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  • Is it a good practice to create a reference to application context and use it anywhere?

    - by kknight
    I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context. public class MainActivity extends Activity { public static Context s_appContext; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); s_appContext = this.getApplicationContext();

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  • Load a model in a Codeigniter library

    - by ci
    Hello, people! I have this piece of code: class MY_Language extends CI_Language { function MY_Language() { parent::CI_Language(); $CI =& get_instance(); $CI->load->model('language_model'); $languages = $this->language_model->get_languages(); print_r($languages); } } But I keep getting "Fatal error: Call to undefined function get_instance() in C:\xampp\htdocs\application\libraries\MY_Language.php on line 44". Any ideas? Thanks in advance!

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  • abstract class need acces to subclass atribute

    - by user1742980
    I have a problem with my code. public abstract class SimplePolygon implements Polygon { ... public String toString(){ String str = "Polygon: vertices ="; for(int i = 0;i<varray.length;i++){ str += " "; str += varray[i]; } return str; } } public class ArrayPolygon extends SimplePolygon { private Vertex2D[] varray; public ArrayPolygon(Vertex2D[] array){ varray = new Vertex2D[array.length]; if (array == null){} for(int i = 0;i<array.length;i++){ if (array[i] == null){} varray[i] = array[i]; } ... } Problem is, that i'm not allowed to add any atribute or method to abstract class SimplePolygon, so i'cant properly initialize varray. It could simply be solved with protected atrib in that class, but for some (stupid) reason i'cant do that. Has anybody an idea how to solve it without that? Thanks for all help.

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  • What's wrong in this simple android Program, I get 'Force Close'.

    - by andyfan
    What is wrong in this program, My eclipse IDE doesn't show any errors....when I execute this simple program the emulator shows force close....Anybody please clarify import android.app.Activity; import android.view.View.OnClickListener; import android.view.View; import android.os.Bundle; import android.widget.*; public class HelloWorld extends Activity implements OnClickListener { /** Called when the activity is first created. */ View Et1,Bt1,TxtDisp; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.name_getter); Bt1=(Button)findViewById(R.id.Btn1); Et1=(EditText)findViewById(R.id.UserInput); TxtDisp=(TextView)findViewById(R.id.TextDisp); Bt1.setOnClickListener(this); } @Override public void onClick(View v) { // TODO Auto-generated method stub String userInput=((EditText) Et1).getText().toString(); ((TextView)TxtDisp).setText(userInput); } }

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  • Returnimng collection of interfaces

    - by apoorv020
    I have created the following interface public interface ISolutionSpace { public boolean isFeasible(); public boolean isSolution(); public Set<ISolutionSpace> generateChildren(); } However, in the implementation of ISolutionSpace in a class called EightQueenSolutionSpace, I am going to return a set of EightQueenSolutionSpace instances, like the following stub: @Override public Set<ISolutionSpace> generateChildren() { return new HashSet<EightQueenSolutionSpace>(); } However this stub wont compile. What changes do I need to make? EDIT: I tried 'HashSet' as well and had tried using the extends keyword. However since 'ISolutionSpace' is an interface and EightQueenSolutionSpace is an implementation(and not a subclass) of 'ISolutionSpace', it is still not working.

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  • Are upper bounds of indexed ranges always assumed to be exclusive?

    - by polygenelubricants
    So in Java, whenever an indexed range is given, the upper bound is almost always exclusive. From java.lang.String: substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1 From java.util.Arrays: copyOfRange(T[] original, int from, int to) from - the initial index of the range to be copied, inclusive to - the final index of the range to be copied, exclusive. From java.util.BitSet: set(int fromIndex, int toIndex) fromIndex - index of the first bit to be set. toIndex - index after the last bit to be set. As you can see, it does look like Java tries to make it a consistent convention that upper bounds are exclusive. My questions are: Is this the official authoritative recommendation? Are there notable violations that we should be wary of? Is there a name for this system? (ala "0-based" vs "1-based")

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  • C++ Typing and OOP child classes

    - by Zack
    I'm a bit confused: If I have a base class A, and a class B which extends A, can a variable of the type A hold a value of the type B and vice versa? If yes, why? Aren't they completely different even if B is derived from A? How about type-safety? If this is possible, what things do I have to mind when taking use of this? How would this work out in terms of performance? Note: Sorry if I asked too many questions, just ignore them and just look out for those "marked" with the list decoration dot :) Also, this is not my homework. I'm a hobby programmer and have skills in scripting languages with OOP, yet I'm relatively new to OOP typing in C++.

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  • trouble setting up TreeViews in pygtk

    - by Chris H
    I've got some code in a class that extends gtk.TreeView, and this is the init method. I want to create a tree view that has 3 columns. A toggle button, a label, and a drop down box that the user can type stuff into. The code below works, except that the toggle button doesn't react to mouse clicks and the label and the ComboEntry aren't drawn. (So I guess you can say it doesn't work). I can add rows just fine however. #make storage enable/disable label user entry self.tv_store = gtk.TreeStore(gtk.ToggleButton, str, gtk.ComboBoxEntry) #make widget gtk.TreeView.__init__(self, self.tv_store) #make renderers self.buttonRenderer = gtk.CellRendererToggle() self.labelRenderer = gtk.CellRendererText() self.entryRenderer = gtk.CellRendererCombo() #make columns self.columnButton = gtk.TreeViewColumn('Enabled') self.columnButton.pack_start(self.buttonRenderer, False) self.columnLabel = gtk.TreeViewColumn('Label') self.columnLabel.pack_start(self.labelRenderer, False) self.columnEntry = gtk.TreeViewColumn('Data') self.columnEntry.pack_start(self.entryRenderer, True) self.append_column(self.columnButton) self.append_column(self.columnLabel) self.append_column(self.columnEntry) self.tmpButton = gtk.ToggleButton('example') self.tmpCombo = gtk.ComboBoxEntry(None) self.tv_store.insert(None, 0, [self.tmpButton, 'example label', self.tmpCombo]) thanks.

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  • Getting data from JFrame AFTER the form is filled

    - by mary jane
    I'm trying to get data for my application from a form set in an external window (getDataWindow extends javax.swing.JFrame). The problem is that functions are executed before form is filled in. getDataWindow dataW=new getDataWindow(); dataW.setVisible(true); size=dataW.returnSize(); I've tried also adding additional boolean variable to getDataWindow getDataWindow dataW=new getDataWindow(); dataW.setVisible(true); while(!dataW.checkIfReady()){wait();} size=dataW.returnSize(); But it makes also the window wait (it appears but it's black inside and nothing happens). I think i should create some threads for that - I've tried to call a window making function getDataWindow in java.awt.EventQueue.invokeLater(new Runnable()) but I had to initialize dataW earlier so dataW.checkIfReady() could be called, so it is a catch 22.

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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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  • Flex custom toggleswitch not working in actionscript

    - by Gavin Jones
    I have a custom Flex Toggleswitch component that changes the text values of the switch. package skins { import spark.skins.mobile.ToggleSwitchSkin; public class MyToggleSwitchSkin extends ToggleSwitchSkin { public function MyToggleSwitchSkin() { super(); selectedLabel="Serviceable"; unselectedLabel="Fault"; } } } If I add the control using the MXML tag, it works fine. However, when I add the component using action script, it does not. import skins.MyToggleSwitchSkin; public function addToggle():void { var myCustomToggle:MyToggleSwitchSkin = new MyToggleSwitchSkin(); hgroup.addElement(myCustomToggle); } The control dsiplays but will not activate. Any ideas what I have missed?

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  • How to obtain listview information without refreshing the page?

    - by user1808098
    I am currently developing an Android Application for my Final Year Project. But to be honest I do not have any basic knowledges and everything started from scratch and referring to online tutorials a lot. Here is my question, I was trying to retrieve data from listview activity. There are two listview in my page using button. I was able to display the first listview but when it get data for the second listview, the data for first listview is disappeared because the page is refreshed, vice versa. What code should I modified to get both the data in the page? (Database not implemented yet) Please help, thanks a lot. Below are my codings. Codings for XML. <!-- Location --> <TextView android:id="@+id/TextViewLocation" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:layout_marginBottom="10dip" android:text="Location Information" android:gravity="center" android:textSize="15dip" android:textColor="#025f7c"/> <!-- Condition Label --> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:textColor="#372c24" android:text="Traffic Condition"/> <Button android:id="@+id/inputListView" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:layout_marginBottom="10dip" android:text="choose one..."/> <!-- Comment Label --> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:textColor="#372c24" android:text="What's Happening?"/> <Button android:id="@+id/inputListView2" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:layout_marginBottom="10dip" android:text="choose one..."/> <!-- Suggestion Label --> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:textColor="#372c24" android:text="Comments / Suggestion"/> <EditText android:layout_width="fill_parent" android:layout_height="80dp" android:layout_marginTop="5dip" android:layout_marginBottom="10dip" android:singleLine="true"/> <!-- Image button --> <Button android:id="@+id/btnImage" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:text="Upload Image"/> <!-- Report button --> <Button android:id="@+id/btnReportCheckin" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:text="Report"/> <!-- Link to Logout --> <TextView android:id="@+id/linkLogout" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="5dip" android:layout_marginBottom="40dip" android:text="Log Out" android:gravity="center" android:textSize="20dip" android:textColor="#025f7c"/> </LinearLayout> <!-- Check or Report Form Ends --> Codings for Activity Class public class CheckinActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set View to checkin.xml setContentView(R.layout.checkin); /* TextView LocationView = (TextView) findViewById(R.id.TextViewLocation); Intent h = getIntent(); // getting attached intent data String address = h.getStringExtra("address"); // displaying selected product name LocationView.setText(address); */ Button ListViewScreen = (Button) findViewById(R.id.inputListView); //Listening to Button ListViewScreen.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { //Switching to ListView Screen Intent i = new Intent(getApplicationContext(), ListViewActivity.class); startActivity(i); } } ); Button SelectedView = (Button) findViewById(R.id.inputListView); Intent i = getIntent(); // getting attached intent data String product = i.getStringExtra("product"); // displaying selected product name SelectedView.setText(product); Button ListView2Screen = (Button) findViewById(R.id.inputListView2); //Listening to Button ListView2Screen.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { //Switching to ListView Screen Intent j = new Intent(getApplicationContext(), ListView2Activity.class); startActivity(j); } } ); Button SelectedView2 = (Button) findViewById(R.id.inputListView2); Intent j = getIntent(); // getting attached intent data String product2 = j.getStringExtra("product2"); // displaying selected product name SelectedView2.setText(product2); TextView Logout = (TextView) findViewById(R.id.linkLogout); // Listening to Log out Logout.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // Closing menu screen // Switching to Login Screen/closing register screen finish(); } }); } } Coding for listview class public class ListViewActivity extends ListActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // storing string resources into Array String[] traffic_condition = getResources().getStringArray(R.array.traffic_condition); // Binding resources Array to ListAdapter this.setListAdapter(new ArrayAdapter<String>(this, R.layout.listitem, R.id.listViewLayout, traffic_condition)); ListView lv = getListView(); // listening to single list item on click lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { // selected item String product = ((TextView) view).getText().toString(); // Launching new Activity on selecting single List Item Intent i = new Intent(getApplicationContext(), CheckinActivity.class); // sending data to new activity i.putExtra("product", product); startActivity(i); } }); } } Hope I made myself clear, I can provide a screen shot of my apps if it is required, thanks!

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  • Java: Reflection against casting when you know superclass

    - by Ema
    I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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  • How can I get a project type on Netbeans Platform?

    - by Fabio
    Hi folks, Is there a way to know the type of a selected project? I would like to do some specific actions depending of the project type like a J2SE project. Below is the only way that I found to do that: public final class MyAction extends CookieAction { @Override public boolean isEnabled() { if(this.getActivatedNodes() == null || this.getActivatedNodes().length != 1) { return false; } Lookup lookup = this.getActivatedNodes()[0].getLookup(); // gets the selected project Project currentProject = lookup.lookup(Project.class); // checks if the selected project is a J2SE Project or a Maven Project if(currentProject != null && (currentProject.getClass().getSimpleName().equals("J2SEProject") || currentProject.getClass().getSimpleName().equals("NbMavenProjectImpl"))) { return true; } return false; }}

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  • get invalid.token result at the first time run action.

    - by Tr.Crab
    I use struts 2.1.8, I use <s:token> between <s:form> and </s:form> in my struts.xml like that ............ <package name="user" namespace="/user" extends="struts-default"> <action name="login"class="user.UserAction"> <result type="tiles">login.view</result> <interceptor-ref name="token"/> <interceptor-ref name="basicStack"/> <result name="invalid.token">/pages/error.jsp</result> </action> </package> ............... at the first time, I run login.do action, I alway get error page. Plz give to me some suggestions thank in advance.

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  • Zend Framework url redirect

    - by Uffo
    <?php class PI_Controller_Plugin_AssetGrabber extends Zend_Controller_Plugin_Abstract { public function dispatchLoopStartup(Zend_Controller_Request_Abstract $request) { /* The module name */ $moduleName = $request->getModuleName(); /* This modules requires the user to be loggedin in order to see the web pages! */ $loginRequiredModules = array('admin'); if (in_array($moduleName,$loginRequiredModules)) { $adminLogin = new Zend_Session_Namespace('adminLogin'); if (!isset($adminLogin->loggedin)) { /*-------------------------------------- Here I want to redirect the user */ $this->_redirect('/something'); } } } } I'm trying to do a redirect $this->_redirect('/something') but doesn't work! Do you know how can I do a redirect in this case? Best Regards,

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  • What if I made an explicit reference to 'this' for use inside an inner class?

    - by badp
    So far, I've used this approach to access this from the scope of an inner class: class FooManagementWindow extends JFrame { JButton rejectFoo; //... void getFooAcceptingPanel(){ //... final FooManagementWindow referenceToThis = this; rejectFoo = new JButton("Reject"); rejectFoo.addEventListener(new EventListener() { @Override public void actionPerformed(ActionEvent arg) { referenceToThis.setEnabled(false); //this requires a network call //... referenceToThis.setEnabled(true); //the user may resume his work } }); //... } } However, I just learned that instead of declaring referenceToThis, a direct reference is kept for me as: FooManagementWindow.this I have no reason to think my less standard approach may lead to errors or weird corner cases. Or are there?

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  • I can't set main Class variable in onCreate Method

    - by natrollus
    Main class has two variables that want to reach another class: public class MyClassA extends Activity { int i = 1; Button b1; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); this.i = 31; this.b1 = (Button) findViewById(R.id.btn1); ~~ } } Second class want to call variables in mainClass object: public class MyclassB implements OnClickListener{ MyClassA mainClass = new MyClassA(); Button btn = mainClass.b1; int n = mainClass.i; public void OnClick(View arg0){ Log.v("btn:",btn); Log.v("int:",n); } //btn returns null; //int returns 1; But onCreate method not set variables.. Why not set main class variables like this.i=31 ?

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  • Changing background color in Android SDK by clicking a button does not work

    - by DavidNg
    I have a simple program which is able to change the background color after clicking a button, but it does not work public class ChangeBackgroundActivity extends Activity { /** Called when the activity is first created. */ Button blueButton; LinearLayout myLO; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); myLO=(LinearLayout)findViewById(R.layout.main); blueButton=(Button)findViewById(R.id.button1); blueButton.setOnClickListener(new OnClickListener() { public void onClick(View arg0) { // TODO Auto-generated method stub myLO.setBackgroundColor(0x0000FF); //blue color code #0000FF } }); } }

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  • create an hotspot and set an image without background (like earth icon) to my panel

    - by sirvan
    Hi I try to create an hotspot by Extends of canvas and I try to add it on a panel witch painted by images , so I must to draw an icon (image) instead of clear rectangle of the screen, to do that I override the paint method to draw the icon I want to use, so far there is no problem, the hotspot work true and the icon painted in true size I want(32,24 pixel) I try to add this hotspot after painting image on the my panel in mypanel.paint(g) that override too. The problem , I use an car icon that have no background !!(I hope you can understand me) just car icon must be show on the panel that painted with my images; But an unwanted rectangle created around the icon and made bad view, How I can paint may icon on panel without that background? Please help me.

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  • Proper usage of Java Weak Reference in case of nested collections

    - by Tong Wang
    I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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  • Android how do I wait until a service is actually connected?

    - by Ryan
    I have an Activity calling a Service defined in IDownloaderService.aidl: public class Downloader extends Activity { IDownloaderService downloader = null; // ... In Downloader.onCreate(Bundle) I tried to bindService Intent serviceIntent = new Intent(this, DownloaderService.class); if (bindService(serviceIntent, sc, BIND_AUTO_CREATE)) { // ... and within the ServiceConnection object sc I did this public void onServiceConnected(ComponentName name, IBinder service) { Log.w("XXX", "onServiceConnected"); downloader = IDownloaderService.Stub.asInterface(service); // ... By adding all kinds of Log.xx I found that the code after if(bindService(...)) actually goes BEFORE ServiceConnection.onServiceConnected is being called - that is, when downloader is still null - which gets me into trouble. All the samples in ApiDemos avoid this timing problem by only calling services when triggered by user actions. But what should I do to right use this service after bindService succeeds? How can I wait for ServiceConnection.onServiceConnected being called reliably?

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  • How does array class work in Java?

    - by oks16
    In Java, array is a class and extends Object. I am curious to know about this special array class. I don't find the class definition anywhere. Doing a getClass().getName() gives strange result. String[] array = new String[]{"one","two"}; System.out.println(array.getClass().getName()); // prints [Ljava.lang.String; I want to understand how array works under the hood. Is the array class definition hardcoded in the JVM? Any resources, books, links on this will be helpful. Thank you.

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  • Java Disabled JLabel Reports Mouse Clicked

    - by ikurtz
    colLabels[i].addMouseListener(new MyAdapter()); private class MyAdapter extends MouseAdapter { @Override public void mouseClicked(MouseEvent event) { ColJLabel colJLabel = (ColJLabel)event.getComponent(); System.out.println(colJLabel.ColID); setColumnHeader(false); } } colLabels[i].setEnabled(flag); The situation is this: Mouse clicks are trapped correctly but when i have the JLabel (ColJLabel) control disabled it still reports mouse clicks. How can I make so that mouse clicks are only reported when the control is enabled? Thanks.

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  • Why baseclass calls method of subclass?

    - by twlkyao
    I encounter some code like the following: BaseClass: public class BaseClass { String name = "Base"; public BaseClass() { printName(); } public void printName() { System.out.println(name + "——Base"); } } DrivedClass: public class SubClass extends BaseClass { String name = "Sub"; public SubClass() { printName(); } public void printName() { System.out.println(name + "——Sub"); } public static void main(String[] args) { new SubClass(); } } When run the code, the output is: null——Sub Sub——Sub while it should be: Base——Base Sub——Sub I wonder why the BaseClass constructor calls the SubClass method, can anybody explain this? Thanks in advance.

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