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• migrating Solaris to RH: network latency issue, tcp window size & other tcp parameters

  - by Bastien

  Hello I have a client/server app (Java) that I'm migrating from Solaris to RH Linux. since I started running it in RH, I noticed some issues related to latency. I managed to isolate the problem that looks like this: client sends 5 messages (32 bytes each) in a row (same application timestamp) to the server. server echos messages. client receives replies and prints round trip time for each msg. in Solaris, all is well: I get ALL 5 replies at the same time, roughly 80ms after having sent original messages (client & server are several thousands miles away from each other: my ping RTT is 80ms, all normal). in RH, first 3 messages are echoed normally (they arrive 80ms after they've been sent), however the following 2 arrive 80ms later (so total 160ms RTT). the pattern is always the same. clearly looked like a TCP problem. on my solaris box, I had previously configured the tcp stack with 2 specific options: disable nagle algorithm globally set tcp_deferred_acks_max to 0 on RH, it's not possible to disable nagle globally, but I disabled it on all of my apps' sockets (TCP_NODELAY). so I started playing with tcpdump (on the server machine), and compared both outputs: SOLARIS: 22 2.085645 client server TCP 56150 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 23 2.085680 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=133 Win=50400 Len=0 24 2.085908 client server TCP 56150 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 25 2.085925 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=155 Win=50400 Len=0 26 2.086175 client server TCP 56150 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 27 2.086192 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=177 Win=50400 Len=0 28 2.086243 server client TCP 6006 > 56150 [PSH, ACK] Seq=106 Ack=177 Win=50400 Len=21 "MSG_1 ECHO" 29 2.086440 client server TCP 56150 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 30 2.086454 server client TCP 6006 > 56150 [ACK] Seq=127 Ack=199 Win=50400 Len=0 31 2.086659 server client TCP 6006 > 56150 [PSH, ACK] Seq=127 Ack=199 Win=50400 Len=21 "MSG_2 ECHO" 32 2.086708 client server TCP 56150 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 33 2.086721 server client TCP 6006 > 56150 [ACK] Seq=148 Ack=221 Win=50400 Len=0 34 2.086947 server client TCP 6006 > 56150 [PSH, ACK] Seq=148 Ack=221 Win=50400 Len=21 "MSG_3 ECHO" 35 2.087196 server client TCP 6006 > 56150 [PSH, ACK] Seq=169 Ack=221 Win=50400 Len=21 "MSG_4 ECHO" 36 2.087500 server client TCP 6006 > 56150 [PSH, ACK] Seq=190 Ack=221 Win=50400 Len=21 "MSG_5 ECHO" 37 2.165390 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 38 2.166314 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=190 Win=66588 Len=0 39 2.364135 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 REDHAT: 17 2.081163 client server TCP 55879 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 18 2.081178 server client TCP 6006 > 55879 [ACK] Seq=106 Ack=133 Win=5888 Len=0 19 2.081297 server client TCP 6006 > 55879 [PSH, ACK] Seq=106 Ack=133 Win=5888 Len=21 "MSG_1 ECHO" 20 2.081711 client server TCP 55879 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 21 2.081761 client server TCP 55879 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 22 2.081846 server client TCP 6006 > 55879 [PSH, ACK] Seq=127 Ack=177 Win=5888 Len=21 "MSG_2 ECHO" 23 2.081995 server client TCP 6006 > 55879 [PSH, ACK] Seq=148 Ack=177 Win=5888 Len=21 "MSG_3 ECHO" 24 2.082011 client server TCP 55879 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 25 2.082362 client server TCP 55879 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 26 2.082377 server client TCP 6006 > 55879 [ACK] Seq=169 Ack=221 Win=5888 Len=0 27 2.171003 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 28 2.171019 server client TCP 6006 > 55879 [PSH, ACK] Seq=169 Ack=221 Win=5888 Len=42 "MSG_4 ECHO + MSG_5 ECHO" 29 2.257498 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 so, I got confirmation things are not working correctly for RH: packet 28 is sent TOO LATE, it looks like the server is waiting for packet 27's ACK before doing anything. seems to me it's the most likely reason... then I realized that the "Win" parameters are different on Solaris & RH dumps: 50400 on Solaris, only 5888 on RH. that's another hint... I read the doc about the slide window & buffer window, and played around with the rcvBuffer & sendBuffer in java on my sockets, but never managed to change this 5888 value to anything else (I checked each time directly with tcpdump). does anybody know how to do this ? I'm having a hard time getting definitive information, as in some cases there's "auto-negotiation" that I might need to bypass, etc... I eventually managed to get only partially rid of my initial problem by setting the "tcp_slow_start_after_idle" parameter to 0 on RH, but it did not change the "win" parameter at all. the same problem was there for the first 4 groups of 5 messages, with TCP retransmission & TCP Dup ACK in tcpdump, then the problem disappeared altogether for all following groups of 5 messages. It doesn't seem like a very clean and/or generic solution to me. I'd really like to reproduce the exact same conditions under both OSes. I'll keep researching, but any help from TCP gurus would be greatly appreciated ! thanks !

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• .exe is not created when using launch4j and maven

  - by Ismail Sen

  I'm trying to create an exe file for my JAVA project using launch4j and Maven. Here is my pom.xml <build> <pluginManagement> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.0</version> <configuration> <source>1.7</source> <target>1.7</target> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-jar-plugin</artifactId> <version>2.3.2</version> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-assembly-plugin</artifactId> <version>2.4</version> <configuration> <descriptorRefs> <descriptortRef>jar-with-dependencies</descriptortRef> </descriptorRefs> <archive> <manifest> <mainClass>dev.main.App</mainClass> </manifest> </archive> </configuration> <executions> <execution> <id>make-assembly</id> <phase>package</phase> <goals> <goal>single</goal> </goals> </execution> </executions> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <version>1.7.1</version> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> </execution> </executions> <configuration> <shadedArtifactAttached>true</shadedArtifactAttached> <shadedClassifierName>shaded</shadedClassifierName> <transformers> <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"> <mainClass>dev.main.App</mainClass> </transformer> </transformers> </configuration> </plugin> <plugin> <groupId>com.akathist.maven.plugins.launch4j</groupId> <artifactId>launch4j-maven-plugin</artifactId> <version>1.5.1</version> <executions> <execution> <id>l4j-clui</id> <phase>package</phase> <goals> <goal>launch4j</goal> </goals> <configuration> <headerType>console</headerType> <jar>${project.build.directory}/target/App-jar-with-dependencies.jar</jar> <outfile>${project.build.directory}/target/App.exe</outfile> <downloadUrl>http://java.com/download</downloadUrl> <classPath> <mainClass>dev.main.App</mainClass> </classPath> <jre> <minVersion>1.6.0</minVersion> <jdkPreference>preferJre</jdkPreference> </jre> <versionInfo> <fileVersion>1.0.0.0</fileVersion> <txtFileVersion>${project.version}</txtFileVersion> <fileDescription>${project.name}</fileDescription> <copyright>C</copyright> <productVersion>1.0.0.0</productVersion> <txtProductVersion>1.0.0.0</txtProductVersion> <productName>${project.name}</productName> <internalName>AppName</internalName> <originalFilename>App.exe</originalFilename> </versionInfo> </configuration> </execution> </executions> </plugin> </plugins> </pluginManagement> </build> I run : mvn clean compile assembly:single to create my jar app with all Maven dependencies. To create the .exe I do : mvn package but nothing is created under target folder. Am I missing a goal or a configuration ? Ismail

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• How to connect to bluetoothbee device using j2me?

  - by user1500412

  I developed a simple bluetooth connection application in j2me. I try it on emulator, both server and client can found each other, but when I deploy the application to blackberry mobile phone and connect to a bluetoothbee device it says service search no records. What could it be possibly wrong? is it j2me can not find a service in bluetoothbee? The j2me itself succeed to found the bluetoothbee device, but why it can not find the service? My code is below. What I don't understand is the UUID? how to set UUID for unknown source? since I didn't know the UUID for the bluetoothbee device. class SearchingDevice extends Canvas implements Runnable,CommandListener,DiscoveryListener{ //...... public SearchingDevice(MenuUtama midlet, Display display){ this.display = display; this.midlet = midlet; t = new Thread(this); t.start(); timer = new Timer(); task = new TestTimerTask(); /*--------------------Device List------------------------------*/ select = new Command("Pilih",Command.OK,0); back = new Command("Kembali",Command.BACK,0); btDevice = new List("Pilih Device",Choice.IMPLICIT); btDevice.addCommand(select); btDevice.addCommand(back); btDevice.setCommandListener(this); /*------------------Input Form---------------------------------*/ formInput = new Form("Form Input"); nama = new TextField("Nama","",50,TextField.ANY); umur = new TextField("Umur","",50,TextField.ANY); measure = new Command("Ukur",Command.SCREEN,0); gender = new ChoiceGroup("Jenis Kelamin",Choice.EXCLUSIVE); formInput.addCommand(back); formInput.addCommand(measure); gender.append("Pria", null); gender.append("Wanita", null); formInput.append(nama); formInput.append(umur); formInput.append(gender); formInput.setCommandListener(this); /*---------------------------------------------------------------*/ findDevice(); } /*----------------Gambar screen searching device---------------------------------*/ protected void paint(Graphics g) { g.setColor(0,0,0); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(255,255,255); g.drawString("Mencari Device", 20, 20, Graphics.TOP|Graphics.LEFT); if(this.counter == 1){ g.setColor(255,115,200); g.fillRect(20, 100, 20, 20); } if(this.counter == 2){ g.setColor(255,115,200); g.fillRect(20, 100, 20, 20); g.setColor(100,255,255); g.fillRect(60, 80, 20, 40); } if(this.counter == 3){ g.setColor(255,115,200); g.fillRect(20, 100, 20, 20); g.setColor(100,255,255); g.fillRect(60, 80, 20, 40); g.setColor(255,115,200); g.fillRect(100, 60, 20, 60); } if(this.counter == 4){ g.setColor(255,115,200); g.fillRect(20, 100, 20, 20); g.setColor(100,255,255); g.fillRect(60, 80, 20, 40); g.setColor(255,115,200); g.fillRect(100, 60, 20, 60); g.setColor(100,255,255); g.fillRect(140, 40, 20, 80); //display.callSerially(this); } } /*--------- Running Searching Screen ----------------------------------------------*/ public void run() { while(run){ this.counter++; if(counter > 4){ this.counter = 1; } try { Thread.sleep(1000); } catch (InterruptedException ex) { System.out.println("interrupt"+ex.getMessage()); } repaint(); } } /*-----------------------------cari device bluetooth yang -------------------*/ public void findDevice(){ try { devices = new java.util.Vector(); local = LocalDevice.getLocalDevice(); agent = local.getDiscoveryAgent(); local.setDiscoverable(DiscoveryAgent.GIAC); agent.startInquiry(DiscoveryAgent.GIAC, this); } catch (BluetoothStateException ex) { System.out.println("find device"+ex.getMessage()); } } /*-----------------------------jika device ditemukan--------------------------*/ public void deviceDiscovered(RemoteDevice rd, DeviceClass dc) { devices.addElement(rd); } /*--------------Selesai tes koneksi ke bluetooth server--------------------------*/ public void inquiryCompleted(int param) { switch(param){ case DiscoveryListener.INQUIRY_COMPLETED: //inquiry completed normally if(devices.size()>0){ //at least one device has been found services = new java.util.Vector(); this.findServices((RemoteDevice)devices.elementAt(0)); this.run = false; do_alert("Inquiry completed",4000); }else{ do_alert("No device found in range",4000); } break; case DiscoveryListener.INQUIRY_ERROR: do_alert("Inquiry error",4000); break; case DiscoveryListener.INQUIRY_TERMINATED: do_alert("Inquiry canceled",4000); break; } } /*-------------------------------Cari service bluetooth server----------------------------*/ public void findServices(RemoteDevice device){ try { // int[] attributes = {0x100,0x101,0x102}; UUID[] uuids = new UUID[1]; //alamat server uuids[0] = new UUID("F0E0D0C0B0A000908070605040302010",false); //uuids[0] = new UUID("8841",true); //menyiapkan device lokal local = LocalDevice.getLocalDevice(); agent = local.getDiscoveryAgent(); //mencari service dari server agent.searchServices(null, uuids, device, this); //server = (StreamConnectionNotifies)Connector.open(url.toString()); } catch (BluetoothStateException ex) { // ex.printStackTrace(); System.out.println("Errorx"+ex.getMessage()); } } /*---------------------------Pencarian service selesai------------------------*/ public void serviceSearchCompleted(int transID, int respCode) { switch(respCode){ case DiscoveryListener.SERVICE_SEARCH_COMPLETED: if(currentDevice == devices.size() - 1){ if(services.size() > 0){ this.run = false; display.setCurrent(btDevice); do_alert("Service found",4000); }else{ do_alert("The service was not found",4000); } }else{ currentDevice++; this.findServices((RemoteDevice)devices.elementAt(currentDevice)); } break; case DiscoveryListener.SERVICE_SEARCH_DEVICE_NOT_REACHABLE: do_alert("Device not Reachable",4000); break; case DiscoveryListener.SERVICE_SEARCH_ERROR: do_alert("Service search error",4000); break; case DiscoveryListener.SERVICE_SEARCH_NO_RECORDS: do_alert("No records return",4000); break; case DiscoveryListener.SERVICE_SEARCH_TERMINATED: do_alert("Inquiry canceled",4000); break; } } public void servicesDiscovered(int i, ServiceRecord[] srs) { for(int x=0; x<srs.length;x++) services.addElement(srs[x]); try { btDevice.append(((RemoteDevice)devices.elementAt(currentDevice)).getFriendlyName(false),null); } catch (IOException ex) { System.out.println("service discover"+ex.getMessage()); } } public void do_alert(String msg, int time_out){ if(display.getCurrent() instanceof Alert){ ((Alert)display.getCurrent()).setString(msg); ((Alert)display.getCurrent()).setTimeout(time_out); }else{ Alert alert = new Alert("Bluetooth"); alert.setString(msg); alert.setTimeout(time_out); display.setCurrent(alert); } } private String getData(){ System.out.println("getData"); String cmd=""; try { ServiceRecord service = (ServiceRecord)services.elementAt(btDevice.getSelectedIndex()); String url = service.getConnectionURL(ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false); conn = (StreamConnection)Connector.open(url); DataInputStream in = conn.openDataInputStream(); int i=0; timer.schedule(task, 15000); char c1; while(time){ //while(((c1 = in.readChar())>0) && (c1 != '\n')){ //while(((c1 = in.readChar())>0) ){ c1 = in.readChar(); cmd = cmd + c1; //System.out.println(c1); // } } System.out.print("cmd"+cmd); if(time == false){ in.close(); conn.close(); } } catch (IOException ex) { System.err.println("Cant read data"+ex); } return cmd; } //timer task fungsinya ketika telah mencapai waktu yg dijadwalkan putus koneksi private static class TestTimerTask extends TimerTask{ public TestTimerTask() { } public void run() { time = false; } } }

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• Traditional IO vs memory-mapped

  - by Senne

  I'm trying to illustrate the difference in performance between traditional IO and memory mapped files in java to students. I found an example somewhere on internet but not everything is clear to me, I don't even think all steps are nececery. I read a lot about it here and there but I'm not convinced about a correct implementation of neither of them. The code I try to understand is: public class FileCopy{ public static void main(String args[]){ if (args.length < 1){ System.out.println(" Wrong usage!"); System.out.println(" Correct usage is : java FileCopy <large file with full path>"); System.exit(0); } String inFileName = args[0]; File inFile = new File(inFileName); if (inFile.exists() != true){ System.out.println(inFileName + " does not exist!"); System.exit(0); } try{ new FileCopy().memoryMappedCopy(inFileName, inFileName+".new" ); new FileCopy().customBufferedCopy(inFileName, inFileName+".new1"); }catch(FileNotFoundException fne){ fne.printStackTrace(); }catch(IOException ioe){ ioe.printStackTrace(); }catch (Exception e){ e.printStackTrace(); } } public void memoryMappedCopy(String fromFile, String toFile ) throws Exception{ long timeIn = new Date().getTime(); // read input file RandomAccessFile rafIn = new RandomAccessFile(fromFile, "rw"); FileChannel fcIn = rafIn.getChannel(); ByteBuffer byteBuffIn = fcIn.map(FileChannel.MapMode.READ_WRITE, 0,(int) fcIn.size()); fcIn.read(byteBuffIn); byteBuffIn.flip(); RandomAccessFile rafOut = new RandomAccessFile(toFile, "rw"); FileChannel fcOut = rafOut.getChannel(); ByteBuffer writeMap = fcOut.map(FileChannel.MapMode.READ_WRITE,0,(int) fcIn.size()); writeMap.put(byteBuffIn); long timeOut = new Date().getTime(); System.out.println("Memory mapped copy Time for a file of size :" + (int) fcIn.size() +" is "+(timeOut-timeIn)); fcOut.close(); fcIn.close(); } static final int CHUNK_SIZE = 100000; static final char[] inChars = new char[CHUNK_SIZE]; public static void customBufferedCopy(String fromFile, String toFile) throws IOException{ long timeIn = new Date().getTime(); Reader in = new FileReader(fromFile); Writer out = new FileWriter(toFile); while (true) { synchronized (inChars) { int amountRead = in.read(inChars); if (amountRead == -1) { break; } out.write(inChars, 0, amountRead); } } long timeOut = new Date().getTime(); System.out.println("Custom buffered copy Time for a file of size :" + (int) new File(fromFile).length() +" is "+(timeOut-timeIn)); in.close(); out.close(); } } When exactly is it nececary to use RandomAccessFile? Here it is used to read and write in the memoryMappedCopy, is it actually nececary just to copy a file at all? Or is it a part of memorry mapping? In customBufferedCopy, why is synchronized used here? I also found a different example that -should- test the performance between the 2: public class MappedIO { private static int numOfInts = 4000000; private static int numOfUbuffInts = 200000; private abstract static class Tester { private String name; public Tester(String name) { this.name = name; } public long runTest() { System.out.print(name + ": "); try { long startTime = System.currentTimeMillis(); test(); long endTime = System.currentTimeMillis(); return (endTime - startTime); } catch (IOException e) { throw new RuntimeException(e); } } public abstract void test() throws IOException; } private static Tester[] tests = { new Tester("Stream Write") { public void test() throws IOException { DataOutputStream dos = new DataOutputStream( new BufferedOutputStream( new FileOutputStream(new File("temp.tmp")))); for(int i = 0; i < numOfInts; i++) dos.writeInt(i); dos.close(); } }, new Tester("Mapped Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile("temp.tmp", "rw") .getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); for(int i = 0; i < numOfInts; i++) ib.put(i); fc.close(); } }, new Tester("Stream Read") { public void test() throws IOException { DataInputStream dis = new DataInputStream( new BufferedInputStream( new FileInputStream("temp.tmp"))); for(int i = 0; i < numOfInts; i++) dis.readInt(); dis.close(); } }, new Tester("Mapped Read") { public void test() throws IOException { FileChannel fc = new FileInputStream( new File("temp.tmp")).getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_ONLY, 0, fc.size()) .asIntBuffer(); while(ib.hasRemaining()) ib.get(); fc.close(); } }, new Tester("Stream Read/Write") { public void test() throws IOException { RandomAccessFile raf = new RandomAccessFile( new File("temp.tmp"), "rw"); raf.writeInt(1); for(int i = 0; i < numOfUbuffInts; i++) { raf.seek(raf.length() - 4); raf.writeInt(raf.readInt()); } raf.close(); } }, new Tester("Mapped Read/Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile( new File("temp.tmp"), "rw").getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); ib.put(0); for(int i = 1; i < numOfUbuffInts; i++) ib.put(ib.get(i - 1)); fc.close(); } } }; public static void main(String[] args) { for(int i = 0; i < tests.length; i++) System.out.println(tests[i].runTest()); } } I more or less see whats going on, my output looks like this: Stream Write: 653 Mapped Write: 51 Stream Read: 651 Mapped Read: 40 Stream Read/Write: 14481 Mapped Read/Write: 6 What is makeing the Stream Read/Write so unbelievably long? And as a read/write test, to me it looks a bit pointless to read the same integer over and over (if I understand well what's going on in the Stream Read/Write) Wouldn't it be better to read int's from the previously written file and just read and write ints on the same place? Is there a better way to illustrate it? I've been breaking my head about a lot of these things for a while and I just can't get the whole picture..

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• Null-free "maps": Is a callback solution slower than tryGet()?

  - by David Moles

  In comments to "How to implement List, Set, and Map in null free design?", Steven Sudit and I got into a discussion about using a callback, with handlers for "found" and "not found" situations, vs. a tryGet() method, taking an out parameter and returning a boolean indicating whether the out parameter had been populated. Steven maintained that the callback approach was more complex and almost certain to be slower; I maintained that the complexity was no greater and the performance at worst the same. But code speaks louder than words, so I thought I'd implement both and see what I got. The original question was fairly theoretical with regard to language ("And for argument sake, let's say this language don't even have null") -- I've used Java here because that's what I've got handy. Java doesn't have out parameters, but it doesn't have first-class functions either, so style-wise, it should suck equally for both approaches. (Digression: As far as complexity goes: I like the callback design because it inherently forces the user of the API to handle both cases, whereas the tryGet() design requires callers to perform their own boilerplate conditional check, which they could forget or get wrong. But having now implemented both, I can see why the tryGet() design looks simpler, at least in the short term.) First, the callback example: class CallbackMap<K, V> { private final Map<K, V> backingMap; public CallbackMap(Map<K, V> backingMap) { this.backingMap = backingMap; } void lookup(K key, Callback<K, V> handler) { V val = backingMap.get(key); if (val == null) { handler.handleMissing(key); } else { handler.handleFound(key, val); } } } interface Callback<K, V> { void handleFound(K key, V value); void handleMissing(K key); } class CallbackExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; private Callback<String, String> handler; public CallbackExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); handler = new Callback<String, String>() { public void handleFound(String key, String value) { found.add(key + ": " + value); } public void handleMissing(String key) { missing.add(key); } }; } void test() { CallbackMap<String, String> cbMap = new CallbackMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; cbMap.lookup(key, handler); } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } Now, the tryGet() example -- as best I understand the pattern (and I might well be wrong): class TryGetMap<K, V> { private final Map<K, V> backingMap; public TryGetMap(Map<K, V> backingMap) { this.backingMap = backingMap; } boolean tryGet(K key, OutParameter<V> valueParam) { V val = backingMap.get(key); if (val == null) { return false; } valueParam.value = val; return true; } } class OutParameter<V> { V value; } class TryGetExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; public TryGetExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); } void test() { TryGetMap<String, String> tgMap = new TryGetMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; OutParameter<String> out = new OutParameter<String>(); if (tgMap.tryGet(key, out)) { found.add(key + ": " + out.value); } else { missing.add(key); } } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } And finally, the performance test code: public static void main(String[] args) { int size = 200000; Map<String, String> map = new HashMap<String, String>(); for (int i = 0; i < size; i++) { String val = (i % 5 == 0) ? null : "value" + i; map.put("key" + i, val); } long totalCallback = 0; long totalTryGet = 0; int iterations = 20; for (int i = 0; i < iterations; i++) { { TryGetExample tryGet = new TryGetExample(map); long tryGetStart = System.currentTimeMillis(); tryGet.test(); totalTryGet += (System.currentTimeMillis() - tryGetStart); } System.gc(); { CallbackExample callback = new CallbackExample(map); long callbackStart = System.currentTimeMillis(); callback.test(); totalCallback += (System.currentTimeMillis() - callbackStart); } System.gc(); } System.out.println("Avg. callback: " + (totalCallback / iterations)); System.out.println("Avg. tryGet(): " + (totalTryGet / iterations)); } On my first attempt, I got 50% worse performance for callback than for tryGet(), which really surprised me. But, on a hunch, I added some garbage collection, and the performance penalty vanished. This fits with my instinct, which is that we're basically talking about taking the same number of method calls, conditional checks, etc. and rearranging them. But then, I wrote the code, so I might well have written a suboptimal or subconsicously penalized tryGet() implementation. Thoughts?

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• How to convert this procedural programming to object-oriented programming?

  - by manus91

  I have a source code that is needed to be converted by creating classes, objects and methods. So far, I've just done by converting the initial main into a separate class. But I don't know what to do with constructor and which variables are supposed to be private. This is the code : import java.util.*; public class Card{ private static void shuffle(int[][] cards){ List<Integer> randoms = new ArrayList<Integer>(); Random randomizer = new Random(); for(int i = 0; i < 8;) { int r = randomizer.nextInt(8)+1; if(!randoms.contains(r)) { randoms.add(r); i++; } } List<Integer> clonedList = new ArrayList<Integer>(); clonedList.addAll(randoms); Collections.shuffle(clonedList); randoms.addAll(clonedList); Collections.shuffle(randoms); int i=0; for(int r=0; r < 4; r++){ for(int c=0; c < 4; c++){ cards[r][c] = randoms.get(i); i++; } } } public static void play() throws InterruptedException { int ans = 1; int preview; int r1,c1,r2,c2; int[][] cards = new int[4][4]; boolean[][] cardstatus = new boolean[4][4]; boolean gameover = false; int moves; Scanner input = new Scanner(System.in); do{ moves = 0; shuffle(cards); System.out.print("Enter the time(0 to 5) in seconds for the preview of the answer : "); preview = input.nextInt(); while((preview<0) || (preview>5)){ System.out.print("Invalid time!! Re-enter time(0 - 5) : "); preview = input.nextInt(); } preview = 1000*preview; System.out.println(" "); for (int i =0; i<4;i++){ for (int j=0;j<4;j++){ System.out.print(cards[i][j]); System.out.print(" "); } System.out.println(""); System.out.println(""); } Thread.sleep(preview); for(int b=0;b<25;b++){ System.out.println(" "); } for(int r=0;r<4;r++){ for(int c=0;c<4;c++){ System.out.print("*"); System.out.print(" "); cardstatus[r][c] = false; } System.out.println(""); System.out.println(" "); } System.out.println(""); do{ do{ System.out.print("Please insert the first card row : "); r1 = input.nextInt(); while((r1<1) || (r1>4)){ System.out.print("Invalid coordinate!! Re-enter first card row : "); r1 = input.nextInt(); } System.out.print("Please insert the first card column : "); c1 = input.nextInt(); while((c1<1) || (c1>4)){ System.out.print("Invalid coordinate!! Re-enter first card column : "); c1 = input.nextInt(); } if(cardstatus[r1-1][c1-1] == true){ System.out.println("The card is already flipped!! Select another card."); System.out.println(""); } }while(cardstatus[r1-1][c1-1] != false); do{ System.out.print("Please insert the second card row : "); r2 = input.nextInt(); while((r2<1) || (r2>4)){ System.out.print("Invalid coordinate!! Re-enter second card row : "); r2 = input.nextInt(); } System.out.print("Please insert the second card column : "); c2 = input.nextInt(); while((c2<1) || (c2>4)){ System.out.print("Invalid coordinate!! Re-enter second card column : "); c2 = input.nextInt(); } if(cardstatus[r2-1][c2-1] == true){ System.out.println("The card is already flipped!! Select another card."); } if((r1==r2)&&(c1==c2)){ System.out.println("You can't select the same card twice!!"); continue; } }while(cardstatus[r2-1][c2-1] != false); r1--; c1--; r2--; c2--; System.out.println(""); System.out.println(""); System.out.println(""); for(int r=0;r<4;r++){ for(int c=0;c<4;c++){ if((r==r1)&&(c==c1)){ System.out.print(cards[r][c]); System.out.print(" "); } else if((r==r2)&&(c==c2)){ System.out.print(cards[r][c]); System.out.print(" "); } else if(cardstatus[r][c] == true){ System.out.print(cards[r][c]); System.out.print(" "); } else{ System.out.print("*"); System.out.print(" "); } } System.out.println(" "); System.out.println(" "); } System.out.println(""); if(cards[r1][c1] == cards[r2][c2]){ System.out.println("Cards Matched!!"); cardstatus[r1][c1] = true; cardstatus[r2][c2] = true; } else{ System.out.println("No cards match!!"); } Thread.sleep(2000); for(int b=0;b<25;b++){ System.out.println(""); } for(int r=0;r<4;r++){ for(int c=0;c<4;c++){ if(cardstatus[r][c] == true){ System.out.print(cards[r][c]); System.out.print(" "); } else{ System.out.print("*"); System.out.print(" "); } } System.out.println(""); System.out.println(" "); } System.out.println(""); System.out.println(""); System.out.println(""); gameover = true; for(int r=0;r<4;r++){ for( int c=0;c<4;c++){ if(cardstatus[r][c]==false){ gameover = false; break; } } if(gameover==false){ break; } } moves++; }while(gameover != true); System.out.println("Congratulations, you won!!"); System.out.println("It required " + moves + " moves to finish it."); System.out.println(""); System.out.print("Would you like to play again? (1=Yes / 0=No) : "); ans = input.nextInt(); }while(ans == 1); } } The main class is: import java.util.*; public class PlayCard{ public static void main(String[] args) throws InterruptedException{ Card game = new Card(); game.play(); } } Should I simplify the Card class by creating other classes? Through this code, my javadoc has no constructtor. So i need help on this!

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• How can I update a Jtextarea once? (mysql side-?)

  - by user1294196

  Ok what I've been trying to do is figure out how to make it so when I press the search button on my program the code that is currently just being printed to the console will print to the text area I have. I can't figure out how to do this and I've searched google and still found no answer. And while I'm at it if anyone could help me figure out how to send this same line of information to a mysql database that would help greatly. package GTE; import java.awt.EventQueue; public class GTE { private JFrame frmGte; public String hashq = "..."; public String twtresults; public int refresh = 1; public static void main(String[] args) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { try { GTE window = new GTE(); window.frmGte.setVisible(true); } catch (Exception e) {} } }); } /** * Create the application. * @throws IOException * @throws FontFormatException */ public GTE(){ try { initialize(); } catch (FontFormatException e) {} catch (IOException e) {} } /** * Initialize the contents of the frame. * @throws IOException * @throws FontFormatException */ private void initialize() throws FontFormatException, IOException { frmGte = new JFrame(); frmGte.setResizable(false); frmGte.setTitle("GTE"); frmGte.setBounds(100, 100, 450, 390); frmGte.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); GridBagLayout gridBagLayout = new GridBagLayout(); gridBagLayout.columnWidths = new int[]{434, 0}; gridBagLayout.rowHeights = new int[]{21, 0, 0, 0, 0, 0, 0, 0, 0}; gridBagLayout.columnWeights = new double[]{0.0, Double.MIN_VALUE}; gridBagLayout.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE}; frmGte.getContentPane().setLayout(gridBagLayout); JLabel GTETitle = new JLabel("Personal Tweet Extractor"); InputStream is = this.getClass().getResourceAsStream("ultraviolentbb_reg.ttf"); Font GTEFont = Font.createFont(Font.TRUETYPE_FONT,is); Font f = GTEFont.deriveFont(24f); GTETitle.setFont(f); GTETitle.setHorizontalAlignment(SwingConstants.CENTER); GridBagConstraints gbc_GTETitle = new GridBagConstraints(); gbc_GTETitle.insets = new Insets(0, 0, 5, 0); gbc_GTETitle.anchor = GridBagConstraints.NORTH; gbc_GTETitle.fill = GridBagConstraints.HORIZONTAL; gbc_GTETitle.gridx = 0; gbc_GTETitle.gridy = 0; frmGte.getContentPane().add(GTETitle, gbc_GTETitle); Label label_2 = new Label("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"); GridBagConstraints gbc_label_2 = new GridBagConstraints(); gbc_label_2.insets = new Insets(0, 0, 5, 0); gbc_label_2.gridx = 0; gbc_label_2.gridy = 1; frmGte.getContentPane().add(label_2, gbc_label_2); JLabel SearchTweets = new JLabel("Search For Tweets With" + hashq + ":"); GridBagConstraints gbc_SearchTweets = new GridBagConstraints(); gbc_SearchTweets.insets = new Insets(0, 0, 5, 0); gbc_SearchTweets.gridx = 0; gbc_SearchTweets.gridy = 2; frmGte.getContentPane().add(SearchTweets, gbc_SearchTweets); JLabel label = new JLabel("#"); GridBagConstraints gbc_label = new GridBagConstraints(); gbc_label.insets = new Insets(0, 0, 5, 0); gbc_label.gridx = 0; gbc_label.gridy = 3; frmGte.getContentPane().add(label, gbc_label); JButton Search = new JButton("Start Search"); Search.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { TS(hashq); GTE.this.refresh = 0; try { nulll dialog = new nulll(); dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE); dialog.setVisible(true); } catch (Exception e) {} } public void TS(String hashtag){ Twitter twitter = new TwitterFactory().getInstance(); try { System.out.println(hashtag); QueryResult result = twitter.search(new Query("#" + hashtag)); List<Tweet> tweets = result.getTweets(); for (Tweet tweet : tweets) { System.out.println("@" + tweet.getFromUser() + " : " + tweet.getText()); GTE.this.twtresults = ("@" + tweet.getFromUser() + " : " + tweet.getText()); } } catch (TwitterException te) { te.printStackTrace(); System.out.println("Failed to search tweets: " + te.getMessage()); System.exit(-1); } } }); TextField textField = new TextField(); textField.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { GTE.this.hashq = evt.getActionCommand(); } }); GridBagConstraints gbc_textField = new GridBagConstraints(); gbc_textField.ipadx = 99; gbc_textField.insets = new Insets(0, 0, 5, 0); gbc_textField.gridx = 0; gbc_textField.gridy = 4; frmGte.getContentPane().add(textField, gbc_textField); GridBagConstraints gbc_Search = new GridBagConstraints(); gbc_Search.insets = new Insets(0, 0, 5, 0); gbc_Search.gridx = 0; gbc_Search.gridy = 5; frmGte.getContentPane().add(Search, gbc_Search); Label label_1 = new Label("Search Results For Tweets With"); GridBagConstraints gbc_label_1 = new GridBagConstraints(); gbc_label_1.insets = new Insets(0, 0, 5, 0); gbc_label_1.gridx = 0; gbc_label_1.gridy = 6; frmGte.getContentPane().add(label_1, gbc_label_1); TextArea textArea = new TextArea(); textArea.setText(twtresults); textArea.setEditable(false); GridBagConstraints gbc_textArea = new GridBagConstraints(); gbc_textArea.gridx = 0; gbc_textArea.gridy = 7; frmGte.getContentPane().add(textArea, gbc_textArea); JMenuBar menuBar = new JMenuBar(); frmGte.setJMenuBar(menuBar); JMenu Filemenu = new JMenu("File"); menuBar.add(Filemenu); JMenuItem Exititem = new JMenuItem("Exit"); Exititem.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { System.exit(0); } }); Filemenu.add(Exititem); JMenu Helpmenu = new JMenu("Help"); menuBar.add(Helpmenu); JMenuItem Aboutitem = new JMenuItem("About"); Helpmenu.add(Aboutitem); } }

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• Change font size in ListView - Android/Eclipse

  - by Soren

  How can I change the font size in a ListView element? In my main.xml file, I have tried several different values in for android:textSize (pt,px,sp,dp) and nothing seems to change it. Here is what I have currently for the in my main.xml: <ListView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@android:id/list" android:textColor="#ffffff" android:background="#000080" android:layout_width="fill_parent" android:layout_height="wrap_content" android:clickable="true" android:dividerHeight="1px" android:layout_marginTop="5px" android:textSize="8px"/> Here is my Java: package com.SorenWinslow.TriumphHistory; import android.app.ListActivity; import android.os.Bundle; import android.widget.ArrayAdapter; public class TriumphHistory extends ListActivity { String[] HistoryList; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ArrayAdapter<String> adapter; HistoryList = getResources().getStringArray(R.array.history); adapter = new ArrayAdapter<String> (this,android.R.layout.simple_list_item_1,HistoryList); setListAdapter(adapter); } }

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• faster implementation of sum ( for Codility test )

  - by Oscar Reyes

  How can the following simple implementation of sum be faster? private long sum( int [] a, int begin, int end ) { if( a == null ) { return 0; } long r = 0; for( int i = begin ; i < end ; i++ ) { r+= a[i]; } return r; } EDIT Background is in order. Reading latest entry on coding horror, I came to this site: http://codility.com which has this interesting programming test. Anyway, I got 60 out of 100 in my submission, and basically ( I think ) is because this implementation of sum, because those parts where I failed are the performance parts. I'm getting TIME_OUT_ERROR's So, I was wondering if an optimization in the algorithm is possible. So, no built in functions or assembly would be allowed. This my be done in C, C++, C#, Java or pretty much in any other. EDIT As usual, mmyers was right. I did profile the code and I saw most of the time was spent on that function, but I didn't understand why. So what I did was to throw away my implementation and start with a new one. This time I've got an optimal solution [ according to San Jacinto O(n) -see comments to MSN below - ] This time I've got 81% on Codility which I think is good enough. The problem is that I didn't take the 30 mins. but around 2 hrs. but I guess that leaves me still as a good programmer, for I could work on the problem until I found an optimal solution: Here's my result. I never understood what is those "combinations of..." nor how to test "extreme_first"

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• Merge method in MergeSort Algorithm .

  - by Tony

  I've seen many mergeSort implementations .Here is the version in Data Structures and Algorithms in Java (2nd Edition) by Robert Lafore : private void recMergeSort(long[] workSpace, int lowerBound,int upperBound) { if(lowerBound == upperBound) // if range is 1, return; // no use sorting else { // find midpoint int mid = (lowerBound+upperBound) / 2; // sort low half recMergeSort(workSpace, lowerBound, mid); // sort high half recMergeSort(workSpace, mid+1, upperBound); // merge them merge(workSpace, lowerBound, mid+1, upperBound); } // end else } // end recMergeSort() private void merge(long[] workSpace, int lowPtr, int highPtr, int upperBound) { int j = 0; // workspace index int lowerBound = lowPtr; int mid = highPtr-1; int n = upperBound-lowerBound+1; // # of items while(lowPtr <= mid && highPtr <= upperBound) if( theArray[lowPtr] < theArray[highPtr] ) workSpace[j++] = theArray[lowPtr++]; else workSpace[j++] = theArray[highPtr++]; while(lowPtr <= mid) workSpace[j++] = theArray[lowPtr++]; while(highPtr <= upperBound) workSpace[j++] = theArray[highPtr++]; for(j=0; j<n; j++) theArray[lowerBound+j] = workSpace[j]; } // end merge() One interesting thing about merge method is that , almost all the implementations didn't pass the lowerBound parameter to merge method . lowerBound is calculated in the merge . This is strange , since lowerPtr = mid + 1 ; lowerBound = lowerPtr -1 ; that means lowerBound = mid ; Why the author didn't pass mid to merge like merge(workSpace, lowerBound,mid, mid+1, upperBound); ? I think there must be a reason , otherwise I can't understand why an algorithm older than half a center ,and have all coincident in the such little detail.

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• Retrieve GWT radiobutton value in servlet

  - by Florian d'Erfurth

  Hi, I'm having a headache figuring how to retrieve the gwt Radio Buttons values in the server side. Here is my UiBinder form: <g:FormPanel ui:field="form"><g:VerticalPanel ui:field="fruitPanel"> <g:RadioButton name="fruit">apple</g:RadioButton> <g:RadioButton name="fruit">banana</g:RadioButton> <g:SubmitButton>Submit</g:SubmitButton> ... Here is how i initialize the form: form.setAction("/submit"); form.setMethod(FormPanel.METHOD_POST); So i though i would have to do this on the servlet: fruit = req.getParameter("fruit") But of course this doesn't work, parameter fruit doesn't exist :/ Edit: Ok i get parameter fruit but it's always "on" I also did try to add the radio button in java with: RadioButton rb0 = new RadioButton("fruit", "apple"); RadioButton rb1 = new RadioButton("fruit", "banana"); fruitPanel.add(rb0); fruitPanel.add(rb1); So how should i do?

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• Wicket: stateless AJAX behaviors in stateful page without serialization

  - by mschayna

  I have pretty stateful page with plenty of AJAX components. Most of these components have behaviors, which renders JavaScript code for calling AJAX requests to Java code. Because page isn't stateless, each request causes serialization of page. So far so good. But some of these AJAX requests doesn't change page ever, so serialization of page isn't necessary. For example it is forward caching data for (home-brewed) datagrid component. These requests are calling continuously and serialization of page during each request causes delays. There are some projects for stateless wicket components out there, e.g. wicket-stateless, but it solves another situation -- request of stateless components are processed on new instances of stateless pages. I want to process requests on existing stateful page instance but without serialization. I have tried to implement this in my own RequestCycleProcessor.resolve(), but I hung on searching for page from requestParameters because Session.getPage() always touches page and it causes serialization after request processing. Is there any example, idea, whatever for implementing this in Wicket? Hope it's understandable :)

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• How to use JasperDesignViewer to preview a JasperReport?

  - by Jonas

  I'm trying to use JasperReports for the first time, and have written a "Hello World"-document. But I don't know how I can preview my document with JasperDesignViewer. My .jrxml-file compiles fine to a .jasper-file. How do I call JasperDesignViewer? I'm not using Ant. My Java code: import net.sf.jasperreports.engine.JRException; import net.sf.jasperreports.engine.JasperCompileManager; import net.sf.jasperreports.view.JasperDesignViewer; public class ReportTest { public static void main(String[] args) { try { JasperCompileManager.compileReportToFile("reports/ReportFile.jrxml"); //new JasperDesignViewer(); } catch (JRException e) { e.printStackTrace(); } } } My JRXML-file: <?xml version="1.0"?> <!DOCTYPE jasperReport PUBLIC "-//JasperReports//DTD Report Design//EN" "http://jasperreports.sourceforge.net/dtds/jasperreport.dtd"> <jasperReport name="FirstReport"> <detail> <band height="20"> <staticText> <reportElement x="180" y="0" width="200" height="20"/> <text><![CDATA[Hello World!]]></text> </staticText> </band> </detail> </jasperReport>

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• File path for J2ME FileConnection?

  - by Kilnr

  Hi, I'm writing a MIDlet which needs to write file. I'm using FileConnection from JSR-75 to accomplish this. The intention is to have this MIDlet runnning on as much devices as possible (all MIDP 2.0 devices with JSR-75 support, ideally). On several emulators and an HTC Touch Pro2, I can perfectly use the following code to get the root of the filesystem: Enumeration drives = FileSystemRegistry.listRoots(); String root = (String) drives.nextElement(); String path = "file:///" + root; However, on a Nokia S60 5th edition emulator, trying to open a FileConnection to this path throws a java.lang.SecurityException. Apparently S60 devices do not allow connections to the root of the filesystem. I realise I can use something like System.getProperty("fileconn.dir.photos"), but that isn't supported on all devices either. So, my actual question: what is the best approach to get a path to create a FileConnection with, that allows for maximum portability? Thanks. Edit: I suppose I could iterate over all the roots in the Enumeration, and check for a writable one, but that's hardly optimal for two reasons. First, there aren't necessarily any writable roots. Second, this could be the phone memory or a memory card, so the storage method wouldn't be consistent across devices, which is rather ugly.

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• Android NDK r4 san-angeles problem

  - by Goz

  Hi All, I'm starting to learn the android NDK and I've instantly come up against a problem. I'e built the tool chain (which took a LOT longer than I was expecting!!) and I've compiled the C++ code with no problems and now I'm trying to build the java code. Instantly I come up against a problem. There is a file "main.xml" <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" > <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Hello World, DemoActivity" /> </LinearLayout> and I get the following errors: Description Resource Path Location Type error: Error: String types not allowed (at 'layout_height' with value 'match_parent'). main.xml /DemoActivity/res/layout line 2 Android AAPT Problem error: Error: String types not allowed (at 'layout_height' with value 'match_parent'). main.xml /DemoActivity/res/layout line 2 Android AAPT Problem error: Error: String types not allowed (at 'layout_width' with value 'match_parent'). main.xml /DemoActivity/res/layout line 2 Android AAPT Problem error: Error: String types not allowed (at 'layout_width' with value 'match_parent'). main.xml /DemoActivity/res/layout line 7 Android AAPT Problem error: Error: String types not allowed (at 'layout_width' with value 'match_parent'). main.xml /DemoActivity/res/layout line 7 Android AAPT Problem So I can see the problem lies in the fact that these "match_parent" strings are in there. Anyone know how to fix this?

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• Boosting my GA with Neural Networks and/or Reinforcement Learning

  - by AlexT

  As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

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• Need help with fixing Genetic Algorithm that's not evolving correctly

  - by EnderMB

  I am working on a maze solving application that uses a Genetic Algorithm to evolve a set of genes (within Individuals) to evolve a Population of Individuals that power an Agent through a maze. The majority of the code used appears to be working fine but when the code runs it's not selecting the best Individual's to be in the new Population correctly. When I run the application it outputs the following: Total Fitness: 380.0 - Best Fitness: 11.0 Total Fitness: 406.0 - Best Fitness: 15.0 Total Fitness: 344.0 - Best Fitness: 12.0 Total Fitness: 373.0 - Best Fitness: 11.0 Total Fitness: 415.0 - Best Fitness: 12.0 Total Fitness: 359.0 - Best Fitness: 11.0 Total Fitness: 436.0 - Best Fitness: 13.0 Total Fitness: 390.0 - Best Fitness: 12.0 Total Fitness: 379.0 - Best Fitness: 15.0 Total Fitness: 370.0 - Best Fitness: 11.0 Total Fitness: 361.0 - Best Fitness: 11.0 Total Fitness: 413.0 - Best Fitness: 16.0 As you can clearly see the fitnesses are not improving and neither are the best fitnesses. The main code responsible for this problem is here, and I believe the problem to be within the main method, most likely where the selection methods are called: package GeneticAlgorithm; import GeneticAlgorithm.Individual.Action; import Robot.Robot.Direction; import Maze.Maze; import Robot.Robot; import java.util.ArrayList; import java.util.Random; public class RunGA { protected static ArrayList tmp1, tmp2 = new ArrayList(); // Implementation of Elitism protected static int ELITISM_K = 5; // Population size protected static int POPULATION_SIZE = 50 + ELITISM_K; // Max number of Iterations protected static int MAX_ITERATIONS = 200; // Probability of Mutation protected static double MUTATION_PROB = 0.05; // Probability of Crossover protected static double CROSSOVER_PROB = 0.7; // Instantiate Random object private static Random rand = new Random(); // Instantiate Population of Individuals private Individual[] startPopulation; // Total Fitness of Population private double totalFitness; Robot robot = new Robot(); Maze maze; public void setElitism(int result) { ELITISM_K = result; } public void setPopSize(int result) { POPULATION_SIZE = result + ELITISM_K; } public void setMaxIt(int result) { MAX_ITERATIONS = result; } public void setMutProb(double result) { MUTATION_PROB = result; } public void setCrossoverProb(double result) { CROSSOVER_PROB = result; } /** * Constructor for Population */ public RunGA(Maze maze) { // Create a population of population plus elitism startPopulation = new Individual[POPULATION_SIZE]; // For every individual in population fill with x genes from 0 to 1 for (int i = 0; i < POPULATION_SIZE; i++) { startPopulation[i] = new Individual(); startPopulation[i].randGenes(); } // Evaluate the current population's fitness this.evaluate(maze, startPopulation); } /** * Set Population * @param newPop */ public void setPopulation(Individual[] newPop) { System.arraycopy(newPop, 0, this.startPopulation, 0, POPULATION_SIZE); } /** * Get Population * @return */ public Individual[] getPopulation() { return this.startPopulation; } /** * Evaluate fitness * @return */ public double evaluate(Maze maze, Individual[] newPop) { this.totalFitness = 0.0; ArrayList<Double> fitnesses = new ArrayList<Double>(); for (int i = 0; i < POPULATION_SIZE; i++) { maze = new Maze(8, 8); maze.fillMaze(); fitnesses.add(startPopulation[i].evaluate(maze, newPop)); //this.totalFitness += startPopulation[i].evaluate(maze, newPop); } //totalFitness = (Math.round(totalFitness / POPULATION_SIZE)); StringBuilder sb = new StringBuilder(); for(Double tmp : fitnesses) { sb.append(tmp + ", "); totalFitness += tmp; } // Progress of each Individual //System.out.println(sb.toString()); return this.totalFitness; } /** * Roulette Wheel Selection * @return */ public Individual rouletteWheelSelection() { // Calculate sum of all chromosome fitnesses in population - sum S. double randNum = rand.nextDouble() * this.totalFitness; int i; for (i = 0; i < POPULATION_SIZE && randNum > 0; ++i) { randNum -= startPopulation[i].getFitnessValue(); } return startPopulation[i-1]; } /** * Tournament Selection * @return */ public Individual tournamentSelection() { double randNum = rand.nextDouble() * this.totalFitness; // Get random number of population (add 1 to stop nullpointerexception) int k = rand.nextInt(POPULATION_SIZE) + 1; int i; for (i = 1; i < POPULATION_SIZE && i < k && randNum > 0; ++i) { randNum -= startPopulation[i].getFitnessValue(); } return startPopulation[i-1]; } /** * Finds the best individual * @return */ public Individual findBestIndividual() { int idxMax = 0; double currentMax = 0.0; double currentMin = 1.0; double currentVal; for (int idx = 0; idx < POPULATION_SIZE; ++idx) { currentVal = startPopulation[idx].getFitnessValue(); if (currentMax < currentMin) { currentMax = currentMin = currentVal; idxMax = idx; } if (currentVal > currentMax) { currentMax = currentVal; idxMax = idx; } } // Double check to see if this has the right one //System.out.println(startPopulation[idxMax].getFitnessValue()); // Maximisation return startPopulation[idxMax]; } /** * One Point Crossover * @param firstPerson * @param secondPerson * @return */ public static Individual[] onePointCrossover(Individual firstPerson, Individual secondPerson) { Individual[] newPerson = new Individual[2]; newPerson[0] = new Individual(); newPerson[1] = new Individual(); int size = Individual.SIZE; int randPoint = rand.nextInt(size); int i; for (i = 0; i < randPoint; ++i) { newPerson[0].setGene(i, firstPerson.getGene(i)); newPerson[1].setGene(i, secondPerson.getGene(i)); } for (; i < Individual.SIZE; ++i) { newPerson[0].setGene(i, secondPerson.getGene(i)); newPerson[1].setGene(i, firstPerson.getGene(i)); } return newPerson; } /** * Uniform Crossover * @param firstPerson * @param secondPerson * @return */ public static Individual[] uniformCrossover(Individual firstPerson, Individual secondPerson) { Individual[] newPerson = new Individual[2]; newPerson[0] = new Individual(); newPerson[1] = new Individual(); for(int i = 0; i < Individual.SIZE; ++i) { double r = rand.nextDouble(); if (r > 0.5) { newPerson[0].setGene(i, firstPerson.getGene(i)); newPerson[1].setGene(i, secondPerson.getGene(i)); } else { newPerson[0].setGene(i, secondPerson.getGene(i)); newPerson[1].setGene(i, firstPerson.getGene(i)); } } return newPerson; } public double getTotalFitness() { return totalFitness; } public static void main(String[] args) { // Initialise Environment Maze maze = new Maze(8, 8); maze.fillMaze(); // Instantiate Population //Population pop = new Population(); RunGA pop = new RunGA(maze); // Instantiate Individuals for Population Individual[] newPop = new Individual[POPULATION_SIZE]; // Instantiate two individuals to use for selection Individual[] people = new Individual[2]; Action action = null; Direction direction = null; String result = ""; /*result += "Total Fitness: " + pop.getTotalFitness() + " - Best Fitness: " + pop.findBestIndividual().getFitnessValue();*/ // Print Current Population System.out.println("Total Fitness: " + pop.getTotalFitness() + " - Best Fitness: " + pop.findBestIndividual().getFitnessValue()); // Instantiate counter for selection int count; for (int i = 0; i < MAX_ITERATIONS; i++) { count = 0; // Elitism for (int j = 0; j < ELITISM_K; ++j) { // This one has the best fitness newPop[count] = pop.findBestIndividual(); count++; } // Build New Population (Population size = Steps (28)) while (count < POPULATION_SIZE) { // Roulette Wheel Selection people[0] = pop.rouletteWheelSelection(); people[1] = pop.rouletteWheelSelection(); // Tournament Selection //people[0] = pop.tournamentSelection(); //people[1] = pop.tournamentSelection(); // Crossover if (rand.nextDouble() < CROSSOVER_PROB) { // One Point Crossover //people = onePointCrossover(people[0], people[1]); // Uniform Crossover people = uniformCrossover(people[0], people[1]); } // Mutation if (rand.nextDouble() < MUTATION_PROB) { people[0].mutate(); } if (rand.nextDouble() < MUTATION_PROB) { people[1].mutate(); } // Add to New Population newPop[count] = people[0]; newPop[count+1] = people[1]; count += 2; } // Make new population the current population pop.setPopulation(newPop); // Re-evaluate the current population //pop.evaluate(); pop.evaluate(maze, newPop); // Print results to screen System.out.println("Total Fitness: " + pop.totalFitness + " - Best Fitness: " + pop.findBestIndividual().getFitnessValue()); //result += "\nTotal Fitness: " + pop.totalFitness + " - Best Fitness: " + pop.findBestIndividual().getFitnessValue(); } // Best Individual Individual bestIndiv = pop.findBestIndividual(); //return result; } } I have uploaded the full project to RapidShare if you require the extra files, although if needed I can add the code to them here. This problem has been depressing me for days now and if you guys can help me I will forever be in your debt.

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• A tool to aid completion of missing or incomplete source code documentation

  - by Pekka

  I have several finished, older PHP projects with a lot of includes that I would like to document in javadoc/phpDocumentor style. While working through each file manually and being forced to do a code review alongside the documenting would be the best thing, I am, simply out of time constraints, interested in tools to help me automate the task as much as possible. The tool I am thinking about would ideally have the following features: Parse a PHP project tree and tell me where there are undocumented files, classes, and functions/methods (i.e. elements missing the appropriate docblock comment) Provide a method to half-way easily add the missing docblocks by creating the empty structures and, ideally, opening the file in an editor (internal or external I don't care) so I can put in the description. Optional: Automatic recognition of parameter types, return values and such. But that's not really required. The language in question is PHP, though I could imagine that a C/Java tool might be able to handle PHP files after some tweaking. Looking forward to your suggestions! Bounty There are already very good suggestions for this (that I have not yet had the time to check out) to point out the gaps, but none yet providing aid in filling them. I want to give the question some more exposure, maybe there is some sort of a graphical extension to php_codesniffer to achieve the level of automation I'm dreaming of. Looking forward to any additional input!

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• WSDLs generated by Axis2 services can't be read by SoapUI or WSDL2Java

  - by RJCantrell

  I'm converting some services from Apache SOAP to Axis2, so the Java service classes already exist. I created a new project in Eclipse, imported the source, made sure that the Axis2 project facets were installed, and Axis2 emitter properties are correct. Then, in Eclipse, I selected the service class and chose "Create Web Service," choosing the Axis2 runtime. The service is up and running on my PC, and when I append "?wsdl" to the service's path, I do indeed get a WSDL that I save locally. Attempting to import this into SoapUI to build a client gives the error: ERROR:org.apache.xmlbeans.XmlException: C:\projects\soapUI\Axis2\DALService.wsdl:0: error: src-resolve: type 'SOAPException@http://www.w3.org/2001/XMLSchema' not found. The type it's referring to (SOAPException) is a holdover from the Apache SOAP services, and in the service code, I changed all "import" references in the service code (not the WSDL) from org.apache.soap.SOAPException (the old Apache SOAP package name) to javax.xml.soap.SOAPException (the Axis2 location). The code compiles and works, once I can access it, but I can't access it without generating a client. Any thoughts as to why changing the namespace of an object would keep the generated WSDLs from having the proper namespace references?

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• Cannot load rJava because cannot load a shared library

  - by Farrel

  I have been struggling to load the rJava package in R. I get the following messages > library(rJava) Error in inDL(x, as.logical(local), as.logical(now), ...) : unable to load shared library \ 'C:/PROGRA~1/R/R-210~1.1/library/rJava/libs/rJava.dll': LoadLibrary failure: The specified module could not be found. Error : .onLoad failed in 'loadNamespace' for 'rJava' Error: package/namespace load failed for 'rJava' I have tried so many solutions that they are all bamboozeled in my head. At some point I even got > R Console: Rgui.exe - System Error The > program can't start because > MSVCR71.dll is is missing from your > computer. Try reinstalling the program > to fix this problem. I made sure everything I could think of was on the path > C:\Program Files\R\Rtools\bin;C:\Program Files\R\Rtools\perl\bin; C:\Program Files\R\Rtools\MinGW\bin;%SystemRoot%\system32; %SystemRoot%;%SystemRoot%\System32\Wbem; %SYSTEMROOT%\System32\WindowsPowerShell\v1.0\; C:\Program Files\QuickTime\QTSystem\; C:\Program Files\R\R-2.10.1\library\rJava\libs\; C:\Program Files\R;C:\Program Files\Java\jre6\bin\client What should I try next? I am running R version 2.10.1 (2009-12-14) and I have also tried R version 2.10.1 Patched (2010-03-03 r51210). It is on a Windows machine running windows 7 enterprise

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• jax-ws on glassfish3 init method

  - by Alex

  Hi all, I've created simple jax-ws (anotated Java 6 class to web service) service and deploied it on glassfish v3. The web.xml <?xml version="1.0" encoding="ISO-8859-1"?> <web-app> <servlet> <servlet-name>MyServiceName</servlet-name> <description>Blablabla</description> <servlet-class>com.foo-bar.somepackage.TheService</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>MyServiceName</servlet-name> <url-pattern>/MyServiceName</url-pattern> </servlet-mapping> <session-config> <session-timeout>30</session-timeout> </session-config> </web-app> There is no sun-jaxws.xml in the war. The service works fine but I have 2 issues: I'm using apache common configuration package to read my configuration, so i have init function that calls configuration stuff. 1. How can I configure init method for jaxws service (like i can do for the servlets for example) 2. the load on startup parameter is not affecting the service, I see that for every request init function called again (and c-tor). How can I set scope for my service? Thanks a lot,

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• BlazeDS - Conversion from ArrayList <BaseClass> on java side to Actionscript

  - by user294280

  Hi, So we have a java class with two ArrayLists of generics. It looks like public class Blah { public ArrayList<ConcreteClass> a; public ArrayList<BaseClass> b; } by using [ArrayElementType('ConcreteClass')] in the actionscript class, we are able to get all the "a"s converted fine. However with "b", since the actual class coming across the line is a heterogeneous mix of classes like BaseClassImplementation1, BaseClassImplementation2 etc, it gets typed as an object. Is there a way to convert it to the specific concrete class assuming that a strongly typed AS version of the java class exists on the client side thanks for your help! Regis

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• Set margins in a LinearLayout programmatically.

  - by Timmmm

  I'm trying to use Java (not XML) to create a LinearLayout with buttons that fill the screen, and have margins. Here is code that works without margins: LinearLayout buttonsView = new LinearLayout(this); buttonsView.setOrientation(LinearLayout.VERTICAL); for (int r = 0; r < 6; ++r) { Button btn = new Button(this); btn.setText("A"); LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.FILL_PARENT); // Verbose! lp.weight = 1.0f; // This is critical. Doesn't work without it. buttonsView.addView(btn, lp); } ViewGroup.LayoutParams lp = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT); setContentView(buttonsView, lp); So that works fine, but how on earth do you give the buttons margins so there is space between them? I tried using LinearLayout.MarginLayoutParams, but that has no weight member so it's no good. And it doesn't work if you pass it lp in its constructor either. Is this impossible? Because it sure looks it, and it wouldn't be the first Android layout task you can only do in XML.

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• Using JBoss EL with Websphere

  - by rat

  Hey, I'm doing a project which is going to run on Websphere. I'm using JSF/Facelets/Richfaces for this project. I want to use the JBoss EL implementation as it allows calling methods with parameters from EL etc. ... usually this is accomplished by getting the JBoss EL jar and then putting this in the web.xml: <context-param> <param-name>com.sun.faces.expressionFactory</param-name> <param-value>org.jboss.el.ExpressionFactoryImpl</param-value> </context-param> However this isn't working ... I don't know if its a problem with Websphere or ...??? I get a stack trace when going to the page saying it can't parse the EL where I have passed a method a parameter: <a4j:commandLink value="Delete" action="#{mcsaAdmin.deleteLanguage(1234)}" /> Looking at the stacktrace it appears to still be using the standard sun EL: Caused by: javax.el.ELException: Error Parsing: #{mcsaAdmin.deleteLanguage(1234)} at com.sun.el.lang.ExpressionBuilder.createNodeInternal(Unknown Source) at com.sun.el.lang.ExpressionBuilder.build(Unknown Source) at com.sun.el.lang.ExpressionBuilder.createMethodExpression(Unknown Source) at com.sun.el.ExpressionFactoryImpl.createMethodExpression(Unknown Source) at com.sun.facelets.tag.TagAttribute.getMethodExpression(TagAttribute.java:141) Note the 'com.sun.el.ExpressionFactoryImpl' instead of 'org.jboss.el.ExpressionFactoryImpl' as specified above ... Am I doing something obviously wrong? Anyone have any ideas... I'm using standard JSF implementation from majorra project or whatever provided on sun website and richfaces 3.1.4 and facelets 1.1.14.

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• Scaling gwt's "Contacts" (sample project) AppController with MVP

  - by brad

  I'm just learning GWT so I'm still trying to sort out all of its quirks and features. I'm reading through the example they give illustrating the MVP pattern, and I pretty much get it, except I'm wondering about one thing. The AppController they use implements the ValueChangeHandler interface and the onValueChange method is triggered when history changes. My problem is with this onValueChange in the AppController (i've included it below for anyone who hasn't seen the sample project). It's doing a string comparison on the history token sent in and instantiating the appropriate presenter to handle the action. This is all fine and dandy for the sample app with 3 actions, but how would one scale this to a real app with many more actions? Sticking to this pattern would lead to a pretty large/ugly else if, but I'm still too new to GWT (and java) to infer a better pattern for larger apps. Any help is greatly appreciated! public class AppController implements Presenter, ValueChangeHandler<String> { ... public void onValueChange(ValueChangeEvent<String> event) { String token = event.getValue(); if (token != null) { Presenter presenter = null; if (token.equals("list")) { presenter = new ContactsPresenter(rpcService, eventBus, new ContactsView()); } else if (token.equals("add")) { presenter = new EditContactPresenter(rpcService, eventBus, new EditContactView()); } else if (token.equals("edit")) { presenter = new EditContactPresenter(rpcService, eventBus, new EditContactView()); } if (presenter != null) { presenter.go(container); } } } }

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