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  • How to delete Drawn Line in java?

    - by Jeyjey
    Hello Folks, well this is my code: import javax.swing.; import javax.; import java.awt.; import java.awt.Color; import java.awt.Graphics.; import java.awt.event.*; import javax.swing.UIManager; public class SimpleGUI extends JFrame{ public SimpleGUI(){ this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ; } public void go(){ Drawpanel = new Mypanel(); JFrame frame = new JFrame("Chasing Line"); frame.getContentPane().add(BorderLayout.CENTER, Drawpanel); frame.setSize(300,300); frame.setVisible(true); Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() { public void mouseMoved(java.awt.event.MouseEvent evt) { DrawpanelMouseMoved(evt); } }); } public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) { xpos=evt.getX(); ypos=evt.getY(); System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos); Drawpanel.paintImage(xpos,ypos); } class Mypanel extends JPanel{ public void paintImage(int xpost,int ypost){ Graphics d = getGraphics(); d.setColor(Color.black); d.drawLine(xpost, 0, xpost, this.getHeight()); d.setColor(Color.red); d.drawLine(0, ypost, this.getWidth(),ypost); this.validate(); } } // end the inner class public static void main(String[] args){ try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); } catch(Exception e) { System.err.println("Look and feel not set"); } SimpleGUI win = new SimpleGUI(); win.go(); } Mypanel Drawpanel; private int xpos=0; private int ypos=0; } // close SimpleGUI class The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer. thanks for any reply.

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  • [C#] How do I make hierarchy of objects from two alternating classes?

    - by Millicent
    Here's the scenario: I have two classes ("Page" and "Field"), that are descended from a common class ("Pield"). They represent tags in an XML file and are in the following hierarchy: <page> <field> <page> ... </page> ... </field> ... </page> I.e.: Page and Field objects are in a hierarchy of alternating type (there may be more than one Page or Field to each rung of the hierarchy). Every Field and Page object has a parent property, which points to the respective parent object of the other type. This is not a problem unless the parent-child mechanism is controlled by the base class (Pield), which is shared by the two descended classes (Page and Field). Here is one try, that fails at the line "Pield child = new Pield(pchild, this);": class Pield<T> { private T _pield_parent; ... private void get_children() { ... Pield<Page> child = new Pield<Page>(pchild, this); ... } ... } class Page : Pield<Field> { ... } class Field : Pield<Page> { ... } Any ideas about how to solve this elegantly? Best, Millicent

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  • Make an abstract class or use a processor?

    - by Tim Murphy
    I'm developing a class to compare two directories and run an action when a directory/file in the source directory does not exist in destination directory. Here is a prototype of the class: public abstract class IdenticalDirectories { private DirectoryInfo _sourceDirectory; private DirectoryInfo _destinationDirectory; protected abstract void DirectoryExists(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void DirectoryDoesNotExist(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void FileExists(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void FileDoesNotExist(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); public IdenticalDirectories(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory) { ... } public void Run() { foreach (DirectoryInfo sourceSubDirectory in _sourceDirectory.GetDirectories()) { DirectoryInfo destinationSubDirectory = this.GetDestinationDirectoryInfo(subDirectory); if (destinationSubDirectory.Exists()) { this.DirectoryExists(sourceSubDirectory, destinationSubDirectory); } else { this.DirectoryDoesNotExist(sourceSubDirectory, destinationSubDirectory); } foreach (FileInfo sourceFile in sourceSubDirectory.GetFiles()) { FileInfo destinationFile = this.GetDestinationFileInfo(sourceFile); if (destinationFile.Exists()) { this.FileExists(sourceFile, destinationFile); } else { this.FileDoesNotExist(sourceFile, destinationFile); } } } } } The above prototype is an abstract class. I'm wondering if it would be better to make the class non-abstract and have the Run method receiver a processor? eg. public void Run(IIdenticalDirectoriesProcessor processor) { foreach (DirectoryInfo sourceSubDirectory in _sourceDirectory.GetDirectories()) { DirectoryInfo destinationSubDirectory = this.GetDestinationDirectoryInfo(subDirectory); if (destinationSubDirectory.Exists()) { processor.DirectoryExists(sourceSubDirectory, destinationSubDirectory); } else { processor.DirectoryDoesNotExist(sourceSubDirectory, destinationSubDirectory); } foreach (FileInfo sourceFile in sourceSubDirectory.GetFiles()) { FileInfo destinationFile = this.GetDestinationFileInfo(sourceFile); if (destinationFile.Exists()) { processor.FileExists(sourceFile, destinationFile); } else { processor.FileDoesNotExist(sourceFile, destinationFile); } } } } What do you see as the pros and cons of each implementation?

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  • Singleton pattern in C++

    - by skydoor
    I have a question about the singleton pattern. I saw two cases concerning the static member in the singleton class. First it is an object, like this class CMySingleton { public: static CMySingleton& Instance() { static CMySingleton singleton; return singleton; } // Other non-static member functions private: CMySingleton() {} // Private constructor ~CMySingleton() {} CMySingleton(const CMySingleton&); // Prevent copy-construction CMySingleton& operator=(const CMySingleton&); // Prevent assignment }; One is an pointer, like this class GlobalClass { int m_value; static GlobalClass *s_instance; GlobalClass(int v = 0) { m_value = v; } public: int get_value() { return m_value; } void set_value(int v) { m_value = v; } static GlobalClass *instance() { if (!s_instance) s_instance = new GlobalClass; return s_instance; } }; What's the difference between the two cases? Which one is correct?

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  • excel:mysql: rs.Update not working

    - by every_answer_gets_a_point
    i am updating a table using an ODBC connection from excel to mysql unfortunately the only column that gets updated is this one: .Fields("instrument") = "NA" where i am assigning variables to .Fields, it is putting NULL values!! what is going on here? here's the code Option Explicit Dim oConn As ADODB.Connection Private Sub ConnectDB() Set oConn = New ADODB.Connection oConn.Open "DRIVER={MySQL ODBC 5.1 Driver};" & _ "SERVER=localhost;" & _ "DATABASE=employees;" & _ "USER=root;" & _ "PASSWORD=pas;" & _ "Option=3" End Sub Function esc(txt As String) esc = Trim(Replace(txt, "'", "\'")) End Function Private Sub InsertData() Dim dpath, atime, rtime, lcalib, aname, rname, bstate, instrument As String Dim rs As ADODB.Recordset Set rs = New ADODB.Recordset ConnectDB With wsBooks rs.Open "batchinfo", oConn, adOpenKeyset, adLockOptimistic, adCmdTable Worksheets.Item("Report 1").Select dpath = Trim(Range("B2").Text) atime = Trim(Range("B3").Text) rtime = Trim(Range("B4").Text) lcalib = Trim(Range("B5").Text) aname = Trim(Range("B6").Text) rname = Trim(Range("B7").Text) bstate = Trim(Range("B8").Text) ' instrument = GetInstrFromXML(wbBook.FullName) With rs .AddNew ' create a new record ' add values to each field in the record .Fields("datapath") = dpath .Fields("analysistime") = atime .Fields("reporttime") = rtime .Fields("lastcalib") = lcalib .Fields("analystname") = aname .Fields("reportname") = rname .Fields("batchstate") = bstate .Fields("instrument") = "NA" .Update ' stores the new record End With ' get the last id Set rs = oConn.Execute("SELECT @@identity", , adCmdText) 'MsgBox capture_id rs.Close Set rs = Nothing End With End Sub

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  • image list, listview,picturebox

    - by user548694
    I wanted to show my pics in picturebox. but also wanted to show a preview of pics. When user select a pic, it is shown in picbox but i have problem in resoulution. Here is my code private void openToolStripMenuItem_Click(object sender, EventArgs e) { ofd = new OpenFileDialog(); ofd.Title = "Open an Image File"; ofd.FileName = ""; ofd.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp"; if (ofd.ShowDialog() == DialogResult.OK) { DirectoryInfo dir = new DirectoryInfo(@"c:\pic"); foreach (FileInfo file in dir.GetFiles()) { this.imageList1.Images.Add(Image.FromFile(file.FullName)); } this.listView1.View = View.LargeIcon; this.imageList1.ImageSize = new Size(40, 40); this.listView1.LargeImageList = this.imageList1; for (int j=0; j < this.imageList1.Images.Count; j++) { ListViewItem item = new ListViewItem(); item.ImageIndex = j; listView1.Items.Add(item); ListViewItem item2 = new ListViewItem(); item2.SubItems.Add(j.ToString()); } private void listView1_SelectedIndexChanged(object sender, EventArgs e) { int i = this.listView1.FocusedItem.Index; this.PicBox1.Image = this.imageList1.Images[i]; } On click i see only image of resolution of (40,40) becuse i have set it this.imageList1.ImageSize = new Size(40, 40); and not orignal size. How can I have it. 2- I want to write also image names and index(image no) under each images. Its it possible. reagrsd,

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  • Add Custom Control to DataGridViewCell

    - by Kovscer
    Hello, I create a custom control inherited from Windows.System.Forms.Controls. This is my code of this control: public partial class MonthEventComponent : Control { private Color couleur; private Label labelEvenement; public MonthEventComponent(Color couleur_c, String labelEvenement_c ) { InitializeComponent(); this.couleur = couleur_c; this.labelEvenement.Text = labelEvenement_c; this.labelEvenement.ForeColor = couleur; this.labelEvenement.BackColor = Color.White; this.labelEvenement.TextAlign = ContentAlignment.MiddleLeft; this.labelEvenement.Dock = DockStyle.Fill; this.Controls.Add(labelEvenement); } public MonthEventComponent() { InitializeComponent(); this.couleur = Color.Black; this.labelEvenement = new Label(); this.labelEvenement.ForeColor = couleur; this.labelEvenement.BackColor = Color.White; this.labelEvenement.Text = "Evénement Initialiser"; this.labelEvenement.TextAlign = ContentAlignment.MiddleLeft; this.labelEvenement.Dock = DockStyle.Fill; this.Controls.Add(labelEvenement); } protected override void OnClick(EventArgs e) { base.OnClick(e); MessageBox.Show("Click"); } } I would like to insert this control or multiple of this control on a DataGridViewCell but i don't know how to do this. Thank you in advance for your answer, Best Regards, PS: I'm french, i'm apologize for any can of language errors.

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  • c# How to implement a collection of generics

    - by Amy
    I have a worker class that does stuff with a collection of objects. I need each of those objects to have two properties, one has an unknown type and one has to be a number. I wanted to use an interface so that I could have multiple item classes that allowed for other properties but were forced to have the PropA and PropB that the worker class requires. This is the code I have so far, which seemed to be OK until I tried to use it. A list of MyItem is not allowed to be passed as a list of IItem even though MyItem implements IItem. This is where I got confused. Also, if possible, it would be great if when instantiating the worker class I don't need to pass in the T, instead it would know what T is based on the type of PropA. Can someone help get me sorted out? Thanks! public interface IItem<T> { T PropA { get; set; } decimal PropB { get; set; } } public class MyItem : IItem<string> { public string PropA { get; set; } public decimal PropB { get; set; } } public class WorkerClass<T> { private List<T> _list; public WorkerClass(IEnumerable<IItem<T>> items) { doStuff(items); } public T ReturnAnItem() { return _list[0]; } private void doStuff(IEnumerable<IItem<T>> items) { foreach (IItem<T> item in items) { _list.Add(item.PropA); } } } public void usage() { IEnumerable<MyItem> list= GetItems(); var worker = new WorkerClass<string>(list);//Not Allowed }

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  • JAVA : How to get the positions of all matches in a String?

    - by user692704
    I have a text document and a query (the query could be more than one word). I want to find the position of all occurrences of the query in the document. I thought of the documentText.indexOf(query) and using regular expression but I could not make it work. I end up with the following method: First, I have create a dataType called QueryOccurrence public class QueryOccurrence implements Serializable{ public QueryOccurrence(){} private int start; private int end; public QueryOccurrence(int nameStart,int nameEnd,String nameText){ start=nameStart; end=nameEnd; } public int getStart(){ return start; } public int getEnd(){ return end; } public void SetStart(int i){ start=i; } public void SetEnd(int i){ end=i; } } Then, I have used this datatype in the following method: public static List<QueryOccurrence>FindQueryPositions(String documentText, String query){ // Normalize do the following: lower case, trim, and remove punctuation String normalizedQuery = Normalize.Normalize(query); String normalizedDocument = Normalize.Normalize(documentText); String[] documentWords = normalizedDocument.split(" ");; String[] queryArray = normalizedQuery.split(" "); List<QueryOccurrence> foundQueries = new ArrayList(); QueryOccurrence foundQuery = new QueryOccurrence(); int index = 0; for (String word : documentWords) { if (word.equals(queryArray[0])){ foundQuery.SetStart(index); } if (word.equals(queryArray[queryArray.length-1])){ foundQuery.SetEnd(index); if((foundQuery.End()-foundQuery.Start())+1==queryArray.length){ //add the found query to the list foundQueries.add(foundQuery); //flush the foundQuery variable to use it again foundQuery= new QueryOccurrence(); } } index++; } return foundQueries; } This method return a list of all occurrence of the query in the document each one with its position. Could you suggest any easer and faster way to accomplish this task. Thanks

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  • c# - sqllite dosnt save data i inserted

    - by samy
    I'm messing around with SQL lite and learning it. I got a table called People, I got some method that connect to the database and do some stuff, like show all the info. Now I'm trying to insert some data and here it get wierd for me. I have this method: private void ExecuteQuery(string txtQuery) { SetConnection(); sql_con.Open(); sql_cmd = sql_con.CreateCommand(); sql_cmd.CommandText = txtQuery; sql_cmd.ExecuteNonQuery(); sql_con.Close(); } and to see all the data I've got this method: private void LoadData() { SetConnection(); sql_con.Open(); sql_cmd = sql_con.CreateCommand(); string CommandText = "SELECT * FROM People"; DB = new SQLiteDataAdapter(CommandText, sql_con); DS.Reset(); DB.Fill(DS); DT = DS.Tables[0]; dataGridView1.DataSource = DT; sql_con.Close(); } When I inset some data and right afther it I call the LoadData(), I can see all the changes I made. After I close the program, and then open it agian and call LoadData(), I don't see the new info that I inserted before. I got some data that I used SQL lite GUI app to insert, and I can see that data every time I call the LoadData() method, but not mine. Do I need to do somthing else to make sure SQL lite saves all the data?

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  • Singletons and constants

    - by devoured elysium
    I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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  • Initializing ExportFactory using MEF

    - by Riz
    Scenario Application has multiple parts. Each part is in separate dll and implements interface IFoo All such dlls are present in same directory (plugins) The application can instantiate multiple instances of each part Below is the code snippet for the interfaces, part(export) and the import. The problem I am running into is, the "factories" object is initialized with empty list. However, if I try container.Resolve(typeof(IEnumerable< IFoo )) I do get object with the part. But that doesn't serve my purpose (point 4). Can anyone point what I am doing wrong here? public interface IFoo { string Name { get; } } public interface IFooMeta { string CompType { get; } } Implementation of IFoo in separate Dll [ExportMetadata("CompType", "Foo1")] [Export(typeof(IFoo), RequiredCreationPolicy = CreationPolicy.NonShared))] public class Foo1 : IFoo { public string Name { get { return this.GetType().ToString(); } } } Main application that loads all the parts and instantiate them as needed class PartsManager { [ImportMany] private IEnumerable<ExportFactory<IFoo, IFooMeta>> factories; public PartsManager() { IContainer container = ConstructContainer(); factories = (IEnumerable<ExportFactory<IFoo, IFooMeta>>) container.Resolve(typeof(IEnumerable<ExportFactory<IFoo, IFooMeta>>)); } private static IContainer ConstructContainer() { var catalog = new DirectoryCatalog(@"C:\plugins\"); var builder = new ContainerBuilder(); builder.RegisterComposablePartCatalog(catalog); return builder.Build(); } public IFoo GetPart(string compType) { var matchingFactory = factories.FirstOrDefault( x => x.Metadata.CompType == compType); if (factories == null) { return null; } else { IFoo foo = matchingFactory.CreateExport().Value; return foo; } } }

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  • How is this function being made use of?

    - by Kay
    Hello all, I am just studying a few classes given to me by my lecturer and I can't understand how the function heapRebuild is being made used of! It doesn't change any global variables and it doesn't print out anything ad it doesn't return anything - so should this even work? It shouldn't, should it? If you were told to make use of heapRebuild to make a new function removeMac would you edit heapRebuild? public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; public T removeMax(){ T rootItem = heap[0]; heap[0] = heap[lastIndex-1]; lastIndex--; heapRebuild(heap, 0, lastIndex); return rootItem; } protected void heapRebuild(T[ ] items, int root, int size){ int child = 2*root+1; if( child < size){ int rightChild = child+1; if ((rightChild < size) && (items[rightChild].compareTo(items[child]) > 0)){ child = rightChild; } if (items[root].compareTo(items[child]) < 0){ T temp = items[root]; items[root] = items[child]; items[child] = temp; heapRebuild(items, child, size);} } } }

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  • java regex for alpha and spaces is including [ ] \

    - by JayAvon
    This is my regex for my JTextField to not be longer than x characters and to not include anything other than letters or spaces. For some reason it is allowing [ ] and \ characters. This is driving me crazy. Is my regex wrong?? package com.jayavon.game.helper; import java.awt.Toolkit; import javax.swing.text.AttributeSet; import javax.swing.text.BadLocationException; import javax.swing.text.PlainDocument; public class CharacterNameCreationDocument extends PlainDocument { private static final long serialVersionUID = 1L; private int limit; public CharacterNameCreationDocument(int limit) { super(); this.limit = limit; } public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException { if (str == null || (getLength() + str.length()) > limit || !str.matches("[a-zA-z\\s]*")){ Toolkit.getDefaultToolkit().beep(); return; } else { super.insertString(offset, str, attr); } } }

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  • polymorphism in C++

    - by user550413
    I am trying to implement the next 2 functions Number& DoubleClass::operator+( Number& x); Number& IntClass::operator+(Number& x); I am not sure how to do it..(their unidirectionality is explained below): class IntClass; class DoubleClass; class Number { //return a Number object that's the results of x+this, when x is either //IntClass or DoubleClass virtual Number& operator+(Number& x) = 0; }; class IntClass : public Number { private: int my_number; //return a Number object that's the result of x+this. //The actual class of the returned object depends on x. //If x is IntClass, then the result if IntClass. //If x is DoubleClass, then the results is DoubleClass. public: Number& operator+(Number& x); }; class DoubleClass : public Number { private: double my_number; public: //return a DoubleClass object that's the result of x+this. //This should work if x is either IntClass or DoubleClass Number& operator+( Number& x); };

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  • wifi provider onLocationChanged is never called

    - by Kelsie
    I got a weird problem. I uses wifi to retrieve user location. I have tested on several phones; on some of them, I could never get a location update. it seemed that the method onLocationChanged is never called. My code is attached below.. Any suggestions appreciated!!! @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); LocationManager locationManager; locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); String provider = locationManager.NETWORK_PROVIDER; Location l = locationManager.getLastKnownLocation(provider); updateWithNewLocation(l); locationManager.requestLocationUpdates(provider, 0, 0, locationListener); } private void updateWithNewLocation(Location location) { TextView myLocationText; myLocationText = (TextView)findViewById(R.id.myLocationText); String latLongString = "No location found"; if (location != null) { double lat = location.getLatitude(); double lng = location.getLongitude(); latLongString = "Lat:" + lat + "\nLong:" + lng; } myLocationText.setText("Your Current Position is:\n" + latLongString); } private final LocationListener locationListener = new LocationListener() { public void onLocationChanged(Location location) { updateWithNewLocation(location); Log.i("onLocationChanged", "onLocationChanged"); Toast.makeText(getApplicationContext(), "location changed", Toast.LENGTH_SHORT).show(); } public void onProviderDisabled(String provider) {} public void onProviderEnabled(String provider) {} public void onStatusChanged(String provider, int status, Bundle extras) {} }; Manifest <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/> <uses-permission android:name="android.permission.INTERNET"/>

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  • Avoiding instanceof in Java

    - by Mark Lutton
    Having a chain of "instanceof" operations is considered a "code smell". The standard answer is "use polymorphism". How would I do it in this case? There are a number of subclasses of a base class; none of them are under my control. An analogous situation would be with the Java classes Integer, Double, BigDecimal etc. if (obj instanceof Integer) {NumberStuff.handle((Integer)obj);} else if (obj instanceof BigDecimal) {BigDecimalStuff.handle((BigDecimal)obj);} else if (obj instanceof Double) {DoubleStuff.handle((Double)obj);} I do have control over NumberStuff and so on. I don't want to use many lines of code where a few lines would do. (Sometimes I make a HashMap mapping Integer.class to an instance of IntegerStuff, BigDecimal.class to an instance of BigDecimalStuff etc. But today I want something simpler.) I'd like something as simple as this: public static handle(Integer num) { ... } public static handle(BigDecimal num) { ... } But Java just doesn't work that way. I'd like to use static methods when formatting. The things I'm formatting are composite, where a Thing1 can contain an array Thing2s and a Thing2 can contain an array of Thing1s. I had a problem when I implemented my formatters like this: class Thing1Formatter { private static Thing2Formatter thing2Formatter = new Thing2Formatter(); public format(Thing thing) { thing2Formatter.format(thing.innerThing2); } } class Thing2Formatter { private static Thing1Formatter thing1Formatter = new Thing1Formatter(); public format(Thing2 thing) { thing1Formatter.format(thing.innerThing1); } } Yes, I know the HashMap and a bit more code can fix that too. But the "instanceof" seems so readable and maintainable by comparison. Is there anything simple but not smelly?

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  • how to create a linked list in java without using util package? [closed]

    - by aparna
    I do not want to use any of the elements of the UTIL package. I tried but I am not able to get to the next node. Can anyone please help me out? Thanks in advance. I have put up this much. public class Element { private String s; private Element next; } public Element(String s) { this.s = s; this.next = null; } public void setNext(Element e) { this.next = e; } public String getString() { return this.s; } public Element getNext() { return this.next; } public String toString() { return "[" + s + "] => "; } public void add(String s) { int index = 0; System.out.println("Adding at index: " + index); Element curr = new Element(s); Element e = this.data[index]; if (e == null) { this.data[index] = curr; return; } while(e.getNext() != null) { e = e.getNext(); } e.setNext(curr); } }

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  • JPA entity relations are not populated after .persist()

    - by Tomik
    Hello, this is a sample of my two entities: @Entity public class Post implements Serializable { @OneToMany(mappedBy = "post", fetch = javax.persistence.FetchType.EAGER) @OrderBy("revision DESC") public List<PostRevision> revisions; @Entity(name="post_revision") public class PostRevision implements Serializable { @ManyToOne public Post post; private Integer revision; @PrePersist private void prePersist() { List<PostRevision> list = post.revisions; if(list.size() >= 1) revision = list.get(list.size() - 1).revision + 1; else revision = 1; } So, there's a "post" and it can have several revisions. During persisting of the revision, entity takes a look at the list of the existing revisions and finds the next revision number. Problem is that Post.revisions is NULL but I think it should be automatically populated. I guess there's some kind of problem in my source code but I don't know where. Here's my "persistence" code: Post post = new Post(); PostRevision revision = new PostRevision(); revision.post = post; em.persist(post); em.persist(revision); em.flush(); I think that after persisting "post", it becomes "managed" and all the relations should be populated from now on. Thanks for help! (Note: public attributes are just for demonstration)

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  • Insertion into BST without header Node JAVA

    - by Petiatil
    I am working on a recursive insertion method for a BST. This function is suppose to be a recursive helper method and is in a private class called Node. The Node class is in a class called BinarySearchTree which contains an instance variable for the root. When I am trying to insert an element, I get a NullPointerException at : this.left = insert(((Node)left).element); I am unsure about why this occurs. If I understand correctly, in a BST, I am suppose to insert the item at the last spot on the path transversed. Any help is appreciated! private class Node implements BinaryNode<E> { E item; BinaryNode<E> left, right; public BinaryNode<E> insert(E item) { int compare = item.compareTo(((Node)root).item); if(root == null) { root = new Node(); ((Node)root).item = item; } else if(compare < 0) { this.left = insert(((Node)left).item); } else if(compare > 0) { this.right = insert(((Node)right).item); } return root; } }

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  • STL in C++ how does it work

    - by helloWorld
    I have very technical question, I was working with C, and now I'm studying C++, if I have for example this class class Team { private: list<Player> listOfPlayers; public: void addPlayer(string firstName, string lastName, int id) { Player newPlayer(string firstName, string lastName, int id); listOfPlayers.push_back(Player(string firstName, string lastName, int id)); } } this is a declaration of the Player: class Player{ private: string strLastName; string strFirstName; int nID; public: Player(string firstName, string lastName, int id); } and this is my constructor of Player: Player::Player(string firstName, string lastName, int id){ nId = id; string strFirstName = firstName; string strLastName = lastName; } so my question is when I call function addPlayer what exactly is going on with program, in my constructor of Account do I need to allocate new memory for new Account(cause in C I always use malloc) for strFirstName and strLastName, or constructor of string of Account and STL do it without me, thanks in advance (if you don't want to answer my question please at least give me some link with information) thanks in advance

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  • What are advantages of using a one-to-one table relationship? (MySQL)

    - by byronh
    What are advantages of using a one-to-one table relationship as opposed to simply storing all the data in one table? I understand and make use of one-to-many, many-to-one, and many-to-many all the time, but implementing a one-to-one relationship seems like a tedious and unnecessary task, especially if you use naming conventions for relating (php) objects to database tables. I couldn't find anything on the net or on this site that could supply a good real-world example of a one-to-one relationship. At first I thought it might be logical to separate 'users', for example, into two tables, one containing public information like an 'about me' for profile pages and one containing private information such as login/password, etc. But why go through all the trouble of using unnecessary JOINS when you can just choose which fields to select from that table anyway? If I'm displaying the user's profile page, obviously I would only SELECT id,username,email,aboutme etc. and not the fields containing their private info. Anyone care to enlighten me with some real-world examples of one-to-one relationships?

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  • How to open a chat window in sender and receiver side [on hold]

    - by DEEPS
    When i am trying to send a message from sender the chat window is always opening in senders side instead of receiver side.so please give a correct code to display chat box in both side. (HTML 5, JAVASCRIPT,JQUERY). This is client side code: //Send private message function sendPvtMsg(data) { var pvtmsg = data; socket.emit('message',JSON.stringify({msg: 'pvtMsg', data: { from: userName, to: toChat, pvtmsg: data }}),roomId); } socket.on('message',function(data) { var command = JSON.parse(data); var itemName = command.msg; var rec_data = command.data.message; var sender = command.data.name; //Receive message from server if (itemName == "message") { document.getElementById("chat").value += sender + " : " + rec_data + "\n"; } //Receive private message else if (itemName == "pvtMsg") { var to = command.data.to; var from = command.data.from; //To display message to sender and receiver if (userName == to || userName == from) { var pvtmsg = command.data.pvtmsg; document.getElementById("chat").value += from + "( to " + to + ")" + " : " + pvtmsg + "\n"; } } function createChatBox(chatboxtitle,minimizeChatBox) { if ($("#chatbox_"+chatboxtitle).length > 0) { if ($("#chatbox_"+chatboxtitle).css('display') == 'none') { $("#chatbox_"+chatboxtitle).css('display','block'); restructureChatBoxes(); } $("#chatbox_"+chatboxtitle+" .chatboxtextarea").focus(); return; }

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  • getting duplicate array output - java

    - by dowln
    Hello, Can someone could be kind and help me out here. Thanks in advance... My code below outputs the string as duplicates. I don't want to use Sets or ArrayList. I am using java.util.Random. I am trying to write a code that checks if string has already been randomly outputted and if it does, then it won't display. Where I am going wrong and how do I fix this. public class Worldcountries { private static Random nums = new Random(); private static String[] countries = { "America", "Candada", "Chile", "Argentina" }; public static int Dice() { return (generator.nums.nextInt(6) + 1); } public String randomCounties() { String aTemp = " "; int numOfTimes = Dice(); int dup = 0; for(int i=0 ; i<numOfTimes; i++) { // I think it's in the if statement where I am going wrong. if (!countries[i].equals(countries[i])) { i = i + 1; } else { dup--; } // and maybe here aTemp = aTemp + countries[nums.nextInt(countries.length)]; aTemp = aTemp + ","; } return aTemp; } } So the output I am getting (randomly) is, "America, America, Chile" when it should be "America, Chile".

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  • How to move image in Applet?

    - by user1609804
    I want to move the character left, right up, and down in applet, but it is not moving at all. here is my code, help please import javax.swing.JPanel; import java.awt.image.BufferedImage; import java.io.*; import javax.imageio.ImageIO; import java.applet.*; import java.awt.event.*; import java.awt.*; public class drawCenter extends Applet { private int x,y;// the x and y of the position of the player private BufferedImage image, pos; public void init( ) { try { image = ImageIO.read(new File("pokemonCenter.png")); pos = ImageIO.read(new File("player/maleInGame.png")); } catch (IOException ex) { } x = 150; y = 171; } public void keyPressed(KeyEvent e) { int keyCode = e.getKeyCode(); switch( keyCode ) { case KeyEvent.VK_UP: if( y>0 ) { y=y-19; repaint(); } break; case KeyEvent.VK_DOWN: if( y<171 ) { y=y+19; repaint(); } break; case KeyEvent.VK_LEFT:if( x>0 ) { x=x-15; repaint(); } break; case KeyEvent.VK_RIGHT:if( x<285 ) { x=x+15; repaint(); } break; } e.consume(); } public void keyReleased(){ } public void paint( Graphics g ) { g.drawImage(image, 0, 0, null); g.drawImage(pos, x, y, null); } }

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