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  • Understanding max JVM heap size

    - by Marcus
    I've read the max heap size on 32bit Windows is ~1.5GB which is due to the fact that the JVM requires contiguous memory. Can someone explain the concept of "contiguous memory" and why you only have max 1.5GB on Windows? Secondly, what then is the max heap size on 64 bit Windows and why is this different than what's available on 32 bit?

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  • HibernateFilter.doFilter ServletException?

    - by Austin R
    I have pretty much zero experience setting up servers, but currently my job is to set one up (don't ask why). It's an an apache-tomcat6 server. I followed some instructions step by step, and when it came time to test that everything was working, here's what I got: I know this is a bit of a shot in the dark, but does anyone know what I can do to fix this? Please let me know if there's any further information I can provide to help!

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  • How does Hibernate detect dirty state of an entity object?

    - by ???'Lenik
    Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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  • How do I create a Thread Manager for an Android App ?

    - by MrBuBBLs
    Hi, I would like to know how to start and code a thread manager for my Android App. My app is going to fill a list with a network I/O and I have to manage threads for that. I never done this before and I don't know where to start. I heard about Thread Pool and other stuff, but I'm quite confused. Could someone please help me make my way through ? Thanks

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  • Are entities cached in jpa by default ?

    - by Nitesh Panchal
    Hello, I add entity to my database and it works fine. But when i retrieve the List, i get the old entity, the new entities i add are not shown until i undeploy the application and redeploy it again. This means are my entities cached by default? But, I haven't made any settings for caching entities in my persistence.xml or any such file. I have even tried calling flush(), refresh() and merge(). But still it shows the old entities only. Am i missing something? Please help me.

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  • Why should I override hashCode() when I override equals() method?

    - by Bragaadeesh
    Ok, I have heard from many places and sources that whenever I override the equals() method, I need to override the hashCode() method as well. But consider the following piece of code package test; public class MyCustomObject { int intVal1; int intVal2; public MyCustomObject(int val1, int val2){ intVal1 = val1; intVal2 = val2; } public boolean equals(Object obj){ return (((MyCustomObject)obj).intVal1 == this.intVal1) && (((MyCustomObject)obj).intVal2 == this.intVal2); } public static void main(String a[]){ MyCustomObject m1 = new MyCustomObject(3,5); MyCustomObject m2 = new MyCustomObject(3,5); MyCustomObject m3 = new MyCustomObject(4,5); System.out.println(m1.equals(m2)); System.out.println(m1.equals(m3)); } } Here the output is true, false exactly the way I want it to be and I dont care of overriding the hashCode() method at all. This means that hashCode() overriding is an option rather being a mandatory one as everyone says. I want a second confirmation.

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  • j2ME setLocationListener()

    - by Jeff Catania
    I'm programming a GPS tracking system using the Motorola i335 running on Sprint's IDEN network. I'm using the javax.microedition.location api to find the GPS coordinates. To set up the updating, you use the [setLocationListener][1] method. I originally tried passing (listener,2,1,1). However there was too many invalid locations being received (where the GPS could not get the fix in the specified time), so I changed the parameters to (listener, 20, 20, 1). Now the system barely throws any invalid locations. My goal is to get the fastest number of updates that are realistic. Have any of you found a happy medium for parameters of this method? [1]: http://www-users.cs.umn.edu/~czhou/docs/jsr179/lapi/javax/microedition/location/LocationProvider.html#setLocationListener(javax.microedition.location.LocationListener, int, int, int)

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  • Collision of dot and line in 2D space

    - by Anderiel
    So i'm trying to make my first game on android. The thing is i have a small moving ball and i want it to bounce from a line that i drew. For that i need to find if the x,y of the ball are also coordinates of one dot from the line. I tried to implement these equations about lines x=a1 + t*u1 y=a2 + t*u2 = (x-a1)/u1=(y-a2)/u2 (t=t which has to be if the point is on the line) where x and y are the coordinates im testing, dot[a1,a2] is a dot that is on the line and u(u1,u2) is the vector of the line. heres the code: public boolean Collided() { float u1 =Math.abs(Math.round(begin_X)-Math.round(end_X)); float u2 =Math.abs(Math.round(begin_Y)-Math.round(end_Y)); float t_x =Math.round((elect_X - begin_X)/u1); float t_y =Math.round((elect_Y - begin_Y)/u2); if(t_x==t_y) { return true; } else { return false; } } points [begin_X,end_X] and [begin_Y,end_Y] are the two points from the line and [elect_X,elect_Y] are the coordinates of the ball theoreticaly it should work, but in the reality the ball most of the time just goes straigth through the line or bounces somewhere else where it shouldnt

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  • Explicitly multiplying values as longs

    - by Bill Szerdy
    I understand that all math is done as the largest data type required to handle the current values but when you transverse a loop how do you explicitly multiply longs? The following code returns 0, I suspect, because of an overflow. long result = 0L; List<Long> temp = (List<Long>) getListOfIntegers(); for (int i = 0; i < temp.size(); i++) { result *= temp.get(i).longValue(); } System.out.println(result);

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  • Should my internal API classes be all in one package?

    - by Chris
    I'm hard at work packaging up an API for public consumption. As such I'm trying to limit the methods that are exposed to only those that I wish to be public and supportable. Underneath this of course there are a multitude of limited access methods. The trouble is that I have a lot of internal code that needs to access these restricted methods without making those methods public. This creates two issues: I can't create interfaces to communicate between classes as this would make these my internal methods public. I can't access protected or default methods unless I put the majority of my internal classes in the same package. So, I have around 70 or 80 internal classes in cleanly segregated packages BUT with overly permissive access modifiers. Would you say that a single package is the lesser of two evils or is there a better way to be able to mask my internal methods whilst keeping more granular packages? I'd be interested to find out the best practice here. I'm already aware of This

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  • Will this SQL screw up

    - by Joshua
    I'm sure everyone knows the joys of concurrency when it comes to threading. Imagine the following scenario on every page-load on a noobily set up MySQL db: UPDATE stats SET visits = (visits+1) If a thousand users load the page at same time, will the count screw up? is this that table locking/row locking crap? Which one mysql use.

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  • Accessing variables of an object of a particular class through a different class within the construc

    - by Haxed
    class Student { private String name; public Student(String name){ this.name = name; } public String getName(){ return name; } } class StudentServer { public StudentServer(){ Student[] s = new Student[30]; s[0] = new Student("Nick"); System.out.println(s[0]); // LINE 01:But this compiles, although prints junk System.out.println(s[0].getName()); // LINE 02:I get a error called cannot find symbol } public static void main(){ new StudentServer(); } } Hey, there are two lines, I want the reader to focus on, the first line prints junk as usual, but suprizingly the second one gives me an error. Do you know why ? Many Thanks

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  • Need help make these classes use Visitor Pattern and generics

    - by Shervin
    Hi. I need help to generify and implement the visitor pattern. We are using tons of instanceof and it is a pain. I am sure it can be modified, but I am not sure how to do it. Basically we have an interface ProcessData public interface ProcessData { public setDelegate(Object delegate); public Object getDelegate(); //I am sure these delegate methods can use generics somehow } Now we have a class ProcessDataGeneric that implements ProcessData public class ProcessDataGeneric implements ProcessData { private Object delegate; public ProcessDataGeneric(Object delegate) { this.delegate = delegate; } } Now a new interface that retrieves the ProcessData interface ProcessDataWrapper { public ProcessData unwrap(); } Now a common abstract class that implements the wrapper so ProcessData can be retrieved @XmlSeeAlso( { ProcessDataMotorferdsel.class,ProcessDataTilskudd.class }) public abstract class ProcessDataCommon implements ProcessDataWrapper { protected ProcessData unwrapped; public ProcessData unwrap() { return unwrapped; } } Now the implementation public class ProcessDataMotorferdsel extends ProcessDataCommon { public ProcessDataMotorferdsel() { unwrapped = new ProcessDataGeneric(this); } } similarly public class ProcessDataTilskudd extends ProcessDataCommon { public ProcessDataTilskudd() { unwrapped = new ProcessDataGeneric(this); } } Now when I use these classes, I always need to do instanceof ProcessDataCommon pdc = null; if(processData.getDelegate() instanceof ProcessDataMotorferdsel) { pdc = (ProcessDataMotorferdsel) processData.getDelegate(); } else if(processData.getDelegate() instanceof ProcessDataTilskudd) { pdc = (ProcessDataTilskudd) processData.getDelegate(); } I know there is a better way to do this, but I have no idea how I can utilize Generics and the Visitor Pattern. Any help is GREATLY appreciated.

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  • Reporting on release changes when using JIRA, Ivy and SVN

    - by HaveAGuess
    Hey guys, We have an Ivy release procedure where resolve our dependancies using Ivy pre-tagging which means that we can pull in changes for releases by other members of the team that we are not expecting We want to generate reports and track changes to dependancies between releases but there doesn't seem to be an easy way of doing this without a significant effort. We also want to generate a JIRA list of all changes not only in the main project but in dependancies that we own. This is an extension of the problem above. Otherwise we simply don't know what we are releasing - any ideas?!

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  • Google App Engine - DELETE JPQL Query and Cascading

    - by Taylor Leese
    I noticed that the children of PersistentUser are not deleted when using the JPQL query below. However, the children are deleted if I perform an entityManager.remove(object). Is this expected? Why doesn't the JPQL query below also perform a cascaded delete? @OneToMany(mappedBy = "persistentUser", cascade = CascadeType.ALL) private Collection<PersistentLogin> persistentLogins; ... @Override @Transactional public final void removeUserTokens(final String username) { final Query query = entityManager.createQuery( "DELETE FROM PersistentUser p WHERE username = :username"); query.setParameter("username", username); query.executeUpdate(); }

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  • Graphing the pitch (frequency) of a sound

    - by Coronatus
    I want to plot the pitch of a sound into a graph. Currently I can plot the amplitude. The graph below is created by the data returned by getUnscaledAmplitude(): AudioInputStream audioInputStream = AudioSystem.getAudioInputStream(new BufferedInputStream(new FileInputStream(file))); byte[] bytes = new byte[(int) (audioInputStream.getFrameLength()) * (audioInputStream.getFormat().getFrameSize())]; audioInputStream.read(bytes); // Get amplitude values for each audio channel in an array. graphData = type.getUnscaledAmplitude(bytes, this); public int[][] getUnscaledAmplitude(byte[] eightBitByteArray, AudioInfo audioInfo) { int[][] toReturn = new int[audioInfo.getNumberOfChannels()][eightBitByteArray.length / (2 * audioInfo. getNumberOfChannels())]; int index = 0; for (int audioByte = 0; audioByte < eightBitByteArray.length;) { for (int channel = 0; channel < audioInfo.getNumberOfChannels(); channel++) { // Do the byte to sample conversion. int low = (int) eightBitByteArray[audioByte]; audioByte++; int high = (int) eightBitByteArray[audioByte]; audioByte++; int sample = (high << 8) + (low & 0x00ff); if (sample < audioInfo.sampleMin) { audioInfo.sampleMin = sample; } else if (sample > audioInfo.sampleMax) { audioInfo.sampleMax = sample; } toReturn[channel][index] = sample; } index++; } return toReturn; } But I need to show the audio's pitch, not amplitude. Fast Fourier transform appears to get the pitch, but it needs to know more variables than the raw bytes I have, and is very complex and mathematical. Is there a way I can do this?

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  • PostgreSQL like + Hibernate problem

    - by Marat_Galiev
    Hi all. I want to do search in PostgreSQL for INTEGER based columns. if (!sSearch.isEmpty()) { sSearch = sSearch.replaceAll("[^a-zA-Z0-9]", "_").toLowerCase(); String[] search = sSearch.split(" "); sWhere = " "; for (NewsColumns column : NewsColumns.values()) { for (String s : search) { sWhere += "lower(" + column + "::TEXT) LIKE '%" + s + "%' OR "; } } sWhere = sWhere.substring(0,sWhere.length()-3); } Ok, I want to convert INT value to String before search, with '::TEXT' expression. But after executing I'm getting: org.hibernate.QueryException: Not all named parameters have been set: [:TEXT] [select * from news WHERE lower(ID::TEXT) LIKE '%5%' Exception. Looks like hibernate parse my convert exp as parameter. Any help is appreciated. Thanks.

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  • Cannot access implict object from within method in custom JSP tag file

    - by David Hamilton
    I'm attempting to create a custom jsp tag. Everything is working fine, except for the fact that I the request seems to be out-of-scope for my custom function. Here is the relevant bit from the .tag file: <%! private String process(String age, BigDecimal amount) { //Attempting to access request here results in an compile time error trying to: String url=request.getURL; } %> I'm very new to JSP so I'm sure I'm missing something obvious..but I can't seem to figure out what. Any help is appreciated.

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  • Request attributes in jsf / icefaces behaves strange (survive request end)

    - by hubertg
    I have the following code in a listener method: FacesContext.getCurrentInstance().getExternalContext().getRequestMap().put("time", new Date()); When a button is clicked the following code is executed System.out.println(FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("time")); One could except that "time" is null when the listener was not executed while processing the current request, but: it seems like the "time" object survives the request processing. So when "time" has been set sometimes in the past it stays there... can anybody explain this? Thanks.

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  • Do Hibernate table classes need to be Serializable?

    - by Scott Leis
    I have inherited a Websphere Portal project that uses Hibernate 3.0 to connect to a SQL Server database. There are about 130 Hibernate table classes in this project. They all implement Serializable. None of them declare a serialVersionUID field, so the Eclipse IDE shows a warning for all of these classes. Is there any actual need for these classes to implement Serializable? If so, is there any tool to add a generated serialVersionUID field to a large number of classes at once (just to make the warnings go away) ?

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  • Send data from Service to Widget on Android.

    - by Jose Vega
    I am writing a widget on Android 1.6 that shows the minutes that a person has used on the current month. The way I have it setup is by having a service that listens to the state of the phone and when the phone is picked up, it starts the timer and when the person hangs up, ends a timer. I would like to send this variable(long duration) over to my appWidgetProvider so I could update the edit text on it.

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