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  • Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

    - by gojomo
    I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

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  • LinkedList insert tied to inserted object

    - by wrongusername
    I have code that looks like this: public class Polynomial { List<Term> term = new LinkedList<Term>(); and it seems that whenever I do something like term.add(anotherTerm), with anotherTerm being... another Term object, it seems anotherTerm is referencing the same thing as what I've just inserted into term so that whenever I try to change anotherTerm, term.get(2) (let's say) get's changed too. How can I prevent this from happening?

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  • Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

    - by Ricket
    Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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  • Streaming large result sets with MySQL

    - by configurator
    I'm developing a spring application that uses large MySQL tables. When loading large tables, I get an OutOfMemoryException, since the driver tries to load the entire table into application memory. I tried using statement.setFetchSize(Integer.MIN_VALUE); but then every ResultSet I open hangs on close(); looking online I found that that happens because it tries loading any unread rows before closing the ResultSet, but that is not the case since I do this: ResultSet existingRecords = getTableData(tablename); try { while (existingRecords.next()) { // ... } } finally { existingRecords.close(); // this line is hanging, and there was no exception in the try clause } The hangs happen for small tables (3 rows) as well, and if I don't close the RecordSet (which happened in one method) then connection.close() hangs.

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  • Practicing inserting data into an array by using binary search, few problems

    - by HelpNeeder
    I'm trying to create a method which inserts and then sort elements in form of binary form. The problem I am experiencing that my code doesn't insert data correctly which means that output does not appear to be in order at all. The list is not organized, and data is added in order that is being inserted. Now, 2 questions, what am I doing wrong here? And how to fix this? public void insertBinarySearch(long value) // put element into array { int j = 0; int lower = 0; int upper = elems-1; int cur = 0; while (cur < elems) { curIn = (lower + upper ) / 2; if(a[cur] < value) { j = cur + 1; break; } else if(a[cur] > value) { j = cur; break; } else { if(a[cur] < value) lower = cur + 1; else upper = cur - 1; } } for(int k = elems; k > j; k--) a[k] = a[k-1]; a[j] = value; elems++; }

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  • How to avoid the linebreak inside a word (Static Layout

    - by Addev
    I'm trying to make a text as big as I can making it fit a Rect. basically I use a StaticLayout for pre-calculate the text size and make it fit the Rect's height: // Since the width is fixed for the StaticLayout it should only fit the height while (currentHeight>Rect.getHeight()){ size-=2; } textPaint.setTextSize(size); The problem is that if the Rect is very high, the exit condition is reached but breaking the words (see the capture). Is there a way for avoid this? Goal: Actual: Current code: textSize=MAX_TEXT_SIZE do { if (textSize < mMinTextSize) { Log.i(TAG, "Min reached"); textSize = mMinTextSize; textPaint.setTextSize(textSize); fits = true; } else { textPaint.setTextSize(textSize); StaticLayout layout = new StaticLayout(text, textPaint, targetWidth, Alignment.ALIGN_NORMAL, 1.0, 0, true); layout.draw(canvas); float heightRatio= (float) layout.getHeight() / (float) targetHeight; boolean fitsHeight = heightRatio<= 1f; if (fitsHeight) { fits = true; } else { textSize -= 2; } } Log.i(TAG, "textSize=" + textSize + " fits=" + fits); } while (!fits); thanks

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  • How to make a swing app aware of screen size change?

    - by Marton Sigmond
    Hi, while my swing app is running I change the size of the screen (e.g. from 1024x768 to 800x600). Is there any event I can listen to to be notified about this? Alternatively I could check the screen size in every couple of second, but the Toolkit.getScreenSize() keeps telling me the old value. How could I get the real screen size after the change? Environment: Linux (tested on SuSE ES 11 and Ubuntu 9.04) I appreciate your help. Marton

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  • How to execute maven tasks in eclipse (Sonatype plugin)

    - by Bruce
    Hi all I know it must be something simple, but I just can't figure it out.. I'm using the Sonatype maven plugin on eclipse. When I want to build a war file for a webapp project, the only way I know to do it is to use the command line and type mvn package. I've looked all through the right click menu and I can't find any way to do it from eclipse. There's a maven submenu that seems to have no options to do with building, and there's a run menu that doesn't seem right - I don't want to run my project - I just want to build it. There is a maven build option in the run menu, but if I run it, a configuration window pops up for me to enter goals in.. How I do I just do a simple mvn package, but through gui? What am I missing? Thanks!

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  • Using an unencoded key vs a real Key, benefits?

    - by user246114
    Hi, I am reading the docs for Key generation in app engine. I'm not sure what effect using a simple String key has over a real Key. For example, when my users sign up, they must supply a unique username: class User { /** Key type = unencoded string. */ @PrimaryKey private String name; } now if I understand the docs correctly, I should still be able to generate named keys and entity groups using this, right?: // Find an instance of this entity: User user = pm.findObjectById(User.class, "myusername"); // Create a new obj and put it in same entity group: Key key = new KeyFactory.Builder( User.class.getSimpleName(), "myusername") .addChild(Goat.class.getSimpleName(), "baa").getKey(); Goat goat = new Goat(); goat.setKey(key); pm.makePersistent(goat); the Goat instance should now be in the same entity group as that User, right? I mean there's no problem with leaving the User's primary key as just the raw String? Is there a performance benefit to using a Key though? Should I update to: class User { /** Key type = unencoded string. */ @PrimaryKey private Key key; } // Generate like: Key key = KeyFactory.createKey( User.class.getSimpleName(), "myusername"); user.setKey(key); it's almost the same thing, I'd still just be generating the Key using the unique username anyway, Thanks

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  • JBoss - does app have to be compiled under same jdk as JBOSS is running under?

    - by dcp
    I'm a little confused about JBOSS and running it under different JDKs. For example, let's say I'm running JBOSS 5.1, and before starting it I set my JAVA_HOME to point to JDK5. Let's also assume that my JEE application is compiled under JDK6. If I deploy the JEE app (compiled under JDK6) to JBOSS, when I try to look up my EJBs I get errors like: javax.naming.NameNotFoundException: tc_test_project not bound But if I recompile my code under JDK5 and redeploy it, it works fine and is able to lookup the EJBs ok. Likewise, I can set JAVA_HOME to JDK6 and start JBOSS, and my code (compiled under JDK6) will run ok under that scenario (it's able to find the EBJs, etc.). So it seems that your JEE app needs to be compiled under the same JAVA_HOME that the JBOSS server is going to be running under, or am I misunderstanding something? Just wanted to get confirmation, thanks.

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  • Matching Class arrays

    - by frinkz
    I'm writing a routine to invoke methods, found by a name and an array of parameter Class values Matching the Method by getName works, but when trying to match the given Class[] for parameters, and Method.getParameterTypes(), I'm having trouble. I assumed that this would work: Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); if(methodParams == searchParams) { m.invoke(this, paramValues); } But apparantly not - m.invoke is never reached. I've checked, and methodParams gives the same classes as searchParams. The code below works, and picks the right method, but it seems like a very dirty way of doing things, I'm sure I'm missing something obvious. Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); boolean isMatch = true; for(int i = 0; i < searchParams.length; i++) { if(!searchParams.getClass().equals(methodParams.getClass())) { isMatch = false; } } if(isMatch) { m.invoke(this, paramValues); }

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  • null pointer exception on list.add

    - by Eric
    I've been working on this one error for a few hours so I thought I'd pick the brains of some pros. I am getting a null pointer exception at the modelData.add(i, es) method. I know from debugging that es isn't null. I'm really confused, thanks. public class EventTableModel extends AbstractTableModel { //private int rowCount = 0; protected List<EventSeat> modelData; private static final int COLUMN_COUNT = 3; private Event e; Event j = GUIpos.m; int i = 1; public EventTableModel(Event e) { this.e = e; try { System.out.println(modelData); for (EventSeat es : e.getEventSeats()) { modelData.add(i, es); i++; } } catch (DataException ex) { Logger.getLogger(EventTableModel.class.getName()).log(Level.SEVERE, null, ex); } }

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  • Help choosing the right data structure

    - by devoured elysium
    I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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  • How to handle injecting dependencies into rich domain models?

    - by Arne
    In a web server project with a rich domain model (application logic is in the model, not in the services) how do you handle injecting the dependencies into the model objects? What are your experiences? Do you use some form of AOP? Like Springs @Configurable annotation? Load time or build time weawing? Problems you encountered? Do you use manual injection? Then how do you handle different instantiation scenarios (creating of the objects through an library [like Hibernate], creating objects with "new" ...)? Or do you use some other way of injecting the dependencies?

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  • JDOQL Any way to avoid multiple .contains() calls in the query when searching for the presence of on

    - by Finbarr
    The question pretty much says it all. If I have a class Class A public class A { ... private List<String> keys; ... } And I want to select all A instances from the DataStore that have atleast one of a List of keys, is there a better way of doing it than this: query = pm.newQuery(A.class); query.setFilter("keys.contains(:key1) || keys.contains(:key2) || keys.contains(:key3)"); List<A> results = (List<A>)query.execute(key1, key2, key3); This has not yet been implemented, so I am open to radical suggestions.

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  • how to make an array of arrays

    - by yuliya
    hi, how would you write an array of values to other array. In instance, I have a list of IPs and list of requests. I want to have something like [{ip1, request1}, {ip2, request2}, ....]. It's how I would do it, but sure obj will change every time and array will have all the time the same values. ArrayList array = new ArrayList(); Object[] obj = new Object[2]; for (int i=0; i<listSize; i++){ obj[0] = ipList.get(i).toString(); obj[1] = requestList.get(i); array.add(obj);

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  • How to define a class with variable properties?

    - by user1723326
    I'm making a database program. I want the user to be able to define their own columns, as many as they want. How would I then define each record in its class file?(Since the properties would be different user to user) EDIT: It's part of a school assignment-it's going to hold different scores and the likes for the teacher for different students they can add, but they will also be able to add a new assignment, test(a column) .

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  • Can using non primitive Integer/ Long datatypes too frequently in the application, hurt the performance??

    - by Marcos
    I am using Long/Integer data types very frequently in my application, to build Generic datatypes. I fear that using these wrapper objects instead of primitive data types may be harmful for performance since each time it needs to create objects which is an expensive operation. but also it seems that I have no other choice(when I have to use primtives with generics) rather than just using them. However, still it would be great if you can suggest if there is anything I could do to make it better. or any way if I could just avoid it ?? Also What may be the downsides of this ? Suggestions welcomed!

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