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• Java Pack No Resize

  - by ikurtz

  i am learning Java at the moment and have the following question: i am adding my controls to JFrame and then pack() before displaying. this runs the application and all is very nice. i was wondering is there a way to stop the user from resizing the application window? also is there a way to for the image in JLabel to expand as the user changes the application window? at the moment i have it as: constraints.fill = GridBagConstraints.BOTH; constraints.anchor = GridBagConstraints.CENTER; and it only centers the image, i would like to be able to expand/shrink the image. thanks.

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• The right way to implement communication between java objects

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that I has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• Running interrelated methods continously using java

  - by snehalata

  I have written application which downloads data from a website every 10 mins and writes to a file.Then these files are merged into one file and then R program is run on this merged file to perform sentiment analysis and result is stored in hbase. I want the process of merging files,running R and then storing to HBase to run continuosly on the downloaded data. For running R,we are running R script from java program.We have used Runtime.getRuntime().exec() method to run R program but it doesn't wait for R program to complete and method in the next line starts executing.Using p.waitFor() did not help . What approach should I use to do merge then run R and finally store results in Hbase?Should I use timer class??

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• String comparison in Java

  - by Kliver Max

  I want to compare two strings using Java. First sting name i get from .mif file using GDAL in cp1251 encoding. Second kadname i get from jsp. To compare i do this: if (attrValue instanceof String) { String string3 = new String((attrValue.toString()).getBytes("ISO-8859-1"), "cp1251"); dbFeature.setAttribute(name, string3); System.out.println("Name=" + name); System.out.println("kadname=" + kadname); if (name.equalsIgnoreCase(kadname)) { kadnum = string3; System.out.println("string3" + string3); } } And in console i get this: Name = kadnumm kadname = kadnumm Whats wrong with this?

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• Operation Problems in Java Generic

  - by alantheweasel

  I got some problem when i was learning Java Generic : interface calculator<T, R> { public void execute(T t, R r); } class executeAdd<T, R> implements calculator<T, R> { private T first; private R second; public executeAdd(T first, R second) { super(); this.first = first; this.second = second; } @Override public void execute(T t, R r) { // TODO Auto-generated method stub Object o = t + r // ERROR ! What i could do it ? } }

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• Drawing graphs on java

  - by nunos

  I want to draw graphs (nodes and edges) in Java. However, since I don't know how to go about it, I would like to have some advice before starting. How should I do this? use Graphics2D package, right? How about the labels for the nodes? should I use something like drawString and handle all the "centering" manually or create a JLabel for that? Can I put a JLabel on a Graphics2D environment? I have searched but haven't found any simple implementation of this. If you know of one, please provide the link in your answer. Thanks.

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• Java swing center JDialog over parent

  - by Chris Drappier

  I have a Java swing application with a button that produces a popup window when a certain action is performed. I'd like to align the center point of the popup window with the center point of the parent window when it is rendered. How can I calculate the x,y coordinates to plug into setLocation() for the popup window? EDIT: just to clarify. I do not want the behavior of setLocationRelativeTo() because that sets the top-left pixel of the popup over the center pixel of the parent frame. I want to set the center pixel of the popup over the center pixel of the parent frame. Also, I'm not interested in whether or not a popup window is good practice. I'm past that now. thanks

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• Simple Java library for storing statistical observations and calculating statistics such as stddev,

  - by knorv

  For logging purposes I want to collect the response times of an external system, and periodically fetch various statistics (such as min/max/stddev) of the response times. I'm looking for a pure in-memory solution. What Java library can help me with this simple task? I'm looking for an API that would ideally look something along the lines of: StatisticsCollector s = new StatisticsCollector(); while (...) { double responseTime = ...; s.addObservation(responseTime); } double stddev = s.getStandardDeviation(); double mean = s.getMean();

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• Java deserialization speed

  - by celicni

  I am writing a Java application that among other things needs to read a dictionary text file (each line is one word) and store it in a HashSet. Each time I start the application this same file is being read all over again (6 Megabytes unicode file). That seemed expensive, so I decided to serialize resulting HashSet and store it to a binary file. I expected my application to run faster after this. Instead it got slower: from ~2,5 seconds before to ~5 seconds after serialization. Is this expected result? I thought that in similar cases serialization should increase speed.

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• Java exception translations

  - by user3079275

  Apologies if this has been discussed on other threads but I find it helps clarify my thinking when I am forced to write down my questions. I am trying to properly understand the concept of checked vs unchecked exceptions and exception translation in Java but I am getting confused. So far I understood that checked exceptions are exceptions that need to be always caught in a try/catch block otherwise I get a compile time error. This is to force programmers to think about abnormal situations that might happen at run time (like disk full etc). Is this right? What I did not get was why we have unchecked exceptions, when are they useful? Is it only during development time to debug code that might access an illegal array index etc? This confusion is because I see that Error exceptions are also unchecked as is RunTimeException but its not clear to me why they are both lumped together into an unchecked category?

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• Debugging in netbeans (java)

  - by Daen

  I have been asking this myself for a while. Debugging in visual studio goes smooth. But when i debugg in Netbeans(java) i find myself more then half of the time browsing trough the system code itself. This makes it almost unpossible for me to detect hard to find bugs, cause debugging simply is to tedious and unmanageable. How can this be avoided? Stepping out all the time takes a insane amount of time, and i only wish to debug the code i have written down. I usally add all the controls myself without using any drag and drop for forms if that makes any difference in the total picture. Regards.

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• how to generate XML (in String representation) in java

  - by flyingfromchina

  I have defined a java class, but only need to output some of the fields of this class into an XML. The returned type must be a String. I first opted for the easiest way using a StringBuffer. However, when I tried to process the output String represenation, it failed. I think it is mostly likely because there are some characters that are not encoded in the UTF-8 in the input. Could someone tell me what is the best way to handle this? Thanks.

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• cron library for java

  - by nutsiepully

  I am looking for a cron expression library in java. Something that can parse cron expressions and return me future fire times for the trigger. API on the lines of. CronExpression cronExpression = new CronExpression("0 30 4 * * *"); List<Date> fireTimes = cronExpression.getFireTimes(todaysDate, nextWeekDate); I don't want to use something as complicated as quartz. The purpose is to basically use cron like a regex for timings. That's all. I do not want a background scheduler. I tried googling but wasn't able to find anything very helpful. Any suggestions would be appreciated. Regards, Pulkit P.S - I looked at using the CronExpression class out of quartz. Wasn't very helpful - failing some tests.

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• How do I make a OnClickListener in Java

  - by Bob

  I used to program with html and to make a alert all I had to do was make an alert("Hello World"); but with java it is much more advanced. I need help to make a button that when someone clicks it, it has an alert message on the screen. This is my code right now: MyOnClickListener onClickListener = new MyOnClickListener() { @Override public void onClick(View v) { Intent returnIntent = new Intent(); returnIntent.putExtra("deleteAtIndex",idx); setResult(RESULT_OK, returnIntent); finish(); } }; for (int i =0;i<buttonList.size();i++) { buttonList.get(i).setText("Remove"); buttonList.get(i).setOnClickListener(onClickListener); }

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• Defining Proper Classes with Java

  - by user2579706

  Ok, I'm studying Java and have the following question: "Assume you defined a class named MyClass. A student wants to use your class and tries to declare an instance named myObj and instantiate it. He tried the following: MyObj MyClass = new MyClass( ); Why won't his code work? Show how he should correct it. " I'm not sure how to do this? Can anyone point me in the right direction? Many thanks.

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• Java, UnmarshallingException caused by XML attribute with special chars: ;ìè+òàù-<^èç°§_>!£$%&/()=?~

  - by segolas

  Hi, my xml file has a tag with an attribute "containsValue" which contains the "special" characters you can see in the subject: <original_msg_body id="msgBodySpecialCharsRule" containsValue=";ìè+òàù-<^èç°§_>!£$%&/()=?~`'#;" /> in my xml schema the attribute has xs:string: <xs:attribute name="containsValue" type="xs:string" /> I use this value inside a Java software which check if this value is contained inside another String. but I always obtain this Exception: javax.xml.bind.UnmarshalException - with linked exception: [org.xml.sax.SAXParseException: The value of attribute "containsValue" associated with an element type "original_msg_body" must not contain the '<' character.] How can I solve it? I've tried changing the attribute type to xs:NMTOKEN, ut I get the same exception. Is there any other type? I think I could change the characters encoding, for example using the HTML representation, like <, but than could be tricky for the string comparison...

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• Managing User & Role Security with Oracle SQL Developer

  - by thatjeffsmith

  With the advent of SQL Developer v3.0, users have had access to some powerful database administration features. Version 3.1 introduced more powerful features such as an interface to Data Pump and RMAN. Today I want to talk about some very simple but frequently ran tasks that SQL Developer can assist with, like: identifying privs granted to users managing role privs assigning new roles and privs to users & roles Before getting started, you’ll need a connection to the database with the proper privileges. The common ROLE used to accomplish this is the ‘DBA‘ role. Curious as to what the DBA role is actually comprised of? Let’s find out! Open the DBA Console First make sure you’re connected to the database you want to manage security on with a privileged administrator account. Then open the View menu and select ‘DBA.’ Accessing the DBA panel ‘Create’ a Connection Click on the green ‘+’ button in the DBA panel. It will ask you to choose a previously defined SQL Developer connection. Defining a DBA connection in Oracle SQL Developer Once connected you will see a tree list of DBA features you can start interacting with. Expand the ‘Security’ Tree Node As you click on an object in the DBA panel, the ‘viewer’ will open on the right-hand-side, just like you are accustomed to seeing when clicking on a table or stored procedure. Accessing the DBA role If I’m a newly hired Oracle DBA, the first thing I might want to do is become very familiar with the DBA role. People will be asking you to grant them this role or a subset of its privileges. Once you see what the role can do, you will become VERY protective of it. My favorite 3-letter 4-letter word is ‘ANY’ and the DBA role is littered with privileges like this: ANY TABLE privs granted to DBA role So if this doesn’t freak you out, then maybe you should re-consider your career path. Or in other words, don’t be granting this role to ANYONE you don’t completely trust to take care of your database. If I’m just assigned a new database to manage, the first thing I might want to look at is just WHO has been assigned the DBA role. SQL Developer makes this easy to ascertain, just click on the ‘User Grantees’ panel. Who has the keys to your car? Making Changes to Roles and Users If you mouse-right-click on a user in the Tree, you can do individual tasks like grant a sys priv or expire an account. But, you can also use the ‘Edit User’ dialog to do a lot of work in one pass. As you click through options in these dialogs, it will build the ‘ALTER USER’ script in the SQL panel, which can then be executed or copied to the worksheet or to your .SQL file to be ran at your discretion. A Few Clicks vs a Lot of Typing These dialogs won’t make you a DBA, but if you’re pressed for time and you’re already in SQL Developer, they can sure help you make up for lost time in just a few clicks!

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• How to populate Java (web) application with initial data using Spring/JPA/Hibernate

  - by Tuukka Mustonen

  I want to setup my database with initial data programmatically. I want to populate my database for development runs, not for testing runs (it's easy). The product is built on top of Spring and JPA/Hibernate. Developer checks out the project Developer runs command/script to setup database with initial data Developer starts application (server) and begins developing/testing then: Developer runs command/script to flush the database and set it up with new initial data because database structures or the initial data bundle were changed What I want is to setup my environment by required parts in order to call my DAOs and insert new objects into database. I do not want to create initial data sets in raw SQL, XML, take dumps of database or whatever. I want to programmatically create objects and persist them in database as I would in normal application logic. One way to accomplish this would be to start up my application normally and run a special servlet that does the initialization. But is that really the way to go? I would love to execute the initial data setup as Maven task and I don't know how to do that if I take the servlet approach. There is somewhat similar question. I took a quick glance at the suggested DBUnit and Unitils. But they seem to be heavily focused in setting up testing environments, which is not what I want here. DBUnit does initial data population, but only using xml/csv fixtures, which is not what I'm after here. Then, Maven has SQL plugin, but I don't want to handle raw SQL. Maven also has Hibernate plugin, but it seems to help only in Hibernate configuration and table schema creation (not in populating db with data). How to do this?

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• generic DAO in java

  - by akshay

  I am trying to develop generic DAO in java.I have tried the following.Is this a good way to implement generic dao?I dont want to use hibernate.I am trying to make it as generic as possible so that i dont have to repeate the same code again and again. public abstract class AbstractDAO<T> { protected ResultSet findbyId(String tablename, Integer id){ ResultSet rs= null; try { // the following lins in not working; pStmt = cn.prepareStatement("SELECT * FROM "+ tablename+ "WHERE id = ?"); pStmt.setInt(1, id); rs = pStmt.executeQuery(); } catch (SQLException ex) { System.out.println("ERROR in findbyid " +ex.getMessage() +ex.getCause()); ex.printStackTrace(); }finally{ return rs; } } } Now i have public class UserDAO extends AbstractDAO<User>{ public List<User> findbyid(int id){ Resultset rs =findbyid("USERS",id) //USERS is tablename in db List<Users> users = convertToList(rs); return users; } private List<User> convertToList(ResultSet rs) { List<User> userList= new ArrayList(); User user= new User();; try { while (rs.next()) { user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setFname(rs.getString("fname")); user.setLname(rs.getString("lname")); user.setUsertype(rs.getInt("usertype")); user.setPasswd(rs.getString("passwd")); userList.add(user); } } catch (SQLException ex) { Logger.getLogger(UserDAO.class.getName()).log(Level.SEVERE, null, ex); } return userList; } }

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• Java complex validation in Dropwizard?

  - by miku

  I'd like to accept JSON on an REST endpoint and convert it to the correct type for immediate validation. The endpoint looks like this: @POST public Response createCar(@Valid Car car) { // persist to DB // ... } But there are many subclasses of Car, e.g. Van, SelfDrivingCar, RaceCar, etc. How could I accept the different JSON representations on the endpoint, while keeping the validation code in the Resource as concise as something like @Valid Car car? Again: I send in JSON like (here, it's the representation of a subclass of Car, namely SelfDrivingCar): { "id" : "t1", // every Car has an Id "kind" : "selfdriving", // every Car has a type-hint "max_speed" : "200 mph", // some attribute "ai_provider" : "fastcarsai ltd." // this is SelfDrivingCar-specific } and I'd like the validation machinery look into the kind attribute, create an instance of the appropriate subclass, here e.g. SelfDrivingCar and perform validation. I know I could create different endpoints for all kind of cars, but thats does not seem DRY. And I know that I could use a real Validator instead of the annotation and do it by hand, so I'm just asking if there's some elegant shortcut for this problem.

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• How to structure applications as multiple projects an name the packages in Java

  - by lostiniceland

  Hello Everyone I would like to know how you set up your projects in Java For example, in my current work-project, a six year old J2EE app with approximately 2 million LoC, we only have one project in Eclipse. The package structure is split into tiers and then domains, so it follows guidelines from Sun/Oracle. A huge ant-script is building different jars out of this one source-folder Personally I think it would be better to have multiple projects, at least for each tier. Recently I was playing around with a projects-structure like this: Domainproject (contains only annotated pojos, needed by all other projects) Datalayer (only persistence) Businesslogic (services) Presenter View This way, it should be easier to exchange components and when using a build tool like Maven I can have everything in a repository so when only working on the frontend I can get the rest as a dependecy in my classpath. Does this makes sense to you? Do you use different approaches and how do they look like? Furthermore I am struggeling how to name my packages/projects correctly. Right now, the above project-structure reflects in the names of the packages, eg. de.myapp.view and it continues with some technical subfolders like internal or interfaces. What I am missing here, and I dont know how to do this properly, is the distinction to a certain domain. When the project gets bigger it would be nice to recognise a particular domain but also the technical details to navigate more easily within the project. This leads to my second question: how do you name your projects and packages?

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• java GC periodically enters into several full GC cycles

  - by Peter

  Environment: sun JDK 1.6.0_16 vm settings: -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -Xms1024 -Xmx1024M -XX:MaxNewSize=448m -XX:NewSize=448m -XX:SurvivorRatio=4(6 also checked) -XX:MaxPermSize=128M OS: windows server 2003 processor: 4 cores of INTEL XEON 5130, 2000 Hz my application description: high intensity of concurrent(java 5 concurrency used) operations completed each time by commit to oracle. it's about 20-30 threads run non stop, doing tasks. application runs in JBOSS web container. My GC starts work normally, I see a lot of small GCs and all that time CPU shows good load, like all 4 cores loaded to 40-50%, CPU graph is stable. Then , after 1 min of good work, CPU starts drop to 0% on 2 cores from 4, it's graph becomes unstable, goes up and down("teeth"). I see, that my threads work slower(I have monitoring), I see that GC starts produce a lot of FULL GC during that time and next 4-5 minutes this situation remains as is, then for short period of time, like 1 minute, it gets back to normal situation, but shortly after that all bad thing repeats. Question: Why I have so frequent full GC??? How to prevent that? I played with SurvivorRatio - does not help. I noticed, that application behaves normally until first FULL GC occurs, while I have enough memory. Then it runs badly. my GC LOG: starts good then long period of FULL GCs(many of them) 1027.861: [GC 942200K-623526K(991232K), 0.0887588 secs] 1029.333: [GC 803279K(991232K), 0.0927470 secs] 1030.551: [GC 967485K-625549K(991232K), 0.0823024 secs] 1030.634: [GC 625957K(991232K), 0.0763656 secs] 1033.126: [GC 969613K-632963K(991232K), 0.0850611 secs] 1033.281: [GC 649899K(991232K), 0.0378358 secs] 1035.910: [GC 813948K(991232K), 0.3540375 secs] 1037.994: [GC 967729K-637198K(991232K), 0.0826042 secs] 1038.435: [GC 710309K(991232K), 0.1370703 secs] 1039.665: [GC 980494K-972462K(991232K), 0.6398589 secs] 1040.306: [Full GC 972462K-619643K(991232K), 3.7780597 secs] 1044.093: [GC 620103K(991232K), 0.0695221 secs] 1047.870: [Full GC 991231K-626514K(991232K), 3.8732457 secs] 1053.739: [GC 942140K(991232K), 0.5410483 secs] 1056.343: [Full GC 991232K-634157K(991232K), 3.9071443 secs] 1061.257: [GC 786274K(991232K), 0.3106603 secs] 1065.229: [Full GC 991232K-641617K(991232K), 3.9565638 secs] 1071.192: [GC 945999K(991232K), 0.5401515 secs] 1073.793: [Full GC 991231K-648045K(991232K), 3.9627814 secs] 1079.754: [GC 936641K(991232K), 0.5321197 secs]

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• Social Media Java Design Problem

  - by jboyd

  I need to put something together quickly that will take blog posts and place them on social media sites, the requirements are as follows: Blog Entries are independent records that already exist, they have a published date and a modified date, the blog entry application cannot be changed, at least not substantially A new blog entry, or update needs to be sent to social media sites I currently do not need to update or delete social media communications if the blog entry is edited, or deleted, though I may need to later My design problems here are as follows: how do I know the status of each update how can I figure out what blog entry updates and postings have already been sent out? how can I quickly poll the blog entry table for postings that haven't yet been sent out? Avoiding looking at each Entry record from the DB as an object and asking if it's been sent already. That would be too slow. I cannot hook into any Blog Entry update code, my only option would be to create a trigger that an update queues something to be processed I'm looking for general guiding principles here, the biggest problem I'm having is coming up with any reasonable way to figure out if a blog entry should be sent to our social media sites in the first place

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• add database Tablenames to the JList in java

  - by Litecia

  // Declare JList private JList jlstTab, jlstCol; . . . DefaultListModel dlmTables = new DefaultListModel(); DefaultListModel dlmCol = new DefaultListModel(); // Instantiate dlmTables.addElement("kl"); jlstTab= new JList(dlmTables); jlstTab.setSelectedIndex(0); jlstTab.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); . . . . Connect to the database public static void main(String args[]) { DBToolSwing cs = new DBToolSwing("DB Tool Swing"); try DBAccessObject dbAccess1 = new DBAccessObject("jdbc:odbc:JavaClassDSN"); DBAccessObject dbAccess2 = new DBAccessObject(); ResultSet rsTables = dbAccess1.getDatabaseTableNames(); while (rsTables.next()) System.out.println(rsTables.getString("TABLE_NAME")); I need to get the table names from the database, the output shouldn't be printed on the screen, instead I need the output added to the JlstTab so dlmTables.addElement("TABLE_NAME"); Please if someone can help I would appreciate it. Thanks in advance.

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• StringBufferInputStream Question in Java

  - by JJG

  I want to read an input string and return it as a UTF8 encoded string. SO I found an example on the Oracle/Sun website that used FileInputStream. I didn't want to read a file, but a string, so I changed it to StringBufferInputStream and used the code below. The method parameter jtext, is some Japanese text. Actually this method works great. The question is about the deprecated code. I had to put @SuppressWarnings because StringBufferInputStream is deprecated. I want to know is there a better way to get a string input stream? Is it ok just to leave it as is? I've spent so long trying to fix this problem that I don't want to change anything now I seem to have cracked it. @SuppressWarnings("deprecation") private String readInput(String jtext) { StringBuffer buffer = new StringBuffer(); try { StringBufferInputStream sbis = new StringBufferInputStream (jtext); InputStreamReader isr = new InputStreamReader(sbis, "UTF8"); Reader in = new BufferedReader(isr); int ch; while ((ch = in.read()) > -1) { buffer.append((char)ch); } in.close(); return buffer.toString(); } catch (IOException e) { e.printStackTrace(); return null; } }

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