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  • how does serializable work in java?

    - by Karl Trumstedt
    If I have an instance of a class that I store in a session I need to make it serializable. This class has a static variable, will this be serialized in every instance stored? The static variable is a reference to a cache containing a lot of data in the background. Will all of this data be serialized? If so, it seems preferable to make this variable transient and re-fetch the cache instance each time the instance is restored. Maybe not store the cache instance at all in the class. Will the constructor execute when a class is restored from a serialized state? if not is there any other method I can use to re-instate a transient variable?

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  • Java Swing how to create a task reminder

    - by newbie123
    How to create a event reminder. Example, an user created an event which is today 5.00pm and stored it into database. When ruun the program the reminder will pop up if the system time is 5.00pm. Is there any API can do that? From google what I got was those freeware.

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  • PLEASE HELP JAVA/SQL question

    - by fred-ghosn
    Hello everyone, well I'm new here and I really need some help.. I want to create a table and this table's name will be inserted from a textfield. However when I run the query it's giving me an error, any help on this one? Ill paste the code here: public boolean CreateTable() { TableNumber=jTextField4.getText(); try { String password = null; String s = "CREATE TABLE '"+TableNumber+'" (Item char(50),Price char(50))"; ConnectionForOrders(); stmt = conn.createStatement(); stmt.executeUpdate(s); boolean f=false; ConnectionForOrdersclose();

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  • Web Form based login in Java

    - by BrunoLM
    How can I block access to the site if a user is not logged in? Under web.xml Security I checked Form authentication then I selected Login and Error page, but I don't know how to block the access and redirect the user to the login page. Do I need a filter? If so, how can I get the login url I specified? And how should I call the validation method? I saw in some examples this code <form method=post action="j_security_check"> <input type="text" name="j_username" /> <input type="password" name="j_password" /> </form> What does it do?

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  • Java Logger only to file, no screen output!

    - by Tom Taylor
    Hello there SO'ers, I got a quite simple problem but cant find a solution for it. I have a logger with a file handler added, but it still spams to hell out of my console. How could I get the logger to solely route all output to a file, with NO console outputs? Thanks a lot, cru

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  • Is HashMap in Java collision safe

    - by changed
    Hi I am developing a parser that needs to put key value pairs in hashmap. But a key can have multiple values which i can do in this way HashMap<String,ArrayList<String>> . But what happens if number of keys are very large and it start matching with other key's hashcode. Will that rewrite previous key's value ? thanks -devSunday

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  • Return an Object in Java

    - by digby12
    I've been struggling to work out how to return an object. I have the following array of objects. ArrayList<Object> favourites; I want to find an object in the array based on it's "description" property. public Item finditem(String description) { for (Object x : favourites) { if(description.equals(x.getDescription())) { return Object x; else { return null; Can someone please show me how I would write this code. Thanks.

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  • Update music file details - Java.

    - by Desorder
    Hi all, Well, I'm a music fan guy, and now with my 18000 music collection, it's getting very hard to maintain. So, I would like to ask I could of question to help to write an app to maintain it for me. 1- How can I access a music file and read details of it? I mean, I would like to write some code and passing the directory, my app would read all the music files (understand mp3 files) and with that I would like to access details like title, artist, length and so on... 2- Is there a public source that I could access and update my file? A webservice somewhere that I could connect, query some information based on song name, or artist or whatever. I would like to achieve a final result of given a directory, my app would read the file, collect some information and query the source for a complete list of detail and update my file. Thank you guys for any help...

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  • Java regex skipping matches

    - by Mihail Burduja
    I have some text; I want to extract pairs of words that are not separated by punctuation. Thi is the code: //n-grams Pattern p = Pattern.compile("[a-z]+"); if (n == 2) { p = Pattern.compile("[a-z]+ [a-z]+"); } if (n == 3) { p = Pattern.compile("[a-z]+ [a-z]+ [a-z]+"); } Matcher m = p.matcher(text.toLowerCase()); ArrayList<String> result = new ArrayList<String>(); while (m.find()) { String temporary = m.group(); System.out.println(temporary); result.add(temporary); } The problem is that it skips some matches. For example "My name is James", for n = 3, must match "my name is" and "name is james", but instead it matches just the first. Is there a way to solve this?

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  • JAVA-I don't want clicking on my app make other apps lose focus

    - by Auxiliary
    Wow, what a stupid question you might say. But is it possible? I have a mouse move event in a Jpanel and it works even when the application is not in focus, now can I have something like that for the clicking event or something similar. And most importantly I don't want other apps (even something like the main menu) to lose focus when i click on my app. I was the system's event queue but i'm not sure where that would lead me to. Thanks in advance.

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  • Java compilation with two versions of Eclipse

    - by lepnio
    I've got an old project in Eclipse 2.1 and compiled with a JDK 1.4.2_12. I want to upgrade the version of Eclipse to Eclipse Galileo. I've imported my project and set the compilation level to 1.4 and I've also updated my build path to use the correct JDK. The problem is that when I compare the compiled files in the classes folder in the two versions of Eclipse, the MD5 checksum are different. Should I be worried about that fact or this is normal?

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  • Java, Massive message processing with queue manager (trading)

    - by Ronny
    Hello, I would like to design a simple application (without j2ee and jms) that can process massive amount of messages (like in trading systems) I have created a service that can receive messages and place them in a queue to so that the system won't stuck when overloaded. Then I created a service (QueueService) that wraps the queue and has a pop method that pops out a message from the queue and if there is no messages returns null, this method is marked as "synchronized" for the next step. I have created a class that knows how process the message (MessageHandler) and another class that can "listen" for messages in a new thread (MessageListener). The thread has a "while(true)" and all the time tries to pop a message. If a message was returned, the thread calls the MessageHandler class and when it's done, he will ask for another message. Now, I have configured the application to open 10 MessageListener to allow multi message processing. I have now 10 threads that all time are in a loop. Is that a good design?? Can anyone reference me to some books or sites how to handle such scenario?? Thanks, Ronny

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  • How to append to an array that contains blank spaces - Java

    - by Cameron Townley
    I'm trying to append to a char[] array that contains blank spaces on the end. The char array for example contains the characters 'aaa'. When I append the first time the method functions properly and outputs 'aaabbb'. The initial capacity of the array is set to 80 or multiples of 80. The second time I try and append my output looks like"aaabbb bbb". Any psuedocode would be great.

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  • java beginner- in which folder should I place a "database.properties" file

    - by Arvind
    I read some tutorials on how to read data from a database.properties file- which basically stored key-value pairs. What i want to know is, in which folder should I place this file? Is it in the root (ie "src") or within a package... And how do I access this file, if it is placed in "src"- my code will be within a package (and the package's directory will be under src)- so how do I access the properties file, which is in "src", from a class within a package?

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  • Reading lines of data from text files using java

    - by razshan
    I have a text file with x amount of lines. each line holds a integer number. When the user clicks a button, an action is performed via actionlistener where it should list all the values as displayed on the text file. However, right now I have linenum set to 10 implying I already told the code that just work with 10 lines of the text file. So, if my text file has only 3 rows/lines of data...it will list those lines and for rest of the other 7 lines, it will spit out "null". I recall there is a way to use ellipsis to let the program know that you don't know the exact value but at the end it calculates it based on the given information. Where my given information will the number of lines with numbers(data). Below is part of the code. private class thehandler implements ActionListener{ public void actionPerformed(ActionEvent event){ BufferedReader inputFile=null; try { FileReader freader =new FileReader("Data.txt"); inputFile = new BufferedReader(freader); String MAP = ""; int linenum=10; while(linenum > 0) { linenum=linenum-1; MAP = inputFile.readLine();//read the next line until the specfic line is found System.out.println(MAP); } } catch( Exception y ) { y.printStackTrace(); } }}

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  • Rad upload Java applet and z-index

    - by Belgurinn
    I'm using Rad upload for drag and drop upload. It's working perfectly except I'm having a problem with the z-index. I'm also using jquery UI on the site and the overlay doesn't cover the applet. Any ideas on how to control the z-index. It would be nice if there where a setting like in flash where you control wmode. But I've tried z-index on the div that controls it and no result.

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  • Transfering a set with a Wildcarded Generic to a List in Java

    - by Daniel Bingham
    I have a data type that contains a set and a method that expects List<? extends MyClass>. The data type has Set<? extends MyClass>. I need to be able to move the stuff out of the set and into the List. The order it goes into the list doesn't matter, it just needs to start keeping track of it so that it can be reordered when displayed. Suffice to say that changing the Set into a List in the data type is out of the question here. This seems pretty easy at first. Create a new method that takes a Set instead of a List, changes it into a list and then passes it on to the old method that just took a list. The problem comes in changing the set to a list. public void setData(Set<? extends MyClass> data) { List<? extends Myclass> newData = ArrayList< /* What goes here? */ >(); for(ConcordaEntityBean o : data) { newData.add(o); } setData(newData); } Obviously, I can't instantiate an ArrayList with a wildcard, it chokes. I don't know the type at that point. Is there some way to pull the type out of data and pass it to ArrayList? Can I just instantiate it with MyClass? Is there some other way to do this?

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  • Pattern for version-specific implementations of a Java class

    - by Mike Monkiewicz
    So here's my conundrum. I am programming a tool that needs to work on old versions of our application. I have the code to the application, but can not alter any of the classes. To pull information out of our database, I have a DTO of sorts that is populated by Hibernate. It consumes a data object for version 1.0 of our app, cleverly named DataObject. Below is the DTO class. public class MyDTO { private MyWrapperClass wrapper; public MyDTO(DataObject data) { wrapper = new MyWrapperClass(data); } } The DTO is instantiated through a Hibernate query as follows: select new com.foo.bar.MyDTO(t1.data) from mytable t1 Now, a little logic is needed on top of the data object, so I made a wrapper class for it. Note the DTO stores an instance of the wrapper class, not the original data object. public class MyWrapperClass { private DataObject data; public MyWrapperClass(DataObject data) { this.data = data; } public String doSomethingImportant() { ... version-specific logic ... } } This works well until I need to work on version 2.0 of our application. Now DataObject in the two versions are very similar, but not the same. This resulted in different sub classes of MyWrapperClass, which implement their own version-specific doSomethingImportant(). Still doing okay. But how does myDTO instantiate the appropriate version-specific MyWrapperClass? Hibernate is in turn instantiating MyDTO, so it's not like I can @Autowire a dependency in Spring. I would love to reuse MyDTO (and my dozens of other DTOs) for both versions of the tool, without having to duplicate the class. Don't repeat yourself, and all that. I'm sure there's a very simple pattern I'm missing that would help this. Any suggestions?

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  • Java URL Connection Time Out

    - by webren
    Hello, I am attempting to connect to a website where I'd like to extract its HTML contents. My application will never connect to the site - only time out. Here is my code: URL url = new URL("www.website.com"); URLConnection connection = url.openConnection(); connection.setConnectTimeout(2000); connection.setReadTimeOut(2000); BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()); String line; while ((line = reader.readLine()) != null) { // do stuff with line } reader.close(); Any ideas would be greatly appreciated. Thanks!

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  • Java for loop with multiple incrementers

    - by user2517280
    Im writing a program which combines the RGB pixel values for 3 images, e.g. red pixel of image 1, green pixel of image 2 and blue pixel of image 3 and I want to then create a final image of it. Im using the code below, but this seems to be incrementing x2 and x3 whilst x1 is the same, i.e. not giving the right pixel value for same co-ordinate for each image. for (int x = 0; x < image.getWidth(); x++) { for (int x2 = 0; x2 < image2.getWidth(); x2++) { for (int x3 = 0; x3 < image3.getWidth(); x3++) { for (int y = 0; y < image.getHeight(); y++) { for (int y2 = 0; y2 < image2.getHeight(); y2++) { for (int y3 = 0; y3 < image3.getHeight(); y3++) { So I was wondering if anyone can tell me how to iterate through each of the 3 images on the same co-ordinate, so for example read 1, 1 of each image and record the red, green and blue value accordingly. Apologies if it doesnt make complete sense, its a bit hard to explain. I can iterate the values for one image fine but when I add in another, things start to go a bit wrong as obviously its quite a bit more complicated! I was thinking it might be easier to create an array and replace the according values in that just not sure how to do that effectively either. Thanks

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