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  • How to implement iterator as an attribute of a class in Java

    - by de3
    Hi, let's say I have this simple MyArray class, with two simple methods: add, delete and an iterator. In the main method we can see how it is supposed to be used: public class MyArray { int start; int end; int[] arr; myIterator it; public MyArray(){ this.start=0; this.end=0; this.arr=new int[500]; it=new myIterator(); } public void add(int el){ this.arr[this.end]=el; this.end++; } public void delete(){ this.arr[this.start]=0; this.start++; } public static void main(String[] args){ MyArray m=new MyArray(); m.add(3); m.add(299); m.add(19); m.add(27); while(m.it.hasNext()){ System.out.println(m.it.next()); } } And then MyIterator should be implemented somehow: import java.util.Iterator; public class myIterator implements Iterator{ @Override public boolean hasNext() { // TODO Auto-generated method stub return false; } @Override public Object next() { // TODO Auto-generated method stub return null; } @Override public void remove() { // TODO Auto-generated method stub } } MyIterator should iterate arr from MyArray class, from start to end values; both are also attributes of MyArray. So, as MyIterator should use MyArray attributes, how should MyIterator be implemented? Perhaps I can send the current object in the initialization: it=new myIterator(this); But I guess it's not the best soultion. Or maybe MyArray itself should implement Iterator interface? How is this solved?

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  • Is this use of PreparedStatements in a Thread in JAVA correct?

    - by Gormcito
    I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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  • Detect modification of variable at runtime in C/C++

    - by YuppieNetworking
    Hello, I am developing a library in C++ where users/programmer will extend a class BaseClass that has a method initArray. This method should be implemented by the user/programmer and it should normally initialize all elements of the array m_arr. Here is a snipplet, modified to this example: class BaseClass { public: BaseClass(int n) { m_arr = new double[n]; size = n; }; virtual ~BaseClass(); int size; double* m_arr; virtual int initArray(); }; Sometimes, the user/programmer implements a initArray that does not initialize some elements of m_arr. What I would like is to create a function in my library that checks if initArray did initialize all elements of m_arr. This function should be called by a sanity-check rutine at runtime. My question: is it possible to detect changes on this array? I can only think of initializing the array with some invalid values (like NaN or Inf), call initArray and check that all values have changed. Thanks for your ideas, David

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  • passing reference of class to another class android error

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

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  • .NET port with Java's Map, Set, HashMap

    - by Nikos Baxevanis
    I am porting Java code in .NET and I am stuck in the following lines that (behave unexpectedly in .NET). Java: Map<Set<State>, Set<State>> sets = new HashMap<Set<State>, Set<State>>(); Set<State> p = new HashSet<State>(); if (!sets.containsKey(p)) { ... } The equivalent .NET code could possibly be: IDictionary<HashSet<State>, HashSet<State>> sets = new Dictionary<HashSet<State>, HashSet<State>>(); HashSet<State> p = new HashSet<State>(); if (!sets.containsKey(p)) { /* (Add to a list). Always get here in .NET (??) */ } However the code comparison fails, the program think that "sets" never contain Key "p" and eventually results in OutOfMemoryException. Perhaps I am missing something, object equality and identity might be different between Java and .NET. I tried implementing IComparable and IEquatable in class State but the results were the same. Edit: What the code does is: If the sets does not contain key "p" (which is a HashSet) it is going to add "p" at the end of a LinkedList. The State class (Java) is a simple class defined as: public class State implements Comparable<State> { boolean accept; Set<Transition> transitions; int number; int id; static int next_id; public State() { resetTransitions(); id = next_id++; } // ... public int compareTo(State s) { return s.id - id; } public boolean equals(Object obj) { return super.equals(obj); } public int hashCode() { return super.hashCode(); }

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  • Design issue when having classes implement different interfaces to restrict client actions

    - by devoured elysium
    Let's say I'm defining a game class that implements two different views: interface IPlayerView { void play(); } interface IDealerView { void deal(); } The view that a game sees when playing the game, and a view that the dealer sees when dealing the game (this is, a player can't make dealer actions and a dealer can't make player actions). The game definition is as following: class Game : IPlayerView, IDealerView { void play() { ... } void deal() { ... } } Now assume I want to make it possible for the players to play the game, but not to deal it. My original idea was that instead of having public Game GetGame() { ... } I'd have something like public IPlayerView GetGame() { ... } But after some tests I realized that if I later try this code, it works: IDealerView dealerView = (IDealerView)GameClass.GetGame(); this works as lets the user act as the dealer. Am I worrying to much? How do you usually deal with this patterns? I could instead make two different classes, maybe a "main" class, the dealer class, that would act as factory of player classes. That way I could control exactly what I would like to pass on the the public. On the other hand, that turns everything a bit more complex than with this original design. Thanks

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  • getting nullpointer exception when click on button

    - by user1315187
    I am use a button and when u click this button a text field is automatic created and button status is automatic disable but if u click on disable button text field is automatic delete and button status is changed to enable.i going through this process. public class ConfigurationScreen extends MainScreen implements FieldChangeListener{ TextField tf_text; tf_text = new TextField(TextField.TYPE_PLAIN,img_text[1],img_text[0],TextField.FIELD_HCENTER); tf_text.setWidth(Display.getWidth()/2+20); ImageButton btn_en; btn_en = new ImageButton(imgs_tmintrvl1,"enable",ImageButton.FIELD_HCENTER); ImageButton btn_dis; btn_dis=new ImageButton(imgs_tmintrvl1,"Disable",ImageButton.FIELD_HCENTER); add(btn_en); btn_en.setChangeListener(this); public void fieldChanged(Field field, int context) { if( field==btn_en) { delete(btn_en); insert(btn_dis, 4); insert(tf_text, 5); System.out.println(ex); }else if (field == btn_dis){ delete(btn_dis); delete(tf_text); insert(btn_en, 4); System.out.println("Disable Button="+ex); } } But when i run this code i am getting null pointerr exception please help me where i am making mistake. Thanks in Advance

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  • Action listener for JButton array

    - by user530809
    Let's say I have a program with 2D array of buttons, and when you click one of them it turns red. I didn't want to declare every single button seperately so I just created JButton[][] array for them. The problem is that I don't know how to use action listener on any of the buttons in the array so it would change the color of this particular button, and none of related questions is relevant to this. I tried to use "for" but it doesn't help: package appli; import javax.swing.*; import java.awt.*; import java.awt.event.*; public class MainW extends JFrame implements ActionListener { public MainW(){ setSize(640,480); setTitle("title"); setLayout(null); JButton[][] btnz = new JButton[5][5]; for(Integer i=0;i<5;i++) { for(Integer j=0;j<5;j++) { btnz[i][j]= new JButton(""); btnz[i][j].setBackground(Color.WHITE); btnz[i][j].setBounds(10+20*i,10+20*j,20,20); add(btnz[i][j]); btnz[i][j].addActionListener(this); } } setDefaultCloseOperation(EXIT_ON_CLOSE); setVisible(true); } public void actionPerformed(ActionEvent e){ for(Integer i=0;i<5;i++) { for(Integer j=0;j<5;j++) { if (e.getSource()==btnz[i][j]); { btnz[i][j].setBackground(Color.RED); } } } } }

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  • Under what circumstances will an entity be able to lazily load its relationships in JPA

    - by Mowgli
    Assuming a Java EE container is being used with JPA persistence and JTA transaction management where EJB and WAR packages are inside a EAR package. Say an entity with lazy-load relationships has just been returned from a JPQL search, such as the getBoats method below: @Stateless public class BoatFacade implements BoatFacadeRemote, BoatFacadeLocal { @PersistenceContext(unitName = "boats") private EntityManager em; @Override public List<Boat> getBoats(Collection<Integer> boatIDs) { if(boatIDs.isEmpty()) { return Collections.<Boat>emptyList(); } Query query = em.createNamedQuery("getAllBoats"); query.setParameter("boatID", boatIDs); List<Boat> boats = query.getResultList(); return boats; } } The entity: @Entity @NamedQuery( name="getAllBoats", query="Select b from Boat b where b.id in : boatID") public class Boat { @Id private long id; @OneToOne(fetch=FetchType.LAZY) private Gun mainGun; public Gun getMainGun() { return mainGun; } } Where will its lazy-load relationships be loadable (assuming the same stateless request): Same JAR: A method in the same EJB A method in another EJB A method in a POJO in the same EJB JAR Same EAR, but outside EJB JAR: A method in a web tier managed bean. A method in a web tier POJO. Different EAR: A method in a different EAR which receives the entity through RMI. What is it that restricts the scope, for example: the JPA transaction, persistence context or JTA transaction?

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  • Creating a procedure with PLSQL

    - by user1857460
    I am trying to write a PLSQL function that implements a constraint that an employee cannot be both a driver and a mechanic at the same time, in other words, the same E# from TRKEMPLOYEE cannot be in TRKDRIVER and TRKMECHANIC at the same time. The abovementioned tables are something like as follows: TRKEMPLOYEE(E# NUMBER(12) NOT NULL CONSTRAINT TRKEMPLOYEE_PKEY PRIMARY KEY(E#)) TRKDRIVER(E# NUMBER(12) NOT NULL CONSTRAINT TRKDRIVER_PKEY PRIMARY KEY(E#), CONSTRAINT TRKDRIVER_FKEY FOREIGN KEY(E#) REFERENCES TRKEMPLOYEE(E#)) TRKMECHANIC(E# NUMBER(12) NOT NULL CONSTRAINT TRKMECHANIC_PKEY PRIMARY KEY(E#), CONSTRAINT TRKMECHANIC_FKEY FOREIGN KEY(E#) REFERENCES TRKEMPLOYEE(E#)) I have attempted to write a function but keep getting a compile error in line 1 column 7. Can someone tell me why my code doesn't work? My code is as follows CREATE OR REPLACE FUNCTION Verify() IS DECLARE E# TRKEMPLOYEE.E#%TYPE; CURSOR C1 IS SELECT E# FROM TRKEMPLOYEE; BEGIN OPEN C1; LOOP FETCH C1 INTO EMPNUM; IF(EMPNUM IN(SELECT E# FROM TRKMECHANIC )AND EMPNUM IN(SELECT E# FROM TRKDRIVER)) SELECT E#, NAME FROM TRKEMPLOYEE WHERE E#=EMPNUM; ELSE dbms_output.put_line(“OK”); ENDIF EXIT WHEN C1%NOTFOUND; END LOOP; CLOSE C1; END; / Any help would be appreciated. Thanks.

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  • Sending a password securely using gwt and app engine?

    - by user246114
    Hi, I set up session handling on a google app project. This is supposed to allow my users to login and maintain state across pages. I just dumped it into the default greeting service to try it out: public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService { public void sessionTest(String username) { HttpSession session = getThreadLocalRequest().getSession(false); session.setAttribute("username", username); } } then attempting to pull it out in my landing project.jsp page: <% String username = null; HttpSession mysession = request.getSession(false); if (mysession.getAttribute("username") != null) { username = (String)mysession.getAttribute("username"); } else { username = "(not logged in yet)"; } <p>You are: <%= username %> </p> %> It works, but I don't know how to send the data in sessionTest() securely. If I were sending the user's password in there too, it would be in the clear. This would be ok (I think) if I was using https, but google app engine does not allow you to use https under custom domains (like www.mysite.com), they have to be under the (mysite.appspot.com) domain. I'm kind of stuck here - how do we send passwords securely? If I was using php, I think I could use digest authentication (I'm not too experienced here) - can we do something like that with gwt + gae? Thanks

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  • Hibernate CreateSQL Query Problem

    - by Shaded
    Hello All I'm trying to use hibernates built in createsql function but it seems that it doesn't like the following query. List =hibernateSession.createSQLQuery("SELECT number, location FROM table WHERE other_number IN (SELECT f.number FROM table2 AS f JOIN table3 AS g on f.number = g.number WHERE g.other_number = " + var + ") ORDER BY number").addEntity(Table.class).list(); I have a feeling it's from the nested select statement, but I'm not sure. The inner select is used elsewhere in the code and it returns results fine. This is my mapping for the first table: <hibernate-mapping> <class name="org.efs.openreports.objects.Table" table="table"> <id name="id" column="other_number" type="java.lang.Integer"> <generator class="native"/> </id> <property name="number" column="number" not-null="true" unique="true"/> <property name="location" column="location" not-null="true" unique="true"/> </class> </hibernate-mapping> And the .java public class Table implements Serializable { private Integer id;//panel_facility private Integer number; private String location; public Table() { } public void setId(Integer id) { this.id = id; } public Integer getId() { return id; } public void setNumber(Integer number) { this.number = number; } public Integer number() { return number; } public String location() { return location; } public void setLocation(String location) { this.location = location; } } Any suggestions? Edit (Added mapping)

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  • Cannot make a static reference to the non-static type MyRunnable

    - by kaiwii ho
    Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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  • C# generics with MVVM, pulling the T out of <T>

    - by bufferz
    My Model is a generic class that contains a (for example) Value property which can be int, float, string, bool, etc. So naturally this class is represented something like Model<T>. For the sake of collections Model<T> implements the interface IModel, although IModel is itself empty of any content. My ViewModel contains and instance of Model<T> and it is passed in through ViewModel's constructor. I still want to know what T is in ViewModel, so when I expose Model to the View I know the datatype of Model's buried Value property. The class for ViewModel ends up looking like the following: class ViewModel<T> { private Model<T> _model; public ViewModel(Model<T> model) { ....blah.... } public T ModelsValue {get; set; } } This works fine, but is limited. So now I need to expose a collection of IModels with varying Ts to my View, so I'm trying to set up an ObservableCollection of new ViewModel<T>s to a changing list of IModels. The problem is, I can't figure out how to get T from Model<T> from IModel to construct ViewModel<T>(Model<T>) at runtime. In the VS2010 debugger I can mouseover any IModel object and see its full Model<int> for example at runtime so I know the data is in there. Any ideas?

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  • Java Generics Issue (w/ Spring)

    - by drewzilla
    I think I may be a victim of type erasure but thought I'd check with others here first. I have the requirement to do something like this: public interface FooFactory { public <T extends Bar> Foo<T> createFoo( Class<T> clazz ); } It is perfectly valid to write this code. However, I'm trying to implement this functionality using a Spring BeanFactory and I can't do it. What I'd like to do is this... public class FooFactoryImpl implements BeanFactoryAware { private BeanFactory beanFactory; public <T extends Bar> Foo<T> createFoo( Class<T> clazz ) { return beanFactory.getBean( ????????? ); } public void setBeanFactory( BeanFactory beanFactory ) { this.beanFactory = beanFactory; } } As you can see, I've put in ???????? where I'd like to retrieve a bean of type Foo<T>, where T extends Bar. However, it is not possible to derive a Class object of type Foo<T> and so I assume what I'm trying to do is impossible? Anyone else see a way round this or an alternative way of implementing what I'm trying to do? Thanks, Andrew

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  • .NET: Calling GetInterface method of Assembly obj with a generic interface argument

    - by Khnle
    I have the following interface: public interface PluginInterface<T> where T : MyData { List<T> GetTableData(); } In a separate assembly, I have a class that implements this interface. In fact, all classes that implement this interface are in separate assemblies. The reason is to architect my app as a plugin host, where plugin can be done in the future as long as they implement the above interface and the assembly DLLs are copied to the appropriate folder. My app discovers the plugins by first loading the assembly and performs the following: List<PluginInterface<MyData>> Plugins = new List<PluginInterface<MyData>>(); string FileName = ...;//name of the DLL file that contains classes that implement the interface Assembly Asm = Assembly.LoadFile(Filename); foreach (Type AsmType in Asm.GetTypes()) { //Type type = AsmType.GetInterface("PluginInterface", true); // Type type = AsmType.GetInterface("PluginInterface<T>", true); if (type != null) { PluginInterface<MyData> Plugin = (PluginInterface<MyData>)Activator.CreateInstance(AsmType); Plugins.Add(Plugin); } } The trouble is because neither line where I am getting the type as by doing Type type = ... seems to work, as both seems to be null. I have the feeling that the generic somehow contributes to the trouble. Do you know why?

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  • How can I use CssResources in UiBinder a generated Cell?

    - by confile
    I want to generate a Cell for a CellWidget with the UiBinder (UiRenderer). What I did to generate the cell is in MyCell.java: public class MyCell implements AbstractCell<MyDto> { public interface Resources extends ClientBundle { @Source({Css.DEFAULT_CSS }) Css css(); } public interface Css extends CssResource { String DEFAULT_CSS = "test/MyStyle.css"; String test(); } interface MyUiRenderer extends UiRenderer { void render(SafeHtmlBuilder sb, String name, SafeStyles styles); } private static MyUiRenderer renderer = GWT.create(MyUiRenderer.class); Resources resources = GWT.create(Resources.class); @Override public void render(SafeHtmlBuilder safeHtmlBuilder, MyDto model) { SafeStyles style = SafeStylesUtils.fromTrustedString(resources.css().test().toString()); renderer.render(safeHtmlBuilder, model.getName(), style); } } My MyCell.ui.xml file looks like this: <!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent"> <ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'> <ui:with field="name" type="java.lang.String" /> <ui:with field='styles' type='com.google.gwt.safecss.shared.SafeStyles'/> <div style="{styles}"><ui:text from="{name}" /></div> </ui:UiBinder> MyStyle.css: .test { background-color: red; font-size: 20px; display: flex; ... } When I run my code I get the following error: [DEBUG] [mobile] - Rebinding test.client.app.MyCell.MyUiRenderer [DEBUG] [mobile] - Invoking generator com.google.gwt.uibinder.rebind.UiBinderGenerator [ERROR] [mobile] - java.lang.String required, but {styles} returns com.google.gwt.safecss.shared.SafeStyles: <div style='{styles}'> (:9) [ERROR] [mobile] - Deferred binding failed for 'test.client.app.MyCell.MyUiRenderer'; expect subsequent failures [ERROR] [mobile] - (GWT.java:72) 2014-06-08 17:15:05,214 [FATAL] Uncaught Exception: Then I tried to this: in my UiBinder but it does not work. How can I use css style from a CssResource in my UiRenderer?

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  • creating an object within a function of a program

    - by user1066524
    could someone please tell me what I need to do in order to create an object in a function. I will try to explain by making up some sort of example... Let's say I have a program named TimeScheduler.cpp that implements the class Schedule.h (and I have the implementation in a separate file Schedule.cpp where we define the methods). In the declaration file we have declared two constructors Schedule(); //the default and Schedule(int, int, int);//accepts three arguments to get to the point--let's say in the main program file TimeScheduler.cpp we created our own functions in this program apart from the functions inherited from the class Schedule. so we have our prototypes listed at the top. /*prototypes*/ void makeSomeTime(); etc..... we have main(){ //etc etc... } we then define these program functions void makeSomeTime(){ //process } let's say that inside the function makeSomeTime(), we would like to create an array of Schedule objects like this Schedule ob[]={ summer(5,14, 49), fall(9,25,50) }; what do I have to do to the function makeSomeTime() in order for it to allow me to create this array of objects. The reason I ask is currently i'm having difficulty with my own program in that it WILL allow me to create this array of objects in main()....but NOT in a function like I just gave an example of. The strange thing is it will allow me to create a dynamic array of objects in the function..... like Schedule *ob = new Schedule[n+1]; ob[2]= Schedule(x,y,z); Why would it let me assign to a non-dynamic array in main(), but not let me do that in the function?

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  • Java Generics error when implementing Hibernate message interpolator

    - by Jayaprakash
    Framework: Spring, Hibernate. O/S: Windows I am trying to implement hibernate's Custom message interpolator following the direction of this Link. When implementing the below class, it gives an error "Cannot make a static reference to the non-static type Locale". public class ClientLocaleThreadLocal<Locale> { private static ThreadLocal tLocal = new ThreadLocal(); public static void set(Locale locale) { tLocal.set(locale); } public static Locale get() { return tLocal.get(); } public static void remove() { tLocal.remove(); } } As I do not know generics enough, not sure how is being used by TimeFilter class below and the purpose of definition in the above class. public class TimerFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException { try { ClientLocaleThreadLocal.set(req.getLocale()); filterChain.doFilter(req, res); }finally { ClientLocaleThreadLocal.remove(); } } public void init(FilterConfig arg0) throws ServletException { } } Will doing the following be okay? Change static method/field in ClientLocaleThreadLocal to non-static method/fields In TimeFilter, set locale by instantiating new object as below. new ClientLocaleThreadLocal().set(req.getLocale()) Thanks for your help in advance

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  • Need a design approach or suggestion for a simple structure using Servlet.

    - by akshay
    Hi I have to design such that whenever user pass a query I process it using servlet and then call the js page to draw the chart 1 user writes a query on a page 2 the page call the servelt class public class MyServlet extends Httpservlet implements DataSourceServlet {..... return data The user see a beautiful string like this.. google.visualization.Query.setResponse......... /Tiger'},{v:80.0}, {v:false}]}]}}); 3 when the user hits on different html page myhtml.js it draws the chart. I want the Myservlet class itself call the myhtml.js page and draw the chart directly. and want to eliminate the beautiful string google.visualization.Query.setResponse......... /Tiger'},{v:80.0}, {v:false}]}]}}); from coming on user's browser What should i do? I tried using functions to call another page like request dispatcher(), redirect() calling myhtml.js page directly after myservlet process the query results. But i get the result like this google.visualization.Query.setResponse......... /Tiger'},{v:80.0}, {v:false}]}]}}); and the entire myhtml.js code page below it on the browsers that to without the chart been draw. Is there anyway to element the beautiful string from coming on clients browser and only show them the chart been drawn ? :) This is the small tutorial i am following http://code.google.com/apis/visualization/documentation/dev/dsl_get_started.html

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  • Is there a case for parameterising using Abstract classes rather than Interfaces?

    - by Chris
    I'm currently developing a component based API that is heavily stateful. The top level components implement around a dozen interfaces each. The stock top-level components therefore sit ontop of a stack of Abstract implementations which in turn contain multiple mixin implementations and implement multiple mixin interfaces. So far, so good (I hope). The problem is that the base functionality is extremely complex to implement (1,000s of lines in 5 layers of base classes) and therefore I do not wish for component writers to implement the interfaces themselves but rather to extend my base classes (where all the boiler plate code is already written). If the API therefore accepts interfaces rather than references to the Abstract implementation that I wish for component writers to extends, then I have a risk that the implementer will not perform the validation that is both required and assumed by other areas of code. Therefore, my question is, is it sometimes valid to paramerise API methods using an abstract implementation reference rather than a reference to the interface(s) that it implements? Do you have an example of a well-designed API that uses this technique or am I trying to talk myself into bad-practice?

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  • Java Detect Variable Change Using PropertyChangeSupport and PropertyChangeListener

    - by Sam
    I'm trying to print out debug statements when some third party code changes a variable. For example, consider the following: public final class MysteryClass { private int secretCounter; public synchronized int getCounter() { return secretCounter; } public synchronized void incrementCounter() { secretCounter++; } } public class MyClass { public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // add code here to detect calls to incrementCounter and print a debug message } I don't have the ability to change the 3rd party MysteryClass, so I thought that I could use PropertyChangeSupport and PropertyChangeListener to detect changes to the secretCounter: public class MyClass implements PropertyChangeListener { private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this); public MyClass() { propertySupport.addPropertyChangeListener(this); } public void propertyChange(PropertyChangeEvent evt) { System.out.println("property changing: " + evt.getPropertyName()); } public static void main(String[] args) { MysteryClass mysteryClass = new MysteryClass(); // do logic which involves increment and getting the value of MysteryClass } } Unfortunately, this did not work and I have no debug messages printed out. Does anyone see what is wrong with my implementation of the PropertyChangeSupport and Listener interfaces? I want to print a debug statement whenever incrementCounter is called or the value of secretCounter changes.

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  • Make conversion to a native type explicit in C++

    - by Tal Pressman
    I'm trying to write a class that implements 64-bit ints for a compiler that doesn't support long long, to be used in existing code. Basically, I should be able to have a typedef somewhere that selects whether I want to use long long or my class, and everything else should compile and work. So, I obviously need conversion constructors from int, long, etc., and the respective conversion operators (casts) to those types. This seems to cause errors with arithmetic operators. With native types, the compiler "knows" that when operator*(int, char) is called, it should promote the char to int and call operator*(int, int) (rather than casting the int to char, for example). In my case it gets confused between the various built-in operators and the ones I created. It seems to me like if I could flag the conversion operators as explicit somehow, that it would solve the issue, but as far as I can tell the explicit keyword is only for constructors (and I can't make constructors for built-in types). So is there any way of marking the casts as explicit? Or am I barking up the wrong tree here and there's another way of solving this? Or maybe I'm just doing something else wrong...

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  • Accessing to Request object will lead to ReadEntityBody to return 0 (in a HttpHandler class)

    - by EBAG
    I created a httpHandler that successfully implements IHttpHandler for handling file uploads. It works perfectly fine. You send the file with the form, the class receives it and will save it to hard disk. It reads chunks of file with ReadEntityBody function of HttpWorkerRequest class. Here is the situation i'm faced with.If at any stage before trying to read the file with ReadEntityBody, I try to access Request object (even Request.InputStream.Length!) ReadEntityBody would return 0 means it won't read from file stream. After further testing I found out the reason behind it. Accessing to Context.Current.Request object will trigger some sort of functionality that will cause asp.net to handle file uploads at that moment by it's own! I believe this is a bug. for example exactly after this line of code, asp.net will upload the file completely, and so there will be no stream for ReadEntityBody to read from later. int FileSize = context.Request.InputStream.Length; Can anybody tell how to stop this?

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  • Is a web-server (e.g servlets) a good solution for an IM server?

    - by John
    I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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