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  • about Sorting Algorithms

    - by matin1234
    Hi I want to know that we always use Sorting algorithm like (Insertion Sort or Merge Sort,...) just for lists and arrays?? and we do not use these algorithms for stack or queue ??? thanks

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  • Doubt in abstract classes

    - by mohit
    public abstract class Person { private String name; public Person(String name) { this.name = name; System.out.println("Person"); } public String getName() { return name; } abstract public String getDescription(); } public class Student extends Person { private String major; public Student(String name, String major) { super(name); this.major = major; } public String getMajor() { return major; } @Override public String getDescription() { return "student" + super.getName() + " having" + major; } } public class PersonTest { public static void main(String[] args) { Person person = new Student("XYZ", "ABC"); System.out.println(person.getDescription()); } } Ques: We cannot create objects of abstract classes, then why Person Constructor has been invoked, even its an abstract class?

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  • Loading child entities with JPA on Google App Engine

    - by Phil H
    I am not able to get child entities to load once they are persisted on Google App Engine. I am certain that they are saving because I can see them in the datastore. For example if I have the following two entities. public class Parent implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; @OneToMany(cascade=CascadeType.ALL) private List<Child> children = new ArrayList<Child>(); //getters and setters } public class Child implements Serializable{ @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; private String name; @ManyToOne private Parent parent; //getters and setters } I can save the parent and a child just fine using the following: Parent parent = new Parent(); Child child = new Child(); child.setName("Child Object"); parent.getChildren().add(child); em.persist(parent); However when I try to load the parent and then try to access the children (I know GAE lazy loads) I do not get the child records. //parent already successfully loaded parent.getChildren.size(); // this returns 0 I've looked at tutorial after tutorial and nothing has worked so far. I'm using version 1.3.3.1 of the SDK. I've seen the problem mentioned on various blogs and even the App Engine forums but the answer is always JDO related. Am I doing something wrong or has anyone else had this problem and solved it for JPA?

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  • String doesn't match regex when read from keyboard.

    - by athspk
    public static void main(String[] args) throws IOException { String str1 = "??123456"; System.out.println(str1+"-"+str1.matches("^\\p{InGreek}{2}\\d{6}")); //??123456-true BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String str2 = br.readLine(); //??123456 same as str1. System.out.println(str2+"-"+str2.matches("^\\p{InGreek}{2}\\d{6}")); //?”??123456-false System.out.println(str1.equals(str2)); //false } The same String doesn't match regex when read from keyboard. What causes this problem, and how can we solve this? Thanks in advance. EDIT: I used System.console() for input and output. public static void main(String[] args) throws IOException { PrintWriter pr = System.console().writer(); String str1 = "??123456"; pr.println(str1+"-"+str1.matches("^\\p{InGreek}{2}\\d{6}")+"-"+str1.length()); String str2 = System.console().readLine(); pr.println(str2+"-"+str2.matches("^\\p{InGreek}{2}\\d{6}")+"-"+str2.length()); pr.println("str1.equals(str2)="+str1.equals(str2)); } Output: ??123456-true-8 ??123456 ??123456-true-8 str1.equals(str2)=true

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  • Eclipse error: This project needs to migrate WTP metadata

    - by larf311
    We started a Web Project in Eclipse 3.2 a ways back and we've since upgraded to Eclipse 3.4 but now the Project has the error: "This project needs to migrate WTP metadata" We've tried right-clicking and doing the "quick-fix" which is in fact to Migrate WTP Metadata. Unfortunately nothing happens and the error remains. We can delete that error from the Problems and everything works as it should, however, every time we re-import the project from source control, the error re-appears. Any ideas on how to permanently get rid of this error or how to ACTUALLY migrate WTP metadata? UPDATE: Everyone, please vote on the answer that works for you rather than adding your own answer that references a previous person's answer.

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  • Create JTable in a JPanel and add row

    - by DK64
    On my program I've dinamically created a JFrame that contains a JPanel called jp. jp also contains a JTable that I would like to fill with some rows. case KeyEvent.VK_R: JFrame frame = new JFrame("Snake v2.0 - Rankings"); JPanel jp = new JPanel(); jp.setPreferredSize(new Dimension(300,300)); JTable table = new JTable(); JScrollPane tableContainer = new JScrollPane(table); jp.add(tableContainer, BorderLayout.CENTER); DefaultTableModel tm = (DefaultTableModel) table.getModel(); tm.addRow(new Object[] {"#","Player","Score","Date"}); frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE); frame.setLocationRelativeTo(null); frame.setResizable(false); frame.getContentPane().add(jp); frame.pack(); frame.setVisible(true); break; This is my code. When I press R on the keyboard, the JFrame with that JPanel inside appears but the table doesnt (picture). What could I do?

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  • Linking Apache to Tomcat with multiple domains.

    - by Royce Thigpen
    Okay, so I've been working for a while on this, and have been searching, but so far I have not found any answers that actually answer what I want to know. I'm a little bit at the end of my rope with this one, but I'm hoping I can figure this out sometime soon. So I have Apache 2 installed and serving up standard webpages, but I also have that linked to a Tomcat instance for one of my domains currently supported. However, I want to add another domain to the server via Apache that points to a separate code base from the one I already have. I have been coming at this from several different angles, and I have determined that I just don't know enough about setting up these servers to really do what I want to do. Little information on my server: Currently running a single Tomcat5.5 instance with Apache 2, using mod_jk to connect them together. I have a worker in workers.properties that points it's "host" field to "localhost" with the correct port my Tomcat instance, so that all works. In my Tomcat server.xml file, I have a host defined as "localhost" that points at my webapp that I am currently serving up, with that host set as the defaultHost as well. One thought I had was that I could add a new worker with a different host than "localhost" (i.e. host2) and then define a new host in my server.xml file called "host2" to match it, but after reading around some on the internet, It seems the "host" of the worker must point to a server, and not a hostname in the Tomcat instance, is this correct? Again, a simple rundown of what I want: Setup in apache/tomcat combo such that www.domain1.com points at "webapp1" and www.domain2.com points at "webapp2".

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  • Logback: Logging with two loggers

    - by gammay
    I would like to use slf4j+logback for two purposes in my application - log and audit. For logging, I log the normal way: static final Logger logger = LoggerFactory.getLogger(Main.class); logger.debug("-> main()"); For Audit, I create a special named logger and log to it: static final Logger logger = LoggerFactory.getLogger("AUDIT_LOGGER"); Object[] params = { new Integer(1) /* TenantID */, new Integer(10) /* UserID */, msg}; logger.info("{}|{}|{}", params); logback configuration: <logger name="AUDIT_LOGGER" level="info"> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%d{HH:mm:ss.SSS}|%msg%n </pattern> </encoder> </appender> </logger> <root level="all"> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n </pattern> </encoder> </appender> </root> Problem: Messages logged through audit logger appear twice - once under the AUDIT_LOGGER and once under the root logger. 14:41:57.975 [main] DEBUG com.gammay.example.Main - - main() 14:41:57.978|1|10|welcome to main 14:41:57.978 [main] INFO AUDIT_LOGGER - 1|10|welcome to main How can I make sure audit messages appear only once under the audit logger?

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  • Simple explaination of Arraylists

    - by Jeremy
    I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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  • Questions about my program and Polymorphism

    - by Strobe_
    Ok, so basically I'm creating a program which allows the user to select a shape (triangle, square, circle) and then it takes in a int and calculates the boundary length and area. I have no problem doing this and have a program that's working perfectly. (https://gist.github.com/anonymous/c63a03c129560a7b7434 4 classes) But now I have to implement this with polymorphism concepts and I'm honestly struggling as to how to do it. I have a basic idea of what I want to do when it comes to inheritance Main | Shapes / | \ triangle circle square But I don't understand how I'm supposed to override when all the methods within the triangle/square/circle classes are unique, there are no "abstract" methods as such that I could inherit from the "Shapes" class. If somebody could make look quickly at the code I linked and suggest a way to do this it would be much appreciated. Sorry if I was bad at explaining this. Thanks.

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  • Sun App Server Deployment Error

    - by Nick Long
    Sun App Server Deployment : When choose to precompile JSP : Throw this error com.sun.enterprise.admin.common.exception.MBeanConfigException: Component not registered then have to do asadmin undeploy Anyone know what is the reason for this error?

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  • How to determine whether a spread-sheet cell contains a date, or a real number?

    - by Everyone
    When a cell in a spreadsheet contains a simple date (mm/dd/yyyy) the poi API flags the cell-type as 'numeric'. This is probably because spreadsheets ( IMO ) historically recognize only strings and real numbers. It is possible to hard-code the cell-index, and use it conditionally to call 'getDateCellValue'. But this feels like a hack. What other ways are there in the poi API to determine whether the content in a cell is a Date rather than a real number?

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  • ANDROID : how to get value stored in ArrayList<HashMap<key,value>>?

    - by Roshni Kyada
    I have ArrayList. At another activity i want to access all values stored in ArrayList. I tried following code. ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>(); for(Hashmap<String, String> map: mylist) { for(Entry<String, String> mapEntry: map) { String key = mapEntry.getKey(); String value = mapEntry.getValue(); } } but it shows an error at for(Entry mapEntry: map) that it only interate over Array.

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  • Better product to develop for, iPad or Android based tablet in a purely business related application

    - by Caylem
    Hey guys Just wondering what you'd suggest as the best platform for developing a business application for a tablet device. The application needs to be multitouch, have access to a maps API, a database on the device. It will not be going on sale in the app store or Androids market, it is purely for specific business task and not for the general consumer. Obviously the options seem to be iPhone OS and the iPad or Android and an Android tablet device. The form factor for the end product requires something in the region of 8 inch+ screen and enough processing power to provide a good experience for the end user. Any help would be much appreciated. Thanks

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  • Choosing design method for ladder-like word game.

    - by owca
    I'm trying to build a simple application, with the finished program looking like this : I will also have to implement two different GUI layouts for this. Now I'm trying to figure out the best method to perform this task. My professor told me to introduce Element class with 4 states : - empty - invisible (used in GridLayout) - first letter - other letter I've thought about following solutions (by List I mean any sort of Collection) : 1. Element is a single letter, and each line is Element[]. Game class will be array of arrays Element[]. I guess that's the dumbest way, and the validation might be troublesome. 2. Like previously but Line is a List of Element. Game is an array of Lines. 3. Like previously but Game is a List of Lines. Which one should I choose ? Or maybe do you have better ideas ? What collection would be best if to use one ?

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  • Simple question about the lunarlander example.

    - by Smills
    I am basing my game off the lunarlander example. This is the run loop I am using (very similar to what is used in lunarlander). I am getting considerable performance issues associated with my drawing, even if I draw almost nothing. I noticed the below method. Why is the canvas being created and set to null each cycle? @Override public void run() { while (mRun) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas();//null synchronized (mSurfaceHolder) { updatePhysics(); doDraw(c); } } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } Most of the times I have read anything about canvases it is more along the lines of: mField = new Bitmap(...dimensions...); Canvas c = new Canvas(mField); My question is: why is Google's example done that way (null canvas), what are the benefits of this, and is there a faster way to do it?

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  • Websphere 5.1 add SSL certificate

    - by Mikhail
    Hi All. I have the following instruction: Import ++++ certificate (in order to allow SSL connections) – it is done in Administrative Console for the corresponding WAS profile (Security-SSL certificate and key management-Key stores and certificates-NodeDefaultTrustStore-Signer certificates). Here you can simply add the attached trkd_cert.cer (“Add” button) or get it from port (“Retrieve from port” button, host: ++++.com, port 443) But this is valid for Websphere 6.1. Do somebody know how this can be done in WebSphere 5.1?

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  • JSF Servlet Arch Help needed.

    - by abc
    i want a mechanism in my web app as described below: user will enter mydomain.com/CompanyName , depending upon the CompanyNameit will show its logo and its customized page, and i will take that parsed parameter in session again upon each request i will compare the parsed CompanyName and one stored in session , and if they matched then application will show the requested page with user's data.else it will be redirected to login page. and the main thing is i want this thing in JSF arch. i tried taking a servlet that will resolve all request and it will parse and then will dispatch the request to prefered servlet,but problem is it goes in loop as again it resolves to the same controller servlet,

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  • Is there a concise way to create an InputSupplier for an InputStream in Google Guava?

    - by Fabian Steeg
    There are a few factory methods in Google Guava to create InputSuppliers, e.g. from a byte[]: ByteStreams.newInputStreamSupplier(bytes); Or from a File: Files.newInputStreamSupplier(file); Is there a similar way to to create an InputSupplier for a given InputStream? That is, a way that's more concise than an anonymous class: new InputSupplier<InputStream>() { public InputStream getInput() throws IOException { return inputStream; } }; Background: I'd like to use InputStreams with e.g. Files.copy(...) or ByteStreams.equal(...).

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  • Which technology should I choose for 3d globe web application

    - by uther-lightbringer
    Hello, i would like to ask you for an advice. I'm currently developing application in Spring consisting of Spring CRUD application as backend, SpringMVC application as tool for management and third part is where my problem lies as I need have application that renders 3d globe which is fed by data from backend from a data set selected by user (user may switch those at will). It has to be web application (though I would prefer not to implement this in flash/flex), composed of two main parts - main part is classic web GUI where user makes his choices and second part is 3d globe which renders the globe with selected set of data visualised. My question is, what do you think is the best option to implement this? Would be SpringMVC framework usable for this kind of application? I will be gratefull for any leads or directions, thank you.

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  • JMS - How do message selectors work with multiple queue and topic consumers?

    - by Stephen Harmon
    Say you have a JMS queue, and multiple consumers are watching the queue for messages. You want one of the consumers to get all of a particular type of message, so you decide to employ message selectors. For example, you define a property to go in your JMS message header named, "targetConsumer." Your message selector, which you apply to the consumer known as, "A," is something like "WHERE targetConsumer = "CONSUMER_A." It's clear that consumer A will now just grab messages with the property set like it is in in the example. Will the other consumers have awareness of that, though? IOW, will another consumer, unconstrained by a message selector, grab the "CONSUMER_A" messages, if it looks at the queue before Consumer A? Do I need to apply message selectors like, "WHERE targetConsumer < "CONSUMER_A" to the others? I am RTFMing and gathering empirical data now, but was hoping someone might know off the top of their head.

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