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  • SQL constructs translated to OOP

    - by python dude
    As someone who comes from the world of Object Orientation, I find it rather difficult to wrap my head around SQL. Recently, however, I realized that the classical SQL construct select X from Y where Z is basically equivalent to the following OOP construct: List<SomeType> results = db.query(new Matcher<SomeType> () { public boolean match(SomeType candidate) { return ...; // checks condition Z on candidate, returns true for match } }; So my question is: What are the OOP equivalents for other SQL constructs, such as joins?

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  • Php, socket and connecting to pop3-server

    - by Ockonal
    Hi guys, I'm trying to connect to the pop3-server with php. Here is my code: $pop3Server = 'mail.roller.ru'; $pop_conn = fsockopen($pop3Server, 110, $errno, $errstr, 10); print fgets($pop_conn, 1024); Warning: fsockopen() [function.fsockopen]: php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution in /home/ockonal/public_html/mail_parser.php on line 45 Warning: fsockopen() [function.fsockopen]: unable to connect to mail.roller.ru:110 (php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution) in /home/ockonal/public_html/mail_parser.php on line 45 Warning: fgets() expects parameter 1 to be resource, boolean given in /home/ockonal/public_html/mail_parser.php on line 46 What's wrong? I'm sure in pop3-server address. It doesn't print anything.

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  • Dictionary keys don't contain a key that's already contained in keys

    - by ran
    Why is the following 'exist' boolean variable getting a value of false??? foreach (Cell existCell in this.decoratorByCell.Keys) { //this call yield the same hashcode for both cells. still exist==false bool exist = this.decoratorByCell.ContainsKey(existCell); } I've overridden GetHashCode() & Equals() Methods as follows: public override int GetHashCode() { string nodePath = GetNodePath(); return nodePath.GetHashCode() + m_ownerColumn.GetHashCode(); } public bool Equals(Cell other) { bool nodesEqual = (other.OwnerNode == null && this.OwnerNode == null) || (other.GetNodePath() == this.GetNodePath()); bool columnsEqual = (other.OwnerColumn == null && this.OwnerColumn == null) || (other.OwnerColumn == this.OwnerColumn); bool treesEqual = (this.m_ownerTree == other.m_ownerTree); return (nodesEqual && columnsEqual && treesEqual); }

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  • Is this code thread safe?

    - by Shawn Simon
    ''' <summary> ''' Returns true if a submission by the same IP address has not been submitted in the past n minutes. ''' </summary> Protected Function EnforceMinTimeBetweenSubmissions() As Boolean Dim minTimeBetweenRequestsMinutes As Integer = 0 Dim configuredTime = ConfigurationManager.AppSettings("MinTimeBetweenSchedulingRequestsMinutes") If String.IsNullOrEmpty(configuredTime) Then Return True If (Not Integer.TryParse(configuredTime, minTimeBetweenRequestsMinutes)) _ OrElse minTimeBetweenRequestsMinutes > 1440 _ OrElse minTimeBetweenRequestsMinutes < 0 Then Throw New ApplicationException("Invalid configuration setting for AppSetting 'MinTimeBetweenSchedulingRequestsMinutes'") End If If minTimeBetweenRequestsMinutes = 0 Then Return True End If If Cache("submitted-requests") Is Nothing Then Cache("submitted-requests") = New Dictionary(Of String, Date) End If ' Remove old requests. Dim submittedRequests As Dictionary(Of String, Date) = CType(Cache("submitted-requests"), Dictionary(Of String, Date)) Dim itemsToRemove = submittedRequests.Where(Function(s) s.Value < Now).Select(Function(s) s.Key).ToList For Each key As String In itemsToRemove submittedRequests.Remove(key) Next If submittedRequests.ContainsKey(Request.UserHostAddress) Then ' User has submitted a request in the past n minutes. Return False Else submittedRequests.Add(Request.UserHostAddress, Now.AddMinutes(minTimeBetweenRequestsMinutes)) End If Return True End Function

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  • I need some help optimizing my database schema

    - by Steffan
    Here's a layout of my data: Heading 1: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 2: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 3: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 4: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 5: Sub heading Sub heading Sub heading Sub heading Sub heading These headings need to have a 'Completion Status' boolean value which gets linked to a user Id. Currently, this is how my table looks: id | userID | field_1 | field_2 | field_3 | field_4 | etc... ----------------------------------------------------------------------- 1 | 1 | 0 | 0 | 1 | 0 | ----------------------------------------------------------------------- 2 | 2 | 1 | 0 | 1 | 1 | Each field represents one Sub Heading. Having this many columns in my table looks awfully inefficient... How can I go about optimizing this? I can't think of any way to neaten it up :/

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  • Spring constructor injection of SLF4J logger - how to get injection target class?

    - by disown
    I'm trying to use Spring to inject a SLF4J logger into a class like so: @Component public class Example { private final Logger logger; @Autowired public Example(final Logger logger) { this.logger = logger; } } I've found the FactoryBean class, which I've implemented. But the problem is that I cannot get any information about the injection target: public class LoggingFactoryBean implements FactoryBean<Logger> { @Override public Class<?> getObjectType() { return Logger.class; } @Override public boolean isSingleton() { return false; } @Override public Logger getObject() throws Exception { return LoggerFactory.getLogger(/* how do I get a hold of the target class (Example.class) here? */); } } Is FactoryBean even the right way to go? When using picocontainers factory injection, you get the Type of the target passed in. In guice it is a bit trickier. But how do you accomplish this in Spring?

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  • storing data in a database using edit text and button

    - by user1841444
    Hai im trying to Insert data into database using EditText and Button i have created. Im stuck at Activity part of the Code.I unbale to proceed how to write the Onclick action part for Button and EditText part Please help me. Im new to android DBAdapter.java package com.example.database1; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DBAdapter { public static final String KEY_ROWID = "_id"; public static final String KEY_ISBN = "isbn"; public static final String KEY_TITLE = "title"; public static final String KEY_PUBLISHER = "publisher"; private static final String TAG = "DBAdapter"; private static final String DATABASE_NAME = "books"; private static final String DATABASE_TABLE = "titles"; private static final int DATABASE_VERSION = 1; private static final String DATABASE_CREATE = "create table titles (_id integer primary key autoincrement, " + "isbn text not null, title text not null, " + "publisher text not null);"; private final Context context; private DatabaseHelper DBHelper; private SQLiteDatabase db; public DBAdapter(Context ctx) { this.context = ctx; DBHelper = new DatabaseHelper(context); } private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS titles"); onCreate(db); } } //---opens the database--- public DBAdapter open() throws SQLException { db = DBHelper.getWritableDatabase(); return this; } //---closes the database--- public void close() { DBHelper.close(); } //---insert a title into the database--- public long insertTitle(String isbn, String title, String publisher) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_ISBN, isbn); initialValues.put(KEY_TITLE, title); initialValues.put(KEY_PUBLISHER, publisher); return db.insert(DATABASE_TABLE, null, initialValues); } //---deletes a particular title--- public boolean deleteTitle(long rowId) { return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; } //---retrieves all the titles--- public Cursor getAllTitles() { return db.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_ISBN, KEY_TITLE, KEY_PUBLISHER}, null, null, null, null, null); } //---retrieves a particular title--- public Cursor getTitle(long rowId) throws SQLException { Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] { KEY_ROWID, KEY_ISBN, KEY_TITLE, KEY_PUBLISHER }, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } //---updates a title--- public boolean updateTitle(long rowId, String isbn, String title, String publisher) { ContentValues args = new ContentValues(); args.put(KEY_ISBN, isbn); args.put(KEY_TITLE, title); args.put(KEY_PUBLISHER, publisher); return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } } DatabaseActivity.java package com.example.database1; import android.os.Bundle; import android.app.Activity; import android.database.Cursor; import android.view.Menu; import android.widget.Toast; public class DatabaseActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_database); DBAdapter db=new DBAdapter(this); db.open(); } } activity_database.xml: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <EditText android:id="@+id/edit1" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <EditText android:id="@+id/edit2" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <EditText android:id="@+id/edit3" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <Button android:id="@+id/submit" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout>

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  • java: how to get a string representation of a compressed byte array ?

    - by Guillaume
    I want to put some compressed data into a remote repository. To put data on this repository I can only use a method that take the name of the resource and its content as a String. (like data.txt + "hello world"). The repository is moking a filesystem but is not, so I can not use File directly. I want to be able to do the following: client send to server a file 'data.txt' server compress 'data.txt' into a compressed file 'data.zip' server send a string representation of data.zip to the repository repository store data.zip client download from repository data.zip and his able to open it with its favorite zip tool The problem arise at step 3 when I try to get a string representation of my compressed file. Here is a sample class, using the zip*stream and that emulate the repository showcasing my problem. The created zip file is working, but after its 'serialization' it's get corrupted. (the sample class use jakarta commons.io ) Many thanks for your help. package zip; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.zip.ZipEntry; import java.util.zip.ZipInputStream; import java.util.zip.ZipOutputStream; import org.apache.commons.io.FileUtils; /** * Date: May 19, 2010 - 6:13:07 PM * * @author Guillaume AME. */ public class ZipMe { public static void addOrUpdate(File zipFile, File ... files) throws IOException { File tempFile = File.createTempFile(zipFile.getName(), null); // delete it, otherwise you cannot rename your existing zip to it. tempFile.delete(); boolean renameOk = zipFile.renameTo(tempFile); if (!renameOk) { throw new RuntimeException("could not rename the file " + zipFile.getAbsolutePath() + " to " + tempFile.getAbsolutePath()); } byte[] buf = new byte[1024]; ZipInputStream zin = new ZipInputStream(new FileInputStream(tempFile)); ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFile)); ZipEntry entry = zin.getNextEntry(); while (entry != null) { String name = entry.getName(); boolean notInFiles = true; for (File f : files) { if (f.getName().equals(name)) { notInFiles = false; break; } } if (notInFiles) { // Add ZIP entry to output stream. out.putNextEntry(new ZipEntry(name)); // Transfer bytes from the ZIP file to the output file int len; while ((len = zin.read(buf)) > 0) { out.write(buf, 0, len); } } entry = zin.getNextEntry(); } // Close the streams zin.close(); // Compress the files if (files != null) { for (File file : files) { InputStream in = new FileInputStream(file); // Add ZIP entry to output stream. out.putNextEntry(new ZipEntry(file.getName())); // Transfer bytes from the file to the ZIP file int len; while ((len = in.read(buf)) > 0) { out.write(buf, 0, len); } // Complete the entry out.closeEntry(); in.close(); } // Complete the ZIP file } tempFile.delete(); out.close(); } public static void main(String[] args) throws IOException { final String zipArchivePath = "c:/temp/archive.zip"; final String tempFilePath = "c:/temp/data.txt"; final String resultZipFile = "c:/temp/resultingArchive.zip"; File zipArchive = new File(zipArchivePath); FileUtils.touch(zipArchive); File tempFile = new File(tempFilePath); FileUtils.writeStringToFile(tempFile, "hello world"); addOrUpdate(zipArchive, tempFile); //archive.zip exists and contains a compressed data.txt that can be read using winrar //now simulate writing of the zip into a in memory cache String archiveText = FileUtils.readFileToString(zipArchive); FileUtils.writeStringToFile(new File(resultZipFile), archiveText); //resultingArchive.zip exists, contains a compressed data.txt, but it can not //be read using winrar: CRC failed in data.txt. The file is corrupt } }

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  • Expression Tree

    - by nettguy
    My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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  • Problem with Qt::QueuedConnection, signal delivered after disconnect

    - by lutku
    Hi, I just discovered interesting behavior of queued connection in Qt 4.6: First queued connection is made: connect(someSender, SIGNAL(completed()), this, SLOT(handleCompletion()), Qt::QueuedConnection) Then someSender sends the signal: emit completed() Before receiving signal (as it is in queue), I disconnect from the signal: disconnect(someSender, SIGNAL(completed()), this, SLOT(handleCompletion()) Still, handleCompletion slot is invoked at next eventloop iteration. I can prevent this from happening by using someSender-blockSignals(true) at correct point, but it feels awful not to mention having some boolean flag to disable slot's functionality. Especially, I feel amazed that this behavior is not mentioned in Qt documentation (at least I haven't found). Finally the question: any sensible way to avoid this from happening?

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  • createChildren Called Before Component's MXML Bracket Logic Is Evaluated

    - by Nalandial
    I have the following MXML: <mx:Script> var someBoolean:Boolean = determineSomeCondition(); </mx:Script> .... <foo:MyComponent somePropertyExpectingIDataRenderer="{ someBoolean ? new Component1ThatImplementsIDataRenderer() : new Component2ThatImplementsIDataRenderer() }"> </foo:MyComponent> I have also overridden the createChildren() function: override protected function createChildren():void { super.createChildren(); //do something with somePropertyExpectingIDataRenderer } My problem is: createChildren() is being called before the squiggly bracket logic is being evaluated, so in createChildren(), somePropertyExpectingIDataRenderer is null. However if I pass the component via MXML like this: <foo:MyComponent> <bar:somePropertyExpectingIDataRenderer> <baz:Component1ThatImplementsIDataRenderer/> </bar:somePropertyExpectingIDataRenderer> </foo:MyComponent> Then when createChildren() is called, that same property isn't null. Is this supposed to happen and if so, what other workarounds should I consider?

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  • Form gets disposed somehow

    - by mnn
    I have a client-server application, in which I use classic Sockets and threads for receiving/sending data and listening for clients. The application works fine, but after some random time I get the ObjectDisposedException: System.ObjectDisposedException: Cannot access a disposed object. Object name: 'MainForm'. at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at System.Windows.Forms.Control.Invoke(Delegate method) That code is called from client Socket thread and I use Invoke() method to run the code on UI thread. I'm sure that I don't manually dispose the form nor using Close() (form is closed by user clicking Close button), so I don't know what could cause its disposing.

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  • Java == operator. "Invalid assignment operator"

    - by Tom
    Hi, I was trying to write a simple method boolean validate(MyObject o) { return o.getPropertyA() == null && o.getPropertyB()==null; } And got a strange error on the == null part. Maybe my Java is rusty after a season in PLSQL. Consider this: Integer i = 4; i ==null; //compile error: Syntax error on token ==. Invalid assignment operator. Integer i2 = 4; if (i==null); //No problem How can this be ? Any explanation ? Im using jdk160_05.

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  • Invalid Viewstate

    - by murak
    I always got this error guys on my site.Anybody got a solution. Stacktrace at System.Web.UI.Page.DecryptStringWithIV(String s, IVType ivType) at System.Web.UI.Page.DecryptString(String s) at System.Web.Handlers.ScriptResourceHandler.DecryptParameter(NameValueCollection queryString) at System.Web.Handlers.ScriptResourceHandler.ProcessRequestInternal(HttpResponse response, NameValueCollection queryString, VirtualFileReader fileReader) at System.Web.Handlers.ScriptResourceHandler.ProcessRequest(HttpContext context) at System.Web.Handlers.ScriptResourceHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Query String d=J_c3w3Q59U-PnoRlWBPOJMVgHe_9Ile9wANEXiRFLzG8mequestManager._initialize('ctl00%24ScriptManager1' I noticed that there are strings that got appended on the last part of ScriptResource.axd which are not part of the querystring(equestManager._initialize('ctl00%24ScriptManager1').I don't know how this string ends up here.I am using MS ajax, webforms and IIS7 on a shared hosting plan.

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  • Android: Hiding the keyboard in an overrided "Done" keypress of EditText

    - by Marshall Ward
    Hello, I have used a bit of Android code to override the "Done" button in my EditText field: myEditField.setOnEditorActionListener(new TextView.OnEditorActionListener() { @Override public boolean onEditorAction(TextView v, int actionId, KeyEvent event) { if (actionId == EditorInfo.IME_ACTION_DONE) { mySubroutine(); return true; } return false; } }); Activating the field calls up the keyboard, and pressing "Done" evaluates mySubroutine() successfully. However, the keyboard no longer goes away when I press "Done". How do I restore this default behaviour to the routine?

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  • two views ontouchlistener same area how to?

    - by user553465
    I have a two ImageView. 1.ImageView zomeImageMoveable : should zome in,out and moveable. 2.ImageView zomeImageFixed : show zome this is guide line. i want this two views work same touch. { FrameLayout myFrmae = new FrameLayout(this.getContext()); myFrame.addView(zomeImageMoveable); myFrame.addView(zomeImageFixed); } Case 1. below two ImageView have each listener ,but works only one. Case 2. FrameLayout add OnTouchListener and forward. but it doesn't work myFrame.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { zomeImageMoveable.onTouchEvent(event); zomeImageFixed.onTouchEvent(event); return false; } }); how do i have to do? thanks for reading.

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  • Need to convert this for loop to a while loop

    - by Bragaadeesh
    Hi guys, I solved a problem recently. But I have this one piece of code where I dont utilize the for loop initialization and condition check. It looks a bit odd that way for a for loop. I want to convert it into a while loop. Please help me do it. I tried many times, but somewhere something is missing. for(;;current =(current+1)%n){ if(eliminated[current%n]){ continue; }else{ inkiPinki++; if(inkiPinki == m){ eliminated[current%n] = true; printStatus(eliminated, people); remainingGuys--; break; } } } In the above code eliminiated[index] is a boolean.

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  • How to get predecessor and successors from an adjacency matrix

    - by NickTFried
    Hi I am am trying to complete an assignment, where it is ok to consult the online community. I have to create a graph class that ultimately can do Breadth First Search and Depth First Search. I have been able to implement those algorithms successfully however another requirement is to be able to get the successors and predecessors and detect if two vertices are either predecessors or successors for each other. I'm having trouble thinking of a way to do this. I will post my code below, if anyone has any suggestions it would be greatly appreciated. import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import java.util.Stack; public class Graph<T> { public Vertex<T> root; public ArrayList<Vertex<T>> vertices=new ArrayList<Vertex<T>>(); public int[][] adjMatrix; int size; private ArrayList<Vertex<T>> dfsArrList; private ArrayList<Vertex<T>> bfsArrList; public void setRootVertex(Vertex<T> n) { this.root=n; } public Vertex<T> getRootVertex() { return this.root; } public void addVertex(Vertex<T> n) { vertices.add(n); } public void removeVertex(int loc){ vertices.remove(loc); } public void addEdge(Vertex<T> start,Vertex<T> end) { if(adjMatrix==null) { size=vertices.size(); adjMatrix=new int[size][size]; } int startIndex=vertices.indexOf(start); int endIndex=vertices.indexOf(end); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public void removeEdge(Vertex<T> v1, Vertex<T> v2){ int startIndex=vertices.indexOf(v1); int endIndex=vertices.indexOf(v2); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public int countVertices(){ int ver = vertices.size(); return ver; } /* public boolean isPredecessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ /* public boolean isSuccessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ public void getSuccessors(Vertex<T> v1){ } public void getPredessors(Vertex<T> v1){ } private Vertex<T> getUnvisitedChildNode(Vertex<T> n) { int index=vertices.indexOf(n); int j=0; while(j<size) { if(adjMatrix[index][j]==1 && vertices.get(j).visited==false) { return vertices.get(j); } j++; } return null; } public Iterator<Vertex<T>> bfs() { Queue<Vertex<T>> q=new LinkedList<Vertex<T>>(); q.add(this.root); printVertex(this.root); root.visited=true; while(!q.isEmpty()) { Vertex<T> n=q.remove(); Vertex<T> child=null; while((child=getUnvisitedChildNode(n))!=null) { child.visited=true; bfsArrList.add(child); q.add(child); } } clearVertices(); return bfsArrList.iterator(); } public Iterator<Vertex<T>> dfs() { Stack<Vertex<T>> s=new Stack<Vertex<T>>(); s.push(this.root); root.visited=true; printVertex(root); while(!s.isEmpty()) { Vertex<T> n=s.peek(); Vertex<T> child=getUnvisitedChildNode(n); if(child!=null) { child.visited=true; dfsArrList.add(child); s.push(child); } else { s.pop(); } } clearVertices(); return dfsArrList.iterator(); } private void clearVertices() { int i=0; while(i<size) { Vertex<T> n=vertices.get(i); n.visited=false; i++; } } private void printVertex(Vertex<T> n) { System.out.print(n.label+" "); } }

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  • arbitrary typed data in django model

    - by Dmitry Shevchenko
    I have a model, say, Item. I want to store arbitrary amount of attributes on it, like title, description, release_date. And i want them to be not just strings but have python type, so string, boolean, datetime etc. What are my options here? EAV pattern with separate name-value table won't work because of the same DB type across all values. JSONField can probably help, but it doesn't know about datetime, for example. Also i was looking at PickeField, it fits perfectly, but i'm a bit concerned about performance.

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  • Correct Use of .NET Exception

    - by destructo_gold
    What is the correct exception to throw in the following instance? If, for example, I have a class: Album with a collection of Songs: List<Song> And a method within Album to add a Song: public void AddSong(Song song) { songs.Add(song); } Should I throw an exception of a user attempts to add a song that already exists? If so, what type of exception? I have heard the phrase: "Only use exceptions in exceptional circumstances", but I want to tell the client implementing Album exactly what has gone wrong (not just return a Boolean value).

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  • T-SQL Re-Assigning Order Numbering

    - by Meltdown
    Say I have a table with a field called "ordernum" that denotes the order of a given set of rows. Now imagine that I delete one of these rows. What type of query would work best for re-assigning the order numbers so that they remain sequential? Here's an example: id group_id name ordernum active --------------------------------------------------- 0_____0______'Name1'___5__true 1_____0______'Name2'___4__true 2_____0______'Name3'___3__true 3_____1______'Name4'___2__true 4_____1______'Name5'__1__true 5_____1______'Name6'__NULL___false Now if I deleted the column with id='4' how would I reset the values in the 'ordernum' field for that specific group? Is this even possible? Or if I added a new row. (The first time the rows are created they are sorted by date, but then the user has the option to set the order himself.) In my table design I have a column 'active' boolean. If 'active' is set to false, then 'ordernum' is set to NULL. Otherwise it should be given an order number.

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  • What happens to date-times and booleans when using DbLinq with SQLite?

    - by DanM
    I've been thinking about using SQLite for my next project, but I'm concerned that it seems to lack proper datetime and bit data types. If I use DbLinq (or some other ORM) to generate C# classes, will the data types of the properties be "dumbed down"? Will date-time data be placed in properties of type string or double? Will boolean data be placed in properties of type int? If yes, what are the implications? I'm imaging a scenario where I need to write a whole second layer of classes with more specific data types and do a bunch of transformations and casts, but maybe it's not so bad. If you have any experience with this or a similar scenario, what are your "lessons learned"?

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  • PDO update with conditional?

    - by dmontain
    I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. But hopefully there is a way to accomplish this in 1 query?

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  • Route alias, is it possible?

    - by benoror
    I have a Vehicle model: map.resources :vehicles, :has_many => :suppliers Everything works great, but Vehicle has a boolean attribute is_truck. I want to make an Alias so I can get the same resources but with the "truck" word, I tried with: map.trucks '/trucks', :controller => :vehicles, :action => :index, :is_truck => true map.trucks '/trucks/by_supplier/:supplier', :controller => :vehicles, :action => :index, :is_truck => true The first one works well, but when I search within a Form the second doesn't work and searches all suppliers. Is it possible to map.resources for an alias ?

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  • Java assert nasty side-effect - compiler bug?

    - by Alex
    This public class test { public static void main(String[] args) { Object o = null; assert o != null; if(o != null) System.out.println("o != null"); } } prints out "o != null"; both 1.5_22 and 1.6_18. Compiler bug? Commenting out the assert fixes it. The byte code appears to jump directly to the print statement when assertions are disabled: public static main(String[]) : void L0 LINENUMBER 5 L0 ACONST_NULL ASTORE 1 L1 LINENUMBER 6 L1 GETSTATIC test.$assertionsDisabled : boolean IFNE L2 ALOAD 1: o IFNONNULL L2 NEW AssertionError DUP INVOKESPECIAL AssertionError.<init>() : void ATHROW L2 LINENUMBER 8 L2 GETSTATIC System.out : PrintStream LDC "o != null" INVOKEVIRTUAL PrintStream.println(String) : void L3 LINENUMBER 9 L3 RETURN L4

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