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• Permissions in OS X for iTunes library with multiple users

  - by John

  I currently have a lot of music on an external drive and my iTunes set up from there. However, periodically, when the external drive isn't connected, iTunes will default back to the library location of my home directory user path. I don't want to mess with an external drive, as my Mac's HD is large enough to house the music collection. However, I have 4 family members – all with their own logins – using this same gob of music. I don't want four copies of the library, only one with all libraries referencing it. So, what I want to do is: Move all music files to a shared directory at /Macintosh HD/users/music. I created this directory and adjusted permissions, so all four users can read and write to this directory. Get all four accounts to reference this library instead of the external or local home locations I am hoping I can just check the box to keep library organized in my account, which is the admin and let iTunes move it all. Then delete current libraries for each account and re-add from the new shared location. Will the iTunes organization process cause permissions issues either by setting permissions to all the files access to my account only or write permissions or any other 'gotcha'? I am having a hard time coming up with a smooth solution that won't break everything and cause me to have mega duplicates or access issues. I would prefer not to do any XML library file editing if possible. Am I dreaming?

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• Java map / nio / NFS issue causing a VM fault: "a fault occurred in a recent unsafe memory access op

  - by Matthew Bloch

  I have written a parser class for a particular binary format (nfdump if anyone is interested) which uses java.nio's MappedByteBuffer to read through files of a few GB each. The binary format is just a series of headers and mostly fixed-size binary records, which are fed out to the called by calling nextRecord(), which pushes on the state machine, returning null when it's done. It performs well. It works on a development machine. On my production host, it can run for a few minutes or hours, but always seems to throw "java.lang.InternalError: a fault occurred in a recent unsafe memory access operation in compiled Java code", fingering one of the Map.getInt, getShort methods, i.e. a read operation in the map. The uncontroversial (?) code that sets up the map is this: /** Set up the map from the given filename and position */ protected void open() throws IOException { // Set up buffer, is this all the flexibility we'll need? channel = new FileInputStream(file).getChannel(); MappedByteBuffer map1 = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size()); map1.load(); // we want the whole thing, plus seems to reduce frequency of crashes? map = map1; // assumes the host writing the files is little-endian (x86), ought to be configurable map.order(java.nio.ByteOrder.LITTLE_ENDIAN); map.position(position); } and then I use the various map.get* methods to read shorts, ints, longs and other sequences of bytes, before hitting the end of the file and closing the map. I've never seen the exception thrown on my development host. But the significant point of difference between my production host and development is that on the former, I am reading sequences of these files over NFS (probably 6-8TB eventually, still growing). On my dev machine, I have a smaller selection of these files locally (60GB), but when it blows up on the production host it's usually well before it gets to 60GB of data. Both machines are running java 1.6.0_20-b02, though the production host is running Debian/lenny, the dev host is Ubuntu/karmic. I'm not convinced that will make any difference. Both machines have 16GB RAM, and are running with the same java heap settings. I take the view that if there is a bug in my code, there is enough of a bug in the JVM not to throw me a proper exception! But I think it is just a particular JVM implementation bug due to interactions between NFS and mmap, possibly a recurrence of 6244515 which is officially fixed. I already tried adding in a "load" call to force the MappedByteBuffer to load its contents into RAM - this seemed to delay the error in the one test run I've done, but not prevent it. Or it could be coincidence that was the longest it had gone before crashing! If you've read this far and have done this kind of thing with java.nio before, what would your instinct be? Right now mine is to rewrite it without nio :)

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• How can I pipe input to a Java app with Perl?

  - by user319479

  I need to write a Perl script that pipes input into a Java program. This is related to this, but that didn't help me. My issue is that the Java app doesn't get the print statements until I close the handle. What I found online was that $| needs to be set to something greater than 0, in which case newline characters will flush the buffer. This still doesn't work. This is the script: #! /usr/bin/perl -w use strict; use File::Basename; $|=1; open(TP, "| java -jar test.jar") or die "fail"; sleep(2); print TP "this is test 1\n"; print TP "this is test 2\n"; print "tests printed, waiting 5s\n"; sleep(5); print "wait over. closing handle...\n"; close TP; print "closed.\n"; print "sleeping for 5s...\n"; sleep(5); print "script finished!\n"; exit And here is a sample Java app: import java.util.Scanner; public class test{ public static void main( String[] args ){ Scanner sc = new Scanner( System.in ); int crashcount = 0; while( true ){ try{ String input = sc.nextLine(); System.out.println( ":: INPUT: " + input ); if( "bananas".equals(input) ){ break; } } catch( Exception e ){ System.out.println( ":: EXCEPTION: " + e.toString() ); crashcount++; if( crashcount == 5 ){ System.out.println( ":: Looks like stdin is broke" ); break; } } } System.out.println( ":: IT'S OVER!" ); return; } } The Java app should respond to receiving the test prints immediately, but it doesn't until the close statement in the Perl script. What am I doing wrong? Note: the fix can only be in the Perl script. The Java app can't be changed. Also, File::Basename is there because I'm using it in the real script.

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• Retrieve KEYWORDS from META tag in a HTML WebPage using JAVA.

  - by kooldave98

  Hello all, I want to retrieve all the content words from a HTML WebPage and all the keywords contained in the META TAG of the same HTML webpage using Java. For example, consider this html source code: <html> <head> <meta name = "keywords" content = "deception, intricacy, treachery"> </head> <body> My very short html document. <br> It has just 2 'lines'. </body> </html> The CONTENT WORDS here are: my, very, short, html, document, it, has, just, lines Note: The punctuation and the number '2' are ruled out. The KEYWORDS here are: deception, intricacy, treachery I have created a class for this purpose called WebDoc, this is as far as I have been able to get. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.util.Set; import java.util.TreeSet; public class WebDoc { protected URL _url; protected Set<String> _contentWords; protected Set<String> _keyWords public WebDoc(URL paramURL) { _url = paramURL; } public Set<String> getContents() throws IOException { //URL url = new URL(url); Set<String> contentWords = new TreeSet<String>(); BufferedReader in = new BufferedReader(new InputStreamReader(_url.openStream())); String inputLine; while ((inputLine = in.readLine()) != null) { // Process each line. contentWords.add(RemoveTag(inputLine)); //System.out.println(RemoveTag(inputLine)); } in.close(); System.out.println(contentWords); _contentWords = contentWords; return contentWords; } public String RemoveTag(String html) { html = html.replaceAll("\\<.*?>",""); html = html.replaceAll("&",""); return html; } public Set<String> getKeywords() { //NO IDEA ! return null; } public URL getURL() { return _url; } @Override public String toString() { return null; } }

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• The battle between Java vs. C#

  The battle between Java vs. C# has been a big debate amongst the development community over the last few years. Both languages have specific pros and cons based on the needs of a particular project. In general both languages utilize a similar coding syntax that is based on C++, and offer developers similar functionality. This being said, the communities supporting each of these languages are very different. The divide amongst the communities is much like the political divide in America, where the Java community would represent the Democrats and the .Net community would represent the Republicans. The Democratic Party is a proponent of the working class and the general population. Currently, Java is deeply entrenched in the open source community that is distributed freely to anyone who has an interest in using it. Open source communities rely on developers to keep it alive by constantly contributing code to make applications better; essentially they develop code by the community. This is in stark contrast to the C# community that is typically a pay to play community meaning that you must pay for code that you want to use because it is developed as products to be marketed and sold for a profit. This ties back into my reference to the Republicans because they typically represent the needs of business and personal responsibility. This is emphasized by the belief that code is a commodity and that it can be sold for a profit which is in direct conflict to the laissez-faire beliefs of the open source community. Beyond the general differences between Java and C#, they also target two different environments. Java is developed to be environment independent and only requires that users have a Java virtual machine running in order for the java code to execute. C# on the other hand typically targets any system running a windows operating system and has the appropriate version of the .Net Framework installed. However, recently there has been push by a segment of the Open source community based around the Mono project that lets C# code run on other non-windows operating systems. In addition, another feature of C# is that it compiles into an intermediate language, and this is what is executed when the program runs. Because C# is reduced down to an intermediate language called Common Language Runtime (CLR) it can be combined with other languages that are also compiled in to the CLR like Visual Basic (VB) .Net, and F#. The allowance and interaction between multiple languages in the .Net Framework enables projects to utilize existing code bases regardless of the actual syntax because they can be compiled in to CLR and executed as one codebase. As a software engineer I personally feel that it is really important to learn as many languages as you can or at least be open to learn as many languages as you can because no one language will work in every situation.  In some cases Java may be a better choice for a project and others may be C#. It really depends on the requirements of a project and the time constraints. In addition, I feel that is really important to concentrate on understanding the logic of programming and be able to translate business requirements into technical requirements. If you can understand both programming logic and business requirements then deciding which language to use is just basically choosing what syntax to write for a given business problem or need. In regards to code refactoring and dynamic languages it really does not matter. Eventually all projects will be refactored or decommissioned to allow for progress. This is the way of life in the software development industry. The language of a project should not be chosen based on the fact that a project will eventually be refactored because they all will get refactored.

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• Linking LAPACK/BLAS libraries

  - by Daniel Bremberg

  Background: I am working on a project written in a mix of C and Fortran 77 and now need to link the LAPACK/BLAS libraries to the project (all in a Linux environment). The LAPACK in question is version 3.2.1 (including BLAS) from netlib.org. The libraries were compiled using the top level Makefile (make lapacklib and make blaslib). Problem: During linking, error messages claimed that certain (not all) BLAS-routines called from LAPACK-routines were undefined. This gave me some headache but the problem was eventually solved when (in the Makefile) the order of appearance of the libraries to be linked was changed. Code: In the following, (a) gives errors while (b) does not. The linking is performed by (c). (a) LIBS = $(LAPACK)/blas_LINUX.a $(LAPACK)/lapack_LINUX.a (b) LIBS = $(LAPACK)/lapack_LINUX.a $(LAPACK)/blas_LINUX.a (c) gcc -Wall -O -o $@ project.o project.a $(LIBS) Question: What could be the reason for the undefined references of only some routines and what makes the order of appearance relevant?

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• Good reasons to migrate PHP libraries to namespaces

  - by Joseph Mastey

  I have a significant number of object libraries written for PHP 5.2.5, and I'm trying to weigh the benefits of retrofitting them for namespaces. I don't have any concerns about the server PHP version at the moment, since any relevant machines are under my control, so I'm not worried about backwards compatibility. As far as the structure of the libraries, I use the same convention as Zend Framework, (Library_Module_Class_Name e.g.) so I don't currently have any naming conflicts internal to the libraries. I'd anticipate moving the Library and Module parts of those classnames to namespaces. That said, if the code is already written, is there any good reason to move over to namespaces? Thanks, Joe

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• Error in Mono Compiler: Files in libraries or multiple-file applications must begin with a namespace

  - by leon

  I am trying to compile this example in mono on ubuntu. However I get the error wingsit@wingsit-laptop:~/MyFS/kitty$ fsc.exe -o kitty.exe kittyAst.fs kittyParser.fs kittyLexer.fs main.fs Microsoft (R) F# 2.0 Compiler build 2.0.0.0 Copyright (c) Microsoft Corporation. All Rights Reserved. /home/wingsit/MyFS/kitty/kittyAst.fs(1,1): error FS0222: Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule' /home/wingsit/MyFS/kitty/kittyParser.fs(2,1): error FS0222: Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule' /home/wingsit/MyFS/kitty/kittyLexer.fsl(2,1): error FS0222: Files in libraries or multiple-file applications must begin with a namespace or module declaration, e.g. 'namespace SomeNamespace.SubNamespace' or 'module SomeNamespace.SomeModule' wingsit@wingsit-laptop:~/MyFS/kitty$ I am a newbie in F#. Is there something obvious I miss?

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• shared libraries creating a soft link

  - by robUK

  Hello, Redhat 5.5 gcc version 4.1.2 I have a directory call lib, and in that directory I have all the shared libraries (about 30) that we get from our customer as we use their API. We link with this API. directory structure: /usr/CSAPI/lib However, our customer will update their API so we get new libraries, normally about 3 or 4. What I have been doing is when I get new libraries. Is to remove the old one and put in another directory. And replace them with the new libaries in the lib directory. /usr/CSAPI/Old_libs The new and old will have the same name. i.e. libcs.so < old libcs.so < new Is there a better way to manage this? I was thinking of creating a soft line, but as the names are the same, I am not sure that this will work. Many thanks,

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• macdeployqt and third party libraries

  - by user338170

  I've got an application project that depends on a couple of shared libraries that I have created myself. According to the Qt 4.6 documentation "Deploying an Application on Mac OSX": Note: If you want a 3rd party library to be included in your application bundle, then you must add an excplicit lib entry for that library to your application's .pro file. Otherwise, the macdeployqt tool will not copy the 3rd party .dylib into the bundle. I have added lib entries to my application's .pro file but the libraries that I have written do not get copied into the bundle when I execute macdeployqt. I have the following in my .pro file: LIBS += -L../Libraries -lMyLib Everything builds okay, its just when I try to run from the bundle that I run into problems i.e. "image not found" errors. Is there a bug in macdeployqt or do I have to something more to my .pro file?

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• How do I include external Libraries in CodeIgniter?

  - by user259954

  I'm new to codeigniter, and I'm trying to integrate amazon's FPS into my page. There are a bunch of libraries and models that go with Amazon FPS, which I would need included to make the appropriate calls. How do I include them in CodeIgniter? I tried placing the entire Amazon folder inside the system/libraries directory, and then tried including libraries with $this-load-library( 'Amazon/FPS/Client' ); However, I run into problems with the relative path there, because Client.php contains the statement require_once ('Amazon/FPS/Interface.php'); ... which is in the same folder. There has to be a better way to do all this - can anyone please help? Thanks!!

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• JSF implementations and component libraries

  - by Avinash Nandagiri

  I have just started using JSF and I have three questions related to JSF implementations and component libraries What is the difference between JSF Implementations and Component Libraries? What are the various JSF implementations (like Apache MyFaces) that are available and what is the difference between each one of them? What are the various JSF component libraries (like rich faces and ice faces) that are available and what is the difference between each one of them? Any relevant links giving the exact information on this would also be helpful. Thanks a lot in advance.

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• Including external C++ libraries in version control

  - by m0tive

  I'm currently starting a project which is going to be developed on a few different computer and I'm keeping in sync with bzr. In the project I'm using a couple of 3rd party libraries, like SDL. In the past I've just pushed a copy of the compiled library to my version control, but that usually seems to massively inflate the size of the branch and generally seem like a bad idea. Is that the normal practice, just pushing the required libraries, or is there a better way of added libraries to distributed version control like bzr or git? (I know on svn you can use svn:external to do something similar to this)

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• Including Libraries C++

  - by m00st

  How do I properly include libraries in C++? I'm used to doing the standard libraries in C++ and my own .h files. I'm trying to include wxWidgets or GTK+ in code::blocks and/or netbeans C/C++ plugin. I've included ALL libraries but I constantly get errors such as file not found when it is explicitly in the include! One error: test1.cpp:1:24: wx/msw/wx.rc: No such file or directory : Yes the .h file library is included; what am I missing? Do I need to be importing other things as well? Is there a tutorial for this? Obviously my shoddy textbook hasn't prepared me for this.

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• C++ shared libraries

  - by saminny

  Hi, I am trying to get my head around the way shared libraries work in the c++ unix environment. I understand we only need header files and no shared libraries specification when compiling code. But if I want to create an executable or shared library from my compiled files, do I need to specify shared library dependencies (those are dynamic)? And do the paths of shared libraries need to match the path at runtime loading? I am using Linux 2.6.18-164.11.1.el5 #1 SMP x86_64 GNU/Linux I am having a problem where my code is not able to pick up a library at runtime. I have tried setting LD_LIBRARY_PATH and PATH. But at runtime when I run the executable, I get the following error: Error: librc.so: cannot open shared object file: No such file or directory Sam

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• Can I include both Apache Axis 1 and 2 libraries in the same project?

  - by ian_scho_es

  If it sounds like a ridiculous idea then it is. The client only wants to have to install one project on their server. Our web service will be bridging between mobile phones and various SOAP services made in .NET, Apache Axis 1 and 2, which rely on standards to transfer files such as MTOM and DIME. I am looking for an 'architecture' trick, such as develop the Axis 1 calls in a separate project and compile as a jar, to then pass it into the Axis 2 project.... Hmmm. Anything rather than having to download the source code for Axis 1 & 2 and compile them using the same xml libraries, etc. "It can't be done" is an acceptable answer. Thanks!

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• Unrecognized libraries and functions

  - by John Smith

  I am working in Eclipse 3.7.2 on Ubuntu 12.04 with C++. I have read about a few instances where libraries were not being recognized and the majority said to update the Paths and Symbols but that hasn't fixed my issue. I have 2 projects open in my workspace, one of which is already a completed project that has implemented functions and libraries with no errors from Eclipse. However, when I try to implement some of the same functions or include the same libraries in the 2nd project Eclipse can't resolve them. For example, #include <string> #include <stdio.h> strstr(p, "<Project>"); The include statement will be accepted and stdio.h will be found but the strstr function is not resolved even though it works fine in the other project. Any ideas as to why this might be happening? Thanks.

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• Java: how to avoid circual references when dumping object information with reflection?

  - by Tom

  I've modified an object dumping method to avoid circual references causing a StackOverflow error. This is what I ended up with: //returns all fields of the given object in a string public static String dumpFields(Object o, int callCount, ArrayList excludeList) { //add this object to the exclude list to avoid circual references in the future if (excludeList == null) excludeList = new ArrayList(); excludeList.add(o); callCount++; StringBuffer tabs = new StringBuffer(); for (int k = 0; k < callCount; k++) { tabs.append("\t"); } StringBuffer buffer = new StringBuffer(); Class oClass = o.getClass(); if (oClass.isArray()) { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("["); for (int i = 0; i < Array.getLength(o); i++) { if (i < 0) buffer.append(","); Object value = Array.get(o, i); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if (value.getClass().isPrimitive() || value.getClass() == java.lang.Long.class || value.getClass() == java.lang.String.class || value.getClass() == java.lang.Integer.class || value.getClass() == java.lang.Boolean.class) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } buffer.append(tabs.toString()); buffer.append("]\n"); } else { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("{\n"); while (oClass != null) { Field[] fields = oClass.getDeclaredFields(); for (int i = 0; i < fields.length; i++) { if (fields[i] == null) continue; buffer.append(tabs.toString()); fields[i].setAccessible(true); buffer.append(fields[i].getName()); buffer.append("="); try { Object value = fields[i].get(o); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if ((value.getClass().isPrimitive()) || (value.getClass() == java.lang.Long.class) || (value.getClass() == java.lang.String.class) || (value.getClass() == java.lang.Integer.class) || (value.getClass() == java.lang.Boolean.class)) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } catch (IllegalAccessException e) { System.out.println("IllegalAccessException: " + e.getMessage()); } buffer.append("\n"); } oClass = oClass.getSuperclass(); } buffer.append(tabs.toString()); buffer.append("}\n"); } return buffer.toString(); } The method is initially called like this: System.out.println(dumpFields(obj, 0, null); So, basically I added an excludeList which contains all the previousely checked objects. Now, if an object contains another object and that object links back to the original object, it should not follow that object further down the chain. However, my logic seems to have a flaw as I still get stuck in an infinite loop. Does anyone know why this is happening?

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• org.apache.sling.scripting.jsp.jasper.JasperException: Unable to load tag handler class [migrated]

  - by Babak Behzadi

  I'm developing an Apache Sling WCMS and using java tag libs to rendering some data. I defined a jsp tag lib with following descriptor and handler class: TLD file contains: <?xml version="1.0" encoding="UTF-8"?> <taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"> <tlib-version>1.0</tlib-version> <short-name>taglibdescriptor</short-name> <uri>http://bob/taglibs</uri> <tag> <name>testTag</name> <body-content>tagdependent</body-content> <tag-class>org.bob.taglibs.test.TestTagHandler</tag-class> </tag> </taglib> Tag handler class: package org.bob.taglibs.test; import javax.servlet.jsp.tagext.TagSupport; public class TestTagHandler extends TagSupport{ @Override public int doStartTag(){ try { pageContext.getOut().print("<h1>Helloooooooo</h1>"); } catch(Exception e) { return SKIP_BODY; } return EVAL_BODY_INCLUDE; } } I packaged the tag lib as BobTagLib.jar and deployed it as a bundle using Sling Web Console. I used this tag lib in a jsp page deployed in my Sling repository: index.jsp: <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="bob" uri="http://bob/taglibs" %> <html> <head><title>Simple jsp page</title></head> <body> <bob:testTag/> </body> </html> Calling the page cause the following exception: org.apache.sling.scripting.jsp.jasper.JasperException: /apps/TagTest/index.jsp(7,5) Unable to load tag handler class "org.bob.taglibs.test.TestTagHandler" for tag "bob:testTag" ... Can any one get me a solution? In advance, any help is apreciated.

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• How much freedom should a programmer have in choosing a language and framework?

  - by Spencer

  I started working at a company that is primarily a C# oriented. We have a few people who like Java and JRuby, but a majority of programmers here like C#. I was hired because I have a lot of experience building web applications and because I lean towards newer technologies like JRuby on Rails or nodejs. I have recently started on a project building a web application with a focus on getting a lot of stuff done in a short amount of time. The software lead has dictated that I use mvc4 instead of rails. That might be OK, except I don't know mvc4, I don't know C# and I am the only one responsible for creating the web application server and front-end UI. Wouldn't it make sense to use a framework that I already know extremely well (Rails) instead of using mvc4? The two reasons behind the decision was that the tech lead doesn't know Jruby/rails and there would be no way to reuse the code. Counter arguments: He won't be contributing to the code and is frankly, not needed on this project. So, it doesn't really matter if he knows JRuby/rails or not. We actually can reuse the code since we have a lot of java apps that JRuby can pull code from and vice-versa. In fact, he has dedicated some resources to convert a Java library to C#, instead of just running the Java library on the JRuby on Rails app. All because he doesn't like Java or JRuby I have built many web applications, but using something unfamiliar is causing some spin-up and I am unable to build an awesome application in as short of a time that I'm used to. This would be fine, learning new technologies is important in this field. The problem is, for this project, we need to get a lot done in a short period of time. At what point should a developer be allowed to choose his tools? Is this dependent on the company? Does my company suck or is this considered normal? Do greener pastures exist? Am I looking at this the wrong way? Bonus: Should I just keep my head down and move along at a snails pace, or defy orders and go with what I know in order to make this project more successful? Edit: I had actually created a fully function rails application (on my own time) and showed it to the team and it did not seem to matter. I am currently porting it to mvc4 (slowly).

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• Session Report - Java on the Raspberry Pi

  - by Janice J. Heiss

  On mid-day Wednesday, the always colorful Oracle Evangelist Simon Ritter demonstrated Java on the Raspberry Pi at his session, “Do You Like Coffee with Your Dessert?”. The Raspberry Pi consists of a credit card-sized single-board computer developed in the UK with the intention of stimulating the teaching of basic computer science in schools. “I don't think there is a single feature that makes the Raspberry Pi significant,” observed Ritter, “but a combination of things really makes it stand out. First, it's $35 for what is effectively a completely usable computer. You do have to add a power supply, SD card for storage and maybe a screen, keyboard and mouse, but this is still way cheaper than a typical PC. The choice of an ARM (Advanced RISC Machine and Acorn RISC Machine) processor is noteworthy, because it avoids problems like cooling (no heat sink or fan) and can use a USB power brick. When you add in the enormous community support, it offers a great platform for teaching everyone about computing.”Some 200 enthusiastic attendees were present at the session which had the feel of Simon Ritter sharing a fun toy with friends. The main point of the session was to show what Oracle was doing to support Java on the Raspberry Pi in a way that is entertaining and fun. Ritter pointed out that, in addition to being great for teaching, it’s an excellent introduction to the ARM architecture, and runs well with Java and will get better once it has official hard float support. The possibilities are vast.Ritter explained that the Raspberry Pi Project started in 2006 with the goal of devising a computer to inspire children; it drew inspiration from the BBC Micro literacy project of 1981 that produced a series of microcomputers created by the Acorn Computer company. It was officially launched on February 29, 2012, with a first production of 10,000 boards. There were 100,000 pre-orders in one day; currently about 4,000 boards are produced a day. Ritter described the specification as follows:* CPU: ARM 11 core running at 700MHz Broadcom SoC package Can now be overclocked to 1GHz (without breaking the warranty!) * Memory: 256Mb* I/O: HDMI and composite video 2 x USB ports (Model B only) Ethernet (Model B only) Header pins for GPIO, UART, SPI and I2C He took attendees through a brief history of ARM Architecture:* Acorn BBC Micro (6502 based) Not powerful enough for Acorn’s plans for a business computer * Berkeley RISC Project UNIX kernel only used 30% of instruction set of Motorola 68000 More registers, less instructions (Register windows) One chip architecture to come from this was… SPARC * Acorn RISC Machine (ARM) 32-bit data, 26-bit address space, 27 registers First machine was Acorn Archimedes * Spin off from Acorn, Advanced RISC MachinesNext he presented its features:* 32-bit RISC Architecture–  ARM accounts for 75% of embedded 32-bit CPUs today– 6.1 Billion chips sold last year (zero manufactured by ARM)* Abstract architecture and microprocessor core designs– Raspberry Pi is ARM11 using ARMv6 instruction set* Low power consumption– Good for mobile devices– Raspberry Pi can be powered from 700mA 5V only PSU– Raspberry Pi does not require heatsink or fanHe described the current ARM Technology:* ARMv6– ARM 11, ARM Cortex-M* ARMv7– ARM Cortex-A, ARM Cortex-M, ARM Cortex-R* ARMv8 (Announced)– Will support 64-bit data and addressingHe next gave the Java Specifics for ARM: Floating point operations* Despite being an ARMv6 processor it does include an FPU– FPU only became standard as of ARMv7* FPU (Hard Float, or HF) is much faster than a software library* Linux distros and Oracle JVM for ARM assume no HF on ARMv6– Need special build of both– Raspbian distro build now available– Oracle JVM is in the works, release date TBDNot So RISCPerformance Improvements* DSP Enhancements* Jazelle* Thumb / Thumb2 / ThumbEE* Floating Point (VFP)* NEON* Security Enhancements (TrustZone)He spent a few minutes going over the challenges of using Java on the Raspberry Pi and covered:* Sound* Vision * Serial (TTL UART)* USB* GPIOTo implement sound with Java he pointed out:* Sound drivers are now included in new distros* Java Sound API– Remember to add audio to user’s groups– Some bits work, others not so much* Playing (the right format) WAV file works* Using MIDI hangs trying to open a synthesizer* FreeTTS text-to-speech– Should work once sound works properlyHe turned to JavaFX on the Raspberry Pi:* Currently internal builds only– Will be released as technology preview soon* Work involves optimal implementation of Prism graphics engine– X11?* Once the JavaFX implementation is completed there will be little of concern to developers-- It’s just Java (WORA). He explained the basis of the Serial Port:* UART provides TTL level signals (3.3V)* RS-232 uses 12V signals* Use MAX3232 chip to convert* Use this for access to serial consoleHe summarized his key points. The Raspberry Pi is a very cool (and cheap) computer that is great for teaching, a great introduction to ARM that works very well with Java and will work better in the future. The opportunities are limitless. For further info, check out, Raspberry Pi User Guide by Eben Upton and Gareth Halfacree. From there, Ritter tried out several fun demos, some of which worked better than others, but all of which were greeted with considerable enthusiasm and support and good humor (even when he ran into some glitches).  All in all, this was a fun and lively session.

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• Merge sort. ArrayIndexOutOfBoundsException [migrated]

  - by user94892

  When I execute the program I am getting an error as stated below the program. Please help me figure out the problem.. import java.util.*; class Mergesort { public static void main(String args[]) { Scanner in= new Scanner(System.in); System.out.println("Enter the number of elements"); int n= in.nextInt(); int a[]= new int[n]; System.out.println("Enter the contents"); for(int i=0; i<n; i++) { a[i]=in.nextInt(); } a = mergesort(a,n); for(int i=0; i<n; i++) { System.out.println(a[i]); } } public static int[] mergesort(int[] x, int z) { if(z==1) { return x; } int b[]=new int[z/2]; int c[]=new int[z-z/2]; int i,j,k; for(int p=0;p<z/2; p++) { b[p]= x[p]; c[p]= x[p+z/2]; } c[z-z/2-1]= x[z-1]; b= mergesort(b,z/2); c= mergesort(c,z-z/2); for(i=0,j=0,k=0; k<z; k++) { if(b[i]<=c[j]) { x[k]=b[i]; i++; } else if( b[i]>c[j]) { x[k]=c[j]; j++; } else if(i== z/2) { x[k]= c[j]; j++; } else if(j == z-z/2) { x[k]= b[i]; i++; } } return x; } } Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 at Mergesort.mergesort(Mergesort.java:41) at Mergesort.mergesort(Mergesort.java:36) at Mergesort.main(Mergesort.java:16)

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• Monitoring C++ applications

  - by Scott A

  We're implementing a new centralized monitoring solution (Zenoss). Incorporating servers, networking, and Java programs is straightforward with SNMP and JMX. The question, however, is what are the best practices for monitoring and managing custom C++ applications in large, heterogenous (Solaris x86, RHEL Linux, Windows) environments? Possibilities I see are: Net SNMP Advantages single, central daemon on each server well-known standard easy integration into monitoring solutions we run Net SNMP daemons on our servers already Disadvantages: complex implementation (MIBs, Net SNMP library) new technology to introduce for the C++ developers rsyslog Advantages single, central daemon on each server well-known standard unknown integration into monitoring solutions (I know they can do alerts based on text, but how well would it work for sending telemetry like memory usage, queue depths, thread capacity, etc) simple implementation Disadvantages: possible integration issues somewhat new technology for C++ developers possible porting issues if we switch monitoring vendors probably involves coming up with an ad-hoc communication protocol (or using RFC5424 structured data; I don't know if Zenoss supports that without custom Zenpack coding) Embedded JMX (embed a JVM and use JNI) Advantages consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions somewhat simple implementation (we already do this today for other purposes) Disadvantages: complexity (JNI, thunking layer between native C++ and Java, basically writing the management code twice) possible stability problems requires a JVM in each process, using considerably more memory JMX is new technology for C++ developers each process has it's own JMX port (we run a lot of processes on each machine) Local JMX daemon, processes connect to it Advantages single, central daemon on each server consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions Disadvantages: complexity (basically writing the management code twice) need to find or write such a daemon need a protocol between the JMX daemon and the C++ process JMX is new technology for C++ developers CodeMesh JunC++ion Advantages consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions single, central daemon on each server when run in shared JVM mode somewhat simple implementation (requires code generation) Disadvantages: complexity (code generation, requires a GUI and several rounds of tweaking to produce the proxied code) possible JNI stability problems requires a JVM in each process, using considerably more memory (in embedded mode) Does not support Solaris x86 (deal breaker) Even if it did support Solaris x86, there are possible compiler compatibility issues (we use an odd combination of STLPort and Forte on Solaris each process has it's own JMX port when run in embedded mode (we run a lot of processes on each machine) possibly precludes a shared JMX server for non-C++ processes (?) Is there some reasonably standardized, simple solution I'm missing? Given no other reasonable solutions, which of these solutions is typically used for custom C++ programs? My gut feel is that Net SNMP is how people do this, but I'd like other's input and experience before I make a decision.

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• Deploying web services on a RHEL 5 box using Apache/Tomcat/Axis/Java.

  - by Deepak Konidena

  Hi, I am new to the Web services scene. I currently have access to a RHEL5 box and i need to deploy a java web service on it. It runs apache and i know this because i have a website hosted on this machine. Now, i want to deploy a web service on to this website to be able to just pass a link to someone when they need to access my web service. Could someone point out a resource or explain what all i need to get the webservice deployed using Tomcat/Apache Axis and Java. I have done this on Windows (hosted on localhost) but couldn't quite figure out things on linux. Any help is greatly appreciated. Thanks. Deepak.

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• How do you keep Flash, Quicktime, Java etc up to date for your non-admin users?

  - by Scott

  How do you keep Flash, Quicktime, Java etc up to date for your non-admin users? Thanks

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