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  • How do I alias the scala setter method 'myvar_$(myval)' to something more pleasing when in java?

    - by feydr
    I've been converting some code from java to scala lately trying to tech myself the language. Suppose we have this scala class: class Person() { var name:String = "joebob" } Now I want to access it from java so I can't use dot-notation like I would if I was in scala. So I can get my var's contents by issuing: person = Person.new(); System.out.println(person.name()); and set it via: person = Person.new(); person.name_$eq("sallysue"); System.out.println(person.name()); This holds true cause our Person Class looks like this in javap: Compiled from "Person.scala" public class Person extends java.lang.Object implements scala.ScalaObject{ public Person(); public void name_$eq(java.lang.String); public java.lang.String name(); public int $tag() throws java.rmi.RemoteException; } Yes, I could write my own getters/setters but I hate filling classes up with that and it doesn't make a ton of sense considering I already have them -- I just want to alias the _$eq method better. (This actually gets worse when you are dealing with stuff like antlr because then you have to escape it and it ends up looking like person.name_\$eq("newname"); Note: I'd much rather have to put up with this rather than fill my classes with more setter methods. So what would you do in this situation?

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  • Avoiding duplicate objects in Java deserialization

    - by YGL
    I have two lists (list1 and list2) containing references to some objects, where some of the list entries may point to the same object. Then, for various reasons, I am serializing these lists to two separate files. Finally, when I deserialize the lists, I would like to ensure that I am not re-creating more objects than needed. In other words, it should still be possible for some entry of List1 to point to the same object as some entry in List2. MyObject obj = new MyObject(); List<MyObject> list1 = new ArrayList<MyObject>(); List<MyObject> list2 = new ArrayList<MyObject>(); list1.add(obj); list2.add(obj); // serialize to file1.ser ObjectOutputStream oos = new ObjectOutputStream(...); oos.writeObject(list1); oos.close(); // serialize to file2.ser oos = new ObjectOutputStream(...); oos.writeObject(list2); oos.close(); I think that sections 3.4 and A.2 of the spec say that deserialization strictly results in the creation of new objects, but I'm not sure. If so, some possible solutions might involve: Implementing equals() and hashCode() and checking references manually. Creating a "container class" to hold everything and then serializing the container class. Is there an easy way to ensure that objects are not duplicated upon deserialization? Thanks.

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  • How to implement a list fold in Java

    - by Peter Kofler
    I have a List and want to reduce it to a single value (functional programing term "fold", Ruby term "inject"), like Arrays.asList("a", "b", "c") ... fold ... "a,b,c" As I am infected with functional programing ideas (Scala), I am looking for an easier/shorter way to code it than sb = new StringBuilder for ... { append ... } sb.toString

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  • java shift elements in array

    - by Lightk3ira
    Hey I am trying to shift elements forward sending the last element in the array to data[0]. I did the opposite direction but I can't seem to find my mistake in going in this direction. Pos is users inputed shift times amount temp is the temporary holder. data is the array if(pos 0) { do { temp = data[data.length -1]; for(int i =0; i < data.length; i++) { if(i == data.length-1) { data[0] = temp; } else { data[i+1] = data[i]; } } pos--; }while(pos > 0); } Thanks.

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  • Clone List Elements in Java

    - by Amir Rachum
    Hi all, I have a variable of type List<RelationHeader>. Now I want to copy all the elements in this list to a new list, but I want to actually copy all the members by value (clone them). Is there a quick command to do this, or do I need to iterate over the list and copy them one at a time?

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  • Java Hibernate Lazy=false

    - by Noor
    When setting Lazy=false, then hibernate will automatically loads the objects into the required sets e.g. <set name="Options" table="ATTRIBUTEOPTION" inverse="false" cascade="all" lazy="false"> <key> <column name="ATTRIBUTEID" /> </key> <one-to-many class="com.BiddingSystem.Models.AttributeOption" /> </set> but if in my xml mapping, I place lazy=true and in some place in my application i decide that i want to load all attribute options, should i do it manually, or is there a technique which lets tells hibernate that now i want to set lazy=false??

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  • Java: serial thread confinement question

    - by denis
    Assume you have a Collection(ConcurrentLinkedQueue) of Runnables with mutable state. Thread A iterates over the Collection and hands the Runnables to an ExecutorService. The run() method changes the Runnables state. The Runnable has no internal synchronization. The above is a repetitive action and the worker threads need to see the changes made by previous iterations. So a Runnable gets processed by one worker thread after another, but is never accessed by more than one thread at a time - a case of serial thread confinement(i hope ;)). The question: Will it work just with the internal synchronization of the ConcurrentLinkedQueue/ExecutorSerivce? To be more precise: If Thread A hands Runnable R to worker thread B and B changes the state of R, and then A hands R to worker thread C..does C see the modifications done by B?

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  • Java: Convenient way to refactor the application.

    - by Harshal
    Hi, Everyone We have an agile enterprise application built on JSP and Servlet without any design strategy. This application was built in early 2002 considering 1000 users. After 2002, we received lots of requests from the marketing partners. Currently, the application has lots of spaghetti code with lots of Ifs and elses. One class has more than 20,000 lines of code with a huge body of functions without abstraction. Now, we need to support billions of records, what we need to do immediately and gradually? We have to refactor the application? Which framework, we need to use? How the usage of the framework will be helpful to the end users? How to convince the leaders to do the refactoring? How to gain the faster response time as compare to the current system?

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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: remove current scheduled job in a class that implements IScheduledJob

    - by ufk
    Hi. In the execution of the scheduled job itself i want to stop it from being executed again and again, how can i do so without having the string that i received when i created the job in the first place ? public class UfkJob implements IScheduledJob { public void execute(ISchedulingService service) { if (...) { /* here i want to remove the current running job */ } } I executed the job outside by using the commands: ISchedulingService service = (ISchedulingService) getScope().getContext().getBean(ISchedulingService.BEAN_NAME); service.addScheduledJobAfterDelay(5000,new UfkJob(),200);

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  • Java: JButton actionListener explantation

    - by MrDoctorProfessorTyler
    I am extremely confused as to how a JButton works. I have read over the oracle documents of the JButton, but I have failed to see how a JButton can have an actionlistener added to it. I have really always wondered how things like JFrames and all that can have things like .addMouseListener and all that. Can anyone explain how a JButton can have an actionListener added to it like the .addActionListener(...) syntax?

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  • creating Sites using java

    - by rajalakshmi
    Hi i developed one application used to create google sites by referring the developer guide in which i don't know what are the three parameters in this is particular line SitesService client = new SitesService("yourCo-yourAppName-v1"). This is my problem. help me

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  • Blackberry (Java) - Setting scrolling be not focused on objects on the screen

    - by paullb
    I have a mainscreen which currently scrolls (and I have the arrows on the right) but the scrolling seems to be focused on the ButtonField objects that I have on the page. Is there any way to set the scrolling to be non-focused scrolling (moving a few pixels each time). Is there a way to set this? Other ideas I have had (which sound hacky so I want to avoid): - Placing NullFields around to scroll - Manually listening to the trackwheelRoll event and moving appropriately

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  • Internal Java code best practice for dealing with invalid REST API parameters

    - by user326389
    My colleague wrote the following stackoverflow question: other stack overflow question on this topic The question seems to have been misinterpreted and I want to find out the answer, so I'm starting this new question... hopefully a little more clear. Basically, we have a REST API. Users of our API call our methods with parameters. But sometimes users call them with the wrong parameters!! Maybe a mistake in their code, maybe they're just trying to play with us, maybe they're trying to see how we respond, who knows! We respond with HTTP status error codes and maybe a detailed description of the invalid parameter in the XML response. All is well. But internally we deal with these invalid parameters by throwing exceptions. For example, if someone looks up a Person object by giving us their profile id, but the profile id doesn't exist... we throw a PersonInvalidException when looking them up. Then we catch this exception in our API controller and send back an HTTP 400 status error code. Our question is... is this the best practice, throwing exceptions internally for this kind of user error? These exceptions never get propogated back to the user, this is a REST API. They only make our code cleaner. Otherwise we could have a validation method in each of our API controllers to make sure the parameters all make sense, but that seems inefficient. We have to look up things in our database potentially twice. Or we could return nulls and check for them, but that sucks... What are your thoughts?

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  • Java: Typecasting to Generics

    - by bguiz
    This method that uses method-level generics, that parses the values from a custom POJO, JXlistOfKeyValuePairs (which is exactly that). The only thing is that both the keys and values in JXlistOfKeyValuePairs are Strings. This method wants to taken in, in addition to the JXlistOfKeyValuePairs instance, a Class<T> that defines which data type to convert the values to (assume that only Boolean, Integer and Float are possible). It then outputs a HashMap with the specified type for the values in its entries. This is the code that I have got, and it is obviously broken. private <T extends Object> Map<String, T> fromListOfKeyValuePairs(JXlistOfKeyValuePairs jxval, Class<T> clasz) { Map<String, T> val = new HashMap<String, T>(); List<Entry> jxents = jxval.getEntry(); T value; String str; for (Entry jxent : jxents) { str = jxent.getValue(); value = null; if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } else if (clasz.isAssignableFrom(Float.class)) { value = (T)(Float.parseFloat(str)); } else { logger.warn("Unsupported value type encountered in key-value pairs, continuing anyway: " + clasz.getName()); } val.put(jxent.getKey(), value); } return val; } This is the bit that I want to solve: if (clasz.isAssignableFrom(Boolean.class)) { value = (T)(Boolean.parseBoolean(str)); } else if (clasz.isAssignableFrom(Integer.class)) { value = (T)(Integer.parseInt(str)); } I get: Inconvertible types required: T found: Boolean Also, if possible, I would like to be able to do this with more elegant code, avoiding Class#isAssignableFrom. Any suggestions? Sample method invocation: Map<String, Boolean> foo = fromListOfKeyValuePairs(bar, Boolean.class);

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  • Strange Java Socket Behavior (Connects, but Doesn't Send)

    - by Donald Campbell
    I have a fairly complex project that boils down to a simple Client / Server communicating through object streams. Everything works flawlessly for two consecutive connections (I connect once, work, disconnect, then connect again, work, and disconnect). The client connects, does its business, and then closes. The server successfully closes both the object output stream and the socket, with no IO errors. When I try to connect a third time, the connection appears to go through (the ServerSocket.accept() method goes through and an ObjectOutputStream is successfully created). No data is passed, however. The inputStream.readUnshared() method simply blocks. I have taken the following memory precautions: When it comes time to close the sockets, all running threads are stopped, and all objects are nulled out. After every writeUnshared() method call, the ObjectOutputBuffer is flushed and reset. Has anyone encountered a similar problem, or does anyone have any suggestions? I'm afraid my project is rather large, and so copying code is problematic. The project boils down to this: SERVER MAIN ServerSocket serverSocket = new ServerSocket(port); while (true) { new WorkThread(serverSocket.accept()).start(); } WORK THREAD (SERVER) public void run() { ObjectInputBuffer inputBuffer = new ObjectInputBuffer(new BufferedInputStream(socket.getInputStream())); while (running) { try { Object myObject = inputBuffer.readUnshared(); // do work is not specified in this sample doWork(myObject); } catch (IOException e) { running = false; } } try { inputBuffer.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } CLIENT public Client() { Object myObject; Socket mySocket = new Socket(address, port); try { ObjectOutputBuffer output = new ObjectOutputBuffer(new BufferedOutputStream(mySocket.getOutputStream())); output.reset(); output.flush(); } catch (Exception e) { System.out.println("Could not get an input."); mySocket.close(); return; } // get object data is not specified in this sample. it simply returns a serializable object myObject = getObjectData(); while (myObject != null) { try { output.writeUnshared(myObject); output.reset(); output.flush(); } catch (Exception e) { e.printStackTrace(); break; } // catch } // while try { output.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } Thank you to everyone who may be able to help!

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  • Java generics question with wildcards

    - by Sean
    Just came across a place where I'd like to use generics and I'm not sure how to make it work the way I want. I have a method in my data layer that does a query and returns a list of objects. Here's the signature. public List getList(Class cls, Map query) This is what I'd like the calling code to look like. List<Whatever> list = getList(WhateverImpl.class, query); I'd like to make it so that I don't have to cast this to a List coming out, which leads me to this. public <T> List<T> getList(Class<T> cls, Map query) But now I have the problem that what I get out is always the concrete List<WhateverImpl> passed in whereas I'd like it to be the Whatever interface. I tried to use the super keyword but couldn't figure it out. Any generics gurus out there know how this can be done?

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  • Real life Java Swing Project

    - by santiagobasulto
    Hi everybody! I've been working with swing for the last 2 years, but i'm still not satisfy with my own work. The apps are "fast" enough, but the development isn't enough "clean". Can you recommend me any real world project, book, or something similar that shows me how a real world swing app work. May be a framework, something structured, etc. For example, i'm thinking i may code a "window manager" that has all the window of the app in an unified resource, may be cached, etc. I think all those good ideas must be implemented already. Thanks!

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  • java multiple operations depending on the type of the object passed

    - by mixm
    assuming i create a method which is passed an object, and that method would perform an action depending on the object passed. how should i identify the object? i thought of using the class name to identify the object, but may be impractical since i could easily change the class name of objects, and generate headaches during future development. am i right?

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  • Why doesn't Java Map extends Collection?

    - by polygenelubricants
    I was surprised by the fact that Map<?,?> is not a Collection<?>. I thought it'd make a LOT of sense if it was declared as such: public interface Map<K,V> extends Collection<Map.Entry<K,V>> After all, a Map<K,V> is a collection of Map.Entry<K,V>, isn't it? So is there a good reason why it's not implemented as such?

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  • performing auditing in java with sql server DB - before and/or after do not get audited

    - by Domingos
    When auditing, sometimes the before value does not get audited, other times the after value does not get audited, other times both values do not get audited at all. After researching, I found out that only values from a specific codes table get audited. the code was: compareCodesTableInteger(audit, int, int, objectBefore, objectAfter, stringDescription, stringCodesTable); I then changed it to: compareCodesTableInteger(audit, int, int, objectBefore, objectAfter, stringDescription, booleanCheck ? stringCodesTableIfTrue : stringCodesTableIfFalse); Description: if objectBefore AND objectAfter are both from stringCodesTableIfTrue OR from stringCodesTableIfFalse, auditing takes place as expected. The problem is: most of the times, objectBefore is from stringCodesTableIfTrue, and objectAfter is from stringCodesTableIfFalse, or vice-versa. In this scenario auditing fails. How do I go around this? Please assist

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