e43e mono_sigsegv_signal_handler + 313 2 libSystem.B.dylib 0x903e946b _sigtramp + 43 3 ??? 0xffffffff 0x0 + 4294967295 4 MessageUI 0x01a9f6b7 -[MFMailComposeController _close] + 284 5 UIKit 0x01f682f1 -[UIActionSheet(Private) _buttonClicked:] + 258 6 UIKit 0x01be1a6e -[UIApplication sendAction:to:from:forEvent:] + 119 7 UIKit 0x01c701b5 -[UIControl sendAction:to:forEvent:] + 67 8 UIKit 0x01c72647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527 9 UIKit 0x01c711f4 -[UIControl touchesEnded:withEvent:] + 458 10 UIKit 0x01c060d1 -[UIWindow _sendTouchesForEvent:] + 567 11 UIKit 0x01be737a -[UIApplication sendEvent:] + 447 12 UIKit 0x01bec732 _UIApplicationHandleEvent + 7576 13 GraphicsServices 0x03eb7a36 PurpleEventCallback + 1550 14 CoreFoundation 0x00df9064 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 52 15 CoreFoundation 0x00d596f7 __CFRunLoopDoSource1 + 215 16 CoreFoundation 0x00d56983 __CFRunLoopRun + 979 17 CoreFoundation 0x00d56240 CFRunLoopRunSpecific + 208 18 CoreFoundation 0x00d56161 CFRunLoopRunInMode + 97 19 GraphicsServices 0x03eb6268 GSEventRunModal + 217 20 GraphicsServices 0x03eb632d GSEventRun + 115 21 UIKit 0x01bf042e UIApplicationMain + 1160 22 ??? 0x0a1e4bd9 0x0 + 169757657 23 ??? 0x0a1e4b12 0x0 + 169757458 24 ??? 0x0a1e4515 0x0 + 169755925 25 ??? 0x0a1e4451 0x0 + 169755729 26 ??? 0x0a1e44ac 0x0 + 169755820 27 MailDialog 0x0000e202 mono_jit_runtime_invoke + 1360 28 MailDialog 0x001c92af mono_runtime_invoke + 137 29 MailDialog 0x001caf6b mono_runtime_exec_main + 714 30 MailDialog 0x001ca891 mono_runtime_run_main + 812 31 MailDialog 0x00094fe8 mono_jit_exec + 200 32 MailDialog 0x0027cf05 main + 3494 33 MailDialog 0x00002ca1 _start + 208 34 MailDialog 0x00002bd0 start + 40 Debug info from gdb: warning: Could not find object file "/var/folders/Ny/NyElTwhDGD8kZMqIEeLGXE+++TI/-Tmp-//cc6F1tBs.o" - no debug information available for "template.m". warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog Error connecting stdout and stderr (127.0.0.1:10001) warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Couldn't open object file '/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)' Attaching to process 9992. Reading symbols for shared libraries . done Reading symbols for shared libraries ....................................................................................................................... done 0x9038e459 in read$UNIX2003 () 8 0x903a8a12 in __workq_kernreturn () 7 "WebThread" 0x903830fa in mach_msg_trap () 6 0x903b10a6 in __semwait_signal () 5 0x90383136 in semaphore_wait_trap () 4 0x903830fa in mach_msg_trap () 3 0x903a8a12 in __workq_kernreturn () 2 "com.apple.libdispatch-manager" 0x903a9982 in kevent () * 1 "com.apple.main-thread" 0x9038e459 in read$UNIX2003 () Thread 8 (process 9992): 0 0x903a8a12 in __workq_kernreturn () 1 0x903a8fa8 in _pthread_wqthread () 2 0x903a8bc6 in start_wqthread () Thread 7 (process 9992): 0 0x903830fa in mach_msg_trap () 1 0x90383867 in mach_msg () 2 0x00df94a6 in __CFRunLoopServiceMachPort () 3 0x00d56874 in __CFRunLoopRun () 4 0x00d56240 in CFRunLoopRunSpecific () 5 0x00d56161 in CFRunLoopRunInMode () 6 0x04f7c423 in RunWebThread () 7 0x903b085d in _pthread_start () 8 0x903b06e2 in thread_start () Thread 6 (process 9992): 0 0x903b10a6 in __semwait_signal () 1 0x903dcee5 in nanosleep$UNIX2003 () 2 0x903dce23 in usleep$UNIX2003 () 3 0x0027714c in monotouch_pump_gc () 4 0x903b085d in _pthread_start () 5 0x903b06e2 in thread_start () Thread 5 (process 9992): 0 0x90383136 in semaphore_wait_trap () 1 0x0015ae1d in finalizer_thread (unused=0x0) at ../../../../mono/metadata/gc.c:1026 2 0x002034a3 in start_wrapper (data=0x7b16ba0) at ../../../../mono/metadata/threads.c:661 3 0x002448e2 in thread_start_routine (args=0x8037e34) at ../../../../mono/io-layer/wthreads.c:286 4 0x00274357 in GC_start_routine (arg=0x6ff7f60) at ../../../libgc/pthread_support.c:1390 5 0x903b085d in _pthread_start () 6 0x903b06e2 in thread_start () Thread 4 (process 9992): 0 0x903830fa in mach_msg_trap () 1 0x90383867 in mach_msg () 2 0x0011cc46 in mach_exception_thread (arg=0x0) at ../../../../mono/mini/mini-darwin.c:138 3 0x903b085d in _pthread_start () 4 0x903b06e2 in thread_start () Thread 3 (process 9992): 0 0x903a8a12 in __workq_kernreturn () 1 0x903a8fa8 in _pthread_wqthread () 2 0x903a8bc6 in start_wqthread () Thread 2 (process 9992): 0 0x903a9982 in kevent () 1 0x903aa09c in _dispatch_mgr_invoke () 2 0x903a9559 in _dispatch_queue_invoke () 3 0x903a92fe in _dispatch_worker_thread2 () 4 0x903a8d81 in _pthread_wqthread () 5 0x903a8bc6 in start_wqthread () Thread 1 (process 9992): 0 0x9038e459 in read$UNIX2003 () 1 0x000be81f in mono_handle_native_sigsegv (signal=11, ctx=0xbfffd238) at ../../../../mono/mini/mini-exceptions.c:1826 2 0x0000e43e in mono_sigsegv_signal_handler (_dummy=10, info=0xbfffd1f8, context=0xbfffd238) at ../../../../mono/mini/mini.c:4846 3 4 0x028d6a63 in objc_msgSend () 5 0x01ad469f in func.24012 () 6 0x01a9f6b7 in -[MFMailComposeController _close] () 7 0x01f682f1 in -[UIActionSheet(Private) _buttonClicked:] () 8 0x01be1a6e in -[UIApplication sendAction:to:from:forEvent:] () 9 0x01c701b5 in -[UIControl sendAction:to:forEvent:] () 10 0x01c72647 in -[UIControl(Internal) _sendActionsForEvents:withEvent:] () 11 0x01c711f4 in -[UIControl touchesEnded:withEvent:] () 12 0x01c060d1 in -[UIWindow _sendTouchesForEvent:] () 13 0x01be737a in -[UIApplication sendEvent:] () 14 0x01bec732 in _UIApplicationHandleEvent () 15 0x03eb7a36 in PurpleEventCallback () 16 0x00df9064 in CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION () 17 0x00d596f7 in __CFRunLoopDoSource1 () 18 0x00d56983 in __CFRunLoopRun () 19 0x00d56240 in CFRunLoopRunSpecific () 20 0x00d56161 in CFRunLoopRunInMode () 21 0x03eb6268 in GSEventRunModal () 22 0x03eb632d in GSEventRun () 23 0x01bf042e in UIApplicationMain () 24 0x0a1e4bd9 in ?? () 25 0x0a1e4b12 in ?? () 26 0x0a1e4515 in ?? () 27 0x0a1e4451 in ?? () 28 0x0a1e44ac in ?? () 29 0x0000e202 in mono_jit_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/mini/mini.c:4733 30 0x001c92af in mono_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/metadata/object.c:2615 31 0x001caf6b in mono_runtime_exec_main (method=0xa806e6c, args=0xa6a34e0, exc=0x0) at ../../../../mono/metadata/object.c:3581 32 0x001ca891 in mono_runtime_run_main (method=0xa806e6c, argc=0, argv=0xbfffeef4, exc=0x0) at ../../../../mono/metadata/object.c:3355 33 0x00094fe8 in mono_jit_exec (domain=0x6f8fe58, assembly=0xa200730, argc=1, argv=0xbfffeef0) at ../../../../mono/mini/driver.c:1094 34 0x0027cf05 in main () ================================================================= Got a SIGSEGV while executing native code. This usually indicates a fatal error in the mono runtime or one of the native libraries used by your application. Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr) at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26 at MonoTouch.UIKit.UIApplication.Main (System.String[] args) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31 at MailDialog.Application.Main (System.String[] args) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15 I have a very simple sample project illustrating the problem. I can sent you if required.

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  • When to use weak references in Python?

    - by bodacydo
    Can anyone explain usage of weak references? The documentation doesn't explain it precisely, it just says that the GC can destroy the object linked to via a weak reference at any time. Then what's the point of having an object that can disappear at any time? What if I need to use it right after it disappeared? Can you please explain them with some good examples? Thanks, Boda Cydo.

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  • Garbage collection in Perl

    - by srikfreak
    Unlike Java, Perl uses reference count for garbage collection. I have tried searching some previous questions which speak about C++ RAII and smart pointers and Java GC but have not understood how Perl deals with the circular referencing problem. Can anyone explain how Perl's garbage collector deals with circular references? Is there any way to reclaim circular referenced memory which are no longer used by the program or does Perl just ignores this problem altogether?

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  • Windows Service HTTPListener Memory Issue

    - by crawshaws
    Hi all, Im a complete novice to the "best practices" etc of writing in any code. I tend to just write it an if it works, why fix it. Well, this way of working is landing me in some hot water. I am writing a simple windows service to server a single webpage. (This service will be incorperated in to another project which monitors the services and some folders on a group of servers.) My problem is that whenever a request is recieved, the memory usage jumps up by a few K per request and keeps qoing up on every request. Now ive found that by putting GC.Collect in the mix it stops at a certain number but im sure its not meant to be used this way. I was wondering if i am missing something or not doing something i should to free up memory. Here is the code: Public Class SimpleWebService : Inherits ServiceBase 'Set the values for the different event log types. Public Const EVENT_ERROR As Integer = 1 Public Const EVENT_WARNING As Integer = 2 Public Const EVENT_INFORMATION As Integer = 4 Public listenerThread As Thread Dim HTTPListner As HttpListener Dim blnKeepAlive As Boolean = True Shared Sub Main() Dim ServicesToRun As ServiceBase() ServicesToRun = New ServiceBase() {New SimpleWebService()} ServiceBase.Run(ServicesToRun) End Sub Protected Overrides Sub OnStart(ByVal args As String()) If Not HttpListener.IsSupported Then CreateEventLogEntry("Windows XP SP2, Server 2003, or higher is required to " & "use the HttpListener class.") Me.Stop() End If Try listenerThread = New Thread(AddressOf ListenForConnections) listenerThread.Start() Catch ex As Exception CreateEventLogEntry(ex.Message) End Try End Sub Protected Overrides Sub OnStop() blnKeepAlive = False End Sub Private Sub CreateEventLogEntry(ByRef strEventContent As String) Dim sSource As String Dim sLog As String sSource = "Service1" sLog = "Application" If Not EventLog.SourceExists(sSource) Then EventLog.CreateEventSource(sSource, sLog) End If Dim ELog As New EventLog(sLog, ".", sSource) ELog.WriteEntry(strEventContent) End Sub Public Sub ListenForConnections() HTTPListner = New HttpListener HTTPListner.Prefixes.Add("http://*:1986/") HTTPListner.Start() Do While blnKeepAlive Dim ctx As HttpListenerContext = HTTPListner.GetContext() Dim HandlerThread As Thread = New Thread(AddressOf ProcessRequest) HandlerThread.Start(ctx) HandlerThread = Nothing Loop HTTPListner.Stop() End Sub Private Sub ProcessRequest(ByVal ctx As HttpListenerContext) Dim sb As StringBuilder = New StringBuilder sb.Append("<html><body><h1>Test My Service</h1>") sb.Append("</body></html>") Dim buffer() As Byte = Encoding.UTF8.GetBytes(sb.ToString) ctx.Response.ContentLength64 = buffer.Length ctx.Response.OutputStream.Write(buffer, 0, buffer.Length) ctx.Response.OutputStream.Close() ctx.Response.Close() sb = Nothing buffer = Nothing ctx = Nothing 'This line seems to keep the mem leak down 'System.GC.Collect() End Sub End Class Please feel free to critisise and tear the code apart but please BE KIND. I have admitted I dont tend to follow the best practice when it comes to coding.

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  • Does Marshal.ReleaseComObject call the garbage collector ?

    - by Shimrod
    Hi, I was asked this question today by a colleague, and couldn't find any clue on the Internet... Can someone tell me if calling Marshall.ReleaseComObject()directly calls the garbage collector ? As I understand it, it only removes COM references, and then the G.C. cleans memory on its next pass, but I can be mistaken... Thanks in advance for your help!

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  • Sun permgen & JRockit garbage collection

    - by Striker
    In the Sun JVM, classes that are loaded by the class loader are put in permgen space and never gc'd. (Unless the class loader goes out of scope) It's my understanding that JRockit puts that same data on the heap instead. Is that data then subject to garbage collection? Thanks.

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  • Why Java servlet can't get Paypal IPN messages everytime ?

    - by Frank
    I have a Java servlet running on my notebook with Windows Vista, I set up a static IP, did port forwarding and registered for a free DDNS service, now my servlet is running, I gave the url to Paypal to send me IPN messages, I went on to it's sandbox site got to the test tools page, tried to send test messages by clicking the "Send IPN" button, most of the time it would fail, the error is : "IPN delivery failed. Unable to connect to the specified URL. Please verify the URL and try again." But maybe 1 in 10 times, it might be successful and my servlet would get the message, and I looked at the messages I got, they are in correct format. So I called Paypal asking why, he said I shouldn't run the servlet on my notebook, in stead I should run it on the web server, but I told him my ISP doesn't support Java on their server, and since I did all the above steps, shouldn't it be the same to run the servlet on my notebook ? He said his test showed he couldn't get to my servlet, but I asked why maybe 1 in 10 times it could get through ? If there is something wrong with running it on my notebook, then 100% times it should fail, am I correct on this point ? But anyway he said that's all he could do, and I should troubleshoot it myself. The servlet looks like this : import java.io.*; import java.net.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; public class PayPal_Servlet extends HttpServlet { static boolean Debug=true; static String PayPal_Url="https://www.paypal.com/cgi-bin/webscr",Sandbox_Url="https://www.sandbox.paypal.com/cgi-bin/webscr", Dir_License_Messages="C:/Dir_License_Messages/"; static TransparencyExample Transparency_Example; static PayPal_Message_To_License_File_Worker PayPal_message_to_license_file_worker; // Initializes the servlet. public void init(ServletConfig config) throws ServletException { super.init(config); if (!new File(Dir_License_Messages).exists()) new File(Dir_License_Messages).mkdirs(); System.gc(); } /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods. * @param request servlet request * @param response servlet response */ protected void processRequest(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { // Read post from PayPal system and add 'cmd' Enumeration en=request.getParameterNames(); String str="cmd=_notify-validate"; while (en.hasMoreElements()) { String paramName=(String)en.nextElement(); String paramValue=request.getParameter(paramName); str=str+"&"+paramName+"="+URLEncoder.encode(paramValue); } // Post back to PayPal system to validate // NOTE: change http: to https: in the following URL to verify using SSL (for increased security). // using HTTPS requires either Java 1.4 or greater, or Java Secure Socket Extension (JSSE) and configured for older versions. URL u=new URL(Debug?Sandbox_Url:PayPal_Url); URLConnection uc=u.openConnection(); uc.setDoOutput(true); uc.setRequestProperty("Content-Type","application/x-www-form-urlencoded"); PrintWriter pw=new PrintWriter(uc.getOutputStream()); pw.println(str); pw.close(); BufferedReader in=new BufferedReader(new InputStreamReader(uc.getInputStream())); String res=in.readLine(); in.close(); // Assign posted variables to local variables String itemName=request.getParameter("item_name"); String itemNumber=request.getParameter("item_number"); String paymentStatus=request.getParameter("payment_status"); String paymentAmount=request.getParameter("mc_gross"); String paymentCurrency=request.getParameter("mc_currency"); String txnId=request.getParameter("txn_id"); String receiverEmail=request.getParameter("receiver_email"); String payerEmail=request.getParameter("payer_email"); if (res.equals("VERIFIED")) // Check notification validation { // check that paymentStatus=Completed // check that txnId has not been previously processed // check that receiverEmail is your Primary PayPal email // check that paymentAmount/paymentCurrency are correct // process payment } else if (res.equals("INVALID")) // Log for investigation { } else // Log for error { } // =========================================================================== if (txnId!=null) { Write_File_Safe_Fast(Dir_License_Messages+txnId+".txt",new StringBuffer(str.replace("&","\n")),false); } // =========================================================================== String Message_File_List[]=Tool_Lib.Get_File_List_From_Dir(Dir_License_Messages); response.setContentType("text/html"); PrintWriter out=response.getWriter(); String title="Reading All Request Parameters",Name="",Value; out.println("<Html><Head><Title>"+title+"</Title></Head>\n<Body Bgcolor=\"#FDF5E6\">\n<H1 Align=Center>"+title+"</H1>\n"+ "<Table Border=1 Align=Center>\n"+"<Tr Bgcolor=\"#FFAD00\"><Th>Parameter Name</Th><Th>Parameter Value(s) Messages = "+Message_File_List.length+"</Th></Tr>"); Enumeration paramNames=request.getParameterNames(); while(paramNames.hasMoreElements()) { String paramName=(String)paramNames.nextElement(); out.print("<Tr><Td>"+paramName+"</Td><Td>"); String[] paramValues=request.getParameterValues(paramName); if (paramValues.length == 1) { String paramValue=paramValues[0]; if (paramValue.length() == 0) out.print("<I>No Value</I>"); else { out.println(paramValue+"</Td></Tr>"); // Out("paramName = "+paramName+" paramValue = "+paramValue); // if (paramName.startsWith("Name")) Name=paramValue; // else if (paramName.startsWith("Value")) Write_File_Safe_Fast("C:/Dir_Data/"+Name,new StringBuffer(paramValue),false); } } else { out.println("<Ul>"); for (int i=0;i<paramValues.length;i++) out.println("<Li>"+paramValues[i]); out.println("</Ul></Td</Tr>"); } } out.println("</Table>\n</Body></Html>"); } /** Handles the HTTP <code>GET</code> method. * @param request servlet request * @param response servlet response */ protected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { processRequest(request,response); } /** Handles the HTTP <code>POST</code> method. * @param request servlet request * @param response servlet response */ protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { processRequest(request,response); } // Returns a short description of the servlet. public String getServletInfo() { return "Short description"; } // Destroys the servlet. public void destroy() { System.gc(); } public static void Write_File_Safe_Fast(String File_Path,StringBuffer Str_Buf,boolean Append) { FileOutputStream fos=null; BufferedOutputStream bos=null; try { fos=new FileOutputStream(File_Path,Append); bos=new BufferedOutputStream(fos); for (int j=0;j<Str_Buf.length();j++) bos.write(Str_Buf.charAt(j)); } catch (Exception e) { e.printStackTrace(); } finally { try { if (bos!=null) { bos.close(); bos=null; } if (fos!=null) { fos.close(); fos=null; } } catch (Exception ex) { ex.printStackTrace(); } } System.gc(); } } I use Netbean6.7 to develop the servlet, and the code was from Paypal's JSP sample code, what can I do to debug the problem ?

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