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• singleton pattern in java- lazy Intialization

  - by flash

  public static MySingleton getInstance() { if (_instance==null) { synchronized (MySingleton.class) { _instance = new MySingleton(); } } return _instance; } 1.is there a flaw with the above implementation of the getInstance method? 2.What is the difference between the two implementations.? public static synchronized MySingleton getInstance() { if (_instance==null) { _instance = new MySingleton(); } return _instance; } I have seen a lot of answers on the singleton pattern in stackoverflow but the question I have posted is to know mainly difference of 'synchronize' at method and block level in this particular case.

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• How can I assign a DBNull in a better way?

  - by Mike

  Hi, I need to parse value from a datarow and assign it to another datarow.If the input is valid, then I need to parse it to double or else add a dbnull value to the output.I'm doing the following, is there a better way to do it? public double? GetVolume(object data) { string colValue = data == null ? string.Empty : data.ToString(); double volume; if (!Double.TryParse(colValue.ToString(), out volume)) { return null; } return volume; } public void Assign(DataRow theRowInput,DataRow theRowOutput) { double? volume = GetVolume(theRowInput[0]); if(volumne.HasValue) theRowOutput[0] = volume.value; else theRowOutput[0] = DbNull.Value; return theRowOutput; } Thanks, -M

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• Can MySQL automatically specify `_utf8` for inserts to UTF-8 columns?

  - by Neil

  I have a table like this, where one column is latin1, the other is UTF-8: Create Table: CREATE TABLE `names` ( `name_english` varchar(255) character NOT NULL, `name_chinese` varchar(255) character set utf8 default NULL, ) ENGINE=MyISAM DEFAULT CHARSET=latin1 When I do an insert, I have to type _utf8 before values being inserted into UTF-8 columns: insert into names (name_english = "hooey", name_chinese = _utf8 "??"); However, since MySQL should know that name_chinese is a UTF-8 column, it should be able to know to use _utf8 automatically. Is there any way to tell MySQL to use _utf8 automatically, so when I'm programatically making prepared statements, I don't have to worry about including it with the right parameters?

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• Sqlite insertion problem

  - by Devi

  Hi, I had sqlite database for my application I am able to retrieve values from my sqlite table and inserting values with no sql error but unable to find in sqlite table....please do needful help for this problem. I just stucked up at this point plz help me here is my code NSMutableString *registrationquery=[NSMutableString stringWithFormat:@"insert into tbl_kicks values ('%@','%@','%@')",[totalkicks text],[sessionstart text],[sessionstart text],@"0"]; //NSString *sqlNSString = [NSString stringWithFormat:@"INSERT INTO 'tbl_kicks' VALUES('%d','%@','%@');", // 4,sessionstart.text, appDelegate.note]; const char *sqlString = [registrationquery UTF8String]; char *sqlError; sqlite3_exec( appDelegate.database, sqlString, NULL, NULL, &sqlError );

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• Extending struts 2 "property" data tag

  - by John B.

  Hi, We are currently developing a project with Struts2. We have a module on which we display a large amount of data on read-only fields from a group of beans via the "property" Struts 2 data tag (i.e. <s:property value="aBeanProperty" /) on a jsp file. In some cases most of the fields might come empty, so a blank is being displayed on screen. Our customer is now requesting us to display default string (i.e. "N/A") whenever a property comes empty, so that it is displayed in place of the blank spaces currently shown. We are looking for a way to achieve this in a clean and maintainable way. The 'property' tag comes with a 'default' attribute on which one can define a default value in cases when the accessed property comes as null. However, most of our properties are empty strings, therefore it does not work in our case. Another solution we are thinking of is to define a base class for all of our beans, and define a util method which will validate if a string is null or empty and then return the default value. Then we would call this method from each bean getter. And yes this would be tiresome and kind of ugly :), therefore we are holding out on this one in case of a better solution. Now, we have in mind a solution which we think would be the best but have not had luck on how implement it. We are planning on extending the 'property' tag some way, defining a new 'default' attribute so that besides working on null properties, it also do so on empty strings ("", " ", etc). Therefore we would only need to replace the original s:property tag with our new custom tag, and the desired result would be achieved without touching java code. Do you have an idea on how to do this? Also, any other clever solution (maybe some sort of design pattern?) on how to default the values of a large amount of property beans are welcome too! (Or maybe, even there might be some tag that does this already in Struts2??) Thanks in advance.

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• Showing an image after laoding it from sql database

  - by user330075

  I have a problem showing the image form database in a view Details and a ImageController. Inside the view i have: img src=Url.Action("GetFile","Image", new {id= Model.id}) and in controller: public FileContentResult GetFile(int idl) { //int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } When the view is called, function GetFile it just wont work,but if i cut out the parameter int id1 and i instantiate it as a variable it'l work. public FileContentResult GetFile() { int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } Why?

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• pthread_exit return value

  - by Manty

  This is surprising for me. void * thread_func(void *arg) { pthread_exit(&ret); } int main(void) { pthread_t thr; int *exit_status; pthread_create(&thr, NULL, thread_func, NULL); sleep(2); pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); ret = 20; pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); return 0; } The output is value of exit status - 50 value of exit status - 20 I was expecting both the times the exit_status would be the actual exit value(50 in my case) of the thread. Instead it is just returning the value of the global variable which I used for pthread_exit. Is it not a bug?

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• How to store byte[] from Android Camera onPictureTaken method within application for later use

  - by Kiel Wood

  I am writing a larger Android application and I use the camera within the app. All I want to do with the camera is have the user take a picture, then start a new activity to show that image and allow the user to decide if they want to keep the image or not. I am having the hardest time figuring out how to simply store the byte[] data from the onPictureTaken method so that I can display it to the user in the next activity. I have tried many different routes and none of them have worked. The last thing I tried was creating a globalsettings class that extends the Application class and creating a byte[] field within it to store the byte[] from the camera so that I could use it within another activity, but my global variable is still not getting set. My CameraActivity code is shown below: public class CameraActivity extends Activity { CameraPreview Preview; Intent intent; byte[] image; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.cameralayout); Preview = new CameraPreview(this); ((FrameLayout)findViewById(R.id.uxfmlayPreview)).addView(Preview); intent = new Intent(this, PostCaptureActivity.class); } public void uxbtnCaptureSnap_Click(View v) { Preview.DeviceCamera.setPreviewCallback(null); Preview.DeviceCamera.takePicture(shutterCallback, rawCallback, jpegCallback); startActivity(intent); finish(); } public void uxbtnCaptureExit_Click(View v) { Intent i = new Intent(this, ExploreMenuActivity.class); setResult(RESULT_OK); startActivity(i); finish(); } ShutterCallback shutterCallback = new ShutterCallback() { public void onShutter() {} }; PictureCallback rawCallback = new PictureCallback() { public void onPictureTaken(byte[] data, Camera camera) {} }; PictureCallback jpegCallback = new PictureCallback() { public void onPictureTaken(byte[] data, Camera camera) { ((GlobalSettings)getApplication()).setGlobalImage(data); camera.release(); camera = null; } }; } Here is my code from my PostCaptureActivity onCreate() method where I attempt to convert and set the image as the source for an imageview: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.postcapturelayout); SnapShot = ((ImageView)findViewById(R.id.uximgSnapshot)); if(((GlobalSettings)this.getApplication()).getGlobalImage() != null) { Bitmap b = BitmapFactory.decodeByteArray(((GlobalSettings)this.getApplication()).getGlobalImage(), 0, ((GlobalSettings)this.getApplication()).getGlobalImage().length); SnapShot.setImageBitmap(b); } else { Toast.makeText(this, "Oops! Picture cannot be saved", Toast.LENGTH_SHORT).show(); } }

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• Android SurfaceView/Canvas flickering after trying to clear it

  - by Mark D

  So I am trying to clear the Canvas using canvas.drawColor(Color.BLACK) but if I just call this once, the display flickers and displays the old drawing which should have been covered up by the drawColor. Here is the important bits of my code - public void update() { //This method is called by a Thread Canvas canvas = holder.lockCanvas(null); if (canvas != null) { onDraw(canvas); } holder.unlockCanvasAndPost(canvas); } @Override protected void onDraw(Canvas canvas) { if (toClear) { canvas.drawColor(Color.BLACK); //if this is not set to change back to false, it does not flicker toClear = false; } //Draw some objects that are moving around } public void clearScreen() { //This method is called when the user pressed a button toClear = true; } After Googling around a litte, I heard about double buffering but came to the understanding that lockCanvas() and unlockCanvasAndPost() should handle this for me. What is going wrong here?

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• Why is there garbage in my TCHAR, even after ZeroMemory()?

  - by samoz

  I have inherited the following line of code: TCHAR temp[300]; GetModuleFileName(NULL, temp, 300); However, this fails as the first 3 bytes are filled with garbage values (always the same ones though, -128, -13, 23, in that order). I said, well fine and changed it to: TCHAR temp[300]; ZeroMemory(temp, 300); GetModuleFileName(NULL, temp, 300); but the garbage values persisted! Can someone explain what is going on and how to fix it?

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• How to change Session for only one route in asp.net mvc?

  - by denis_n

  How to handle Application_BeginRequest using a custom filter in asp.net mvc? I want to restore session only for one route (~/my-url). It would be cool, if I could create a custom filter and handle that. protected void Application_BeginRequest(object sender, EventArgs e) { var context = HttpContext.Current; if (string.Equals("~/my-url", context.Request.AppRelativeCurrentExecutionFilePath, StringComparison.OrdinalIgnoreCase)) { string sessionId = context.Request.Form["sessionId"]; if (sessionId != null) { HttpCookie cookie = context.Request.Cookies.Get("ASP.NET_SessionId"); if (cookie == null) { cookie = new HttpCookie("ASP.NET_SessionId"); } cookie.Value = sessionId; context.Request.Cookies.Set(cookie); } }

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• Question about custom events

  - by Malfist

  I'm making custom events for C# and sometimes it isn't working. This is how I'm making the event happen: private bool isDoorOpen; public bool IsDoorOpen { get { return isDoorOpen;} private set { isDoorOpen = value; DoorsChangeState(this, null);} } And these are the event declarations: //events public delegate void ChangedEventHandler(Elevator sender, EventArgs e); public event ChangedEventHandler PositionChanged; public event ChangedEventHandler DirectionChanged; public event ChangedEventHandler BreaksChangeState; public event ChangedEventHandler DoorsChangeState; This works as long as there are methods attached to the events, but if there isn't, it throws a null ref exception. What am I doing wrong?

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• Send a String[] ArrayList over Socket connection

  - by Duncan Palmer

  So i'm trying to send a String[] Array/List over an open socket connection. I currently have this code: Sending: public void sendData() { try { OutputStream socketStream = socket.getOutputStream(); ObjectOutputStream objectOutput = new ObjectOutputStream(socketStream); objectOutput.writeObject(new String[] {"Test", "Test2", "Test3"}); objectOutput.close(); socketStream.close(); } catch (Exception e) { System.out.println(e.toString()); } } Recieving: public Object readData() { try { InputStream socketStream = socket.getInputStream(); ObjectInputStream objectInput = new ObjectInputStream(new GZIPInputStream(socketStream)); Object a = objectInput.readObject(); return a; } catch(Exception e) { return null; } } After I have recieved the String array/list on the other end I want to be able to iterate through it like I would do normally so I can get the values. My current code doesn't seem to works as it returns null as the value. is this possible?

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• Data structure name: combination array/linked list

  - by me_and

  I have come up with a data structure that combines some of the advantages of linked lists with some of the advantages of fixed-size arrays. It seems very obvious to me, and so I'd expect someone to have thought of it and named it already. Does anyone know what this is called: Take a small fixed-size array. If the number of elements you want to put in your array is greater than the size of the array, add a new array and whatever pointers you like between the old and the new. Thus you have: Static array ————————————————————————— |1|2|3|4|5|6|7|8|9|a|b|c| ————————————————————————— Linked list ———— ———— ———— ———— ———— |1|*->|2|*->|3|*->|4|*->|5|*->NULL ———— ———— ———— ———— ———— My thing: ———————————— ———————————— |1|2|3|4|5|*->|6|7|8|9|a|*->NULL ———————————— ————————————

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• Resolve property at runtime. C#

  - by user1031381

  I have some class which have some code public IEnumerable<TypeOne> TypeOne { get { if (db != null) { var col = db.Select<TypeOne>(); if (col.Count > 0) return col; } return db2.TypeOne; } } public IEnumerable<TypeTwo> TypeTwo { get { if (db != null) { var col = db.Select<TypeTwo>(); if (col.Count > 0) return col; } return db2.TypeTwo; } } So as You can see there is a lot of duplicated Code and there are same property name and item type of enumerable. I want to call some property of object like "obj.MyProp". And MyProp must be resolved at runtime with some generic or non-generic method. Is it possible?

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• Noob question about hibernate criteria

  - by Dimitri

  Hello, I have a class called User which has 2 properties : login/password. I am trying to authenticate a user in my application using hibernate criteria but my request doesn't work. [EDIT] The returned value is NULL. I have two users in my database for testing. Here is my code : @Override public User authenticate(String login, String password) throws NullPointerException { Session session = this.getSession(); User user = (User) session .createCriteria(User.class) .add( Restrictions.and( Property.forName("login").eq(login), Property.forName("password").eq(password) )).uniqueResult(); if (user == null){ throw new NullPointerException("User not found"); } return user; } Can someone tells me what is wrong with my code? Happy new Year 2011 !!

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• sql .................................... [closed]

  - by sagar

  create table tony ( id int(10) NOT NULL,name varchar(20),dob DATE,primary key(id) ); is it right query

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• Queues And Wait Handles in C#

  - by Michael Covelli

  I've had the following code in my application for some years and have never seen an issue from it. while ((PendingOrders.Count > 0) || (WaitHandle.WaitAny(CommandEventArr) != 1)) { lock (PendingOrders) { if (PendingOrders.Count > 0) { fbo = PendingOrders.Dequeue(); } else { fbo = null; } } // Do Some Work if fbo is != null } Where CommandEventArr is made up of the NewOrderEvent (an auto reset event) and the ExitEvent (a manual reset event). But I just realized today that its not thread safe at all. If this thread gets interrupted right after the first (PendingOrder.Count 0) check has returned false. And then the other thread both enqueues an order and sets the NewOrderEvent before I get a chance to wait on it, the body of the while loop will never run. What's the usual pattern used with a Queue and an AutoResetEvent to fix this and do what I'm trying to do with the code above?

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• I was making this program and the server wont send to the client

  - by crstin

  void CApplication::SendData( const char pBuffer[] ) { if( pBuffer == NULL ) { Log()->Write( ELogMessageType_ERROR, "Cannot send NULL message."); return; } // calculate the size of that data unsigned long messageSize = strlen( pBuffer ); // fix our byte ordering messageSize = htonl( messageSize ); if( isServer == true ) { for( unsigned int i = ESocket_CLIENT0; i < ESocket_MAX; ++i ) { // send the message size if( m_Socket[ i ] > 0 ) { if( send( m_Socket[ i ], (char*)&messageSize, sizeof( messageSize ), 0 ) == SOCKET_ERROR ) { Log()->Write( ELogMessageType_ERROR, "[Application] Send error: %i to socket %i", WSAGetLastError(), m_Socket[ i ] ); continue; } // fix our message size back to host ordering messageSize = ntohl(messageSize); // send the actual message if( send( m_Socket[ i ], pBuffer, messageSize, 0 ) == SOCKET_ERROR ) { Log()->Write( ELogMessageType_ERROR, "[Application] Send error: %i to socket %i", WSAGetLastError(), m_Socket[ i ] ); continue; } Log()->Write( ELogMessageType_MESSAGE, "[Application] SEND: %s", pBuffer ); } } }

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• setting up linked list Java

  - by erp

  I'm working on some basic linked list stuff, like insert, delete, go to the front or end of the list, and basically i understand the concept of all of that stuff once i have the list i guess but im having trouble setting up the list. I was wondering of you guys could tell me if im going in the right direction. (mostly just the setup) this is what i have so far: public class List { private int size; private List linkedList; List head; List cur; List next; /** * Creates an empty list. * @pre * @post */ public List(){ linkedList = new List(); this.head = null; cur = head; } /** * Delete the current element from this list. The element after the deleted element becomes the new current. * If that's not possible, then the element before the deleted element becomes the new current. * If that is also not possible, then you need to recognize what state the list is in and define current accordingly. * Nothing should be done if a delete is not possible. * @pre * @post */ public void delete(){ // delete size--; } /** * Get the value of the current element. If this is not possible, throw an IllegalArgumentException. * @pre the list is not empty * @post * @return value of the current element. */ public char get(){ return getItem(cur); } /** * Go to the last element of the list. If this is not possible, don't change the cursor. * @pre * @post */ public void goLast(){ while (cur.next != null){ cur = cur.next; } } /** * Advance the cursor to the next element. If this is not possible, don't change the cursor. * @pre * @post */ public void goNext(){ if(cur.next != null){ cur = cur.next;} //else do nothing } /** * Retreat the cursor to the previous element. If this is not possible, don't change the cursor. * @pre * @post */ public void goPrev(){ } /** * Go to top of the list. This is the position before the first element. * @pre * @post */ public void goTop(){ } /** * Go to first element of the list. If this is not possible, don't change the cursor. * @pre * @post */ public void goFirst(){ } /** * Insert the given parameter after the current element. The newly inserted element becomes the current element. * @pre * @post * @param newVal : value to insert after the current element. */ public void insert(char newVal){ cur.setItem(newVal); size++; } /** * Determines if this list is empty. Empty means this list has no elements. * @pre * @post * @return true if the list is empty. */ public boolean isEmpty(){ return head == null; } /** * Determines the size of the list. The size of the list is the number of elements in the list. * @pre * @post * @return size which is the number of elements in the list. */ public int size(){ return size; } public class Node { private char item; private Node next; public Node() { } public Node(char item) { this.item = item; } public Node(char item, Node next) { this.item = item; this.next = next; } public char getItem() { return this.item; } public void setItem(char item) { this.item = item; } public Node getNext() { return this.next; } public void setNext(Node next) { this.next = next; } } } I got the node class alright (well i think it works alright), but is it necessary to even have that class? or can i go about it without even using it (just curious). And for example on the method get() in the list class can i not call that getItem() method from the node class because it's getting an error even though i thought that was the whole point for the node class. bottom line i just wanna make sure im setting up the list right. Thanks for any help guys, im new to linked list's so bear with me!

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• javascript popup window with correct data

  - by Christian

  I want this code below open in a popup window. How do I do? html- <td align="right"><a onclick="confirmSubmit();" target="paywin" class="button"><span><?php echo $button_continue; ?></span></a></td> Java - var newwin = null; function confirmSubmit() { $.ajax({ type: 'GET', url: 'index.php?route=payment/dibs/confirm', success: function() { $('#checkout-form').submit(); } }); } //--></script> I tried something like this: var newwin = null; function confirmSubmit() { $.ajax({ type: 'GET', url: 'index.php?route=payment/dibs/confirm', success: window.onload = function() { $('#checkout-form').submit(); } }); window.open('http://www.melacs.com/index.php?route=payment/dibs/confirm') } //--></script>

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• XMLHttpRequest.status always returning 0

  - by Michael

  html <a href="#" onclick="MyObj.startup()">click me</a> js code var MyObj = { startup : function() { var ajax = null; ajax = new XMLHttpRequest(); ajax.open('GET', 'http://www.nasa.gov', true); ajax.onreadystatechange = function(evt) { if(ajax.readyState == 4) { if (ajax.status == 200) { window.dump(":)\n"); } else { window.dump(":(\n"); } } } ajax.send(null); } } ajax.status always returning 0, no matter which site it is, no matter what is the actual return code. I say actual, because ajax.statusText returning correct value, eg OK or Redirecting... ajax.readyState also returns proper values and 4 at the end.

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• Positioning child panels using FlowLayout

  - by extro

  I have two panels: main_panel child_panel The main_panel layout is set using: main_panel.setLayout(flowlayout) I then added child_panel to main_panel: main_panel.add(child_panel) The child_panel gets added to main_panel but its position is at the cross-section of horizontal midpoint and top vertical section of screen. I want child_panel to be at the top left corner, something I could have done by using child_panel.setlocation(a,b) method, if I have set the layout of main_panel as null. I have used FlowLayout here because I want components in the JPanel to keep adjusting with the size of JFrame. So can I add child_panel to main_panel at the exact location I want, even if I set the Layout of main_panel as not null?

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• VS JavaScript intellisense with paramaters

  - by TonyB

  here is some sample javascript: SomeObjectType = function() { } SomeObjectType.prototype = { field1: null, field2: null } SomeOtherObject = function() { } SomeOtherObject.prototype = { doSomething: function(val) { /// <param name="val" type="SomeObjectType"></param> var val2 = new SomeObjectType(); //val2. shows intellisense correctly //val1. does NOT } } Shouldn't visual studio be giving me intellisence when i do "val." inside the "doSomething" function? I would expect it to give me field1 and field2 as options, but it doesn't. I DO get field1 and field2 if I type "val2." so intellisence works when I create a new object of the same type that I specify in the param comment. Any ideas what I am doing wrong or is this just not supported?

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• How to get google app engine logs in C#?

  - by Max

  I am trying to retrieve app engine logs the only result I get is "# next_offset=None", below is my code: internal string GetLogs() { string result = _connection.Get("/api/request_logs", GetPostParameters(null)); return result; } private Dictionary<string, string> GetPostParameters(Dictionary<string, string> customParameters) { Dictionary<string, string> parameters = new Dictionary<string, string>() { { "app_id", _settings.AppId }, { "version", _settings.Version.ToString() } }; if (customParameters != null) { foreach (string key in customParameters.Keys) { if (parameters.ContainsKey(key)) { parameters[key] = customParameters[key]; } else { parameters.Add(key, customParameters[key]); } } } return parameters; }

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