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• Portable Eclipse

  - by Jeach

  I'm trying to port my entire 'workspace' to a USB key (including the Eclipse executable) so that I can carry my work anywhere with me and work off the key directly. My directory hierarchy is similar to this: /workspace/eclipse - Where my current eclipse binary is stored /workspace/codebase - Where I keep the root of all my eclipse projects /workspace/resources - Where I keep all project files (images, docs, libs, etc.) It all works perfectly fine on one system. But when I change over to another system, the USB key gets mounted on another drive. For example, on my laptop, I get 'E:\', on my PC, I get 'K:\' and at work I get 'F:\', etc, etc. This means that because Eclipse (for 'some' reason) seems to only use full path names (including driver letters) in every single one of its configuration files (such as .classpath), nothing ever works when I want to work on another system. I put a 'libs' directory in the base of every project and populate it with its dependent JAR files. Why doesn't it use relative names instead, so that I could specify something like "../../libs/log4j.jar"? Anyone know how to fix this problem? Does anyone know of a workaround for this? For some reason, I really doubt I'm the first developer to do this! Thanks for your help and any suggestions.

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• TreeView update bug in the VB.NET

  - by CFP

  Consider the following code: Dim Working As Boolean = False Private Sub TreeView1_AfterCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterCheck If Working Then Exit Sub Working = True e.Node.Checked = Not e.Node.Checked Working = False End Sub Private Sub TreeView1_MouseClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TreeView1.MouseClick If e.Button = Windows.Forms.MouseButtons.Right Then MsgBox("Checked = " & TreeView1.SelectedNode.Checked) End Sub Where TreeView1 is a TreeView added to the form, with CheckBoxes set to true and one node added. The code basically cancel any node checking occuring on the form. Single-clicking the top node to check it works well : your click is immediately canceled. Yet if you double-click the checkbox, it will display a tick. But verifying the check state through a right click will yield a Checked = False dialog. How come? Is it a bug (I'm using the latest .Net Framework 4.0, and he same occurs in 2.0), or am I doing something wrong here? Is there a work around? Thanks! EDIT: Additionally, the MouseDoubleClick event is not raised before you click once again. EDIT 2: Posted a bug report at Microsoft Connect

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• Namespace scoped aliases for generic types in C#

  - by TN

  Let's have a following example: public class X { } public class Y { } public class Z { } public delegate IDictionary<Y, IList<Z>> Bar(IList<X> x, int i); public interface IFoo { // ... Bar Bar { get; } } public class Foo : IFoo { // ... public Bar Bar { get { return null; //... } } } void Main() { IFoo foo; //= ... IEnumerable<IList<X>> source; //= ... var results = source.Select(foo.Bar); } The compiler says: The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. It's because, it cannot convert Bar to Func<IList<X>, int, IDictionary<Y, IList<Z>>>. It would be great if I could create type namespace scoped type aliases for generic types in C#. Then I would define Bar not as a delegate, but rather I would define it as an namespace scoped alias for Func<IList<X>, int, IDictionary<Y, IList<Z>>>. public alias Bar = Func<IList<X>, int, IDictionary<Y, IList<Z>>>; I could then also define namespace scoped alias for e.g. IDictionary<Y, IList<Z>>. And if used appropriately:), it will make the code more readable. Now I have inline the generic types and the real code is not well readable:( Have you find the same trouble:)? Is there any good reason why it is not in C# 3.0? Or there is no good reason, it's just matter of money and/or time? EDIT: I know that I can use using, but it is not namespace based - not so convenient for my case.

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• Error handling approach on PHP

  - by Industrial

  Hi everybody, We have a web server that we're about to launch a number of applications onto. They will all share database and memcached servers, but each application has it's own mySQL database and all memcached keys per application, is prefixed. Possible scenario: If a memcached server in our cluster goes boom, we want someone (operative system admin) to be automatically contacted by email/iphone push notification or in any other appropriate way. If we we're about to install 150 identical applications for our customers on our servers, and a memcached server dies - all 150 applications will individually find this out and contact our system admin, which most certainly is going to think about getting a new job where he or she isn't about to be woken up by getting 150 messages sent 4:15 in the morning. Possible solution: One idea is to set up an external server for error handling that gets a $_POST or cURL request sent, and handles storage of the error message depending on the seriousness of the actual error message. It would of course check upon receiving the error call, that if the same memcached server have already been reported as offline, there would be no need to spam the system admin with additional reminders... The questions: What's a good approach on how to handle errors? How does the big guys in the industry handle this? Thanks!

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• Finding occurrences of element before and after the element in Array

  - by user3718040

  I am writing a algorithm, if an array contain 3 does not contain between two 1s. like this int array={5, 2, 10, 3, 15, 1, 2, 2} the above array contain 3, before 3 there is no 1 and after 3 is one 1 it should return True. int array={3,2,18,1,0,3,-11,1,3} in this array after first element of 3 there is two 1 it should return False. I have try following code public class Third { public static void main(String[] args){ int[] array = {1,2,4,3, 1}; for(int i=0;i<array.length;i++) { if(array[i]==3) { for(int j=0;j<array[i];j++) { if(array[j]==1) { System.out.println("I foud One before "+array[j]); }else { break; } System.out.println("yes i found the array:"+array[i]); } for(int z=0;z>array[i];z++) { if(array[z]==1) { System.out.println("I found after 3 is :"+array[z]); } break; } } } } } I am not getting exact result from my above code which i want.

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• How to re-enable the idle timer in ios once it has been disabled (to allow the display to sleep again)?

  - by lindon fox

  I have figured out how to stop an iOS device from going to sleep (see below), but I am having troubles undoing that setting. According to the Apple Documentation, it should just be changing the value of the idleTimerDisabled property. But when I test this, it does not work. This is how I am initially stopping the device from going to sleep: //need to switch off and on for it to work initially [UIApplication sharedApplication].idleTimerDisabled = NO; [UIApplication sharedApplication].idleTimerDisabled = YES; I would have thought that the following would do the trick: [UIApplication sharedApplication].idleTimerDisabled = NO; From the Apple Documentation: The default value of this property is NO. When most applications have no touches as user input for a short period, the system puts the device into a "sleep” state where the screen dims. This is done for the purposes of conserving power. However, applications that don't have user input except for the accelerometer—games, for instance—can, by setting this property to YES, disable the “idle timer” to avert system sleep. Important: You should set this property only if necessary and should be sure to reset it to NO when the need no longer exists. Most applications should let the system turn off the screen when the idle timer elapses. This includes audio applications. With appropriate use of Audio Session Services, playback and recording proceed uninterrupted when the screen turns off. The only applications that should disable the idle timer are mapping applications, games, or similar programs with sporadic user interaction. Has anyone come across this problem? I am testing on iOS6 and iOS5. Thanks in advance.

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• Java: Inputting text from a file using split

  - by 00PS

  I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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• transferring binary files between systems

  - by tim

  Hi guys I'm trying to transfer my files between 2 UNIX clusters, the data is pure numeric (vectors of double) in binary form. Unfortunately one of the systems is IBM ppc997 and the other is AMD Opteron, It seems the format of binary numbers in these systems are different. I have tried 3 ways till now: 1- Changed my files to ASCII format (i.e. saved a number at each line in a text file), sent them to the destination and changed them again to binary on the target system (they both are UNIX, no end of line character difference??!) 2- Sent pure binaries to the destination 3- used uuencode sent them to the destination and decoded them Unfortunately any of these methods does not work (my code in the destination system generates garbage, while it works on the first system, I'm 100% sure the code itself is portable). I don't know what else I can do? Do you have any idea? I'm not a professional, please don't use computer scientists terminology! And: my codes are in C, so by binary I mean a one to one mapping between memory and hard disk. Thanks

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• Parsing Windows Event Logs, is it possible?

  - by xceph

  Hello, I am doing a little research into the feasibility of a project I have in mind. It involves doing a little forensic work on images of hard drives, and I have been looking for information on how to analyze saved windows event log files. I do not require the ability to monitor current events, I simply want to be able to view events which have been created, and record the time and application/process which created those events. However I do not have much experience in the inner workings of the windows system specifics, and am wondering if this is possible? The plan is to create images of a hard drive, and then do the analysis on a second machine. Ideally this would be done in either Java or Python, as they are my most proficient languages. The main concerns I have are as follows: Is this information encrypted in anyway? Are there any existing API for parsing this data directly? Is there information available regarding the format in which these logs are stored, and how does it differ from windows versions? This must be possible from analyzing the drive itself, as ideally the installation of windows on the drive would not be running, (as it would be a mounted image on another system) The closest thing I could find in my searches is http://www.j-interop.org/ but that seems to be aimed at remote clients. Ideally nothing would have to be installed on the imaged drive. The other solution which seemed to also pop up is the JNI library, but that also seems to be more so in the area of monitoring a running system. Any help at all is greatly appreciated. :)

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• Can this line of code really throw an IndexOutOfRange exception?

  - by Jonathan M

  I am getting an IndexOutOfRange exception on the following line of code: var searchLastCriteria = (SearchCriteria)Session.GetSafely(WebConstants.KeyNames.SEARCH_LAST_CRITERIA); I'll explain the above here: SearchCriteria is an Enum with only two values Session is the HttpSessionState GetSafely is an extension method that looks like this: public static object GetSafely(this HttpSessionState source, string key) { try { return source[key]; } catch (Exception exc) { log.Info(exc); return null; } } WebConstants.KeyNames.SEARCH_LAST_CRITERIA is simply a constant I've tried everything to replicate this error, but I cannot reproduce it. I am beginning to think the stack trace is wrong. I thought perhaps the exception was actually coming from the GetSafely call, but it is swallowing the exceptions, so that can't be the case, and even if it was, it should show up in the stack trace. Is there anything in the line of code above that could possible throw an IndexOutOfRange exception? I know the line will throw an NullReferenceException if GetSafely returns null, and it will also throw an InvalidCastException if it returns anything that cannot be cast to SearchCriteria, but an IndexOutOfRange exception? I'm scratching my head here. Here is the stack trace: $LOG--> 2010-06-11 07:01:33,814 [ERROR] SERVERA (14) Web.Global - Index was outside the bounds of the array. System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.IndexOutOfRangeException: Index was outside the bounds of the array. at IterateSearchResult(Boolean next) in C:\Projects\Web\UserControls\AccountHeader.ascx.cs:line 242 at nextAccountLink_Click(Object sender, EventArgs e) in C:\Projects\Web\UserControls\AccountHeader.ascx.cs:line 232

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• log activity. intrusion detection. user event notification ( interraction ). messaging

  - by Julian Davchev

  Have three questions that I somehow find related so I put them in same place. Currently building relatively large LAMP system - making use of messaging(activeMQ) , memcache and other goodies. I wonder if there are best practices or nice tips and tricks on howto implement those. System is user aware - meaning all actions done can be bind to particular logged user. 1. How to log all actions/activities of users? So that stats/graphics might be extracted later for analysing. At best that will include all url calls, post data etc etc. Meaning tons of inserts. I am thinking sending messages to activeMQ and later cron dumping in DB and cron analysing might be good idea here. Since using Zend Framework I guess I may use some request plugin so I don't have to make the log() call all over the code. 2.How to log stuff so may be used for intrusion detection? I know most things might be done on http level using apache mods for example but there are also specific cases like (5 failed login attempts in a row (leads to captcha) etc etc..) This also would include tons of inserts. Here I guess direct usage of memcache might be best approach as data don't seem vital to be permanantly persisted. Not sure if cannot use data from point 1. 3.System will notify users of some events. Like need approval , something broke..whatever.Some events will need feedback(action) from user, others are just informational. Wonder if there is common solutions for needs like this. Example: Based on occuring event(s) user will be notifed (user inbox for example) what happend. There will be link or something to lead him to details of thingy that happend and take action accordingly. Those seem trivial at first look but problem I see if coding it directly is becoming really fast hard to maintain.

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• [VB.Net] TreeView update bug in the .net framework

  - by CFP

  Consider the following code: Dim Working As Boolean = False Private Sub TreeView1_AfterCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterCheck If Working Then Exit Sub Working = True e.Node.Checked = Not e.Node.Checked Working = False End Sub Private Sub TreeView1_MouseClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TreeView1.MouseClick If e.Button = Windows.Forms.MouseButtons.Right Then MsgBox("Checked = " & TreeView1.SelectedNode.Checked) End Sub Where TreeView1 is a TreeView added to the form, with CheckBoxes set to true and one node added. The code basically cancel any node checking occuring on the form. Single-clicking the top node to check it works well : your click is immediately canceled. Yet if you double-click the checkbox, it will display a tick. But verifying the check state through a right click will yield a Checked = False dialog. How come? Is it a bug (I'm using the latest .Net Framework 4.0, and he same occurs in 2.0), or am I doing something wrong here? Is there a work around? Thanks! EDIT: Additionally, the MouseDoubleClick event is not raised before you click once again.

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• Computer Science taxonomy

  - by Bakhtiyor

  I am developing web application where users have collection of tags. I need to create a suggestion list for users based on the similarity of their tags. For example, when a user logs in to the system, system gets his tags and search these tags in the DB of users and showing users who have similar tags. For instance if User 1 has following tags [Linux, Apache, MySQL, PHP] and User 2 has [Windows, IIS, PHP, MySQL] it says that User 2 matchs User 1 with a weight of 50%, because he has 2 similar tags(PHP and MySQL). But imagine the situation where User 1 has [ASP, IIS, MS Access] and User 2 has [PHP, Apache, MySQL]. In this situation my system doesn't suggest User 2 as a "friend" to User 1 or vice versa. But we now that these two users has similarity on the the field of work, both works on Web Technology (or Web Programming, etc). So, that is why I need kind of taxonomy of computer science (right now, but probably I would need taxonomy of other fields also, like medicine, physics, mathematics, etc.) where these concepts are categorized and so that when I search for similarity of ASP and PHP, for example, it can say that they have similarity and belong into one group(or category). I hope I described my problem clearly, but if something wrong explained would be happy for your corrections. Thanks

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• Java File Handling, what did I do wrong?

  - by Urda

  Wrote up a basic file handler for a Java Homework assignment, and when I got the assignment back I had some notes about failing to catch a few instances: Buffer from file could have been null. File was not found File stream wasn't closed Here is the block of code that is used for opening a file: /** * Create a Filestream, Buffer, and a String to store the Buffer. */ FileInputStream fin = null; BufferedReader buffRead = null; String loadedString = null; /** Try to open the file from user input */ try { fin = new FileInputStream(programPath + fileToParse); buffRead = new BufferedReader(new InputStreamReader(fin)); loadedString = buffRead.readLine(); fin.close(); } /** Catch the error if we can't open the file */ catch(IOException e) { System.err.println("CRITICAL: Unable to open text file!"); System.err.println("Exiting!"); System.exit(-1); } The one comment I had from him was that fin.close(); needed to be in a finally block, which I did not have at all. But I thought that the way I have created the try/catch it would have prevented an issue with the file not opening. Let me be clear on a few things: This is not for a current assignment (not trying to get someone to do my own work), I have already created my project and have been graded on it. I did not fully understand my Professor's reasoning myself. Finally, I do not have a lot of Java experience, so I was a little confused why my catch wasn't good enough.

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• Why doesn't `stdin.read()` read entire buffer?

  - by Shookie

  I've got the following code: def get_input(self): """ Reads command from stdin, returns its JSON form """ json_string = sys.stdin.read() print("json string is: "+json_string) json_data =json.loads(json_string) return json_data It reads a json string that was sent to it from another process. The json is read from stdin. For some reason I get the following output: json string is: <Some json here> json string is: Traceback (most recent call last): File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 63, in <module> manager.accept_commands() File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 49, in accept_commands json_data = self.get_input() File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 42, in get_input json_data =json.loads(json_string) File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py", line 338, in loads return _default_decoder.decode(s) File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py", line 365, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py", line 383, in raw_decode raise ValueError("No JSON object could be decoded") So for some reason it reads an empty string from stdin instead of reading only the json. I've checked, and the code that writes to this process's stdin writes to it only once. What's wrong here?

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• open a text file only if not opened alread (open in NotePad)

  - by Mr_Green

  In my project, I am trying to open a text file. Well the below code works but when the user click the button again and again, many files are being opened. (which I dont want) System.Diagnostics.Process.Start(filePath); I also tried Link , File.Open and File.OpenText which are not opening the text file and also not showing any error (tried with try catch block) File.Open(filePath); (or) File.OpenText(filePath); (or) FileStream fileStream = new FileStream(filePath, FileMode.Open); I also tried this: (ERROR : Cannot be accessed with instance reference qualify with a type name instead) System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.Start(filePath); /*red scribbles here*/ proc.WaitForExit(); How to show only one instance of the Text file(.txt). am I doing something wrong in my attempts? please suggest. EDIT: I want to open other text files afterwards but not the same and also the application should be accessible after opening a text file(or many). I have only one form.

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• How to create anroid to send to work in my place?

  - by aj-sin-dhal

  Hi I would like to create a life like android/robot to send to work in my place. Requirements 1) People should not be able to tell the difference between me and the android. My first attempt may not be perfect but I can tell people that its my twin that was dropped on its head while we were growing up. 2) Should have the same weight as me so it won't crush small children if it falls over. By small children I mean those above 7 years old. Those below 7 can easily be crushed by a normal human adult so it is not important to consider that special case. 3) Should run on linux. I have a tight budget and cannot afford to pay for any propreitary operating system. Will consider writing my own operating system if this is the best way to go. I am reading "The design of the unix operating system" by Maurice J. Bach currently. That should be useful. I also have an old copy of the dragon book. What other books should I read? I would like to finish this by monday if possible. I don't like working on mondays. I have made a start and have picked some clothes and shoes for my android worker. Any help will be appreciated. This is a serious question. AJ

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• database table design

  - by e.b.white

  I design the tables as below for the system which looks like a package delivering system For example, after user received the package, postman should record in system, and the state(history table) is "delivered",and operator is this postman, the current state(state table) is of course "delivered" history table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | package_state | +---------------+--------------------------+ | operators | operators | +---------------+--------------------------+ | create_time| create_time | +---------------+--------------------------+ state table: +---------------+--------------------------+ | Field | Desc | +---------------+--------------------------+ | id | PRIMARY KEY | +---------------+--------------------------+ | package_id | package_tacking_id | +---------------+--------------------------+ | state | latest_package_state | +---------------+--------------------------+ Above is just the basic information to record, some other information( like invoice, destination,...) should be recored as well. But there are different service types like s1 and s2, for s1 it is not needed to record invoice but s1 need, and maybe s1 need some other information to record (like the tel of end user). After all, at delivering way stations there are additional information to record, and for different service type the information type is different. My question is: 1. For different service type, shall I need to declare different tables(option A) or just one big table which can record all information for all types(option B)? 2. If option A, since the basic information above is MUST, how can prevent from declaring there duplicate fields in different tables?

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• Set the amount of rows JList show (Java)

  - by Alex Cheng

  Hi all. Problem: I have a method that creates a list from the parsed ArrayList. I manage to show the list in the GUI, without scrollbar. However, I am having problem setting it to show only the size of ArrayList. Meaning, say if the size is 6, there should only be 6 rows in the shown List. Below is the code that I am using. I tried setting the visibleRowCount as below but it does not work. I tried printing out the result and it shows that the change is made. private void createSuggestionList(ArrayList<String> str) { int visibleRowCount = str.size(); System.out.println("visibleRowCount " + visibleRowCount); listForSuggestion = new JList(str.toArray()); listForSuggestion.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); listForSuggestion.setSelectedIndex(0); listForSuggestion.setVisibleRowCount(visibleRowCount); System.out.println(listForSuggestion.getVisibleRowCount()); listScrollPane = new JScrollPane(listForSuggestion); MouseListener mouseListener = new MouseAdapter() { @Override public void mouseClicked(MouseEvent mouseEvent) { JList theList = (JList) mouseEvent.getSource(); if (mouseEvent.getClickCount() == 2) { int index = theList.locationToIndex(mouseEvent.getPoint()); if (index >= 0) { Object o = theList.getModel().getElementAt(index); System.out.println("Double-clicked on: " + o.toString()); } } } }; listForSuggestion.addMouseListener(mouseListener); textPane.add(listScrollPane); repaint(); } To summarize: I want the JList to show as many rows as the size of the parsed ArrayList, without a scrollbar. Any ideas? Please help. Thanks. Please let me know if a picture of the problem is needed in case I did not phrase my question correctly.

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• Downloading Large JSON File to local file using Java

  - by user1279675

  I'm attempting to download a JSON from the following URL - http://api.crunchbase.com/v/1/companies.js - to a local file. I'm using Java 1.7 and the following JSON Libraries - http://www.json.org/java/ - to attempt to make it work. Here's my code: public static void download(String address, String localFileName) { OutputStream out = null; URLConnection conn = null; InputStream in = null; try { URL url = new URL(address); out = new BufferedOutputStream( new FileOutputStream(localFileName)); conn = url.openConnection(); in = conn.getInputStream(); byte[] buffer = new byte[1024]; int numRead; long numWritten = 0; while ((numRead = in.read(buffer)) != -1) { out.write(buffer, 0, numRead); numWritten += numRead; System.out.println(buffer.length); System.out.println(" " + buffer.hashCode()); } System.out.println(localFileName + "\t" + numWritten); } catch (Exception exception) { exception.printStackTrace(); } finally { try { if (in != null) { in.close(); } if (out != null) { out.close(); } } catch (IOException ioe) { } } } When I run the code everything seems to work until midway through the loop the program seems to stop and not continue reading the JSON Object. Does anyone know why this would stop reading? How could I fix the issue?

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• Why doesn't String's hashCode() cache 0?

  - by polygenelubricants

  I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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• I'm confused about Polymorphism

  - by Vtanathip

  I'm know polymorphism rule that we can send it via parameter like this code interface Animal { void whoAmI(); } class A implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("A"); } } class B implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("B"); } } class RuntimePolymorphismDemo { public void WhoRU(List t){ System.out.println(t.getClass()); } public static void main(String[] args) { A a = new A(); B b = new B(); RuntimePolymorphismDemo rp = new RuntimePolymorphismDemo(); rp.WhoRU(a); rp.WhoRU(b); } } but List<Example> examples = new ArrayList<Example>(); This code,I'm don't understand why we must use List. why we can't use like this? ArrayList<Example> examples = new ArrayList<Example>(); Because when we use List we can't use method that only have in ArrayList class like trimToSize() and How I know when to use or not use?

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• Stopping process in /etc/inittab kills spawned process. Doesn't happen in rc.local.

  - by Paul

  Hi, I'm trying to execute a firmware upgrade while my programming is running in inittab. My program will run 2 commands. One to extract the installer script from the tarball and the other to execute the installer script. In my code I'm using the system() function call. These are the 2 command strings below, system ( "tar zvxf tarball.tar.gz -C / installer.sh 2>&1" ); system( "nohup installer.sh tarball >/dev/null 2>&1 &" ); The installer script requires the tarball to be an argument. I've tried using sudo but i still have the same problem. I've tried nohup with no success. The installer script has to kill my program when doing the firmware upgrade but the installer script will stay alive. If my program is run from the command line or rc.local, on my target device, my upgrade works fine, i.e. when my program is killed my installer script continues. But I need to run my program from /etc/inittab so it can respawn if it dies. To stop my program in inittab the installer script will hash it out and execute "telinit q". This is where my program dies (but thats what I want it to do), but it also kills my installer script. Does anyone know why this is happening and what can I do to solve it? Thanks in advance.

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• If not following correct procedure?

  - by ct2k7

  Hi, I'm working on a Content Management System, and so far so good. I'm trying to get the system to work with a maintenance mode system. This is the code in the script to display the maintenance stuff: if ($maintenance['value'] == "1") {?> <div id="content"> <div id="errmsg"> <?php echo $maintenance['notes']; ?> </div> </div> <? } else {?> <h1><?php echo $title; ?></h1> <hr /><br /> <div id="content"> <?php echo $contents; if (!$content) { include ('includes/error/404.php');}?> </div> <? } ?> I can verify that the $maintenance['value'] variable is working as it should, but this portion o the script isn't working as it should. The value is currently set to 1, but it still displays the stuff in the else. Any ideas?

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• Can I make a derived class inherit a derived member from its base class in Java?

  - by Eric

  I have code that looks like this: public class A { public void doStuff() { System.out.print("Stuff successfully done"); } } public class B extends A { public void doStuff() { System.out.print("Stuff successfully done, but in a different way"); } public void doMoreStuff() { System.out.print("More advanced stuff successully done"); } } public class AWrapper { public A member; public AWrapper(A member) { this.member = member; } public void doStuffWithMember() { a.doStuff(); } } public class BWrapper extends AWrapper { public B member; public BWrapper(B member) { super(member); //Pointer to member stored in two places: this.member = member; //Not great if one changes, but the other does not } public void doStuffWithMember() { member.doMoreStuff(); } } However, there is a problem with this code. I'm storing a reference to the member in two places, but if one changes and the other does not, there could be trouble. I know that in Java, an inherited method can narrow down its return type (and perhaps arguments, but I'm not certain) to a derived class. Is the same true of fields?

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