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  • What is the effect of final variable declaration in methods?

    - by Finbarr
    Classic example of a simple server: class ThreadPerTaskSocketServer { public static void main(String[] args) throws IOException { ServerSocket socket = new ServerSocket(80); while (true) { final Socket connection = socket.accept(); Runnable task = new Runnable() { public void run() { handleRequest(connection); } }; new Thread(task).start(); } } } Why should the Socket be declared as final? Is it because the new Thread that handles the request could refer back to the socket variable in the method and cause some sort of ConcurrentModificationException?

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  • runtime/compile time polymorphism

    - by dmadhavaraj
    Hi , In the below code , why b1.subtract() fails . Please explain me the reason ie., what happens in JVM while invoking that method . class Base { public void add() { System.out.println("Base ADD"); } } class Child extends Base { public void add(){ System.out.println("Child ADD"); } public void subtract() { System.out.println("Child Subtract"); } } class MainClass { public static void main(String args[]) { Base b1 = new Base(); Base b2 = new Child(); Child b3 = new Child(); b1.add(); b1.subtract(); // ?????????** b2.add(); b3.subtract(); } }

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  • Spring MVC simple case

    - by coure2011
    Trying to understand a sample code... I am returning a modelview successfully from my AthuenticationController like this modelAndView = new ModelAndView("redirect:/home/"); .... return modelAndView; and my browser url is changed to /home/ but its showing a 404 page I have a HomePageController and it has methods @RequestMapping(method = RequestMethod.GET) public String loadHome and @RequestMapping(method = RequestMethod.GET, value = "/main") public String reloadHome but System.out.println("Message") is not executing in any of the above methods. When authenticated I want to load a home.jsp page? It is in WEB-INF/jsp/...

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  • Mixing expressions and expression language (<%= %> inside of c:if)

    - by Jack
    I need to access some constants in my jsp, and sadly the EL does not offer any functionality for it. There are some options like the unstandard tag library, but I'd like to keep it a bit more standard. I tried: <%@ page import = "com.jackdane.Constants"%> <c:if test="${object.display == '<%=com.jackdane.Constants.YES %>}'"> //some display logic </c:if> But that doesn't appear to do the trick. It's been a while since I've used an expression so I might have made an error. Any input is appreciated. Edit: To clarify, the constants class is not in my control. It's inside a jar file that I recieved. It contains no getters/setters. Just private static final Strings.

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  • Common Utility for Exception Searching

    - by Andrew
    I wrote this little helper method to search the exception chain for a particular exception (either equals or super class). However, this seems like a solution to a common problem, so was thinking it must already exist somewhere, possibly in a library I have already imported. So, any ideas on if/where this might exist? boolean exceptionSearch(Exception base, Class<?> search) { Throwable e = base; do { if (search.isAssignableFrom(e.getClass())) { return true; } } while ((e = e.getCause()) != null); return false; }

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  • Annotations: methods vs variables

    - by Zenzen
    I was always sure (don't know why) that it's better to add annotations to variables, but while browsing the Hibernate doc http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-hibspec-collection I noticed they tend to annotate the methods. So should I put my annotations before methods, like this: @Entity public class Flight implements Serializable { private long id; @Id @GeneratedValue public long getId() { return id; } public void setId(long id) { this.id = id; } } Or is it better to do it like this: @Entity public class Flight implements Serializable { @Id @GeneratedValue private long id; public long getId() { return id; } public void setId(long id) { this.id = id; } } Or maybe there's no difference?

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  • using Hibernate to loading 20K products, modifying the entity and updating to db

    - by Blankman
    I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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  • Create automatically only getters in Eclipse

    - by lerad
    In Eclipse is it possible to create automatically Getters and Setters for a field. But I have a lot of private fields for which only getters should exist. Is somewhere in Eclipse a "create Getters" Function which does not create setters too? Well, it is not so much work to write getters, but doing it automatically would be nice :) Thank you, lerad

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  • dao as a member of a servlet - normal?

    - by EugeneP
    I guess, DAO is thread safe, does not use any class members. So can it be used without any problem as a private field of a Servlet ? We need only one copy, and multiple threads can access it simultaneously, so why bother creating a local variable, right?

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  • How to view my Android app created database, via my android app?

    - by suufang
    I'm creating an application that collects users location (Cell broadcast location code) and saves that location with a name of users option, for example say my CB location code is 546034, now my app allows me to store that location code with a name of my choice say 'Home'. So, essentially my app has that following modules, To collect users CB location. To collect a custom name from user of that location. To store these values in a database. I've succeeded in doing all the above modules. I have a sub-module for my third module which has an option for user, of showing and deleting the database values, the screen shot looks as follows, Now, Users should be able to view and delete entries when he chooses the option 'View my database of locations' I've learned how to query my database values and I'm stuck with creating a list view and providing the delete option. My code for getting the database values and querying values goes as follows, submit.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { String locname = name.getText().toString(); if(locname.length()==0) { Toast.makeText(getBaseContext(), "Please enter the location name, for example 'Home'.", Toast.LENGTH_LONG).show(); } else { SQLiteDatabase cd = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null); cd.execSQL("CREATE TABLE IF NOT EXISTS MLITable (CblocationCode INT(10), CblocationName VARCHAR);"); cd.execSQL("INSERT INTO MLITable VALUES ('"+str+ "','"+locname+ "');"); cd.close(); Toast.makeText(getBaseContext(), "value successfully entered.", Toast.LENGTH_LONG).show(); } } }); viewdb.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // here comes the code for viewing the database and deleting SQLiteDatabase db = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null); Cursor c = db.rawQuery("SELECT * FROM MLITble", null); db.close(); } }); I can see that I've read the table values, but I'm not able to create a display for those values. Help required. Thank you.

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  • Automatically selecting and creating class objects

    - by Omin
    Lets say that we have a box class: class Box { private int width; private int height; //Box Constructor public Box( int height ) { this.height = height; width = 450; } } and a series of Box objects in our main: Box Box1 = new Box(147); Box Box2 = new Box(178); Box Box3 = new Box(784); Is there a way to use a "for" loop to go through these objects? Also, how would you make the computer create class objects for us? eg. create 10 objects using: for( int i=0; i>10; i++) { //method }

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  • problem with update the counter value

    - by Edan
    Hello, I having problem to update the counter (integer value). this is the definitions of the class: public class Item_Actions { private final int MAX_ITEMS = 100; private Item myItem[]; private int counter; public Item_Actions() { myItem = new Item[MAX_ITEMS]; counter++; } //Constructor add item into the menu (Description, type & price of Item) public void addItem(Item itm) { myItem[counter] = itm; counter++; }....... Now everytime I call the addItem constructor from another class, the counter always stays on zero. What causing it and how do I save the data inside? thanks

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  • Does <T> need to be imported as a class for this to work?

    - by zxc
    In order for this to work, do you have to have an import statement for the T class? private static <T> void invertOrdering(List<T> list) { for (int i = 0; i < list.size() / 2; i++) { int j = list.size() - 1 - i; T item1 = list.get(i); T item2 = list.get(j); list.set(i, item2); list.set(j, item1); } }

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  • passing reference of class to another class android error

    - by prolink007
    I recently asked the precursor to this question and had a great reply. However, when i was working this into my android application i am getting an unexpected error and was wondering if everyone could take a look at my code and help me see what i am doing wrong. Link to the initial question: passing reference of class to another class My ERROR: "The constructor ConnectDevice(new View.OnClickListener(){}) is undefined" The above is an error detected by eclipse. Thanks in advance! Below are My code snippets: public class SmartApp extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.intro); final Button connectDeviceButton = (Button) findViewById(R.id.connectDeviceButton); connectDeviceButton.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { Thread cThread = new Thread(new ConnectDevice(this)); cThread.start(); } }); } } public class ConnectDevice implements Runnable { private boolean connected; private SmartApp smartAppRef; private ObjectInputStream ois; public ConnectDevice(SmartApp smartAppRef) { this.smartAppRef = smartAppRef; } }

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  • Interface with generic parameters- can't get it to compile

    - by user997112
    I have an interface like so: public interface MyInterface<E extends Something1> { public void meth1(MyClass1<E> x); } and I have a subclass whose superclass implements the above interface: public class MyClass2<E extends Something1> extends Superclass{ public MyClass2(){ } public void meth1(MyClass1 x) { // TODO Auto-generated method stub } } superclass: public abstract class Superclass<E extends Something1> implements MyInterface{ MyClass1<E> x; protected E y; public Superclass(){ } } the problem is that the parameter for meth1() is supposed to be generic. If I do MyClass1 it doesn't like it and the only way I can get it to compile is by leaving out generic parameters- which feels wrong. What's going wrong?

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  • JavaFX InternalFrame or WindowNode

    - by user1493549
    I was looking for an InternalFrame for JavaFX. Apparently I it seems like there is no InternalFrame available. How does one create an MDI application with JavaFX? I have tried to simulate this behavior by using a custom Region that can be dragged around. Is that the way to go? What about typical window elements such as titlebar, possibility to resize etc. Do I have to implement that myself via custom controls? Thanks, miho

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  • FileNotFoundException when cropping a photo

    - by James G
    I'm trying to crop a photo to use in a Live Wallpaper but I'm getting a FileNotFoundException when the crop activity tries to save my new cropped image. This is the code I'm using: File file = new File(getFilesDir(), "wallpaper.jpg"); Intent intent = new Intent("com.android.camera.action.CROP"); intent.setData(uri); DisplayMetrics metrics = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(metrics); intent.putExtra("outputX", metrics.widthPixels * 2); intent.putExtra("outputY", metrics.heightPixels); intent.putExtra("aspectX", metrics.widthPixels * 2); intent.putExtra("aspectY", metrics.heightPixels); intent.putExtra("scale", true); intent.putExtra("noFaceDetection", true); intent.putExtra("output", Uri.parse("file:/" + file.getAbsolutePath())); startActivityForResult(intent, REQUEST_CROP_IMAGE); The wallpaper.jpg file seems to exist on DDMS file explorer so I'm not sure what I'm doing wrong. Any advice is greatly appreciated.

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  • How to detect if a form input element of type file is empty

    - by Ankur
    I have some code which reads a file through a form field of type file <input type="file" ... /> I want to give the user another option of providing a url to a file rather than having to upload it as many are already online. How can I detect when this field is empty on the server side. I am using Apache Commons FileUpload FileItemStream item = iter.next(); name = item.getFieldName(); stream = item.openStream(); if(!item.isFormField()){ if(item.toString()!=""){ .... I need to detect when item is empty. The above code doesn't work, nor does using: if(item.equals(null)){ ....

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