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  • Refactor java code

    - by Alfred
    I would like to refactor code which looks something like this: String input; // input from client socket. if (input.equals(x) { doX(); } else if (input.equals(y) { doY(); } else { unknown_command(); } It is code which checks input from socket to perform some action, but I don't like the if else construction because every time a new command is added to the server (code) a new if else has to be added which is ugly. Also when deleting a command the if else has to be modified.

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  • Is there a way to compare two Java war files

    - by nzpcmad
    We built some war files for our web server a while back and have now rebuilt them. To ensure that nothing has changed (and as a quality check), we tried to compare them using WinMerge. The differences we can see look like they are due to some kind of meta data e.g. the files being built on different dates? The difference in the lines seems to be consistent e.g. «d}< and ³Ze< The war files are still both the same size. Is there a way to compare them that strips out the meta data such as date?

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  • Is the Cloud ready for an Enterprise Java web application? Seeking a JEE hosting advice.

    - by Jakub Holý
    Greetings to all the smart people around here! I'd like to ask whether it is feasible or a good idea at all to deploy a Java enterprise web application to a Cloud such as Amazon EC2. More exactly, I'm looking for infrastructure options for an application that shall handle few hundred users with long but neither CPU nor memory intensive sessions. I'm considering dedicated servers, virtual private servers (VPSs) and EC2. I've noticed that there is a project called JBoss Cloud so people are working on enabling such a deployment, on the other hand it doesn't seem to be mature yet and I'm not sure that the cloud is ready for this kind of applications, which differs from the typical cloud-based applications like Twitter. Would you recommend to deploy it to the cloud? What are the pros and cons? The application is a Java EE 5 web application whose main function is to enable users to compose their own customized Product by combining the available Parts. It uses stateless and stateful session beans and JPA for persistence of entities to a RDBMS and fetches information about Parts from the company's inventory system via a web service. Aside of external users it's used also by few internal ones, who are authenticated against the company's LDAP. The application should handle around 300-400 concurrent users building their product and should be reasonably scalable and available though these qualities are only of a medium importance at this stage. I've proposed an architecture consisting of a firewall (FW) and load balancer supporting sticky sessions and https (in the Cloud this would be replaced with EC2's Elastic Load Balancing service and FW on the app. servers, in a physical architecture the load-balancer would be a HW), then two physical clustered application servers combined with web servers (so that if one fails, a user doesn't loose his/her long built product) and finally a database server. The DB server would need a slave backup instance that can replace the master instance if it fails. This should provide reasonable availability and fault tolerance and provide good scalability as long as a single RDBMS can keep with the load, which should be OK for quite a while because most of the operations are done in the memory using a stateful bean and only occasionally stored or retrieved from the DB and the amount of data is low too. A problematic part could be the dependency on the remote inventory system webservice but with good caching of its outputs in the application it should be OK too. Unfortunately I've only vague idea of the system resources (memory size, number and speed of CPUs/cores) that such an "average Java EE application" for few hundred users needs. My rough and mostly unfounded estimate based on actual Amazon offerings is that 1.7GB and a single, 2-core "modern CPU" with speed around 2.5GHz (the High-CPU Medium Instance) should be sufficient for any of the two application servers (since we can handle higher load by provisioning more of them). Alternatively I would consider using the Large instance (64b, 7.5GB RAM, 2 cores at 1GHz) So my question is whether such a deployment to the cloud is technically and financially feasible or whether dedicated/VPS servers would be a better option and whether there are some real-world experiences with something similar. Thank you very much! /Jakub Holy PS: I've found the JBoss EAP in a Cloud Case Study that shows that it is possible to deploy a real-world Java EE application to the EC2 cloud but unfortunately there're no details regarding topology, instance types, or anything :-(

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  • Java getMethod with superclass parameters in method

    - by Jonathon
    Given: class A { public void m(List l) { ... } } Let's say I want to invoke method m with reflection, passing an ArrayList as the parameter to m: List myList = new ArrayList(); A a = new A(); Method method = A.class.getMethod("m", new Class[] { myList.getClass() }); method.invoke(a, Object[] { myList }); The getMethod on line 3 will throw NoSuchMethodException because the runtime type of myList is ArrayList, not List. Is there a good generic way around this that doesn't require knowledge of class A's parameter types?

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  • Java: Moving Away from XML Encode

    - by bguiz
    Hi, We have this software which loads various bits of data from files that are written using XMLEncode (serialization using XML). We want to migrate from that to our own proprietary file format (can be XML based). Is there a automated way to achieve this initial conversion, without having to perform a deserialization, and then write those objects out in the new format? XMLEncode format --> New proprietary file format Thanks!

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  • Java IndexOutOfBoundsException

    - by Meko
    Hi all ... I made an little shoot em up game..It works normal but I want also implement if fires intersects they will disappear. I have two list for Player bullets and for computer bullets ...But if I have more bullets from computer or reverse .Here my loop for (int i = 0; i < cb.size(); i++) { for (int j = 0; j < b.size(); j++) { if (b.get(j).rect.intersects(cb.get(i).rect)) { cb.remove(i); b.remove(j); continue; } if (cb.get(i).rect.intersects(b.get(j).rect)) { b.remove(j); cb.remove(i); continue; } } }

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  • Question about Java File Reader.

    - by Cris Carter
    Hello. I'm having some problems with the FileReader class. How do I specify an offset in the lines it goes through, and how do I tell it when to stop? Let's say I want it to go through each line in a .txt file, but only lines 100-200 and then stop? How would I do this? Right now I'm using ReadLine() but I don't think there's a way to specify offset with that. Any fast help is VERY appreciated. Thanks.

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  • Java Finalize method call

    - by Rajesh Kumar J
    I need to find when finalized method called in the JVM. I Created a test Class which write into file when finalized method called by Overriding the protected finalize method It is not executing. Can anybody tell me the reason why it is not executing?? Thanks in Advance

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  • Java Regex Matcher Question

    - by Yang
    How do I match an URL string like this: img src = "http://stackoverflow.com/a/b/c/d/someimage.jpg" where only the domain name and the file extension (jpg) is fixed while others are variables? The following code does not seem working: Pattern p = Pattern.compile("<img src=\"http://stachoverflow.com/.*jpg"); // Create a matcher with an input string Matcher m = p.matcher(url); while (m.find()) { String s = m.toString(); }

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  • Java System.in issue

    - by theo
    `public static void main(String[] args) { Scanner sc = new Scanner(System.in); while (sc.hasNext()) { if (sc.next().equals("exit")){ System.out.println("EXITING"); System.exit(0); } else { System.out.println("IM STILL WORKING ok?"); } } } }` So here is a piece of code i was writing the other day to try and figure sth out (doesn't really matter what). The result of executing this code is : eIM STILL WORKING ok? eIM STILL WORKING ok? exit IM STILL WORKING ok? exit EXITING Can somebody kindly explain why this has happened?

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  • java simple JPanel management (see screenshot)

    - by Allen
    I have a JPanel that encapsulates two JPanels, one on top of the other. The first holds two JLabels which hold the playing cards. The second holds the player's text (name and score). However, when I remove the player's cards, the lower JPanel moves up to the top, which i would prefer that it not do. Is there a way to keep it in place regardless of whether the top JPanel is occupied or not? Thanks

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  • How do I run different threads in Java?

    - by Cris Carter
    Hey. I'm having some problems with threads. I understand how they work, but since they all use the same method, how do I run different threads that do completely different things, but at the same time? To me, it seems that they always use the same standard method which makes them do the same thing. So, let's say I have a big .txt file where I want to go through each line and do something to the line. In this case, I would like to have each thread do 1/10th of the .txt file, but I don't understand how the threads can communicate with each other, and how they could organize so each thread does the right part? Could anyone explain or help me with this? Would be very much appreciated!

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  • Binary Search Tree in Java

    - by John R
    I want to make a generic BST, that can be made up of any data type, but i'm not sure how I could add things to the tree, if my BST is generic. All of my needed code is below. I want my BST made up of Locations, and sorted by the x variable. Any help is appreciated. Major thanks for looking. public void add(E element) { if (root == null) root = element; if (element < root) add(element, root.leftChild); if (element > root) add(element, root.rightChild); else System.out.println("Element Already Exists"); } private void add(E element, E currLoc) { if (currLoc == null) currLoc = element; if (element < root) add(element, currLoc.leftChild); if (element > root) add(element, currLoc.rightChild); else System.out.println("Element Already Exists); } Other Code public class BinaryNode<E> { E BinaryNode; BinaryNode nextBinaryNode; BinaryNode prevBinaryNode; public BinaryNode() { BinaryNode = null; nextBinaryNode = null; prevBinaryNode = null; } } public class Location<AnyType> extends BinaryNode { String name; int x,y; public Location() { name = null; x = 0; y = 0; } public Location(String newName, int xCord, int yCord) { name = newName; x = xCord; y = yCord; } public int equals(Location otherScene) { return name.compareToIgnoreCase(otherScene.name); } }

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  • How to share connection pool among multiple Java applications

    - by Wilson
    Hi all. I'm implementing several JavaSE applications on single server. Is it possible to setup a single connection pool (e.g. C3P0) and share among these applications? I just want to have an easy way to manage the total number of DB connections. Is there any drawbacks using such centralized connection pool? Thank you, Wilson

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  • java distributed cache for low latency, high availability

    - by Shahbaz
    I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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  • Complex string split in Java

    - by c0mrade
    Consider the following String : 5|12345|value1|value2|value3|value4+5|777|value1|value2|value3|value4?5|777|value1|value2|value3|value4+ Here is how I want to split string, split it with + so I get this result : myArray[0] = "5|12345|value1|value2|value3|value4"; myArray[1] = "5|777|value1|value2|value3|value4?5|777|value1|value2|value3|value4"; if string has doesn't contain char "?" split it with "|" and continue to part II, if string does contain "?" split it and for each part split it with "|" and continue to part II. Here is part II : myObject.setAttribute1(newString[0]); ... myObject.setAttribute4(newString[3]); Here what I've got so far : private static String input = "5|12345|value1|value2|value3|value4+5|777|value1|value2|value3|value4?5|777|value1|value2|value3|value4+"; public void mapObject(String input){ String[] myArray = null; if (input.contains("+")) { myArray = input.split("+"); } else { myArray = new String[1]; myArray[0] = input; } for (int i = 0; i < myArray.length; i++) { String[] secondaryArray = null; String[] myObjectAttribute = null; if (myArray[i].contains("?")) { secondaryArray = temporaryString.myArray[i].split("?"); for (String string : secondaryArray) { myObjectAttribute = string.split("\\|"); } } else { myObjectAttribute = myArray[i].toString().split("\\|"); } myObject.setAttribute1(myObjectAttribute[0]); ... myObject.setAttribute4(myObjectAttribute[3]); System.out.println(myObject.toString()); } Problem : When I split myArray, going trough for with myArray[0], everything set up nice as it should. Then comes the myArray[1], its split into two parts then the second part overrides the value of the first(how do I know that?). I've overridden toString() method of myObject, when I finish I print the set values so I know that it overrides it, does anybody know how can I fix this?

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  • "Fix" String encoding in Java

    - by Nico
    I have a String created from a byte[] array, using UTF8 encoding. However, it should have been created using another encoding (windows-1252). Is there a way to convert this string back to the right encoding? I know it's easy to do if you have access to the original byte array, but it my case it's too late because it's given by a closed source library. Thanks, Nico

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  • Any simple shape recognition libraries for Java?

    - by Phil
    I am working on a on-screen keyboard for Android, and I need to recognize starting points, turning points and end points of lines drawn by the user on the keyboard. A simple straightening function would be nice, as it is difficult to draw a perfectly straight line even with a stylus, not to mention finger-only touchscreens today. What I am trying to write is something like Swype. Any good libraries that I can use or make reference to?

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  • Java Threading Concept Understanding

    - by Nirmal
    Hello All... Recently I have gone through with one simple threading program, which leads me some issues for the related concepts... My sample program code looks like : class NewThread implements Runnable { Thread t; NewThread() { t = new Thread(this, "Demo Thread"); System.out.println("Child thread: " + t); t.start(); // Start the thread } public void run() { try { for (int i = 5; i > 0; i--) { System.out.println("Child Thread: " + i); Thread.sleep(500); } } catch (InterruptedException e) { System.out.println("Child interrupted."); } System.out.println("Exiting child thread."); } } class ThreadDemo { public static void main(String args[]) { new NewThread(); // create a new thread try { for (int i = 5; i > 0; i--) { System.out.println("Main Thread: " + i); Thread.sleep(1000); } } catch (InterruptedException e) { System.out.println("Main thread interrupted."); } System.out.println("Main thread exiting."); } } Now this program giving me the output as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Main Thread: 4 Child Thread: 3 Child Thread: 2 Main Thread: 3 Child Thread: 1 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. So, that's very much clear to me. But as soon as I am replacing the object creation code (calling of a NewThread class constructor) to as follows : NewThread nt = new NewThread(); // create a new thread the output becomes a bit varied like as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Child Thread: 3 Main Thread: 4 Child Thread: 2 Child Thread: 1 Main Thread: 3 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. And some times it's giving me same output in both the cases. So, i am not getting the exact change in both the scenario. I would like to know that you the variation in the output is coming here ? Thanks in advance...

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  • Java doesn't work with regex \s, says: invalid escape sequence

    - by Jayomat
    hi, I want to replace all whitespace characters in a string with a "+" and all "ß" with "ss"... it works well for "ß", but somehow eclipse won't let me use \s for a whitespace.. I tried "\t" instead, but it doesn't work either.. I get the following error: Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \ ) this is my code: try { String temp1 = from.getText().toString(); start_from = temp1.replaceAll("ß", "ss"); start_from = start_from.replaceAll("\s", "+"); } why doesn't it work? is it a problem with android, eclipse or what? thanks in advance!

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  • Java: Using Comman line arguments to process the names of files

    - by Kat
    I'm a writing a program that will determine the number of lines, characters, and average word length for a text file. For the program, the specifications say that the file or files will be entered as a command line argument and that we should make a TestStatistic object for each file entered. I don't understand how to write the code for making the TestStatistic objects if the user enters more than one file.

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  • Java: error handling with try-catch, empty-try-catch, dummy-return

    - by HH
    A searh uses recursively defined function that easily throws exceptions. I have tried 3 ways to handle exeptions: to ignore with an empty-try-catch() add-dummy-return stop err-propagation due to exeption throw a specific except. (this part I don't really understand. If I throw except, can I force it to continue elsewhere, not continuing the old except-thrown-path?) Some exceptions I do not realy care like during execution removed files -exception (NullPointer) but some I really do like unknown things. Possible exceptions: // 1. if a temp-file or some other file removed during execution -> except. // 2. if no permiss. -> except. // 3. ? --> except. The code is Very import for the whole program. I earlier added clittered-checks, try-catches, avoided-empty-try-catches but it really blurred the logic. Some stoned result here would make the code later much easier to maintain. It was annoying to track random exeptions due to some random temp-file removal! How would you handle exceptions for the critical part? Code public class Find { private Stack<File> fs=new Stack<File>(); private Stack<File> ds=new Stack<File>(); public Stack<File> getD(){ return ds;} public Stack<File> getF(){ return fs;} public Find(String path) { // setting this type of special checks due to errs // propagation makes the code clittered if(path==null) { System.out.println("NULL in Find(path)"); System.exit(9); } this.walk(path); } private void walk( String path ) { File root = new File( path ); File[] list = root.listFiles(); //TODO: dangerous with empty try-catch?! try{ for ( File f : list ) { if ( f.isDirectory() ) { walk( f.getAbsolutePath() ); ds.push(f); } else { fs.push(f); } } }catch(Exception e){e.printStackTrace();} } } Code refactored from here.

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