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How to implement a Linked List in Java?

- by nbarraille

Hello! I am trying to implement a simple HashTable in Java that uses a Linked List for collision resolution, which is pretty easy to do in C, but I don't know how to do it in Java, as you can't use pointers... First, I know that those structures are already implemented in Java, I'm not planning on using it, just training here... So I created an element, which is a string and a pointer to the next Element: public class Element{ private String s; private Element next; public Element(String s){ this.s = s; this.next = null; } public void setNext(Element e){ this.next = e; } public String getString(){ return this.s; } public Element getNext(){ return this.next; } @Override public String toString() { return "[" + s + "] => "; } } Of course, my HashTable has an array of Element to stock the data: public class CustomHashTable { private Element[] data; Here is my problem: For example I want to implement a method that adds an element AT THE END of the linked List (I know it would have been simpler and more efficient to insert the element at the beginning of the list, but again, this is only for training purposes). How do I do that without pointer? Here is my code (which could work if e was a pointer...): public void add(String s){ int index = hash(s) % data.length; System.out.println("Adding at index: " + index); Element e = this.data[index]; while(e != null){ e = e.getNext(); } e = new Element(s); } Thanks!

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Get the package of a Java source file

- by Oak

My goal is to find the package (as string) of a Java source file, given as plaintext and not already sorted in folders. I can't just locate the first instance of the keyword package in the file, because it may appear inside a comment. So I was thinking about two alternatives: Scan the file word-by-word, maintaining a "inside-a-comment" flag for the scanner. The first time the package keyword is encountered while not inside a comment, stop the scanning and report the result. Use a regex - should be theoretically possible because block comments do not next in Java, but I tried making such a regex and it turned out to be quite complicated - for me, at least. Another difference between the two approaches is that when scanning manually I can stop the scan when I can be certain the package keyword can no longer appear, saving some time... and I'm not sure I can do something similar with regexes. On the other hand, the decision "when it can no longer appear" is not necessarily simple, though I could use some heuristic for that. I would like to hear any input on this problem, and would welcome any help with the regex. My solution is written in Java as well.

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java.awt -- when java outputs an image to my monitor (screen), where is the file that is output to the monitor card?

- by user1405870

Suppose that I am drawing a set of images using java graphics objects. Suppose that I java is outputting these images to my monitor. Where is the file or files that are sent to the monitor card (the graphical representation files). How can I take this file and save it to disk, or how can I take this file and write it to an array, or how can I take these files and combine the results of their output (to the monitor) into a single file for saving? I don't want to use a screen shot feature, I want to be able to redirect (xor capture also) the output to the monitor to some sort of byte-stream. I note that monitors are much better than semaphores, when you are talking about display capabilities; I don't need a counter example. I might not be asking the correct question. It might be that I want to capture the file while it is still in User Space, before it is put into 'Device Space'. I would like to try and capture the byte stream so that I can convert it to MPEG-4 format. I either need a streaming output from the MPEG-4 converter, coming from the streaming input, or else, I need to take static images at discrete times and convert the images. What format will the output from User Space be in? What format will the Device Space output be in? Try to keep speculation to a minimum. http://docs.oracle.com/javame/config/cdc/opt-pkgs/api/jsr927/index.html I guess that Java has made a means of displaying AWT objects on a television screen. Thank you. Ryan Zoerner

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Java code optimization on matrix windowing computes in more time

- by rano

I have a matrix which represents an image and I need to cycle over each pixel and for each one of those I have to compute the sum of all its neighbors, ie the pixels that belong to a window of radius rad centered on the pixel. I came up with three alternatives: The simplest way, the one that recomputes the window for each pixel The more optimized way that uses a queue to store the sums of the window columns and cycling through the columns of the matrix updates this queue by adding a new element and removing the oldes The even more optimized way that does not need to recompute the queue for each row but incrementally adjusts a previously saved one I implemented them in c++ using a queue for the second method and a combination of deques for the third (I need to iterate through their elements without destructing them) and scored their times to see if there was an actual improvement. it appears that the third method is indeed faster. Then I tried to port the code to Java (and I must admit that I'm not very comfortable with it). I used ArrayDeque for the second method and LinkedLists for the third resulting in the third being inefficient in time. Here is the simplest method in C++ (I'm not posting the java version since it is almost identical): void normalWindowing(int mat[][MAX], int cols, int rows, int rad){ int i, j; int h = 0; for (i = 0; i < rows; ++i) { for (j = 0; j < cols; j++) { h = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { for (int rx =- rad; rx <= rad; rx++) { int x = j + rx; if (x >= 0 && x < cols) { h += mat[y][x]; } } } } } } } Here is the second method (the one optimized through columns) in C++: void opt1Windowing(int mat[][MAX], int cols, int rows, int rad){ int i, j, h, y, col; queue<int>* q = NULL; for (i = 0; i < rows; ++i) { if (q != NULL) delete(q); q = new queue<int>(); h = 0; for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][rx]; } } q->push(mem); h += mem; } } for (j = 1; j < cols; j++) { col = j + rad; if (j - rad > 0) { h -= q->front(); q->pop(); } if (j + rad < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][col]; } } q->push(mem); h += mem; } } } } And here is the Java version: public static void opt1Windowing(int [][] mat, int rad){ int i, j = 0, h, y, col; int cols = mat[0].length; int rows = mat.length; ArrayDeque<Integer> q = null; for (i = 0; i < rows; ++i) { q = new ArrayDeque<Integer>(); h = 0; for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][rx]; } } q.addLast(mem); h += mem; } } j = 0; for (j = 1; j < cols; j++) { col = j + rad; if (j - rad > 0) { h -= q.peekFirst(); q.pop(); } if (j + rad < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][col]; } } q.addLast(mem); h += mem; } } } } I recognize this post will be a wall of text. Here is the third method in C++: void opt2Windowing(int mat[][MAX], int cols, int rows, int rad){ int i = 0; int j = 0; int h = 0; int hh = 0; deque< deque<int> *> * M = new deque< deque<int> *>(); for (int ry = 0; ry <= rad; ry++) { if (ry < rows) { deque<int> * q = new deque<int>(); M->push_back(q); for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int val = mat[ry][rx]; q->push_back(val); h += val; } } } } deque<int> * C = new deque<int>(M->front()->size()); deque<int> * Q = new deque<int>(M->front()->size()); deque<int> * R = new deque<int>(M->size()); deque< deque<int> *>::iterator mit; deque< deque<int> *>::iterator mstart = M->begin(); deque< deque<int> *>::iterator mend = M->end(); deque<int>::iterator rit; deque<int>::iterator rstart = R->begin(); deque<int>::iterator rend = R->end(); deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); for (mit = mstart, rit = rstart; mit != mend, rit != rend; ++mit, ++rit) { deque<int>::iterator pit; deque<int>::iterator pstart = (* mit)->begin(); deque<int>::iterator pend = (* mit)->end(); for(cit = cstart, pit = pstart; cit != cend && pit != pend; ++cit, ++pit) { (* cit) += (* pit); (* rit) += (* pit); } } for (i = 0; i < rows; ++i) { j = 0; if (i - rad > 0) { deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); deque<int>::iterator pit; deque<int>::iterator pstart = (M->front())->begin(); deque<int>::iterator pend = (M->front())->end(); for(cit = cstart, pit = pstart; cit != cend; ++cit, ++pit) { (* cit) -= (* pit); } deque<int> * k = M->front(); M->pop_front(); delete k; h -= R->front(); R->pop_front(); } int row = i + rad; if (row < rows && i > 0) { deque<int> * newQ = new deque<int>(); M->push_back(newQ); deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); int rx; int tot = 0; for (rx = 0, cit = cstart; rx <= rad; rx++, ++cit) { if (rx < cols) { int val = mat[row][rx]; newQ->push_back(val); (* cit) += val; tot += val; } } R->push_back(tot); h += tot; } hh = h; copy(C->begin(), C->end(), Q->begin()); for (j = 1; j < cols; j++) { int col = j + rad; if (j - rad > 0) { hh -= Q->front(); Q->pop_front(); } if (j + rad < cols) { int val = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { val += mat[y][col]; } } hh += val; Q->push_back(val); } } } } And finally its Java version: public static void opt2Windowing(int [][] mat, int rad){ int cols = mat[0].length; int rows = mat.length; int i = 0; int j = 0; int h = 0; int hh = 0; LinkedList<LinkedList<Integer>> M = new LinkedList<LinkedList<Integer>>(); for (int ry = 0; ry <= rad; ry++) { if (ry < rows) { LinkedList<Integer> q = new LinkedList<Integer>(); M.addLast(q); for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int val = mat[ry][rx]; q.addLast(val); h += val; } } } } int firstSize = M.getFirst().size(); int mSize = M.size(); LinkedList<Integer> C = new LinkedList<Integer>(); LinkedList<Integer> Q = null; LinkedList<Integer> R = new LinkedList<Integer>(); for (int k = 0; k < firstSize; k++) { C.add(0); } for (int k = 0; k < mSize; k++) { R.add(0); } ListIterator<LinkedList<Integer>> mit; ListIterator<Integer> rit; ListIterator<Integer> cit; ListIterator<Integer> pit; for (mit = M.listIterator(), rit = R.listIterator(); mit.hasNext();) { Integer r = rit.next(); int rsum = 0; for (cit = C.listIterator(), pit = (mit.next()).listIterator(); cit.hasNext();) { Integer c = cit.next(); Integer p = pit.next(); rsum += p; cit.set(c + p); } rit.set(r + rsum); } for (i = 0; i < rows; ++i) { j = 0; if (i - rad > 0) { for(cit = C.listIterator(), pit = M.getFirst().listIterator(); cit.hasNext();) { Integer c = cit.next(); Integer p = pit.next(); cit.set(c - p); } M.removeFirst(); h -= R.getFirst(); R.removeFirst(); } int row = i + rad; if (row < rows && i > 0) { LinkedList<Integer> newQ = new LinkedList<Integer>(); M.addLast(newQ); int rx; int tot = 0; for (rx = 0, cit = C.listIterator(); rx <= rad; rx++) { if (rx < cols) { Integer c = cit.next(); int val = mat[row][rx]; newQ.addLast(val); cit.set(c + val); tot += val; } } R.addLast(tot); h += tot; } hh = h; Q = new LinkedList<Integer>(); Q.addAll(C); for (j = 1; j < cols; j++) { int col = j + rad; if (j - rad > 0) { hh -= Q.getFirst(); Q.pop(); } if (j + rad < cols) { int val = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { val += mat[y][col]; } } hh += val; Q.addLast(val); } } } } I guess that most is due to the poor choice of the LinkedList in Java and to the lack of an efficient (not shallow) copy method between two LinkedList. How can I improve the third Java method? Am I doing some conceptual error? As always, any criticisms is welcome. UPDATE Even if it does not solve the issue, using ArrayLists, as being suggested, instead of LinkedList improves the third method. The second one performs still better (but when the number of rows and columns of the matrix is lower than 300 and the window radius is small the first unoptimized method is the fastest in Java)

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SecurityNegotiationException in WCF Service Hosted on IIS

- by Ram

Hi, I have hosted a WCF service on IIS. The configuration file is as follows <?xml version="1.0"?>  <configuration> <configSections> <sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/> <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere" /> <section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> <section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> <section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> </sectionGroup> </sectionGroup> </sectionGroup> </configSections> <appSettings/> <connectionStrings/> <system.web>  <compilation debug="false"> <assemblies> <add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </assemblies> </compilation>  <authentication mode="Windows" />  <pages> <controls> <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </controls> </pages> <httpHandlers> <remove verb="*" path="*.asmx"/> <add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> <add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> <add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false"/> </httpHandlers> <httpModules> <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </httpModules> </system.web> <system.codedom> <compilers> <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4" type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <providerOption name="CompilerVersion" value="v3.5"/> <providerOption name="WarnAsError" value="false"/> </compiler> </compilers> </system.codedom> <system.web.extensions> <scripting> <webServices>    </webServices>  </scripting> </system.web.extensions>  <system.webServer> <validation validateIntegratedModeConfiguration="false"/> <modules> <add name="ScriptModule" preCondition="integratedMode" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </modules> <handlers> <remove name="WebServiceHandlerFactory-Integrated"/> <add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> <add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> <add name="ScriptResource" preCondition="integratedMode" verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> </handlers> </system.webServer> <system.serviceModel> <services> <service name="IISTest2.Service1" behaviorConfiguration="IISTest2.Service1Behavior">  <endpoint address="" binding="wsHttpBinding" contract="IISTest2.IService1">  <identity> <dns value="localhost"/> </identity> </endpoint> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/> </service> </services> <behaviors> <serviceBehaviors> <behavior name="IISTest2.Service1Behavior">  <serviceMetadata httpGetEnabled="true"/>  <serviceDebug includeExceptionDetailInFaults="false"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> </configuration> The client configuration file is as follows <?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <bindings> <wsHttpBinding> <binding name="WSHttpBinding_IService1" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard" maxBufferPoolSize="524288" maxReceivedMessageSize="65536" messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true" allowCookies="false"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="Message"> <transport clientCredentialType="Windows" proxyCredentialType="None" realm="" /> <message clientCredentialType="Windows" negotiateServiceCredential="true" algorithmSuite="Default" establishSecurityContext="true" /> </security> </binding> </wsHttpBinding> </bindings> <client> <endpoint address="http://yyy.zzz.xxx.net/IISTest2/Service1.svc" binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IService1" contract="ServTest.IService1" name="WSHttpBinding_IService1"> <identity> <dns value="localhost" /> </identity> </endpoint> </client> </system.serviceModel> </configuration> When I tried to access the service from client application, I got SecurityNegotiationException and details are Secure channel cannot be opened because security negotiation with the remote endpoint has failed. This may be due to absent or incorrectly specified EndpointIdentity in the EndpointAddress used to create the channel. Please verify the EndpointIdentity specified or implied by the EndpointAddress correctly identifies the remote endpoint. If I host the service on ASP .NET Dev server, it work well but if I host on IIS above mentioned error occurs. Thanks, Ram

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JSON Formatting with Jersey, Jackson, & json.org/java Parser using Curl Command

- by socal_javaguy

Using Java 6, Tomcat 7, Jersey 1.15, Jackson 2.0.6 (from FasterXml maven repo), & www.json.org parser, I am trying to pretty print the JSON String so it will look indented by the curl -X GET command line. I created a simple web service which has the following architecture: My POJOs (model classes): Family.java import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class Family { private String father; private String mother; private List<Children> children; // Getter & Setters } Children.java import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class Children { private String name; private String age; private String gender; // Getters & Setters } Using a Utility Class, I decided to hard code the POJOs as follows: public class FamilyUtil { public static Family getFamily() { Family family = new Family(); family.setFather("Joe"); family.setMother("Jennifer"); Children child = new Children(); child.setName("Jimmy"); child.setAge("12"); child.setGender("male"); List<Children> children = new ArrayList<Children>(); children.add(child); family.setChildren(children); return family; } } My web service: import java.io.IOException; import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.PathParam; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; import org.codehaus.jackson.JsonGenerationException; import org.codehaus.jackson.map.JsonMappingException; import org.codehaus.jackson.map.ObjectMapper; import org.codehaus.jettison.json.JSONException; import org.json.JSONObject; import org.json.JSONTokener; import com.myapp.controller.myappController; import com.myapp.resource.output.HostingSegmentOutput; import com.myapp.util.FamilyUtil; @Path("") public class MyWebService { @GET @Produces(MediaType.APPLICATION_JSON) public static String getFamily() throws IOException, JsonGenerationException, JsonMappingException, JSONException, org.json.JSONException { ObjectMapper mapper = new ObjectMapper(); String uglyJsonString = mapper.writeValueAsString(FamilyUtil.getFamily()); System.out.println(uglyJsonString); JSONTokener tokener = new JSONTokener(uglyJsonString); JSONObject finalResult = new JSONObject(tokener); return finalResult.toString(4); } } When I run this using: curl -X GET http://localhost:8080/mywebservice I get this in my Eclipse's console: {"father":"Joe","mother":"Jennifer","children":[{"name":"Jimmy","age":"12","gender":"male"}]} But from the curl command on the command line (this response is more important): "{\n \"mother\": \"Jennifer\",\n \"children\": [{\n \"age\": \"12\",\n \"name\": \"Jimmy\",\n \"gender\": \"male\"\n }],\n \"father\": \"Joe\"\n}" This is adding newline escape sequences and placing double quotes (but not indenting like it should it does have 4 spaces after the new line but its all in one line). Would appreciate it if someone could point me in the right direction.

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Managing highly repetitive code and documentation in Java

- by polygenelubricants

Highly repetitive code is generally a bad thing, and there are design patterns that can help minimize this. However, sometimes it's simply inevitable due to the constraints of the language itself. Take the following example from java.util.Arrays: /** * Assigns the specified long value to each element of the specified * range of the specified array of longs. The range to be filled * extends from index <tt>fromIndex</tt>, inclusive, to index * <tt>toIndex</tt>, exclusive. (If <tt>fromIndex==toIndex</tt>, the * range to be filled is empty.) * * @param a the array to be filled * @param fromIndex the index of the first element (inclusive) to be * filled with the specified value * @param toIndex the index of the last element (exclusive) to be * filled with the specified value * @param val the value to be stored in all elements of the array * @throws IllegalArgumentException if <tt>fromIndex > toIndex</tt> * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex < 0</tt> or * <tt>toIndex > a.length</tt> */ public static void fill(long[] a, int fromIndex, int toIndex, long val) { rangeCheck(a.length, fromIndex, toIndex); for (int i=fromIndex; i<toIndex; i++) a[i] = val; } The above snippet appears in the source code 8 times, with very little variation in the documentation/method signature but exactly the same method body, one for each of the root array types int[], short[], char[], byte[], boolean[], double[], float[], and Object[]. I believe that unless one resorts to reflection (which is an entirely different subject in itself), this repetition is inevitable. I understand that as a utility class, such high concentration of repetitive Java code is highly atypical, but even with the best practice, repetition does happen! Refactoring doesn't always work because it's not always possible (the obvious case is when the repetition is in the documentation). Obviously maintaining this source code is a nightmare. A slight typo in the documentation, or a minor bug in the implementation, is multiplied by however many repetitions was made. In fact, the best example happens to involve this exact class: Google Research Blog - Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken (by Joshua Bloch, Software Engineer) The bug is a surprisingly subtle one, occurring in what many thought to be just a simple and straightforward algorithm. // int mid =(low + high) / 2; // the bug int mid = (low + high) >>> 1; // the fix The above line appears 11 times in the source code! So my questions are: How are these kinds of repetitive Java code/documentation handled in practice? How are they developed, maintained, and tested? Do you start with "the original", and make it as mature as possible, and then copy and paste as necessary and hope you didn't make a mistake? And if you did make a mistake in the original, then just fix it everywhere, unless you're comfortable with deleting the copies and repeating the whole replication process? And you apply this same process for the testing code as well? Would Java benefit from some sort of limited-use source code preprocessing for this kind of thing? Perhaps Sun has their own preprocessor to help write, maintain, document and test these kind of repetitive library code? A comment requested another example, so I pulled this one from Google Collections: com.google.common.base.Predicates lines 276-310 (AndPredicate) vs lines 312-346 (OrPredicate). The source for these two classes are identical, except for: AndPredicate vs OrPredicate (each appears 5 times in its class) "And(" vs Or(" (in the respective toString() methods) #and vs #or (in the @see Javadoc comments) true vs false (in apply; ! can be rewritten out of the expression) -1 /* all bits on */ vs 0 /* all bits off */ in hashCode() &= vs |= in hashCode()

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Java PHP posting using URLConnector, PHP file doesn't seem to receive parameters

- by Emdiesse

Hi there, I am trying to post some simple string data to my php script via a java application. My PHP script works fine when I enter the data myself using a web browser (newvector.php?x1=&y1=...) However using my java application the php file does not seem to pick up these parameters, in fact I don't even know if they are sending at all because if I comment out on of the parameters in the java code when I am writing to dta it doesn't actually return, you must enter 6 parameters. newvector.php if(!isset($_GET['x1']) || !isset($_GET['y1']) || !isset($_GET['t1']) || !isset($_GET['x2']) || !isset($_GET['y2']) || !isset($_GET['t2'])){ die("You must include 6 parameters within the URL: x1, y1, t1, x2, y2, t2"); } $x1 = $_GET['x1']; $x2 = $_GET['x2']; $y1 = $_GET['y1']; $y2 = $_GET['y2']; $t1 = $_GET['t1']; $t2 = $_GET['t2']; $insert = " INSERT INTO vectors( x1, x2, y1, y2, t1, t2 ) VALUES ( '$x1', '$x2', '$y1', '$y2', '$t1', '$t2' ) "; if(!mysql_query($insert, $conn)){ die('Error: ' . mysql_error()); } echo "Submitted Data x1=".$x1." y1=".$y1." t1=".$t1." x2=".$x2." y2=".$y2." t2=".$t2; include 'db_disconnect.php'; ?> The java code else if (action.equals("Play")) { for (int i = 0; i < 5; i++) { // data.size() String x1, y1, t1, x2, y2, t2 = ""; String date = "2010-04-03 "; String ms = ".0"; x1 = data.elementAt(i)[1]; y1 = data.elementAt(i)[0]; t1 = date + data.elementAt(i)[2] + ms; x2 = data.elementAt(i)[4]; y2 = data.elementAt(i)[3]; t2 = date + data.elementAt(i)[5] + ms; try { //Create Post String String dta = URLEncoder.encode("x1", "UTF-8") + "=" + URLEncoder.encode(x1, "UTF-8"); dta += "&" + URLEncoder.encode("y1", "UTF-8") + "=" + URLEncoder.encode(y1, "UTF-8"); dta += "&" + URLEncoder.encode("t1", "UTF-8") + "=" + URLEncoder.encode(t1, "UTF-8"); dta += "&" + URLEncoder.encode("x2", "UTF-8") + "=" + URLEncoder.encode(x2, "UTF-8"); dta += "&" + URLEncoder.encode("y2", "UTF-8") + "=" + URLEncoder.encode(y2, "UTF-8"); dta += "&" + URLEncoder.encode("t2", "UTF-8") + "=" + URLEncoder.encode(t2, "UTF-8"); System.out.println(dta); // Send Data To Page URL url = new URL("http://localhost/newvector.php"); URLConnection conn = url.openConnection(); conn.setDoOutput(true); OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream()); wr.write(dta); wr.flush(); // Get The Response BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream())); String line; while ((line = rd.readLine()) != null) { System.out.println(line); //you Can Break The String Down Here } wr.close(); rd.close(); } catch (Exception exc) { System.out.println("Hmmm!!! " + exc.getMessage()); } }

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Unnecessary Java context switches

- by Paul Morrison

I have a network of Java Threads (Flow-Based Programming) communicating via fixed-capacity channels - running under WindowsXP. What we expected, based on our experience with "green" threads (non-preemptive), would be that threads would switch context less often (thus reducing CPU time) if the channels were made bigger. However, we found that increasing channel size does not make any difference to the run time. What seems to be happening is that Java decides to switch threads even though channels aren't full or empty (i.e. even though a thread doesn't have to suspend), which costs CPU time for no apparent advantage. Also changing Thread priorities doesn't make any observable difference. My question is whether there is some way of persuading Java not to make unnecessary context switches, but hold off switching until it is really necessary to switch threads - is there some way of changing Java's dispatching logic? Or is it reacting to something I didn't pay attention to?! Or are there other asynchronism mechanisms, e.g. Thread factories, Runnable(s), maybe even daemons (!). The answer appears to be non-obvious, as so far none of my correspondents has come up with an answer (including most recently two CS profs). Or maybe I'm missing something that's so obvious that people can't imagine my not knowing it... I've added the send and receive code here - not very elegant, but it seems to work...;-) In case you are wondering, I thought the goLock logic in 'send' might be causing the problem, but removing it temporarily didn't make any difference. I have added the code for send and receive... public synchronized Packet receive() { if (isDrained()) { return null; } while (isEmpty()) { try { wait(); } catch (InterruptedException e) { close(); return null; } if (isDrained()) { return null; } } if (isDrained()) { return null; } if (isFull()) { notifyAll(); // notify other components waiting to send } Packet packet = array[receivePtr]; array[receivePtr] = null; receivePtr = (receivePtr + 1) % array.length; //notifyAll(); // only needed if it was full usedSlots--; packet.setOwner(receiver); if (null == packet.getContent()) { traceFuncs("Received null packet"); } else { traceFuncs("Received: " + packet.toString()); } return packet; } synchronized boolean send(final Packet packet, final OutputPort op) { sender = op.sender; if (isClosed()) { return false; } while (isFull()) { try { wait(); } catch (InterruptedException e) { indicateOneSenderClosed(); return false; } sender = op.sender; } if (isClosed()) { return false; } try { receiver.goLock.lockInterruptibly(); } catch (InterruptedException ex) { return false; } try { packet.clearOwner(); array[sendPtr] = packet; sendPtr = (sendPtr + 1) % array.length; usedSlots++; // move this to here if (receiver.getStatus() == StatusValues.DORMANT || receiver.getStatus() == StatusValues.NOT_STARTED) { receiver.activate(); // start or wake up if necessary } else { notifyAll(); // notify receiver // other components waiting to send to this connection may also get // notified, // but this is handled by while statement } sender = null; Component.network.active = true; } finally { receiver.goLock.unlock(); } return true; }

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Load balancing using Mina example with Java DSL

- by Flame_Phoenix

So, recently I started learning Camel. As part of the process I decided to go through all the examples (listed HERE and available when you DOWNLOAD the package with all the examples and docs) and to see what I could learn. One of the examples, Load Balancing using Mina caught my attention because it uses a Mina in different JVM's and it simulates a load balancer with round robin. I have a few problems with this example. First it uses the Spring DSL, instead of the Java DSL which my project uses and which I find a lot easier to understand now (mainly also because I am used to it). So the first question: is there a version of this example using only the Java DSL instead of the Spring DSL for the routes and the beans? My second questions is code related. The description states, and I quote: Within this demo every ten seconds, a Report object is created from the Camel load balancer server. This object is sent by the Camel load balancer to a MINA server where the object is then serialized. One of the two MINA servers (localhost:9991 and localhost:9992) receives the object and enriches the message by setting the field reply of the Report object. The reply is sent back by the MINA server to the client, which then logs the reply on the console. So, from what I read, I understand that the MINA server 1 (per example) receives a report from the loadbalancer, changes it, and then it sends that report back to some invisible client. Upon checking the code, I see no client java class or XML and when I run, the server simply posts the results on the command line. Where is the client ?? What is this client? In the MINA 1server code presented here: <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:camel="http://camel.apache.org/schema/spring" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd"> <bean id="service" class="org.apache.camel.example.service.Reporting"/> <camelContext xmlns="http://camel.apache.org/schema/spring"> <route id="mina1"> <from uri="mina:tcp://localhost:9991"/> <setHeader headerName="minaServer"> <constant>localhost:9991</constant> </setHeader> <bean ref="service" method="updateReport"/> </route> </camelContext> </beans> I don't understand how the updateReport method magically prints the object on my console. What if I wanted to send message to a third MINA server? How would I do it? (I would have to add a new route, and send it to the URI of the 3rd server correct?) I know most of these questions may sound dumb, but I would appreciate if anyone could help me. A Java DSL version of this would really help me.

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Need a hand understanding this Java code please :-)

- by Brian

Hi all, Just wondering if anyone would be able to take a look at this code for implementing the quicksort algorithm and answer me a few questions, please :-) public class Run { /*************************************************************************** * Quicksort code from Sedgewick 7.1, 7.2. **************************************************************************/ public static void quicksort(double[] a) { //shuffle(a); // to guard against worst-case quicksort(a, 0, a.length - 1, 0); } static void quicksort(final double[] a, final int left, final int right, final int tdepth) { if (right <= left) return; final int i = partition(a, left, right); if ((tdepth < 4) && ((i - left) > 1000)) { final Thread t = new Thread() { public void run() { quicksort(a, left, i - 1, tdepth + 1); } }; t.start(); quicksort(a, i + 1, right, tdepth + 1); try { t.join(); } catch (InterruptedException e) { throw new RuntimeException("Cancelled", e); } } else { quicksort(a, left, i - 1, tdepth); quicksort(a, i + 1, right, tdepth); } } // partition a[left] to a[right], assumes left < right private static int partition(double[] a, int left, int right) { int i = left - 1; int j = right; while (true) { while (less(a[++i], a[right])) // find item on left to swap ; // a[right] acts as sentinel while (less(a[right], a[--j])) // find item on right to swap if (j == left) break; // don't go out-of-bounds if (i >= j) break; // check if pointers cross exch(a, i, j); // swap two elements into place } exch(a, i, right); // swap with partition element return i; } // is x < y ? private static boolean less(double x, double y) { return (x < y); } // exchange a[i] and a[j] private static void exch(double[] a, int i, int j) { double swap = a[i]; a[i] = a[j]; a[j] = swap; } // shuffle the array a[] private static void shuffle(double[] a) { int N = a.length; for (int i = 0; i < N; i++) { int r = i + (int) (Math.random() * (N - i)); // between i and N-1 exch(a, i, r); } } // test client public static void main(String[] args) { int N = 5000000; // Integer.parseInt(args[0]); // generate N random real numbers between 0 and 1 long start = System.currentTimeMillis(); double[] a = new double[N]; for (int i = 0; i < N; i++) a[i] = Math.random(); long stop = System.currentTimeMillis(); double elapsed = (stop - start) / 1000.0; System.out.println("Generating input: " + elapsed + " seconds"); // sort them start = System.currentTimeMillis(); quicksort(a); stop = System.currentTimeMillis(); elapsed = (stop - start) / 1000.0; System.out.println("Quicksort: " + elapsed + " seconds"); } } My questions are: What is the purpose of the variable tdepth? Is this considered a "proper" implementation of a parallel quicksort? I ask becuase it doesn't use implements Runnable or extends Thread... If it doesn't already, is it possible to modify this code to use multiple threads? By passing in the number of threads you want to use as a parameter, for example...? Many thanks, Brian

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Java curious Loop Performance

- by user1680583

I have a big problem while evaluate my java code. To simplify the problem I wrote the following code which produce the same curious behavior. Important is the method run() and given double value rate. For my runtime test (in the main method) I set the rate to 0.5 one times and 1.0 the other time. With the value 1.0 the if-statement will be executed in each loop iteration and with the value 0.5 the if-statement will be executed half as much. For this reason I expected longer runtime by the first case but opposite is true. Can anybody explain me this phenomenon?? The result of main: Test mit rate = 0.5 Length: 50000000, IF executions: 25000856 Execution time was 4329 ms. Length: 50000000, IF executions: 24999141 Execution time was 4307 ms. Length: 50000000, IF executions: 25001582 Execution time was 4223 ms. Length: 50000000, IF executions: 25000694 Execution time was 4328 ms. Length: 50000000, IF executions: 25004766 Execution time was 4346 ms. ================================= Test mit rate = 1.0 Length: 50000000, IF executions: 50000000 Execution time was 3482 ms. Length: 50000000, IF executions: 50000000 Execution time was 3572 ms. Length: 50000000, IF executions: 50000000 Execution time was 3529 ms. Length: 50000000, IF executions: 50000000 Execution time was 3479 ms. Length: 50000000, IF executions: 50000000 Execution time was 3473 ms. The Code public ArrayList<Byte> list = new ArrayList<Byte>(); public final int LENGTH = 50000000; public PerformanceTest(){ byte[]arr = new byte[LENGTH]; Random random = new Random(); random.nextBytes(arr); for(byte b : arr) list.add(b); } public void run(double rate){ byte b = 0; int count = 0; for (int i = 0; i < LENGTH; i++) { if(getRate(rate)){ list.set(i, b); count++; } } System.out.println("Length: " + LENGTH + ", IF executions: " + count); } public boolean getRate(double rate){ return Math.random() < rate; } public static void main(String[] args) throws InterruptedException { PerformanceTest test = new PerformanceTest(); long start, end; System.out.println("Test mit rate = 0.5"); for (int i = 0; i < 5; i++) { start=System.currentTimeMillis(); test.run(0.5); end = System.currentTimeMillis(); System.out.println("Execution time was "+(end-start)+" ms."); Thread.sleep(500); } System.out.println("================================="); System.out.println("Test mit rate = 1.0"); for (int i = 0; i < 5; i++) { start=System.currentTimeMillis(); test.run(1.0); end = System.currentTimeMillis(); System.out.println("Execution time was "+(end-start)+" ms."); Thread.sleep(500); } }

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Struts 2 or JSF?

- by sangamdash

I am just starting with web application. Which framework should I try : struts 2 jsf? Both seem pretty good.

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Need help in creating test appliaction in Java and passing parameters into a new designed Java API.

- by Christophe

Need help, Please!!! By following the protocol, the Request should be built in 5 byte length, including 1 byte for changing Braud rate (Speed), and send request to a RS-232 port. Protocol: --------------- Request for the command processing, with optional extra byte for changing Baud Rate: LGT : length message ( LGT = 5 ) TYPE : 0x06 TO(time out): 0x0000 CMD : (1 byte) 0x02 application update Baud Rate : (1 byte) 0xNN (optional parameter to change baud rate of the Mnt App) where NN can be: 0x00 = No Baud Rate Change (similar to 4-byte command above) 0x09 = Change to 9600 Baud for Application Update speed 0x0A = Change to 19200 Baud for Application Update speed 0x0E = Change to 115200 Baud for Application Update speed All other bytes are not accepted and will result in a status of 0x01. ------------------ I'm trying to test if my code works or not by creating another class (TestApplication.java) and pass the "3 differenr Baut rate" to this CPXAppliaction. the 3 Baud Rate is supposed to input by reading a file.txt. Question: How do you think these code (first half)? please don't warry about the details about the "sending part". I mean, do I need setter/getter for the "speed" parameter pass? I created the demo test class DemoApp.java (input speed by reading a txt file, and pass into CPXAppliaction). how do you think about that code? Many thanks to you guys!! public class CPXApplication extends CPXCommand { private int speed; . public CPXApplication() { speed = 9600; } public CPXApplication(int speedinit) { speed = speedinit; // TODO: where to get the speed? } protected void buildRequest() throws ElitePortException { String trans = ""; // build the full-qualified message following the protocol trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 5); trans = addToRequest(trans, (char) 6); trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 2); switch (speed) { case 9600: trans = addToRequest(trans, (char) 0x09); break; case 19200: trans = addToRequest(trans, (char) 0x0A); break; case 115200: trans = addToRequest(trans, (char) 0x0E); break; default: // TODO: unexpected baud rate. throw(); break; } trans = EncryptBinary(trans); trans = "F0." + trans; wrapRequest(trans); } protected String addToRequest(String req, char c) { return req + c; } protected String addToRequest(String req, String s) { return req + s; } protected String addToRequest(String req) { return req; } public void analyzeResponse() { //.............. } } Here is the demo test code: package com.ingenico.testApp; import com.ingenico.EliteFd.; import java.util.Scanner; import java.io.; class Run { public static void run() { CPXAppliactionUpdate input = new CpXApplicationUpdate(); int lineno = 0; try { FileReader fr = new FileReader("baudRateSpeed.txt"); BufferedReader reader = new BufferedReader(fr); String line = reader.readLine(); Scanner scan = null; while (line != null) { scan = new Scanner(line); String speed; speed = scan.next(); if (lineno == 0) { input.speed = speed; lineno++; } else { input = cpxapplicationupdate(speed, input); } line = reader.readLine(); } reader.close(); } catch (FileNotFoundException e) { System.out.println("Could not find the file"); } catch (IOException e) { System.out.println("Had a problem reading from file"); } } public class DemoApp{ public void main(String args[]) { run(); } } }

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compareTo() method java is acting weird

- by Ron Paul

hi im having trouble getting this to work im getting an error here with my object comparison...how could I cast the inches to a string ( i never used compare to with anything other than strings) , or use comparison operators to compare the intigers, Object comparison = this.inches.compareTo(obj.inches); here is my code so far import java.io.*; import java.util.*; import java.lang.Integer; import java.lang.reflect.Array; public class Distance implements Comparable<Distance> { private static final String HashCodeUtil = null; private int feet; private int inches; private final int DEFAULT_FT = 1; private final int DEFAULT_IN = 1; public Distance(){ feet = DEFAULT_FT; inches = DEFAULT_IN; } public Distance(int ft, int in){ feet = ft; inches = in; } public void setFeet(int ft){ try { if(ft<0){ throw new CustomException("Distance is not negative"); } } catch(CustomException c){ System.err.println(c); feet =ft; } } public int getFeet(){ return feet; } public void setInches(int in){ try { if (in<0) throw new CustomException("Distance is not negative"); //inches = in; } catch(CustomException c) { System.err.println(c); inches = in; } } public int getInches(){ return inches; } public String toString (){ return "<" + feet + ":" + inches + ">"; } public Distance add(Distance m){ Distance n = new Distance(); n.inches = this.inches + m.inches; n.feet = this.feet + m.feet; while(n.inches>12){ n.inches = n.inches - 12; n.feet++; } return n; } public Distance subtract(Distance f){ Distance m = new Distance(); m.inches = this.inches - f.inches; m.feet = this.feet - f.feet; while(m.inches<0){ m.inches = m.inches - 12; feet--; } return m; } @Override public int compareTo(Distance obj) { // TODO Auto-generated method stub final int BEFORE = -1; final int EQUAL = 0; final int AFTER = 1; if (this == obj) return EQUAL; if(this.DEFAULT_IN < obj.DEFAULT_FT) return BEFORE; if(this.DEFAULT_IN > obj.DEFAULT_FT) return AFTER; Object comparison = this.inches.compareTo(obj.inches); if (this.inches == obj.inches) return compareTo(null); assert this.equals(obj) : "compareTo inconsistent with equals"; return EQUAL; } @Override public boolean equals( Object obj){ if (obj != null) return false; if (!(obj intanceof Distance)) return false; Distance that = (Distance)obj; ( this.feet == that.feet && this.inches == that.inches); return true; else return false; } @Override public int hashCode(int, int) { int result = HashCodeUtil.inches; result = HashCodeUtil.hash(result, inches ); result = HashCodeUtil.hash(result, feet); ruturn result; }

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Java Spotlight Episode 108: Patrick Curran and Heather VanCura on JCP.Next @jcp_org

- by Roger Brinkley

Interview with Patrick Curran and Heather VanCura on JCP.Next. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link: Java Spotlight Podcast in iTunes. Show Notes News Welcome to the newly merged JCP EC! The November/December issue of Java Magazine is now out Red Hat announces intent to contribute to OpenJFX New OpenJDK JEPs: JEP 168: Network Discovery of Manageable Java Processes JEP 169: Value Objects Java EE 7 Survey Latest Java EE 7 Status GlassFish 4.0 Embedded (via @agoncal) Events Nov 13-17, Devoxx, Antwerp, Belgium Nov 20, JCP Public Meeting (see details below) Nov 20-22, DOAG 2012, Nuremberg, Germany Dec 3-5, jDays, Göteborg, Sweden Dec 4-6, JavaOne Latin America, Sao Paolo, Brazil Dec 14-15, IndicThreads, Pune, India Feature InterviewPatrick Curran is Chair of the Java Community Process organization. In this role he oversees the activities of the JCP's Program Management Office including evolving the process and the organization, managing its membership, guiding specification leads and experts through the process, chairing Executive Committee meetings, and managing the JCP.org web site.Patrick has worked in the software industry for more than 25 years, and at Sun and then Oracle for 20 years. He has a long-standing record in conformance testing, and before joining the JCP he led the Java Conformance Engineering team in Sun's Client Software Group. He was also chair of Sun's Conformance Council, which was responsible for defining Sun's policies and strategies around Java conformance and compatibility.Patrick has participated actively in several consortia and communities including the W3C (as a member of the Quality Assurance Working Group and co-chair of the Quality Assurance Interest Group), and OASIS (as co-chair of the Test Assertions Guidelines Technical Committee). Patrick's blog is here.Heather VanCura manages the JCP Program Office and is responsible for the day-to-day nurturing, support, and leadership of the community. She oversees the JCP.org web site, JSR management and posting, community building, events, marketing, communications, and growth of the membership through new members and renewals. Heather has a front row seat for studying trends within the community and recommending changes. Several changes to the program in recent years have included enabling broader participation, increased transparency and agility in JSR development. When Heather joined the PMO staff in a community building marketing manager role for the JCP program, she was responsible for establishing the JCP brand logo programs, the JCP.org site, and engaging the community in online surveys and usability studies. She also developed marketing reward programs, campaigns, sponsorships, and events for the JCP program, including the community gathering at the annual JavaOne Conference. Before arriving at the JCP community in 2000, Heather worked with various technology companies. Heather enjoys speaking at conferences, such as Devoxx, Java Zone, and the JavaOne Conferences. She maintains the JCP Blog, Twitter feed (@jcp_org) and Facebook page. Heather resides in the San Francisco Bay Area, California USA. JCP Executive Committee Public Meeting Details Date & Time Tuesday November 20, 2012, 3:00 - 4:00 pm PST Location Teleconference Dial-in +1 (866) 682-4770 Conference code: 627-9803 Security code: 52732 ("JCPEC" on your phone handset) For global access numbers see http://www.intercall.com/oracle/access_numbers.htm Or +1 (408) 774-4073 WebEx Browse for the meeting from https://jcp.webex.com No registration required (enter your name and email address) Password: JCPEC Agenda JSR 355 (the EC merge) implementation report JSR 358 (JCP.next.3) status report 2.8 status update and community audit program Discussion/Q&A Note The call will be recorded and the recording published on jcp.org, so those who are unable to join in real-time will still be able to participate. September 2012 EC meeting PMO report with JCP 2.8 statistics.JSR 358 Project page What’s Cool Sweden: Hot Java in the Winter GE Engergy using Invoke Daynamic for embedded development

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Updated Security Baseline (7u45) impacts Java 7u40 and before with High Security settings

- by costlow

The Java Security Baseline has been increased from 7u25 to 7u45. For versions of Java below 7u45, this means unsigned Java applets or Java applets that depend on Javascript LiveConnect calls will be blocked when using the High Security setting in the Java Control Panel. This issue only affects Applets and Web Start applications. It does not affect other types of Java applications. The Short Answer Users upgrading to Java 7 update 45 will automatically fix this and is strongly recommended. The More Detailed Answer There are two items involved as described on the deployment flowchart: The Security Baseline – a dynamically updated attribute that checks to see which Java version contains the most recent security patches. The Security Slider – the user-controlled setting of when to prompt/run/block applets. The Security Baseline Java clients periodically check in to understand what version contains the most recent security patches. Versions are released in-between that contain bug fixes. For example: 7u25 (July 2013) was the previous secure baseline. 7u40 contained bug fixes. Because this did not contain security patches, users were not required to upgrade and were welcome to remain on 7u25. When 7u45 was released (October, 2013), this critical patch update contained security patches and raised the secure baseline. Users are required to upgrade from earlier versions. For users that are not regularly connected to the internet, there is a built in Expiration Date. Because of the pre-established quarterly critical patch updates, we are able to determine an approximate date of the next version. A critical patch released in July will have its successor released, at latest, in July + 3 months: October. The Security Slider The security slider is located within the Java control panel and determines which Applets & Web Start applications will prompt, which will run, and which will be blocked. One of the questions used to determine prompt/run/block is, “At or Above the Security Baseline.” The Combination JavaScript calls made from LiveConnect do not reside within signed JAR files, so they are considered to be unsigned code. This is correct within networked systems even if the domain uses HTTPS because signed JAR files represent signed "data at rest" whereas TLS (often called SSL) literally stands for "Transport Level Security" and secures the communication channel, not the contents/code within the channel. The resulting flow of users who click "update later" is: Is the browser plug-in registered and allowed to run? Yes. Does a rule exist for this RIA? No rules apply. Does the RIA have a valid signature? Yes and not revoked. Which security prompt is needed? JRE is below the baseline. This is because 7u45 is the baseline and the user, clicked "upgrade later." Under the default High setting, Unsigned code is set to "Don’t Run" so users see: Additional Notes End Users can control their own security slider within the control panel. System Administrators can customize the security slider during automated installations. As a reminder, in the future, Java 7u51 (January 2014) will block unsigned and self-signed Applets & Web Start applications by default.

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Mastering snow and Java development at jDays in Gothenburg

- by JavaCecilia

Last weekend, I took the train from Stockholm to Gothenburg to attend and present at the new Java developer conference jDays. It was professionally arranged in the Swedish exhibition hall close to the amusement park Liseberg and we got a great deal out of the top-level presenters and hallway discussions. Understanding and Improving Your Java Process Our main purpose was to spread information on JVM and our monitoring tools for Java processes, so I held a crash course in the most important terms and concepts if you want to affect the performance of your Java process. From the beginning - the JVM specification to interpretation of heap usage graphs. For correct analysis, you also need to understand something about process memory - you need space for the Java heap (-Xms for initial size and -Xmx for max heap size), but the process memory also contain the thread stacks (to a size of -Xss), JVM internal data structures used for keeping track of Java objects on the heap, method compilation/optimization, native libraries, etc. If you get long pause times, make sure to monitor your application, see the allocation rate and frequency of pause times.My colleague Klara Ward then held a presentation on the Java Mission Control product, the profiling and diagnostics tools suite for HotSpot, coming soon. The room was packed and very appreciated, Klara demonstrated four different scenarios, e.g. how to diagnose and fix latencies due to lock contention for logging.My German colleague, OpenJDK ambassador Dalibor Topic travelled to Sweden to do the second keynote on "Make the Future Java". He let us in on the coming features and roadmaps of Java, now delivering major versions on a two-year schedule (Java 7 2011, Java 8 2013, etc). Also letting us in on where to download early versions of 8, to report problems early on. Software Development in teams Being a scout leader, I'm drilled in different team building and workshop techniques, creating strong groups - of course, I had to attend Henrik Berglund's session on building successful teams. He spoke about the importance of clear goals, autonomy and agreed processes. Thomas Sundberg ended the conference by doing live remote pair programming with Alex in Rumania and a concrete tips for people wanting to try it out (for local collaboration, remember to wash and change clothes). Memory Master Keynote The conference keynote was delivered by the Swedish memory master Mattias Ribbing, showing off by remembering the order of a deck of cards he'd seen once. He made it interactive by forcing the audience to learn a memory mastering technique of remembering ten ordered things by heart, asking us to shout out the order backwards and we made it! I desperately need this - bought the book, will get back on the subject. Continuous Delivery The most impressive presenter was Axel Fontaine on Continuous Delivery. Very well prepared slides with key images of his message and moved about the stage like a rock star. The topic is of course highly interesting, how to create an infrastructure enabling immediate feedback to developers and ability to release your product several times per day. Tomek Kaczanowski delivered a funny and useful presentation on good and bad tests, providing comic relief with poorly written tests and the useful rules of thumb how to rewrite them. To conclude, we had a great time and hope to see you at jDays next year :)

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Install a web certificate on an Android device

- by martani_net

To gain access to WIFI at university I have to login with my user/pass credentials. The certificate of their website (the local home page that asks for the credentials) is not recognized as a trusted certificate, so we install it separately on our computers. The problem is that I don't take my laptop with me often to university, so I usually want to connect using my HTC Magic, but I have no clue on how to install the certificate separately on Android, it is always rejected. [Edit2] : this is what is stated in their website Need for installation of official certificates CyberTrust validated by the CRU (http://www.cru.fr/wiki/scs/) The certificates contain information certified to generate encryption keys for data exchange, called "sensitive" as the password of a user. By connecting to CanalIP-UPMC, for example, the user must validate the identity of the server accepting the certificate appears on the screen in a "popup window". In reality, the user is unable to validate a certificate knowing, because a simple visual check of the license is impossible. Therefore, the certificates of the certification authority (CRU-Cybertrust Educationnal-ca.ca Cybertrust and-global-root-ca.ca) must be installed prior to the browser for the validity of the certificate server can be controlled automatically. Before you connect to the network-UPMC CanalIP you must register in your browser through the certification authority Cybertrust-Educationnal-ca.ca Download the Cybertrust-Educationnal-ca.ca, depending on your browser and select the link below : With Internet Explorer, click on the link following. With Firefox, click on the link following. With Safari, click the link following. If this procedure is not respected, a real risk is incurred by the user: that of being robbed password LDAP directory UPMC. A malicious server may in fact try very easily attack type "man-in-the-middle" by posing as the legitimate server at UPMC. The theft of a password allows the attacker to steal an identity for transactions over the Internet can engage the responsibility of the user trapped ... This is their website : http://www.canalip.upmc.fr/doc/Default.htm (in French, Google-translate it :)) Anyone knows how to install a web certificate on Android?

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Godaddy domain and Bluehost web hosting

- by Digital site

I have a domain from Godaddy and web hosting at Bluehost. I want to make this work as some people say no need to transfer the domain from Godaddy to Bluehost. I was trying to find out how to get this work out by adding name servers for Bluehost ns1.bluehost.com ns2.bluehost.com at Godaddy. This works fine, but not sure if 100% OK yet. The reason why I say that is when I type in my address name on any browser this way: mydomain.com it doesn't work. Instead I get an error message stating that this server is not found or couldn't connect to it... However, when I write the domain name and include the www. prefix it works fine... The other problem is when I search in google or yahoo, the domain shows like this: mydomain.com , which is not really good because my clients think my site is down because of the error message, and most new people don't know if they have to add www. to the domain to work. I just want to make at least the domain works like this: mydomain.com

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Web Application Publishing on Citrix with Restricted Access

- by Kanini

We have a Citrix setup enabling users to access our applications from home. Basically, they login to our site using the Windows Authentication. Once, the are successfully logged in, they see the following icons Desktop - Full Screen (which provides them the Desktop as they would see when the login in our office) We now have a requirement where we would like to publish a web application, hxxp://ourlibrary on Citrix with the following security requirement. (this application is already accessible if the users launch the desktop and launch IE within it and navigate to it) The requirement is this - When the are successfully authenticated to our site, they should be able to see The Internet Explorer icon only, NOT the Dekstop - Full Screen icon. On clicking on the icon, Internet Explorer should open up and should automatically navigate to hxxp://ourlibrary They should not be able to access any other URL, such as Google, Hotmail etc., They should not be able to go FileOpen and Browse They should not be able to do FileSave and Browse In effect, they should be able to view the site and that should be it. Any ideas on how to accomplish the security feature? We have already published the application.

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AWS VPC public web application connecting to database via VPN

- by Chris

What I am trying to do is set up a web application that is public facing but makes calls to a database that is on an internal network. I have been trying to set up an AWS VPC with a public subnet, private subnet, and hardware VPN access but I can't seem to get it to work. Can someone help me understand what the process flow here should be? My understanding is that I need a public subnet to handle the website requests and then a private subnet to connect to the VPN but what I do not understand is how to send requests down the chain and get the response. Basically what I am asking is how can I query the database via VPN from that public website? I've tried during rout forwarding but I can't successfully complete the process. Does anyone have any advice on something I can read on this subject or an FAQ on setting something like this up? Is it even possible? I'm out of my league here, this is not my area of expertise but I'm being asked to solve this problem. Any help would be appreciated. Thanks

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Setting up port forwarding for web server

- by reyjavikvi

This could belong on Super User, but I thought this place was more appropiate. I want to run Apache in my computer and want to make it available to the outside world to test a couple things. Apparently, I have to go into my router's (a TP-LINK TD 8910G) settings and forward port 80 to my PC's IP. So far so good. Thing is, since the router uses a web based interface and it's kind of stupid, it told me that since I was using port 80 for this, I should access its settings through port 8080. Maybe it can't detect requests coming from the LAN, I don't know. Point is, now neither port can't access the configuration, and I can't access Internet. Specifically, trying to access anything (including 192.168.1.1, the router's settings) through port 80 turns up a blank page (maybe if I had the server running in my computer I'd get something, but I don't want to risk trying, I had to reset the router and restore the settings), and port 8080 gives a "Can't establish connection" error in Firefox (and similar ones in other browsers). Is there a way to configure the router to not redirect requests coming from inside the network? I'm a beginner with this stuff, so please try to explain in a simple way. If this is more appropiate in Super User, I'm sorry.

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Add single sign-on into existing web app

- by EvilDr

Apologies if this isn't the best site, I've search for an answer but can't find anything quite right. I don't actually now the correct terminology I should be using here, so any pointers will be appreciated. I have a web application that accessed by many different users across different organisations. Access is provided by each user having a unique username/password which is stored in SQL (database fields are customerID, userID, username). Some organisations are now asking if we can change this to allow "Active Directory single sign-on" so that users don't need to remember yet another set of login details. From research I can see how this is achieved using OpenAuth and Google (etc), but I know hardly anything about AD and can't find much information on this (again I'm sure it helps when you know the terminology). Is this request even possible to achieve, given that most users will be from different (and unrelated) organisations? I saw on a Microsoft Build video not long ago that there is some kind of replication service for AD to allow Cloud authentication. Is this what I should be aiming for?

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Proper web server setup

- by DMin

I just got myself a slicehost basic slice to play around with so I can learn how to setup web-servers. I have Ubuntu 10.04.2 installed on the server. I was able to successfully get the server up and running from scratch, these were the things I did - following this tutorial. I know this is probably just a starters tutorial, so, I was wondering if you guys can tell me what you like to do while setting up production servers. These are the steps that were followed : Update and Upgrade Ubuntu sudo apt-get install apache2 php5-mysql libapache2-mod-php5 mysql-server Backup a copy of and edit apache2.conf Set : 'ServerTokens Full' to 'ServerTokens Prod''ServerSignature On' to 'ServerSignature Off' Backup php.ini and then Change “expose_php = On” to “expose_php = Off” Restart Apache Install Shorewall firewall Configure Shorewall to only accept HTTP and SSH connections(in the rules file) Enable shorewall on startup Add the website to the server : sudo usermod -g www-data root sudo chown -R www-data:www-data /var/www sudo chmod -R 775 /var/www I want make this CommunityWiki but can't seem to find the option to do it. Please feel free to add any feedback on the processes and things I am doing right/wrong. Much appriciated, thanks! :)

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