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  • Java JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • Is it a good or bad practice to call instance methods from a java constructor?

    - by Steve
    There are several different ways I can initialize complex objects (with injected dependencies and required set-up of injected members), are all seem reasonable, but have various advantages and disadvantages. I'll give a concrete example: final class MyClass { private final Dependency dependency; @Inject public MyClass(Dependency dependency) { this.dependency = dependency; dependency.addHandler(new Handler() { @Override void handle(int foo) { MyClass.this.doSomething(foo); } }); doSomething(0); } private void doSomething(int foo) { dependency.doSomethingElse(foo+1); } } As you can see, the constructor does 3 things, including calling an instance method. I've been told that calling instance methods from a constructor is unsafe because it circumvents the compiler's checks for uninitialized members. I.e. I could have called doSomething(0) before setting this.dependency, which would have compiled but not worked. What is the best way to refactor this? Make doSomething static and pass in the dependency explicitly? In my actual case I have three instance methods and three member fields that all depend on one another, so this seems like a lot of extra boilerplate to make all three of these static. Move the addHandler and doSomething into an @Inject public void init() method. While use with Guice will be transparent, it requires any manual construction to be sure to call init() or else the object won't be fully-functional if someone forgets. Also, this exposes more of the API, both of which seem like bad ideas. Wrap a nested class to keep the dependency to make sure it behaves properly without exposing additional API:class DependencyManager { private final Dependency dependency; public DependecyManager(Dependency dependency) { ... } public doSomething(int foo) { ... } } @Inject public MyClass(Dependency dependency) { DependencyManager manager = new DependencyManager(dependency); manager.doSomething(0); } This pulls instance methods out of all constructors, but generates an extra layer of classes, and when I already had inner and anonymous classes (e.g. that handler) it can become confusing - when I tried this I was told to move the DependencyManager to a separate file, which is also distasteful because it's now multiple files to do a single thing. So what is the preferred way to deal with this sort of situation?

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  • How to set up a different context to point to an external directory outside webapps Tomcat/Java

    - by pinkb
    Hi Folks, I am successful to map an external directory by creating an xml file like : <Context path="/uploads" docBase="C:\uploads\photos" crossContext="true"/> And I named this xml file as uploads.xml and saved under "#Tomcat\conf\Catalina\localhost" here # = Directory where Tomcat has been installed. And when I start Tomcat(5) from cammand line (batch file) i.e. startup.bat The images can be accessed normally like "http://localhost:8080/uploads/user1.png" It works. Actually I am using IntelliJ Idea 8 for devevelopment. When I start Tomcat from IntelliJ Idea, I am not able to access the context i.e. the images. "http://localhost:8080/uploads/user1.png" It shows "HTTP 400 Bad Request" The context path for my project is "http://localhost:8080/spark/" Any help or suggestion is needed at the earliest time. Looking forward to as many appreciative responses as possible. Thanx Pink

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  • How to pass a file (read from Java) most effectively to a native method?

    - by soc
    Hi, I have approx. 30000 files (1MB each) which I want to put into a native method, which requires just an byte array and the size of it as arguments. I looked through some examples and benchmarks (like http://nadeausoftware.com/articles/2008/02/java_tip_how_read_files_quickly) but all of them do some other fancy things. Basically I don't care about the contents of the file, I don't want to access something in that file or the byte array or do anything else with it. I just want to put a file into a native method which accepts an byte array as fast as possible. At the moment I'm using RandomAccessFile, but that's horribly slow (10MB/s). Is there anything like byte[] readTheWholeFile(File file){ ... } which I could put into native void fancyCMethod(readTheWholeFile(myFile), myFile.length()) What would you suggest?

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  • How to queue and call actual methods (rather than immediately eval) in java?

    - by alleywayjack
    There are a list of tasks that are time sensitive (but "time" in this case is arbitrary to what another program tells me - it's more like "ticks" rather than time). However, I do NOT want said methods to evaluate immediately. I want one to execute after the other finished. I'm using a linked list for my queue, but I'm not really sure how/if I can access the actual methods in a class without evaluating them immediate. The code would look something like... LinkedList<Method> l = new LinkedList<Method>(); l.add( this.move(4) ); l.add( this.read() ); l.removeFirst().call(); //wait 80 ticks l.removeFirst().call(); move(4) would execute immediately, then 80 ticks later, I would remove it from the list and call this.read() which would then be executed. I'm assuming this has to do with the reflection classes, and I've poked around a bit, but I can't seem to get anything to work, or do what I want. If only I could use pointers...

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  • I have an Xcode static library project, how do I add a test target to it so I can run it there? (Ins

    - by zekel
    I want to be able to test library code in the library target so I don't have to switch over to a separate project to run it. I see how to add a target, but I'm not sure how to set it up to run like the "Command Line Tool" project template does. I tried adding a new "Shell Tool" target, but I don't know how to make it run like one. What build settings do I have to add to that target? What files (main.m?) do I need to start it up?

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  • Is it possible to use inheritance in this situation? (Java)

    - by they changed my name
    I have ClassA and ClassB, with ClassA being the superclass. ClassA uses NodeA, ClassB uses NodeB. First problem: method parameters. ClassB needs NodeB types, but I can't cast from the subclass to the superclass. That means I can't set properties which are unique to NodeB's. Second problem: When I need to add nodes toClassB, I have to instantiate a new NodeB. But, I can't do this in the superclass, so I'd have to rewrite the insertion to use NodeB. Is there a way around it or am I gonna have to rewrite the whole thing?

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  • Java Swing: How to add a CellRenderer for displaying a Date?

    - by HansDampf
    I have a Table: public class AppointmentTableModel extends AbstractTableModel { private int columns; private int rows; ArrayList<Appointment> appointments;... So each row of the table contains one Appointment. public class Appointment { private Date date; private Sample sample; private String comment; private ArrayList<Action> history; public Appointment(Date date, Sample sample, String comment) { this.date = date; this.sample = sample; this.comment = comment; this.history = new ArrayList<Action>(); } public Object getByColumn(int columnIndex) { switch (columnIndex) { case 0: return date;//Date: dd:mm:yyyy case 1: return date;//Time mm:hh case 2: return sample;//sample.getID() int (sampleID) case 3: return sample;//sample.getNumber string (telephone number) case 4: return sample;//sample.getName string (name of the person) case 5: return history;//newst element in history as a string case 6: return comment;//comment as string } return null; I added in comments what this one is going to mean. How would I create CellRenderers to display it like this. table.getColumnModel().getColumn(1).setCellRenderer(new DateRenderer()); I also want to add the whole row to be painted in red when the date is later then the current date. And then another column that holds a JButton to open up another screen with the corresponding Appointment as parameter.

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  • Multithreaded java cache for objects that are heavy to create ?

    - by krosenvold
    I need a cache some objects with fairly heavy creation times, and I need exactly-once creation semantics. It should be possible to create objects for different CacheKeys concurrently. I think I need something that (under the hood) does something like this: ConcurrentHashMap<CacheKey, Future<HeavyObject>> Are there any existing open-source implementations of this that I can re-use ?

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  • Java JTable, how to change cell data (write text in)?

    - by Bob Owuor
    Am looking to change a cell's data in a jtable. How can I do this? When I execute the following code I get errors. JFrame f= new JFrame(); final JTable table= new JTable(10,5); TableModelListener tl= new TableModelListener(){ public void tableChanged(TableModelEvent e){ table.setValueAt("hello world",2,2); } }; table.getModel().addTableModelListener(tl); f.add(table); f.pack(); f.setVisible(true); I have also tried this below but it still doesn't work. What gives? table.getModel().setValueAt("hello world",2,2);

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  • How do i generate thumbnail image for use with img tag ? Java web application.

    - by Nitesh Panchal
    Hello, I am using the below given code, but it is not working properly. Can anybody tell me how do i generate thumbnail of the image? because i am creating a photo album and i want only thumbnail images to be downloaded at first, not the entire 400-500 kb images. File objFile = new File(strImageFullPath); File targetFile = new File(strImageFullPathWithoutExt + "_small" + strFileExtension); Image image = ImageIO.read(objFile); final int WIDTH = 150; final int HEIGHT = 150; Image thumbnailImage = image.getScaledInstance(WIDTH, HEIGHT, Image.SCALE_DEFAULT); BufferedImage objThumbnailBufferedImage = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); Graphics gfx = objThumbnailBufferedImage.getGraphics(); gfx.drawImage(image, 0, 0, null); gfx.dispose(); ImageIO.write(objThumbnailBufferedImage, strFileExtension.substring(1), targetFile); Just assume that few variables like strImageFullPath,strImageFullPathWithoutExt etc they exist. Thanks in advance :)

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  • How to identify/handle text file newlines in Java?

    - by rafrafUk
    Hi Everyone! I get files in different formats coming from different systems that I need to import into our database. Part of the import process it to check the line length to make sure the format is correct. We seem to be having issues with files coming from UNIX systems where one character is added. I suspect this is due to the return carriage being encoded differently on UNIX and windows platform. Is there a way to detect on which file system a file was created, other than checking the last character on the line? Or maybe a way of reading the files as text and not binary which I suspect is the issue? Thanks Guys !

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  • Can Silverlight be linked with a C++ static library ?

    - by Niklaos
    Hi, I'm currently doing research to start a new project. This project will be in 2 parts a light Client (probably console) and an heavy one using silverlight. The light client must be cross-platform. However, they will both use the same Core (by the way, the core will need to use the sockets). I'd like to use C++ to build the light client but given that the core is common to both applications, it would be much appreciated if it's could be the same code. So the question is quite simple : Can Silverlight be compilated with a C++ static library ? And if it's possible, what about cross-platform issues (with moonlight) ? If it's not possible. Which language can i use to work with silverlight while being cross-platform ? Because of performance, a compilated language will be better ! Thanks for your expertise :)

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