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  • Combination of JFreeChart with JXLayer with JHotDraw

    - by Yan Cheng CHEOK
    Recently, I had use JXLayer, to overlay two moving yellow message boxes, on the top of JFreeChart http://yccheok.blogspot.com/2010/02/investment-flow-chart.html I was wondering, had anyone experience using JXLayer + JHotdraw, to overlay all sorts of figures (Re-sizable text box, straight line, circle...), on the top of JFreeChart. I just would like to add drawing capability, without changing the JFreeChart source code. So that, JStock's user may draw trending lines, annotation text on their favorite stock charting. The code skeleton is as follow : // this.chartPanel is JFreeChartPanel final org.jdesktop.jxlayer.JXLayer<ChartPanel> layer = new org.jdesktop.jxlayer.JXLayer<ChartPanel>(this.chartPanel); this.myUI = new MyUI<ChartPanel>(this); layer.setUI(this.myUI); public class MyUI<V extends javax.swing.JComponent> extends AbstractLayerUI<V> { @Override protected void paintLayer(Graphics2D g2, JXLayer<? extends V> layer) { // Previous, I am using my own hand-coded, to draw the yellow box // // Now, How can I make use of JHotDraw at here, to draw various type of // figures? } @Override protected void processMouseEvent(MouseEvent e, JXLayer<? extends V> layer) { // How can I make use of JHotDraw at here? } @Override protected void processMouseMotionEvent(MouseEvent e, JXLayer<? extends V> layer) { // How can I make use of JHotDraw at here? } } As you see, I already got Graphics2D g2 from paintLayer method. How is it possible that I can pass the Graphics2D object to JHotDraw, and let JHotDraw handles all the drawing. My experience in using JHotDraw are with org.jhotdraw.draw.DefaultDrawingView org.jhotdraw.draw.DefaultDrawingEditor I am able to use them to draw various figures, by clicking on the toolbar and click on drawing area. How is it possible I can use DefaultDrawingView and DefaultDrawingEditor within MyUI's paintLayer? Also, shall I let MyUI handles the mouse event, or JHotDraw? Sorry, I start getting confused.

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  • @user.posts.where('status = ?', :unfinished).all returns []

    - by Cheng
    By @user.posts, I can see there is a post with :unfinished status. But @user.posts.where('status = ?', :unfinished).all returns an empty array. I've tried to invoke @user.reload first, but it doesn't resolve the problem. (rdb:568) @user.posts [#<Post id: 1, content: "hehe", user_id: 1, created_at: "2010-04-03 06:16:47", updated_at: "2010-04-03 06:16:47", status: "--- :unfinished\n">] (rdb:568) @user.posts.where('status = ?', :unfinished).all []

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  • Access Violation When Accessing an STL Object Through A Pointer or Reference In A Different DLL or E

    - by Yan Cheng CHEOK
    I experience the following problem while using legacy VC6. I just cann't switch to modern compiler, as I am working on a legacy code base. http://support.microsoft.com/kb/172396 Since there are no way to export map, my planned workaround is using static linking instead of dynamic linking. I was wondering whether you all had encountered the similar situation? What is your workaround for this? Another workaround is to create wrapper class around the stl map, to ensure creation and accessing stl map, are within the same DLL space. Note that, fun0, which uses wrapper class will just work fine. fun1 will crash. Here is the code example : // main.cpp. Compiled it as exe. #pragma warning (disable : 4786) #include <map> #include <string> template <class K, class V> class __declspec(dllimport) map_wrapper { public: map_wrapper(); ~map_wrapper(); map_wrapper(const map_wrapper&); map_wrapper& operator=(const map_wrapper&); V& operator[](const K&); const V& operator[](const K&) const; const V& get(const K&) const; void put(const K&, const V&); int size() const; private: std::map<K, V> *m; }; __declspec(dllimport) void fun0(map_wrapper<std::string, int>& m); __declspec(dllimport) void fun1(std::map<std::string, int>& m); int main () { map_wrapper<std::string, int> m0; std::map<std::string, int> m1; m0["hello"] = 888; m1["hello"] = 888; // Safe. The we create std::map and access map both in dll space. fun0(m0); // Crash! The we create std::map in exe space, and access map in dll space. fun1(m1); return 0; } // dll.cpp. Compiled it as dynamic dll. #pragma warning (disable : 4786) #include <map> #include <string> #include <iostream> /* In map_wrapper.h */ template <class K, class V> class __declspec(dllexport) map_wrapper { public: map_wrapper(); ~map_wrapper(); map_wrapper(const map_wrapper&); map_wrapper& operator=(const map_wrapper&); V& operator[](const K&); const V& operator[](const K&) const; const V& get(const K&) const; void put(const K&, const V&); int size() const; private: std::map<K, V> *m; }; /* End */ /* In map_wrapper.cpp */ template <class K, class V> map_wrapper<K, V>::map_wrapper() : m(new std::map<K, V>()) { } template <class K, class V> map_wrapper<K, V>::~map_wrapper() { delete m; } template <class K, class V> map_wrapper<K, V>::map_wrapper(const map_wrapper<K, V>& map) : m(new std::map<K, V>(*(map.m))) { } template <class K, class V> map_wrapper<K, V>& map_wrapper<K, V>::operator=(const map_wrapper<K, V>& map) { std::map<K, V>* tmp = this->m; this->m = new std::map<K, V>(*(map.m)); delete tmp; return *this; } template <class K, class V> V& map_wrapper<K, V>::operator[](const K& key) { return (*this->m)[key]; } template <class K, class V> const V& map_wrapper<K, V>::operator[](const K& key) const { return (*this->m)[key]; } template <class K, class V> const V& map_wrapper<K, V>::get(const K& key) const { return (*this->m)[key]; } template <class K, class V> void map_wrapper<K, V>::put(const K& key, const V& value) { (*this->m)[key] = value; } template <class K, class V> int map_wrapper<K, V>::size() const { return this->m->size(); } // See : http://www.parashift.com/c++-faq-lite/templates.html#faq-35.15 // [35.15] How can I avoid linker errors with my template classes? template class __declspec(dllexport) map_wrapper<std::string, int>; /* End */ __declspec(dllexport) void fun0(map_wrapper<std::string, int>& m) { std::cout << m["hello"] << std::endl; } __declspec(dllexport) void fun1(std::map<std::string, int>& m) { std::cout << m["hello"] << std::endl; }

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  • Place JComponent On The Top Of JXLayer

    - by Yan Cheng CHEOK
    Hello, currently, I had successful applying JXLayer on my charting component, to draw a yellow information box on the top of it. final org.jdesktop.jxlayer.JXLayer<ChartPanel> layer = new org.jdesktop.jxlayer.JXLayer<ChartPanel>(this.chartPanel); this.chartLayerUI = new ChartLayerUI<ChartPanel>(this); layer.setUI(this.chartLayerUI); At the same time, I wish to add the following JComponent (DefaultDrawingView) on the top of JXLayer. This JComponent has the ability 1) To receive mouse event to draw figures on itself. Within ChartLayerUI, I add the following code @Override @SuppressWarnings("unchecked") public void installUI(JComponent c) { super.installUI(c); JXLayer<JComponent> l = (JXLayer<JComponent>) c; l.getGlassPane().setLayout(new java.awt.BorderLayout()); // this.view is DefaultDrawingView drawing object. l.getGlassPane().add(this.view, java.awt.BorderLayout.CENTER); } However, after having the above code, I get the following outcome 1) My charting component ChartPanel are being blocked by DefaultDrawingView 2) My charting component no longer able to receive mouse event. What I wish is that A) ChartPanel and DefaultDrawingView able to show up B) ChartPanel and DefaultDrawingView able to receive mouse event Is there other steps I had missed out, or did wrong? Thanks.

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  • Why Enumerable.Range is faster than a direct yield loop?

    - by Morgan Cheng
    Below code is checking performance of three different ways to do same solution. public static void Main(string[] args) { // for loop { Stopwatch sw = Stopwatch.StartNew(); int accumulator = 0; for (int i = 1; i <= 100000000; ++i) { accumulator += i; } sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, accumulator); } //Enumerable.Range { Stopwatch sw = Stopwatch.StartNew(); var ret = Enumerable.Range(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } //self-made IEnumerable<int> { Stopwatch sw = Stopwatch.StartNew(); var ret = GetIntRange(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } } private static IEnumerable<int> GetIntRange(int start, int count) { int end = start + count; for (int i = start; i < end; ++i) { yield return i; } } } The result is like this: time = 306; result = 987459712 time = 1301; result = 987459712 time = 2860; result = 987459712 It is not surprising that "for loop" is faster than the other two solutions, because Enumerable.Aggregate takes more method invocations. However, it really surprises that "Enumerable.Range" is faster than the "self-made IEnumerable". I thought that Enumerable.Range will take more overhead than the simple GetIntRange method. What is the possible reason for this?

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  • drupal display submenu when parent has been selected

    - by Steven Cheng
    I've have a menu structure that has a depth of 3 levels on a drupal 6 CMS. When I click on a level 1 that has children, the level 2 menu items display fine. If the level 2 has children, it is not showing the level 3. If I check the expanded box the level 3 is displayed however, it displays all the time irrespective of the level 2 that has been selected. It seems to display whenever it's parent level 1 is selected. For further information, the menu items are a mixture of custom links & content links. i.e. Links I've enetered manually when creating the menu and others generated by when creating a node or view display. All I want is to show the children if there are any for the selected parent. Am I missing something fundamental here? Thanks Steve

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  • ListView causing OutOfMemory Error

    - by Michael
    So I am not really given a reason to the right of this error message. I am not exactly sure why this is happening but my guess though is that it has to do with the fact that there are around ~50 good quality drawables. Upon scrolling really fast, the app crashes. I feel as if I am mitigating most common issues with ListView and crashing such as using View Holders as well as only initiating the inflater once. Process: com.example.michael.myandroidappactivity, PID: 20103 java.lang.OutOfMemoryError at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) Here is the code public class ImageAdapter extends BaseAdapter { private Context context; private ArrayList<Integer> imageIds; private static LayoutInflater inflater; public ImageAdapter(Context _context, ArrayList<Integer> _imageIds) { context = _context; imageIds = _imageIds; } @Override public int getCount() { return imageIds.size(); } @Override public Object getItem(int position) { return null; } @Override public long getItemId(int position) { return 0; } static class ViewHolder{ ImageView img; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder = null; View rowView = null; if(rowView==null) { LayoutInflater inflater = (LayoutInflater) context .getSystemService(Context.LAYOUT_INFLATER_SERVICE); rowView = inflater.inflate(R.layout.listview_layout, parent, false); holder = new ViewHolder(); holder.img = (ImageView) rowView.findViewById(R.id.flag); rowView.setTag(holder); } else { holder = (ViewHolder) rowView.getTag(); } holder.img.setImageResource(imageIds.get(position)); return rowView; } }

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  • Must a Language that Implements Monads be Statically Typed?

    - by Morgan Cheng
    I am learning functional programming style. From this link http://channel9.msdn.com/shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads/, Brian Beckman gave a brilliant introduction about Monad. He mentioned that Monad is about composition of functions so as to address complexity. A Monad includes a unit function that transfers type T to an amplified type M(T); and a Bind function that, given function from T to M(U), transforms type M(T) to another type M(U). (U can be T, but is not necessarily). In my understanding, the language implementing monad should be type-checked statically. Otherwise, type errors cannot be found during compilation and "Complexity" is not controlled. Is my understanding correct?

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  • Convert wchar_t to char

    - by Yan Cheng CHEOK
    I was wondering is it safe to do so? wchar_t wide = /* something */; assert(wide >= 0 && wide < 256 &&); char myChar = static_cast<char>(wide); If I am pretty sure the wide char will fall within ASCII range.

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  • How to check whether user is login in web application?

    - by Morgan Cheng
    I want to learn the whole details of web application authentication. So, I decided to write a CodeIgniter authentication library from scratch. Now, I have to make design decision about how to determine whether one user is login. Basically, after user input username & password pair. A cookie is set for this session, following navigations in the web application will not require username & password. The server side will check whether the session cookie is valid to determine whether current user is login. The question is: how to determine whether cookie is valid cookie issued from server side? I can image the most simple way is to have the cookie value stored in session status as well. For each HTTP request, compare the value from cookie and the value from server session. (Since CodeIgniter session library store session variables in cookies, it is not applicable without some tweak.) This method requires storage in server side. For huge web application that is deployed in multiple datacenters. It is possible that user input username & password when browsing in one datacenter, while he/she access the web application in another datacenter later. The expected behavior is that user just input username & password once. As a result, all datacenters should be able to access the session status. That is possible not applicable even the session status is stored in external storage such as database. I tried Google. I login Google with Asian proxy which is supposed to direct me to datacenters in Asian. Then I switch to North American proxy which should direct me to datacenters in North America. It recognize my login without asking username and password again. So, is there any way to determine whether user is login without server side session status?

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  • Will PHP Die In Web Page Development World?

    - by Morgan Cheng
    I know that PHP is still the most popular web programming language in the world. This question just want to bring some of my concerns about PHP. PHP is naturally bound to C10K problem. Since PHP (generally run in Apache) cannot be event-driven or asynchronous, each HTTP request will occupy at least one thread or process. This makes it resistant to be more scalable. Currently, a lot of web sites (like Facebook) with high performance and scalability still depends on PHP in their front end servers. I suppose it is due to legacy reason. Is it possible that PHP will be replaced by language more suitable for C10K?

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  • How to Treat Race Condition of Session in Web Application?

    - by Morgan Cheng
    I was in a ASP.NET application has heavy traffic of AJAX requests. Once a user login our web application, a session is created to store information of this user's state. Currently, our solution to keep session data consistent is quite simple and brutal: each request needs to acquire a exclusive lock before being processed. This works fine for tradition web application. But, when the web application turns to support AJAX, it turns to not efficient. It is quite possible that multiple AJAX requests are sent to server at the same time without reloading the web page. If all AJAX requests are serialized by the exclusive lock, the response is not so quick. Anyway, many AJAX requests that doesn't access same session variables are blocked as well. If we don't have a exclusive lock for each requests, then we need to treat all race condition carefully to avoid dead lock. I'm afraid that would make the code complex and buggy. So, is there any best practice to keep session data consistent and keep code simple and clean?

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  • How to design data storage for partitioned tagging system?

    - by Morgan Cheng
    How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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  • Is it possible to listen to relational database update?

    - by Morgan Cheng
    Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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  • What's the best way to store Logon User information for Web Application?

    - by Morgan Cheng
    I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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  • AtomicInteger lazySet and set

    - by Yan Cheng CHEOK
    May I know what is the difference among lazySet and set method for AtomicInteger. javadoc doesn't talk much about lazySet : Eventually sets to the given value. It seems that AtomicInteger will not immediately be set to the desired value, but it will be scheduled to be set in some time. But, what is the practical use of this method? Any example?

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  • How can i handle mouse double click event on textbox?

    - by Kar Cheng
    Hello, I want to open one child window on mouse double click of textbox. I know the only event available in Silverlight is MouseLeftButtonDown and you have to simulate double click. However it still doesn't work when i click in the middle of the textbox. It only works when i double click on the border of the textbox. Anybody has any ideas of how can i do this? If any 3rd party library is available then also it's fine. Thanks in advance:)

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  • Usage of VIsual Memory Leak Detector

    - by Yan Cheng CHEOK
    I found a very interesting memory leak detector by using Visual C++. http://www.codeproject.com/KB/applications/visualleakdetector.aspx I try it out, but cannot make it works to detect a memory leak code. I am using MS Visual Studio 2008. Any step I had missed out? #include "stdafx.h" #include "vld.h" #include <iostream> void fun() { new int[1000]; } int _tmain(int argc, _TCHAR* argv[]) { fun(); std::cout << "lead?" << std::endl; getchar(); return 0; } The output when I run in debug mode is : ... ... 'Test.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.4053_x-ww_e6967989\msvcr80.dll', Symbols loaded. 'Test.exe': Loaded 'C:\WINDOWS\system32\msvcrt.dll', Symbols loaded (source information stripped). 'Test.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC90.DebugCRT_1fc8b3b9a1e18e3b_9.0.30729.1_x-ww_f863c71f\msvcp90d.dll', Symbols loaded. 'Test.exe': Loaded 'C:\Program Files\Visual Leak Detector\bin\dbghelp.dll', Symbols loaded (source information stripped). Visual Leak Detector Version 1.9d installed. No memory leaks detected. Visual Leak Detector is now exiting. The program '[5468] Test.exe: Native' has exited with code 0 (0x0).

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  • Is this the intention behavior in JComboBox? How I can avoid this behavior?

    - by Yan Cheng CHEOK
    I realize that if you are having a same selection in JComboBox, using up/down arrow key, will not help you to navigate the selection around. How I can avoid this behavior? See the below screen shoot /* * To change this template, choose Tools | Templates * and open the template in the editor. */ /* * NewJFrame.java * * Created on May 8, 2010, 7:46:28 PM */ package javaapplication26; /** * * @author yccheok */ public class NewJFrame extends javax.swing.JFrame { /** Creates new form NewJFrame */ public NewJFrame() { initComponents(); /* If you are having 3 same strings here. Using, up/down arrow key, * will not move the selection around. */ this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ @SuppressWarnings("unchecked") // <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() { jComboBox1 = new javax.swing.JComboBox(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); jComboBox1.setEditable(true); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(105, 105, 105) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 158, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(137, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(63, 63, 63) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(217, Short.MAX_VALUE)) ); pack(); }// </editor-fold> /** * @param args the command line arguments */ public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new NewJFrame().setVisible(true); } }); } // Variables declaration - do not modify private javax.swing.JComboBox jComboBox1; // End of variables declaration }

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  • xstream handles non-english character

    - by Yan Cheng CHEOK
    I have the following code : /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package helloworld; import com.thoughtworks.xstream.XStream; import java.io.File; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import javax.swing.JOptionPane; /** * * @author yccheok */ public class Test { @SuppressWarnings("unchecked") public static <A> A fromXML(Class c, File file) { XStream xStream = new XStream(); InputStream inputStream = null; try { inputStream = new java.io.FileInputStream(file); Object object = xStream.fromXML(inputStream); if (c.isInstance(object)) { return (A)object; } } catch (Exception exp) { exp.printStackTrace(); } finally { if (inputStream != null) { try { inputStream.close(); inputStream = null; } catch (java.io.IOException exp) { exp.printStackTrace(); return null; } } } return null; } @SuppressWarnings("unchecked") public static <A> A fromXML(Class c, String filePath) { return (A)fromXML(c, new File(filePath)); } public static boolean toXML(Object object, File file) { XStream xStream = new XStream(); OutputStream outputStream = null; try { outputStream = new FileOutputStream(file); xStream.toXML(object, outputStream); } catch (Exception exp) { exp.printStackTrace(); return false; } finally { if (outputStream != null) { try { outputStream.close(); outputStream = null; } catch (java.io.IOException exp) { exp.printStackTrace(); return false; } } } return true; } public static boolean toXML(Object object, String filePath) { return toXML(object, new File(filePath)); } public static void main(String args[]) { String s = "\u6210\u4EA4\u91CF"; // print ??? System.out.println(s); // fine! show ??? JOptionPane.showMessageDialog(null, s); toXML(s, "C:\\A.XML"); String o = fromXML(String.class, "C:\\A.XML"); // show ??? JOptionPane.showMessageDialog(null, o); } } I run the following code through command prompt in Windows Vista. 1) May I know why System.out.println unable to print out Chinese Character in console? 2) I open up the xstream file. The saved value is <string>???</string> How can I make xstream save Chinese Character correctly? Thanks.

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