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  • Suggestions for designing large-scale Java webapp from the ground up

    - by Chris Thompson
    Hi all, I'm about to start developing a large-scale system and I'm struggling with which direction to proceed. I've done plenty of Java web apps before and I have plenty of experience with servlet containers and GWT and some experience with Spring. The problem is most of my webapps have been thrown together just to be a proof of concept and what I'm struggling with is what set of frameworks to use. I need to have both a browser based application as well as a web service designed to support access from mobile devices (Android and iPhone for now). Ideally, I'd like to design this system in such a way that I don't end up rewriting all of my servlets for each client (browser and phone) although I don't mind having some small checks in there to properly format the data. In addition, although I'm the only developer now, that won't necessarily be the case down the road and I'd like to design something that scales well both with regards to traffic and number of developers (isn't just a nightmare to maintain). So where I am now is planning on using GWT to design the browser-based interface but I'm struggling with how to reuse that code with to present the interface (most likely xml) for the mobile devices. Using GWT RPC would, I think, make it relatively easy to do all of the AJAX in the browser, but might make generating xml for the mobile phones difficult. In addition, I like the idea of using something like Hibernate for persistence and Spring Security to secure the whole thing. Again, I'm not sure how well those will cooperate with GWT (I think Hibernate should be fine...) There's obviously a lot more to this than I've presented here, but I've tried to give you the 5-minute overview. I'm a bit stumped and was wondering if anybody in the community had any experience starting from this place. Does what I'm trying to do make sense? Is it realistic? I have no doubt I can make all of these frameworks speak the same language, I'm just wondering if it's worth my time to fight with them. Also, am I missing a framework that would be really beneficial? Thanks in advance and sorry for the relatively broad question... Chris

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  • [Java] Send cookie with http request problem

    - by nkr1pt
    I'm trying to get a certain cookie in a java client by creating a series of Http requests. It looks like I'm getting a valid cookie from the server but when I'm sending out a request to the fnal url with the seemingly valid cookie I should get some lines of xml in the response but the response is blank because the cookie isw rong or is invalidated because a session has closed or an other problem which I can't figure out. The cookie handed out by the server expires at the end of the session. It seems to me the cookie is valid because when I do the same calls in firefox, a similar cookie with the same name and starting with the 3 first same letters and of the same length is stored in firefox, also expiring at the end of the session. If I then make a request to the final url with only this particular cookie stored in firefox (removed all other cookies), the xml is nicely rendered on the page. Any ideas about what I am doing wrong in this piece of code? One other thing, when I use the value from the very similar cookie generated and strored in firefox in this piece of code, the last request does give xml feedback in the http response! // Validate url = new URL(URL_VALIDATE); conn = (HttpURLConnection) url.openConnection(); conn.setRequestProperty("Cookie", cookie); conn.connect(); String headerName = null; for (int i = 1; (headerName = conn.getHeaderFieldKey(i)) != null; i++) { if (headerName.equals("Set-Cookie")) { if (conn.getHeaderField(i).startsWith("JSESSIONID")) { cookie = conn.getHeaderField(i).substring(0, conn.getHeaderField(i).indexOf(";")).trim(); } } } // Get the XML url = new URL(URL_XML_TOTALS); conn = (HttpURLConnection) url.openConnection(); conn.setRequestProperty("Cookie", cookie); conn.connect(); // Get the response StringBuffer answer = new StringBuffer(); BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream())); String line; while ((line = reader.readLine()) != null) { answer.append(line); } reader.close(); //Output the response System.out.println(answer.toString())

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  • java.util.zip - ZipInputStream v.s. ZipFile

    - by lucho
    Hello, community! I have some general questions regarding the java.util.zip library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.: <component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> Please note that the order of the components during import is relevant. Now every component should occupy its own file which should be externally versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions: Q1. May the ZipInputStream guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses ZipOutputStream? I assume reading is something like: ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind. Q2. If I use ZipFile (which I prefer) what is the performance impact of calling getInputStream() hundreds of times? Will it be much slower than the ZipInputStream solution? The zip is opened only once and ZipFile is backed by RandomAccessFile - is this correct? I assume reading is something like: ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } Q3. Are the input streams retrieved from the same ZipFile thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties? Thanks for your answers!

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  • Java Http request on api.stackexchange with json response

    - by taoder
    I'm trying to use the api-stackexchange with java but when I do the request and try to parse the response with a json parser I have an error. public ArrayList<Question> readJsonStream(InputStream in) throws IOException { JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8")); reader.setLenient(true); try { System.out.println(reader.nextString()); // ? special character return readItem(reader); } finally { reader.close(); } } public ArrayList<Question> readItem(JsonReader reader) throws IOException { ArrayList<Question> questions = new ArrayList<Question>(); reader.beginObject(); while (reader.hasNext()) { System.out.println("here");//not print the error is before String name = reader.nextName(); if (name.equals("items")) { questions = readQuestionsArray(reader); } } reader.endObject(); return questions; } public final static void main(String[] args) throws Exception { URIBuilder builder = new URIBuilder(); builder.setScheme("http").setHost("api.stackexchange.com").setPath("/2.0/search") .setParameter("site", "stackoverflow") .setParameter("intitle" ,"workaround") .setParameter("tagged","javascript"); URI uri = builder.build(); String surl = fixEncoding(uri.toString()+"&filter=!)QWRa9I-CAn0PqgUwq7)DVTM"); System.out.println(surl); Test t = new Test(); try { URL url = new URL(surl); t.readJsonStream(url.openStream()); } catch (IOException e) { e.printStackTrace(); } } And the error is: com.google.gson.stream.MalformedJsonException: Expected literal value at line 1 column 19 Here is an example of the Json : { "items": [ { "question_id": 10842231, "score": 0, "title": "How to push oath token to LocalStorage or LocalSession and listen to the Storage Event? (SoundCloud Php/JS bug workaround)", "tags": [ "javascript", "javascript-events", "local-storage", "soundcloud" ], "answers": [ { "question_id": 10842231, "answer_id": 10857488, "score": 0, "is_accepted": false } ], "link": "http://stackoverflow.com/questions/10842231/how-to-push-oath-token-to-localstorage-or-localsession-and-listen-to-the-storage", "is_answered": false },... So what's the problem? Is the Json really malformed? Or did I do something not right? Thanks, Anthony

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  • Is there an open source UIView subclass for creating multiple, dynamic tabs in the iPhone (iPad) SDK

    - by smountcastle
    Is there an open source UIView component that supports multiple, dynamic tabbed views for the iPhone (iPad) SDK? I see several apps in the iPad App Store which utilize tabs, one such example is the Atomic Web Browser which provides a tabbed browsing experience (like Safari on the Mac or Firefox). Instead of reinventing this functionality, I'd like to reuse an existing component.

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  • Translate RoR Code to Java

    - by mnml
    Hi, for some reasons I am trying to translate the following RoR view code to a Java Groovy view: <% modulo_artists = @artists.length % 3 base = @artists.length / 3 base = base.ceil case modulo_artists when 0 cols = [base, base, base] when 1 cols = [base, base + 1, base] when 2 cols = [base + 1, base, base + 1] end counter = 0 %> <% id_hash = {"0" => "url('/images/actorsbg.png');", "1" => "url('/images/musiciansbg.png');", "2" => "url('/images/artistsbg.png') no-repeat; color: #FFF;", "3" => "url('/images/fashionbg.png')"} %> <div id="artists_<%=params[:artist_cat]%>" style="background: <%= id_hash[params[:artist_cat]] %>;" > <table border="0" width="660" height="164" cellpadding="0" cellspacing="0"> <tr valign="middle"> <% 3.times do |i| %> <td width="220" align="center" style="padding-right: 15px;"> <% cols[i].times do %> <h1><a href="/artists/show/<%= @artists[counter].urlname %>" ><%= @artists[counter].name %></a></h1> <% counter = counter + 1 %> <% end %> </td> <% end %> </tr> </table> </div> This is what I got so far: #{extends 'main.html' /} %{ modulo_artists = artists.size() % 3 base = artists.size() / 3 base = Math.ceil(base) if(modulo_artists == 0) cols = [base, base, base] else if(modulo_artists == 1) cols = [base, base + 1, base] else if(modulo_artists == 2) cols = [base + 1, base, base + 1] endif counter = 0 }% <div id="artists_${artist_cat}" style="background:${id_hash};" > <table border="0" width="660" height="164" cellpadding="0" cellspacing="0"> <tr valign="middle"> #{list items:1..3, as:'i'} <td width="220" align="center" style="padding-right: 15px;"> #{list items:cols[i]} <h1><a href="@{Artists.show(artists.get(counter).name.replaceAll(" ", "-"))}" >${artists.get(counter).name}</a></h1> %{ counter = counter + 1 }% #{/list} </td> #{/list} </tr> </table> </div> The idea is to keep the items organised in 3 columns like 1|0|1 4|5|4 or 5|4|5 for example

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  • Is there an open source UITabbedView component available for the iPhone (iPad) SDK?

    - by smountcastle
    Is there an open source UIView component that supports multiple, dynamic tabbed views for the iPhone (iPad) SDK? I see several apps in the iPad App Store which utilize tabs, one such example is the Atomic Web Browser which provides a tabbed browsing experience (like Safari on the Mac or Firefox). Instead of reinventing this functionality, I'd like to reuse an existing component.

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  • Writing to a xml file in java

    - by user243680
    import java.io.*; import javax.xml.parsers.*; import javax.xml.transform.*; import javax.xml.transform.dom.*; import javax.xml.transform.stream.*; import org.w3c.dom.*; public class CreatXMLFile { public static void main(String[] args) throws Exception { BufferedReader bf = new BufferedReader(new InputStreamReader(System.in)); // System.out.print("Enter number to add elements in your XML file: "); // String str = bf.readLine(); int no=2; // System.out.print("Enter root: "); String root = "SMS"; DocumentBuilderFactory documentBuilderFactory =DocumentBuilderFactory.newInstance(); DocumentBuilder documentBuilder =documentBuilderFactory.newDocumentBuilder(); Document document = documentBuilder.newDocument(); Element rootElement = document.createElement(root); document.appendChild(rootElement); // for (int i = 1; i <= no; i++) // System.out.print("Enter the element: "); // String element = bf.readLine(); String element ="Number"; System.out.print("Enter the Number: "); String data = bf.readLine(); Element em = document.createElement(element); em.appendChild(document.createTextNode(data)); rootElement.appendChild(em); String element1 ="message"; System.out.print("Enter the SMS: "); String data1 = bf.readLine(); Element em1 = document.createElement(element1); em1.appendChild(document.createTextNode(data1)); rootElement.appendChild(em1); TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); DOMSource source = new DOMSource(document); StreamResult result = new StreamResult(System.out); transformer.transform(source, result); } } i am working on the above code and it gives the following output run: Enter the Number: 768678 Enter the SMS: ytu <?xml version="1.0" encoding="UTF-8" standalone="no"?><SMS><Number>768678</Number><message>ytu</message></SMS>BUILD SUCCESSFUL (total time: 8 seconds) Now i want to write the output generated(<?xml version="1.0" encoding="UTF-8" standalone="no"?><SMS><Number>768678</Number><message>ytu</message></SMS>) to a XML file on the hard disk.How do i do it?

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  • null pointer exception when starting new activity

    - by acithium
    Okay, I'm getting a null pointer exception when I start my third activity. Here is the LogCat message: 12-28 04:38:00.350: ERROR/AndroidRuntime(776): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.acithium.main/com.acithium.rss.ShowDescription}: java.lang.NullPointerException 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread.access$2100(ActivityThread.java:116) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.os.Handler.dispatchMessage(Handler.java:99) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.os.Looper.loop(Looper.java:123) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread.main(ActivityThread.java:4203) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at java.lang.reflect.Method.invokeNative(Native Method) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at java.lang.reflect.Method.invoke(Method.java:521) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at dalvik.system.NativeStart.main(Native Method) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): Caused by: java.lang.NullPointerException 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at com.acithium.rss.ShowDescription.onCreate(ShowDescription.java:48) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364) 12-28 04:38:00.350: ERROR/AndroidRuntime(776): ... 11 more Here is the section of code where I call the activity: public void onItemClick(AdapterView parent, View v, int position, long id) { Log.i(tag,"item clicked! [" + feed.getItem(position).getTitle() + "]"); Intent itemintent = new Intent(this,com.acithium.rss.ShowDescription.class); //Intent itemintent = new Intent(); //itemintent.setClassName("com.acithium.main", "com.acithium.rss.ShowDescription"); Bundle b = new Bundle(); b.putString("title", feed.getItem(position).getTitle()); b.putString("description", feed.getItem(position).getDescription()); b.putString("link", feed.getItem(position).getLink()); itemintent.putExtra("android.intent.extra.INTENT", b); startActivityForResult(itemintent,0); } And here is new activity class that is called: public class ShowDescription extends Activity { public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.showdescription); String theStory = null; Intent startingIntent = getIntent(); if (startingIntent != null) { Bundle b = startingIntent.getBundleExtra("android.intent.extra.INTENT"); if (b == null) { theStory = "bad bundle?"; } else { theStory = b.getString("title") + "\n\n" + b.getString("description") + "\n\nMore information:\n" + b.getString("link"); } } else { theStory = "Information Not Found."; } TextView db= (TextView) findViewById(R.id.storybox); db.setText(theStory); Button backbutton = (Button) findViewById(R.id.back); backbutton.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { finish(); } }); } }

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  • Dynamically find other hosts in a LAN in Java

    - by Federico Cristina
    A while ago I developed a little LAN chat app. in Java which allows chatting with other hosts, send images, etc. Although it was created just for fun, now it's being used where I work. Currently, there is no "chat server" on the app. where each client registers, updates it's status, etc. (I liked the idea of symmetric design and not depending on a server running on some other machine). Instead, each host is a client/server which has a hosts.properties file with the hostname of the other hosts, and - for instance - broadcasts to each one of them when sending a massive message/image/whatever. In the beginning there were just a couple of hosts, so this hosts.properties file wasn't an issue. But as the amount of users increased, the need of updating that file was a bit daunting. So now I've decided to get rid of it, and each time the app. starts, dynammically find the other active hosts. However, I cannot find the correct way of implement this. I've tried starting different threads, each one of them searching for other hosts in a known range of IP addresses. Something like this (simplified for the sake of readability): /** HostsLocator */ public static void searchForHosts(boolean waitToEnd) { for (int i=0; i < MAX_IP; i+= MAX_IP / threads) { HostsLocator detector = new HostsLocator(i, i+(MAX_IP / threads - 1)); // range: from - to new Thread(detector).start(); } } public void run() { for (int i=from; i<=to; i++) findHosts( maskAddress + Integer.toString(i) ); } public static boolean findHosts(String IP) { InetAddress address = InetAddress.getByName(IP); if ( address.isReachable(CONNECTION_TIME_OUT) ) // host found! } However: With a single thread and a low value in CONNECTION_TIME_OUT (500ms) I get wrong Host Not Found status for for hosts actually active. With a high value in CONNECTION_TIME_OUT (5000ms) and only one single thread takes forever to end With several threads I've also found problems similar like the first one, due to collisions. So... I guess there's a better way of solving this problem but I couldn't find it. Any advice? Thanks!

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  • java web application best practices

    - by Bruce
    Hi all I'm trying to figure out the optimum way to develop and release a fairly simple web application, and I'm running into several problems. I'll outline the decisions I've made, because somewhere I've clearly gone off the rails.. Hugely grateful for any help! I have what I think is a fairly simple web application. It contains a couple of jsps that reference a couple of java beans, and the usual static html, js, css and images. Decision 1) I wanted to have a clear and clean release procedure, such that I could develop on my local machine and then release reliably to a production machine. I therefore made the decision to package the application into a war file (including all the static resources), to minimize the separate bits and pieces I would need to release. So far so good? Decision 2) I wanted things on my local machine to be as similar as possible to the production environment. So in my html, for example, I may have a reference to a static file such as http://static.foo.com/file . To keep this code working seamlessly on dev and prod, I decided to put static.foo.com in my /etc/hosts when developing locally, so that all the urls work correctly without changing anything. Decision 3) I decided to use eclipse and maven to give me a best practice environment for administering and building my project. So I have a nice tight set up now, except that: Every time I want to change anything in development, like one line in an html file, I have to rebuild the entire project and then wait for tomcat to load the war before I can see if it's what I wanted. So my questions are: 1) Is there a way to connect up eclipse and tomcat so that I don't have to rebuild the war each time? ie tomcat is looking straight at my actual workspace to serve up the static files? 2)I think I'm maybe making things harder by using /etc/hosts to reflect production urls - is there a better way that doesn't involve manually changing over urls (relative urls are fine of course, but where you have many subdomains, say one for static files and one for dynamic, you have to write out the full path, surely?) 3) Is this really best practice?? How do people set things up so that they balance the requirement for an automated, all-encompassing build process on the one hand, and the speed and flexibility to be able to develop javascript and html and css quickly, as quickly as if one just pointed apache at the directory and developed live? What do people find works? Many thanks!

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  • Java: Preventing array going out of bounds.

    - by Troy
    I'm working on a game of checkers, if you want to read more about you can view it here; http://minnie.tuhs.org/I2P/Assessment/assig2.html When I am doing my test to see if the player is able to get to a certain square on the grid (i.e. +1 +1, +1 -1 .etc) from it's current location, I get an java.lang.ArrayIndexOutOfBoundsException error. This is the code I am using to make the move; public static String makeMove(String move, int playerNumber) { // variables to contain the starting and destination coordinates, subtracting 1 to match array size int colStart = move.charAt(1) - FIRSTCOLREF - 1; int rowStart = move.charAt(0) - FIRSTROWREF - 1; int colEnd = move.charAt(4) - FIRSTCOLREF - 1; int rowEnd = move.charAt(3) - FIRSTROWREF - 1; // variable to contain which player is which char player, enemy; if (playerNumber==1) { player= WHITEPIECE; enemy= BLACKPIECE; } else { player= BLACKPIECE; enemy= WHITEPIECE; } // check that the starting square contains a player piece if (grid [ colStart ] [ rowStart ] == player) { // check that the player is making a diagonal move if (grid [ colEnd ] [ rowEnd ] == grid [ (colStart++) ] [ (rowEnd++) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart--) ] [ (rowEnd++) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart++) ] [ (rowEnd--) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart--) ] [ (rowEnd--) ]) { // check that the destination square is free if (grid [ colEnd ] [ rowEnd ] == BLANK) { grid [ colStart ] [ rowStart ] = BLANK; grid [ colEnd ] [ rowEnd ] = player; } } // check if player is jumping over a piece else if (grid [ colEnd ] [ rowEnd ] == grid [ (colStart+2) ] [ (rowEnd+2) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart-2) ] [ (rowEnd+2) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart+2) ] [ (rowEnd-2) ] && grid [ colEnd ] [ rowEnd ] == grid [ (colStart-2) ] [ (rowEnd-2) ]) { // check that the piece in between contains an enemy if ((grid [ (colStart++) ] [ (rowEnd++) ] == enemy ) && (grid [ (colStart--) ] [ (rowEnd++) ] == enemy ) && (grid [ (colStart++) ] [ (rowEnd--) ] == enemy ) && (grid [ (colStart--) ] [ (rowEnd--) ] == enemy )) { // check that the destination is free if (grid [ colEnd ] [ rowEnd ] == BLANK) { grid [ colStart ] [ rowStart ] = BLANK; grid [ colEnd ] [ rowEnd ] = player; } } } } I'm not sure how I can prevent the error from happening, what do you recommend?

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  • Java Best Practice for type resolution at runtime.

    - by Brian
    I'm trying to define a class (or set of classes which implement the same interface) that will behave as a loosely typed object (like JavaScript). They can hold any sort of data and operations on them depend on the underlying type. I have it working in three different ways but none seem ideal. These test versions only allow strings and integers and the only operation is add. Adding integers results in the sum of the integer values, adding strings concatenates the strings and adding an integer to a string converts the integer to a string and concatenates it with the string. The final version will have more types (Doubles, Arrays, JavaScript-like objects where new properties can be added dynamically) and more operations. Way 1: public interface DynObject1 { @Override public String toString(); public DynObject1 add(DynObject1 d); public DynObject1 addTo(DynInteger1 d); public DynObject1 addTo(DynString1 d); } public class DynInteger1 implements DynObject1 { private int value; public DynInteger1(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject1 add(DynObject1 d) { return d.addTo(this); } public DynObject1 addTo(DynInteger1 d) { return new DynInteger1(d.value + value); } public DynObject1 addTo(DynString1 d) { return new DynString1(d.toString()+Integer.toString(value)); } } ...and similar for DynString1 Way 2: public interface DynObject2 { @Override public String toString(); public DynObject2 add(DynObject2 d); } public class DynInteger2 implements DynObject2 { private int value; public DynInteger2(int v) { value = v; } @Override public String toString() { return Integer.toString(value); } public DynObject2 add(DynObject2 d) { Class c = d.getClass(); if(c==DynInteger2.class) { return new DynInteger2(value + ((DynInteger2)d).value); } else { return new DynString2(toString() + d.toString()); } } } ...and similar for DynString2 Way 3: public class DynObject3 { private enum ObjectType { Integer, String }; Object value; ObjectType type; public DynObject3(Integer v) { value = v; type = ObjectType.Integer; } public DynObject3(String v) { value = v; type = ObjectType.String; } @Override public String toString() { return value.toString(); } public DynObject3 add(DynObject3 d) { if(type==ObjectType.Integer && d.type==ObjectType.Integer) { return new DynObject3(Integer.valueOf(((Integer)value).intValue()+((Integer)value).intValue())); } else { return new DynObject3(value.toString()+d.value.toString()); } } } With the if-else logic I could use value.getClass()==Integer.class instead of storing the type but with more types I'd change this to use a switch statement and Java doesn't allow switch to use Classes. Anyway... My question is what is the best way to go about something thike this?

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  • What is the best way to create continuously looping background in iPhone SDK ?

    - by catpad
    What is the best way to create a continuously looping background using iPhone SDK so that it seems the foreground object is in perpetual motion ? I have a background image which I want to move continuously at a given speed from right to left and seamlessly start displaying the beginning of the image when its end is reached. What is the best, most efficient way to do it to avoid any jumps and get optimal performance ?

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  • Write PEM encoded certificate in file - java

    - by user1349407
    Good day. I recently create X.509 certificate by using bouncy castle API. I need to save the certificate result rather than display the result. I tried to use FileOutputStream, but it does not work. regards the result is like follows -----BEGIN CERTIFICATE----- MIICeTCCAeKgAwIBAgIGATs8OWsXMA0GCSqGSIb3DQEBCwUAMBsxGTAXBgNVBAMT... -----END CERTIFICATE----- The code is belows import java.io.FileOutputStream; //example of a basic CA public class PKCS10CertCreateExample { public static X509Certificate[] buildChain() throws Exception { //create the certification request KeyPair pair = chapter7.Utils.generateRSAKeyPair(); PKCS10CertificationRequest request = PKCS10ExtensionExample.generateRequest(pair); //create a root certificate KeyPair rootPair=chapter7.Utils.generateRSAKeyPair(); X509Certificate rootCert = X509V1CreateExample.generateV1Certificate (rootPair); //validate the certification request if(!request.verify("BC")) { System.out.println("request failed to verify!"); System.exit(1); } //create the certificate using the information in the request X509V3CertificateGenerator certGen = new X509V3CertificateGenerator(); certGen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis())); certGen.setIssuerDN(rootCert.getSubjectX500Principal()); certGen.setNotBefore(new Date(System.currentTimeMillis())); certGen.setNotAfter(new Date(System.currentTimeMillis()+50000)); certGen.setSubjectDN(request.getCertificationRequestInfo().getSubject()); certGen.setPublicKey(request.getPublicKey("BC")); certGen.setSignatureAlgorithm("SHA256WithRSAEncryption"); certGen.addExtension(X509Extensions.AuthorityKeyIdentifier, false, new AuthorityKeyIdentifierStructure(rootCert)); certGen.addExtension(X509Extensions.SubjectKeyIdentifier, false, new SubjectKeyIdentifierStructure(request.getPublicKey("BC"))); certGen.addExtension(X509Extensions.BasicConstraints, true, new BasicConstraints(false)); //certGen.addExtension(X509Extensions.KeyUsage, true, new BasicConstraints(false)); certGen.addExtension(X509Extensions.KeyUsage, true, new KeyUsage(KeyUsage.digitalSignature | KeyUsage.keyEncipherment)); certGen.addExtension(X509Extensions.ExtendedKeyUsage, true, new ExtendedKeyUsage(KeyPurposeId.id_kp_serverAuth)); //extract the extension request attribute ASN1Set attributes = request.getCertificationRequestInfo().getAttributes(); for(int i=0;i!=attributes.size();i++) { Attribute attr = Attribute.getInstance(attributes.getObjectAt(i)); //process extension request if(attr.getAttrType().equals(PKCSObjectIdentifiers.pkcs_9_at_extensionRequest)) { X509Extensions extensions = X509Extensions.getInstance(attr.getAttrValues().getObjectAt(0)); Enumeration<?> e = extensions.oids(); while(e.hasMoreElements()) { DERObjectIdentifier oid = (DERObjectIdentifier)e.nextElement(); X509Extension ext = extensions.getExtension(oid); certGen.addExtension(oid, ext.isCritical(), ext.getValue().getOctets()); } } } X509Certificate issuedCert = certGen.generateX509Certificate(rootPair.getPrivate()); return new X509Certificate[]{issuedCert, rootCert}; } public static void main(String[] args) throws Exception { X509Certificate[] chain = buildChain(); PEMWriter pemWrt = new PEMWriter(new OutputStreamWriter(System.out)); pemWrt.writeObject(chain[0]); //pemWrt.writeObject(chain[1]); pemWrt.close(); //write it out //FileOutputStream fOut = new FileOutputStream("pkcs10req.req"); //fOut.write(chain[0].toString()); //fOut.write() //System.out.println(chain[0].toString()); //fOut.close(); } }

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  • Linked lists in Java - help with assignment

    - by user368241
    Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. Here is my try to write the method indexOf (int ch). Kindly assist me with fixing the bugs so I can move on. public int indexOf (int ch) { int count = 0; charNode pose = _head; if (pose == null ) { return -1; } for (pose = _head; pose!=null && pose.getNext()!='ch'; pose = pose.getNext()) { count++; } if (pose!=null) return count; else return -1; }

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  • Java - is this an idiom or pattern, behavior classes with no state

    - by Berlin Brown
    I am trying to incorporate more functional programming idioms into my java development. One pattern that I like the most and avoids side effects is building classes that have behavior but they don't necessarily have any state. The behavior is locked into the methods but they only act on the parameters passed in. The code below is code I am trying to avoid: public class BadObject { private Map<String, String> data = new HashMap<String, String>(); public BadObject() { data.put("data", "data"); } /** * Act on the data class. But this is bad because we can't * rely on the integrity of the object's state. */ public void execute() { data.get("data").toString(); } } The code below is nothing special but I am acting on the parameters and state is contained within that class. We still may run into issues with this class but that is an issue with the method and the state of the data, we can address issues in the routine as opposed to not trusting the entire object. Is this some form of idiom? Is this similar to any pattern that you use? public class SemiStatefulOOP { /** * Private class implies that I can access the members of the <code>Data</code> class * within the <code>SemiStatefulOOP</code> class and I can also access * the getData method from some other class. * * @see Test1 * */ class Data { protected int counter = 0; public int getData() { return counter; } public String toString() { return Integer.toString(counter); } } /** * Act on the data class. */ public void execute(final Data data) { data.counter++; } /** * Act on the data class. */ public void updateStateWithCallToService(final Data data) { data.counter++; } /** * Similar to CLOS (Common Lisp Object System) make instance. */ public Data makeInstance() { return new Data(); } } // End of Class // Issues with the code above: I wanted to declare the Data class private, but then I can't really reference it outside of the class: I can't override the SemiStateful class and access the private members. Usage: final SemiStatefulOOP someObject = new SemiStatefulOOP(); final SemiStatefulOOP.Data data = someObject.makeInstance(); someObject.execute(data); someObject.updateStateWithCallToService(data);

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  • iphone sdk - why is the video returned not full res?

    - by ADAM
    im developing an app for the iphone and im able to get a video using a UIImagePickerController the problem is that the video thats returned by the UIImagePickerControllerMediaURL is not full resoultion -- its only 480 x 360 as opposed to 640 x 480 like the videos that sync to my itunes. -please someone tell me this is not a limitation of the current sdk? - how can i work around it and is there a way to set the uiimage picker so its taking full res video?

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  • Base SDK Missing? No, I fixed that. Still?!

    - by Moshe
    XCode 3.2.3 Beta does not allow building for below 3.2. I opened a project that was made in an earlier XCode. For some reason, the base SDK is reported as missing even after changing it to 4.0. Other projects from earlier XCode do not have this issue. What can I do?

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  • run shell command from java

    - by Aykut
    Hi, I am working on an application an have an issue about running shell command from java application. here is the code: public String execRuntime(String cmd) { Process proc = null; int inBuffer, errBuffer; int result = 0; StringBuffer outputReport = new StringBuffer(); StringBuffer errorBuffer = new StringBuffer(); try { proc = Runtime.getRuntime().exec(cmd); } catch (IOException e) { return ""; } try { response.status = 1; result = proc.waitFor(); } catch (InterruptedException e) { return ""; } if (proc != null && null != proc.getInputStream()) { InputStream is = proc.getInputStream(); InputStream es = proc.getErrorStream(); OutputStream os = proc.getOutputStream(); try { while ((inBuffer = is.read()) != -1) { outputReport.append((char) inBuffer); } while ((errBuffer = es.read()) != -1) { errorBuffer.append((char) errBuffer); } } catch (IOException e) { return ""; } try { is.close(); is = null; es.close(); es = null; os.close(); os = null; } catch (IOException e) { return ""; } proc.destroy(); proc = null; } if (errorBuffer.length() > 0) { logger .error("could not finish execution because of error(s)."); logger.error("*** Error : " + errorBuffer.toString()); return ""; } return outputReport.toString(); } but when i try to exec command like : /export/home/test/myapp -T "some argument" myapp reads "some argument" as two seperated arguments.but I want to read "some argument" as only a argument. when i directly run this command from terminal, it executed successfully. I tried '"some argument"' ,""some argument"" , "some\ argument" but did not work for me. how can i read this argument as one argument. Thnaks.

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