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  • Recursively determine average value

    - by theva
    I have to calculate an average value of my simulation. The simulation is ongoing and I want (for each iteration) to print the current average value. How do I do that? I tried the code below (in the loop), but I do not think that the right value is calculated... int average = 0; int newValue; // Continuously updated value. if(average == 0) { average = newValue; } average = (average + newValue)/2; I also taught about store each newValue in an array and for each iteration summarize the whole array and do the calculation. However, I don't think that's a good solution, because the loop is an infinity loop so I can't really determine the size of the array. There is also a possibility that I am thinking too much and that the code above is actually correct, but I don't think so...

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  • Reset JPA generated value between tests

    - by Rythmic
    I'm running spring + hibernate + JUnit with springJunit4runner and transactional set to default rollback I'm using in-memory derbydb as Database. Hibernate is used as a JPA Provider and I am successfully testing CRUD kinds of stuff. However, I have a problem with JPA and the behaviour of @GeneratedValue If I run one of my tests in isolation, two entitys are persisted with id 1 and 2. If i run the whole test suite the ids are instead 6 and 7. Spring does rollbacks just fine so there are only these two entitys in the database after addition and of course zero before. But behaviour of @GeneratedValue doesn't allow me to reliable findById unless I would return the Id from the dao.add(Entity e) //method I don't feel like doing that for the sake of testing, or is it a good practise to return the entity that was persisted so I should be doing it anyway?

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  • How to use ASTRewrite split one field declaration into two?

    - by user307598
    For example: private long p, q, g, h; I want to split this field declaration as: private long p; private long q, g, h; How can I use ASTRewrite to do it? I tried to use ASTNode copyFd = rewriter.createCopyTarget(fd) to copy the field declaration, modify it, then add to field declaration list, but my modification on copyFd is not seen. It's just the same to fd. Why? Anybody can help?

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  • Mysql maven jpa skeleton

    - by coubeatczech
    Hi, is there a skeleton for a project using mysql, some eclipse/top link with RESOURCE_LOCAL as connection type? Preferably using maven. I'm searching for it for hours and can't get running even the sipmlest exaple. So if you had it ready and running, please, post :-). Even something as simple as these two classes only. @Entity public class Message implements Serializable{ public Message() {} public Message(String s){ this.s = s; } @Id String s; public String getS(){ return s; } } public class App { static private EntityManagerFactory emf; static private EntityManager em; public static void main( String[] args ) { emf = Persistence.createEntityManagerFactory("persistence"); em = emf.createEntityManager(); Message m = new Message("abc"); em.persist(m); } }

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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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  • 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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  • 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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  • Interview question : What is the fastest way to generate prime number recursively ?

    - by hilal
    Generation of prime number is simple but what is the fastest way to find it and generate( prime numbers) it recursively ? Here is my solution. However, it is not the best way. I think it is O(N*sqrt(N)). Please correct me, if I am wrong. public static boolean isPrime(int n) { if (n < 2) { return false; } else if (n % 2 == 0 & n != 2) { return false; } else { return isPrime(n, (int) Math.sqrt(n)); } } private static boolean isPrime(int n, int i) { if (i < 2) { return true; } else if (n % i == 0) { return false; } else { return isPrime(n, --i); } } public static void generatePrimes(int n){ if(n < 2) { return ; } else if(isPrime(n)) { System.out.println(n); } generatePrimes(--n); } public static void main(String[] args) { generatePrimes(200); }

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  • Android: The concept for detecting changes of an opened file

    - by niko
    I wrote an application for video recording which stores the recording to a file. Currently I am looking for a way to implement some kind of "listener" to listen for file changes. The concept I would like to implement is the following: Check the file on a set period of time (for example one second), extract changes (get the data that was written in the last period) and do something with these data. I would be very thankful if anyone of you could give any suggestion or point to any useful resource that could help to solve the given problem.

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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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  • A beginner's log4J question

    - by Nitesh Panchal
    Hello, i configured log4j for basic purpose usin the conversion pattern :- log4j.appender.rollingFile.layout.ConversionPattern=%p %t %c - %m%n But now i want to log the class name from which the error came as well as the username(available in session object) as well as the date and time when that event occurs. How do i do this? What changes do i need to make in format string? Thanks in advance :)

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  • Iterating over hashmap in JSP in struts application

    - by Rozer
    I have a HashMap object that I am getting on a JSP page. HashMap<Integer,Gift_product> gift_hm = new HashMap<Integer,Gift_product>(); gift_hm.put(17,new Gift_product("doll",67)); Now I need to iterate this and display content on JSP. The Gift_product class contains two fields: name and price. JSP output should be serial no. product name price 17 Doll 67 How can I achieve it?

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  • Question regarding the method local innerclasses accesing the local variables of the method

    - by flash
    Hi I was going through the SCJP book about the innerclasses, and found this statement, it goes something like this. "A method local class can only refer to the local variables which are marked final" and in the explanation the reason specified is about the scope and lifetime of the local class object and the local variables on the heap, But I am unable to understand that.am I missing anything here about 'final'??

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  • How do I refer to a client_deploy.wsdd file that's in WEB-INF?

    - by Paul
    A basic question, but I can't seem to find the answer. I have an Axis-generated web service that also calls another web service (for which the stubs are also generated with Axis). It's deployed in weblogic 9.2 That called web service requires authentication. I've googled for the code to set up authentication. It requires that I set up a client_deploy.wsdd file which I've done, and added it to WEB-INF. I need to specify this flle to Axis. There seem to be several ways of doing this, including System.setProperty("axis.ClientConfigFile", "client_deploy.wsdd") or EngineConfiguration config = new FileProvider("client_deploy.wsdd"); but these aren't working for me. Is the issue the path for the client_deploy.wsdd file? How do I refer to a file that's at the top level of the WEB-INF directory? Googling tells me how to access it as a stream, but I don't want that, I need to pass a file name to these functions... Please point out the obvious that I have missed

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  • What are the suggested alternatives for Class<T>.isAssignableFrom(Class<?> cls)?

    - by Wing C. Chen
    Currently I am doing the profiling to a piece of code. During the profiling, I discovered that this very method call, Class<T>.isAssignableFrom(Class<?> cls) takes up to quite amount of the entire time. Because this is a method from reflection, it takes a lot of time compared to normal keywords or method calls. I am wondering if there are some good alternatives for this method calls?

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  • Iterative Reduction to Null Matrix

    - by user1459032
    Here's the problem: I'm given a matrix like Input: 1 1 1 1 1 1 1 1 1 At each step, I need to find a "second" matrix of 1's and 0's with no two 1's on the same row or column. Then, I'll subtract the second matrix from the original matrix. I will repeat the process until I get a matrix with all 0's. Furthermore, I need to take the least possible number of steps. I need to print all the "second" matrices in O(n) time. In the above example I can get to the null matrix in 3 steps by subtracting these three matrices in order: Expected output: 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 1 0 0 1 0 0 0 1 1 0 0 I have coded an attempt, in which I am finding the first maximum value and creating the second matrices based on the index of that value. But for the above input I am getting 4 output matrices, which is wrong: My output: 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 My solution works for most of the test cases but fails for the one given above. Can someone give me some pointers on how to proceed, or find an algorithm that guarantees optimality? Test case that works: Input: 0 2 1 0 0 0 3 0 0 Output 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0

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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 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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  • Job queueing and execute Mechanism

    - by Calm Storm
    In my webservice all method calls submits jobs to a queue. Basically these operations take long time to execute, so all these operations submit a Job to a queue and return a status saying "Submitted". Then the client keeps polling using another service method to check for the status of the job. Presently, what I do is create my own Queue, Job classes that are Serializable and persist these jobs (i.e, their serialized byte stream format) into the database. So an UpdateLogistics operation just queues up a "UpdateLogisticsJob" to the queue and returns. I have written my own JobExecutor which wakes up every N seconds, scans the database table for any existing jobs, and executes them. Note the jobs have to persisted because these jobs have to survive app-server crashes. This was done a long time ago, and I used bespoke classes for my Queues, Jobs, Executors etc. But now, I would like to know has someone done something similar before? In particular, Are there frameworks available for this ? Something in Spring/Apache etc Any framework that is easy to adapt/debug and plays well along with libraries like Spring will be great.

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  • Tomcat memory issue

    - by user305210
    Hello, I have noticed that my application that is running on Tomcat 5 starts with 1gig of memory and as soon as it starts receiving requests from client, the memory starts dropping until it is down to 100MBs and troubles start from there. I am looking at /manager/status page of tomcat under JVM section where "Free Memory", "Total Memory", "Max Memory" is listed. Is this an indicator of memory leak? Memory does not seem to be freed-up automatically even if there are no requests coming from client machines.

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