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• Should design, architecture and modeling be part of education?

  - by Gabriel Šcerbák

  I often heard, that those things cannot be teached, because you can master them only through good gut feeling fed with years of experience. However various patterns and principles are quite well documented and I start to think, that you can actually learn quite a lot of good stuff from books, training and exercises. What is your uptake?

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• Can't find method in the activity

  - by Synesso

  I'm starting with Scala + Android. I'm trying to wire a button action to a button without the activity implementing View.OnClickListener. The button click fails at runtime because the method cannot be found. The document I'm working through says that I need only declare a public void method taking a View on the action, and use that method name in the layout. What have I done wrong? MainActivity.scala package net.badgerhunt.hwa import android.app.Activity import android.os.Bundle import android.widget.Button import android.view.View import java.util.Date class MainActivity extends Activity { override def onCreate(savedInstanceState: Bundle) = { super.onCreate(savedInstanceState) setContentView(R.layout.main) } def calculate(button: View): Unit = println("calculating with %s ...".format(button)) } res/layout/main.xml <?xml version="1.0" encoding="utf-8"?> <Button xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/button" android:text="" android:onClick="calculate" android:layout_width="fill_parent" android:layout_height="fill_parent"/> the failure onclick D/AndroidRuntime( 362): Shutting down VM W/dalvikvm( 362): threadid=3: thread exiting with uncaught exception (group=0x4001b188) E/AndroidRuntime( 362): Uncaught handler: thread main exiting due to uncaught exception E/AndroidRuntime( 362): java.lang.IllegalStateException: Could not find a method calculate(View) in the activity E/AndroidRuntime( 362): at android.view.View$1.onClick(View.java:2020) E/AndroidRuntime( 362): at android.view.View.performClick(View.java:2364) E/AndroidRuntime( 362): at android.view.View.onTouchEvent(View.java:4179) E/AndroidRuntime( 362): at android.widget.TextView.onTouchEvent(TextView.java:6540) E/AndroidRuntime( 362): at android.view.View.dispatchTouchEvent(View.java:3709) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107) E/AndroidRuntime( 362): at android.app.Activity.dispatchTouchEvent(Activity.java:2061) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643) E/AndroidRuntime( 362): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691) E/AndroidRuntime( 362): at android.os.Handler.dispatchMessage(Handler.java:99) E/AndroidRuntime( 362): at android.os.Looper.loop(Looper.java:123) E/AndroidRuntime( 362): at android.app.ActivityThread.main(ActivityThread.java:4363) E/AndroidRuntime( 362): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime( 362): at java.lang.reflect.Method.invoke(Method.java:521) E/AndroidRuntime( 362): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) E/AndroidRuntime( 362): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) E/AndroidRuntime( 362): at dalvik.system.NativeStart.main(Native Method) E/AndroidRuntime( 362): Caused by: java.lang.NoSuchMethodException: calculate E/AndroidRuntime( 362): at java.lang.ClassCache.findMethodByName(ClassCache.java:308) E/AndroidRuntime( 362): at java.lang.Class.getMethod(Class.java:1014) E/AndroidRuntime( 362): at android.view.View$1.onClick(View.java:2017) E/AndroidRuntime( 362): ... 20 more

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• Unexpected StackOverflowError in KeyListener

  - by BillThePlatypus

  I am writing a program that can write sets of questions for review to a file for another program to read. The possible answers are typed into JTextFields at the bottom. It has code to ensure that there won't bew more than one blank JTextField at the end. When I type in answers, at varying points it will throw a StackOverflowError. The stack trace: Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232) at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232) at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232) at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232) and the code: package writer; import java.awt.BorderLayout; import java.awt.Font; import java.awt.FontMetrics; import java.awt.GridLayout; import java.awt.Insets; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.util.ArrayList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JSplitPane; import javax.swing.JTextArea; import javax.swing.JTextField; import javax.swing.event.DocumentEvent; import javax.swing.event.DocumentListener; import main.QuestionSet; public class SetPanel extends JPanel implements KeyListener { private QuestionSet set; private WriterPanel writer; private JPanel top=new JPanel(new BorderLayout()),controls=new JPanel(new GridLayout(1,0)),answerPanel=new JPanel(new GridLayout(0,1)); private JSplitPane split; private JTextField title=new JTextField(); private JTextArea question=new JTextArea(); private ArrayList<JTextField> answers=new ArrayList<JTextField>(); public SetPanel(QuestionSet s,WriterPanel writer) { super(new BorderLayout()); top.add(controls,BorderLayout.PAGE_START); title.setFont(title.getFont().deriveFont(40f)); title.addKeyListener(new KeyListener(){ @Override public void keyTyped(KeyEvent e) { title.setText(WriterPanel.convertString(title.getText())); } @Override public void keyPressed(KeyEvent e) { title.setText(WriterPanel.convertString(title.getText())); } @Override public void keyReleased(KeyEvent e) { title.setText(WriterPanel.convertString(title.getText())); } }); title.getDocument().addDocumentListener(new DocumentListener(){ @Override public void insertUpdate(DocumentEvent e) { // TODO Auto-generated method stub fitTitle(); } @Override public void removeUpdate(DocumentEvent e) { // TODO Auto-generated method stub fitTitle(); } @Override public void changedUpdate(DocumentEvent e) { // TODO Auto-generated method stub fitTitle(); } }); top.add(title,BorderLayout.PAGE_END); this.add(top,BorderLayout.PAGE_START); question.setLineWrap(true); question.setWrapStyleWord(true); question.setFont(question.getFont().deriveFont(20f)); question.addKeyListener(new KeyListener(){ @Override public void keyTyped(KeyEvent e) { // TODO Auto-generated method stub question.setText(WriterPanel.convertString(question.getText())); } @Override public void keyPressed(KeyEvent e) { // TODO Auto-generated method stub question.setText(WriterPanel.convertString(question.getText())); } @Override public void keyReleased(KeyEvent e) { // TODO Auto-generated method stub question.setText(WriterPanel.convertString(question.getText())); }}); split=new JSplitPane(JSplitPane.VERTICAL_SPLIT,true,new JScrollPane(question),new JScrollPane(answerPanel)); split.setDividerLocation(150); this.add(split,BorderLayout.CENTER); answers.add(new JTextField()); answerPanel.add(answers.get(0)); answers.get(0).addKeyListener(this); } private void fitTitle() { if(title==null||title.getText().equals("")) return; //title.setText(WriterPanel.convertString(title.getText())); String text=title.getText(); Insets insets=title.getInsets(); int width=title.getWidth()-insets.left-insets.right; int height=title.getHeight()-insets.top-insets.bottom; Font root=title.getFont().deriveFont((float)height); FontMetrics m=title.getFontMetrics(root); if(m.stringWidth(text)<width) { title.setFont(title.getFont().deriveFont((float)height)); return; } float delta=-100; while(Math.abs(delta)>.1f) { m=title.getFontMetrics(root); int w=m.stringWidth(text); if(w==width) break; if(Math.signum(w-width)==Math.signum(delta)||root.getSize2D()+delta<0) { delta/=-10; continue; } root=root.deriveFont(root.getSize2D()+delta); } title.setFont(root); } private void fixAnswers() { //System.out.println(answers); while(answers.get(answers.size()-1).getText().equals("")&&answers.size()>1&&answers.get(answers.size()-2).getText().equals("")) removeAnswer(answers.size()-1); if(!answers.get(answers.size()-1).getText().equals("")) { answers.add(new JTextField()); answerPanel.add(answers.get(answers.size()-1)); answers.get(answers.size()-2).removeKeyListener(this); answerPanel.revalidate(); } answers.get(answers.size()-1).addKeyListener(this); } private void removeAnswer(int i) { answers.remove(i); answerPanel.remove(i); answerPanel.revalidate(); } @Override public void keyTyped(KeyEvent e) { // TODO Auto-generated method stub } @Override public void keyPressed(KeyEvent e) { // TODO Auto-generated method stub fixAnswers(); } @Override public void keyReleased(KeyEvent e) { // TODO Auto-generated method stub } } Thank you in advance for any help.

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• Installing Oracle 11gR2 on RHEL 6.2

  - by Chris

  Hello all I'm having some difficulty installing Oracle 11gR2 on RHEL 6.2 I have compiled a giant list of every single step I have taken so far I installed RHEL 6.2 on VMWARE it did it's easy install automatically I Selected 4gb of memory Selected max size of 80Gb Selected 2 processors Sorry for the bad styling copy paste isn't working correctly The version of oracle i downloaded is Linux x86-64 11.2.0.1 I am installing this on a local machine NOT a remote machine I followed the following documentation http://docs.oracle.com/cd/E11882_01/install.112/e24326/toc.htm I bolded the steps which I was least sure about from my research Easy installed with RHEL 6.2 for VMWARE Registered with red hat so I can get updates Reinstalled vmware-tools by pressing enter at every choice Sudo yum update at the end something about GPG key selected y then y Checked Memory Requirements grep MemTotal /proc/meminfo MemTotal: 3921368 kb uname -m x86_64 grep SwapTotal /proc/meminfo SwapTotal: 6160376 kb free total used free shared buffers cached Mem: 3921368 2032012 1889356 0 76216 1533268 -/+ buffers/cache: 422528 3498840 Swap: 6160376 0 6160376 df -h /dev/shm Filesystem Size Used Avail Use% Mounted on tmpfs 1.9G 276K 1.9G 1% /dev/shm df -h /tmp Filesystem Size Used Avail Use% Mounted on /dev/sda2 73G 2.7G 67G 4% / df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 73G 2.7G 67G 4% / tmpfs 1.9G 276K 1.9G 1% /dev/shm /dev/sda1 291M 58M 219M 21% /boot All looked fine to me except maybe for swap? Software Requirements cat /proc/version Linux version 2.6.32-220.el6.x86_64 ([email protected]) (gcc version 4.4.5 20110214 (Red Hat 4.4.5-6) (GCC) ) #1 SMP Wed Nov 9 08:03:13 EST 2011 uname -r 2.6.32-220.el6.x86_64 (same as above but whatever) According to the tutorial should be On Red Hat Enterprise Linux 6 2.6.32-71.el6.x86_64 or later These are the versions of software I have installed binutils-2.20.51.0.2-5.28.el6.x86_64 compat-libcap1-1.10-1.x86_64 compat-libstdc++-33-3.2.3-69.el6.x86_64 compat-libstdc++-33.i686 0:3.2.3-69.el6 gcc-4.4.6-3.el6.x86_64 gcc-c++.x86_64 0:4.4.6-3.el6 glibc-2.12-1.47.el6_2.12.x86_64 glibc-2.12-1.47.el6_2.12.i686 glibc-devel-2.12-1.47.el6_2.12.x86_64 glibc-devel.i686 0:2.12-1.47.el6_2.12 ksh.x86_64 0:20100621-12.el6_2.1 libgcc-4.4.6-3.el6.x86_64 libgcc-4.4.6-3.el6.i686 libstdc++-4.4.6-3.el6.x86_64 libstdc++.i686 0:4.4.6-3.el6 libstdc++-devel.i686 0:4.4.6-3.el6 libstdc++-devel-4.4.6-3.el6.x86_64 libaio-0.3.107-10.el6.x86_64 libaio-0.3.107-10.el6.i686 libaio-devel-0.3.107-10.el6.x86_64 libaio-devel-0.3.107-10.el6.i686 make-3.81-19.el6.x86_64 sysstat-9.0.4-18.el6.x86_64 unixODBC-2.2.14-11.el6.x86_64 unixODBC-devel-2.2.14-11.el6.x86_64 unixODBC-devel-2.2.14-11.el6.i686 unixODBC-2.2.14-11.el6.i686 8. Probably screwed up here or step 9 /usr/sbin/groupadd oinstall /usr/sbin/groupadd dba(not sure why this isn't in the tutorial) /usr/sbin/useradd -g oinstall -G dba oracle passwd oracle /sbin/sysctl -a | grep sem Xkernel.sem = 250 32000 32 128 /sbin/sysctl -a | grep shm kernel.shmmax = 68719476736 kernel.shmall = 4294967296 kernel.shmmni = 4096 vm.hugetlb_shm_group = 0 /sbin/sysctl -a | grep file-max Xfs.file-max = 384629 /sbin/sysctl -a | grep ip_local_port_range Xnet.ipv4.ip_local_port_range = 32768 61000 /sbin/sysctl -a | grep rmem_default Xnet.core.rmem_default = 124928 /sbin/sysctl -a | grep rmem_max Xnet.core.rmem_max = 131071 /sbin/sysctl -a | grep wmem_max Xnet.core.wmem_max = 131071 /sbin/sysctl -a | grep wmem_default Xnet.core.wmem_default = 124928 Here is my sysctl.conf file I only added the items that were bigger: Kernel sysctl configuration file for Red Hat Linux # For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and sysctl.conf(5) for more details. Controls IP packet forwarding net.ipv4.ip_forward = 0 Controls source route verification net.ipv4.conf.default.rp_filter = 1 Do not accept source routing net.ipv4.conf.default.accept_source_route = 0 Controls the System Request debugging functionality of the kernel kernel.sysrq = 0 Controls whether core dumps will append the PID to the core filename. Useful for debugging multi-threaded applications. kernel.core_uses_pid = 1 Controls the use of TCP syncookies net.ipv4.tcp_syncookies = 1 Disable netfilter on bridges. net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 Controls the maximum size of a message, in bytes kernel.msgmnb = 65536 Controls the default maxmimum size of a mesage queue kernel.msgmax = 65536 Controls the maximum shared segment size, in bytes kernel.shmmax = 68719476736 Controls the maximum number of shared memory segments, in pages kernel.shmall = 4294967296 fs.aio-max-nr = 1048576 fs.file-max = 6815744 kernel.sem = 250 32000 100 128 net.ipv4.ip_local_port_range = 9000 65500 net.core.rmem_default = 262144 net.core.rmem_max = 4194304 net.core.wmem_default = 262144 net.core.wmem_max = 1048576 /sbin/sysctl -p net.ipv4.ip_forward = 0 net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.default.accept_source_route = 0 kernel.sysrq = 0 kernel.core_uses_pid = 1 net.ipv4.tcp_syncookies = 1 error: "net.bridge.bridge-nf-call-ip6tables" is an unknown key error: "net.bridge.bridge-nf-call-iptables" is an unknown key error: "net.bridge.bridge-nf-call-arptables" is an unknown key kernel.msgmnb = 65536 kernel.msgmax = 65536 kernel.shmmax = 68719476736 kernel.shmall = 4294967296 fs.aio-max-nr = 1048576 fs.file-max = 6815744 kernel.sem = 250 32000 100 128 net.ipv4.ip_local_port_range = 9000 65500 net.core.rmem_default = 262144 net.core.rmem_max = 4194304 net.core.wmem_default = 262144 net.core.wmem_max = 1048576 su - oracle ulimit -Sn 1024 ulimit -Hn 1024 ulimit -Su 1024 ulimit -Hu 30482 ulimit -Su 1024 ulimit -Ss 10240 ulimit -Hs unlimited su - nano /etc/security/limits.conf *added to the end of the file * oracle soft nproc 2047 oracle hard nproc 16384 oracle soft nofile 1024 oracle hard nofile 65536 oracle soft stack 10240 exit exit su - mkdir -p /app/ chown -R oracle:oinstall /app/ chmod -R 775 /app/ 9. THIS IS PROBABLY WHERE I MESSED UP I then exited out of the root account so now I'm back in my account chris then I su - oracle echo $SHELL /bin/bash umask 0022 (so it should be set already to what is neccesary) Also from what I have read I do not need to set the DISPLAY variable because I'm installing this on the localhost I then opened the .bash_profile of the oracle and changed it to the following .bash_profile Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi User specific environment and startup programs PATH=$PATH:$HOME/bin; export PATH ORACLE_BASE=/app/oracle ORACLE_SID=orcl export ORACLE_BASE ORACLE_SID I then shutdown the virtual machine shared my desktop folder from my windows 7 then turned back on the virtual machine logged in as chris opened up a terminal then: su - for some reason the shared folder didn't appear so I reinstalled vmware tools again and restarted then same as before su - cp -R linux_oracle/database /db; chown -R oracle:oinstall /db; chmod -R 775 /db; ll /db drwxrwxr-x. 8 oracle oinstall 4096 Jun 5 06:20 database exit su - oracle cd /db/database ./runInstaller AND FINALLY THE INFAMOUS JAVA:132 ERROR MESSAGE Starting Oracle Universal Installer... Checking Temp space: must be greater than 80 MB. Actual 65646 MB Passed Checking swap space: must be greater than 150 MB. Actual 6015 MB Passed Checking monitor: must be configured to display at least 256 colors. Actual 16777216 Passed Preparing to launch Oracle Universal Installer from /tmp/OraInstall2012-06-05_06-47-12AM. Please wait ...[oracle@localhost database]$ Exception in thread "main" java.lang.UnsatisfiedLinkError: /tmp/OraInstall2012-06-05_06-47-12AM/jdk/jre/lib/i386/xawt/libmawt.so: libXext.so.6: cannot open shared object file: No such file or directory at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1751) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1647) at java.lang.Runtime.load0(Runtime.java:769) at java.lang.System.load(System.java:968) at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1751) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1668) at java.lang.Runtime.loadLibrary0(Runtime.java:822) at java.lang.System.loadLibrary(System.java:993) at sun.security.action.LoadLibraryAction.run(LoadLibraryAction.java:50) at java.security.AccessController.doPrivileged(Native Method) at java.awt.Toolkit.loadLibraries(Toolkit.java:1509) at java.awt.Toolkit.(Toolkit.java:1530) at com.jgoodies.looks.LookUtils.isLowResolution(Unknown Source) at com.jgoodies.looks.LookUtils.(Unknown Source) at com.jgoodies.looks.plastic.PlasticLookAndFeel.(PlasticLookAndFeel.java:122) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:242) at javax.swing.SwingUtilities.loadSystemClass(SwingUtilities.java:1783) at javax.swing.UIManager.setLookAndFeel(UIManager.java:480) at oracle.install.commons.util.Application.startup(Application.java:758) at oracle.install.commons.flow.FlowApplication.startup(FlowApplication.java:164) at oracle.install.commons.flow.FlowApplication.startup(FlowApplication.java:181) at oracle.install.commons.base.driver.common.Installer.startup(Installer.java:265) at oracle.install.ivw.db.driver.DBInstaller.startup(DBInstaller.java:114) at oracle.install.ivw.db.driver.DBInstaller.main(DBInstaller.java:132)

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• Just another web startup - platform comparison

  - by Holland

  I'm looking to do a web startup which involves something along the lines of an ecommerce site, yet a little more in depth than that. While it's something that I would rather not go into detail with in terms of the initial idea, I can specify (on a basic level) what would be required of the website. If you have any observations or opinions derived from personal experience, which relate to what you see here, I'd appreciate it if you could share these. Paypal's API interaction (definitely). From what I've read about their API, integration with it into their website is VERY expensive, so I'd probably hold off on that until I've (hopefully) generated money and write my own simple credit-card interaction system. SQL Backend (obviously) PostgreSQL seems like a pretty good choice, as from what I've read, it's structure is a bit more "object-oriented" than, say, MySQL. Then again, I've used MySQL before and haven't had much problem with it whatsoever. Would it be worth learning PostgreSQL for this purpose? Java or .Net implementation (Preferably Mono, so I can use .Net while hosting the website using Apache). The reason for this is because, frankly, while I know PHP is a great platform to develop websites with, I hate developing with it. Before someone chimes in and flames me for saying that, note that I have nothing against the language, I just don't like it for my purposes. While Mono may be good to go with, I'm aware that ASP.Net MVC 3 hasn't been released for Mono yet, which may be a pain to work with, without their Razor syntax. Ontop of that, it seems Java is completely FULL of class libraries which deal with web development, that can be downloaded from the web. If anyone has any experience with these, I'd appreciate if that were posted. From what I've read about Spring and Struts2, they seem to be the best out there - especially since they're (AFAIK) MVC. I've considered Python and Django, which do seem REALLY nice, but I don't know much Python, and I'd rather start with something that I already know (language-wise; not framework-wise) than dive into learning a language AND a new framework. I'd REALLY like to be able to host my website via Apache, rather than using Windows Server or anything like that, as, frankly, I hate their setup. I'm not dissing it in any way, shape, or form, I'm just saying I dislike it. <3 terminal config. If there is a good reason to with Windows Server, however, I'd be willing to learn it. C# has a lot of things that Java appears not to have, including Delegates, unsigned types, and LINQ. Is there anything that Java has which can counter these?

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• Building massively scalable systems, where to start? [closed]

  - by Mahmoud Hossam

  Recently, I've been seeing these job postings about building scalable systems using Java, and some of the technologies mentioned were: Cassandra Thrift Hadoop MapReduce Among others. How can I get started with these technologies? Is there something else I need to know before actually learning any of these technologies? Maybe some general concepts about building highly available and scalable systems? I already know Java SE, so I won't be starting from scratch.

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• What are the steps to grouping related classes into packages

  - by user2368481

  I've been googling this for some time, but what I haven't found are the clear steps needed to be taken to group related classes into packages in Java. In my case, I have about a number of .java files that I'd like to group into 3 packages according to the MVC pattern. One package for Model classes, one package for View classes and one package for Controller classes. I've identified which belong in what package, but not sure of the next step.

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• Conflict Minerals - Design to Compliance

  - by C. Chadwick

  Dr. Christina  Schröder - Principal PLM Consultant, Enterprise PLM Solutions EMEA What does the Conflict Minerals regulation mean? Conflict Minerals has recently become a new buzz word in the manufacturing industry, particularly in electronics and medical devices. Known as the "Dodd-Frank Section 1502", this regulation requires SEC listed companies to declare the origin of certain minerals by 2014. The intention is to reduce the use of tantalum, tungsten, tin, and gold which originate from mines in the Democratic Republic of Congo (DRC) and adjoining countries that are controlled by violent armed militia abusing human rights. Manufacturers now request information from their suppliers to see if their raw materials are sourced from this region and which smelters are used to extract the metals from the minerals. A standardized questionnaire has been developed for this purpose (download and further information). Soon, even companies which are not directly affected by the Conflict Minerals legislation will have to collect and maintain this information since their customers will request the data from their suppliers. Furthermore, it is expected that the public opinion and consumer interests will force manufacturers to avoid the use of metals with questionable origin. Impact for existing products Several departments are involved in the process of collecting data and providing conflict minerals compliance information. For already marketed products, purchasing typically requests Conflict Minerals declarations from the suppliers. In order to address requests from customers, technical operations or product management are usually responsible for keeping track of all parts, raw materials and their suppliers so that the required information can be provided. For complex BOMs, it is very tedious to maintain complete, accurate, up-to-date, and traceable data. Any product change or new supplier can, in addition to all other implications, have an effect on the Conflict Minerals compliance status. Influence on product development  It makes sense to consider compliance early in the planning and design of new products. Companies should evaluate which metals are needed or contained in supplier parts and if these could originate from problematic sources. The answer influences the cost and risk analysis during the development. If it is known early on that a part could be non-compliant with respect to Conflict Minerals, alternatives can be evaluated and thus costly changes at a later stage can be avoided. Integrated compliance management  Ideally, compliance data for Conflict Minerals, but also for other regulations like REACH and RoHS, should be managed in an integrated supply chain system. The compliance status is directly visible across the entire BOM at any part level and for the finished product. If data is missing, a request to the supplier can be triggered right away without having to switch to another system. The entire process, from identification of the relevant parts, requesting information, handling responses, data entry, to compliance calculation is fully covered end-to-end while being transparent for all stakeholders. Agile PLM Product Governance and Compliance (PG&C) The PG&C module extends Agile PLM with exactly this integrated functionality. As with the entire Agile product suite, PG&C can be configured according to customer requirements: data fields, attributes, workflows, routing, notifications, and permissions, etc… can be quickly and easily tailored to a customer’s needs. Optionally, external databases can be interfaced to query commercially available sources of Conflict Minerals declarations which obviates the need for a separate supplier request in many cases. Suppliers can access the system directly for data entry through a special portal. The responses to the standard EICC-GeSI questionnaire can be imported by the supplier or internally. Manual data entry is also supported. A set of compliance-specific dashboards and reports complement the functionality Conclusion  The increasing number of product compliance regulations, for which Conflict Minerals is just one example, requires companies to implement an efficient data and process management in this area. Consumer awareness in this matter increases as well so that an integrated system from development to production also provides a competitive advantage. Follow this link to learn more about Agile's PG&C solution

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• Using public domain source code from JDK in my application

  - by user2941369

  Can I use source code from ThreadPoolExecutor.java taken from JDK 1.7 considering that the following clausule is at the beginning of the ThreadPoolExecutor.java: /* * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/licenses/publicdomain */ And just before that there is also: /* * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */

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• Slick & NiftyGUI. Nifty initialize exception

  - by Romeo

  I found my self into trouble when trying to run a Slick game with a Nifty Game State. This is the code: @Override protected void initGameAndGUI(GameContainer container, StateBasedGame game) throws SlickException { initNifty(container, game); } If i run this i get: java.lang.IllegalStateException: The NiftyGUI was already initialized. Its illegal to do so twice. If i delete the call to initNifty() i get another exception:java.lang.IllegalStateException: NiftyGUI was not initialized.

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• Too much delay while sending object over UDP to server

  - by RomZes

  I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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• Accidental installed jdk 6 and 7 now cant uninstall!

  - by user87587

  I have been trying to install java on my Dedicated server. I have partially installed multiple versions of java and now cannot uninstall them as they all have dependencies. Whenever I try and un-install I get: Errors were encountered whilst processing: openjdk-6-jre-headless openjdk-6-jre E: Sub-process /usr/bin/dpkg returned an error code (1) I AM A NEWBIE Re-install can't be done unless I contact my host and pay 15$ :(

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• Can I develop games for mobile platforms in C++?

  - by James Bern

  I have a good grasp in C++ and C and have also experience developing AAA game using C++. Now, I'm shamelessly thinking to dive into mobile game development either in iOS or Android. Unfortunately, I don't know objective-C and java and neither have courage to learn it. So, As above mentioned reason, Is there any possibility to do mobile development in C++ without using any single statement of JAVA and Objective-C ?

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• Class design issue

  - by user2865206

  I'm new to OOP and a lot of times I become stumped in situations similar to this example: Task: Generate an XML document that contains information about a person. Assume the information is readily available in a database. Here is an example of the structure: <Person> <Name>John Doe</Name> <Age>21</Age> <Address> <Street>100 Main St.</Street> <City>Sylvania</City> <State>OH</State> </Address> <Relatives> <Parents> <Mother> <Name>Jane Doe</Name> </Mother> <Father> <Name>John Doe Sr.</Name> </Father> </Parents> <Siblings> <Brother> <Name>Jeff Doe</Name> </Brother> <Brother> <Name>Steven Doe</Name> </Brother> </Siblings> </Relatives> </Person> Ok lets create a class for each tag (ie: Person, Name, Age, Address) Lets assume each class is only responsible for itself and the elements directly contained Each class will know (have defined by default) the classes that are directly contained within them Each class will have a process() function that will add itself and its childeren to the XML document we are creating When a child is drawn, as in the previous line, we will have them call process() as well Now we are in a recursive loop where each object draws their childeren until all are drawn But what if only some of the tags need to be drawn, and the rest are optional? Some are optional based on if the data exists (if we have it, we must draw it), and some are optional based on the preferences of the user generating the document How do we make sure each object has the data it needs to draw itself and it's childeren? We can pass down a massive array through every object, but that seems shitty doesnt it? We could have each object query the database for it, but thats a lot of queries, and how does it know what it's query is? What if we want to get rid of a tag later? There is no way to reference them. I've been thinking about this for 20 hours now. I feel like I am misunderstanding a design principle or am just approaching this all wrong. How would you go about programming something like this? I suppose this problem could apply to any senario where there are classes that create other classes, but the classes created need information to run. How do I get the information to them in a way that doesn't seem fucky? Thanks for all of your time, this has been kicking my ass.

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• More elegant way to avoid hard coding the format of a a CSV file?

  - by dsollen

  I know this is trivial issue, but I just feel this can be more elegant. So I need to write/read data files for my program, lets say they are CSV for now. I can implement the format as I see fit, but I may have need to change that format later. The simply thing to do is something like out.write(For.getValue()+","+bar.getMinValue()+","+fi.toString()); This is easy to write, but obviously is guilty of hard coding and the general 'magic number' issue. The format is hard-coded, requires parsing of the code to figure out the file format, and changing the format requires changing multiple methods. I could instead have my constants specifying the location that I want each variable to be saved in the CSV file to remove some of the 'magic numbers'; then save/load into the an array at the location specified by the constants: int FOO_LOCATION=0; int BAR_MIN_VAL_LOCATION=1; int FI_LOCATION=2 int NUM_ARGUMENTS=3; String[] outputArguments=new String[NUM_ARGUMENTS]; outputArguments[FOO_LOCATION] = foo.getValue(); outputArgumetns[BAR_MIN_VAL_LOCATION] = bar.getMinValue(); outptArguments[FI_LOCATOIN==fi.toString(); writeAsCSV(outputArguments); But this is...extremely verbose and still a bit ugly. It makes it easy to see the format of existing CSV and to swap the location of variables within the file easily. However, if I decide to add an extra value to the csv I need to not only add a new constant, but also modify the read and write methods to add the logic that actually saves/reads the argument from the array; I still have to hunt down every method using these variables and change them by hand! If I use Java enums I can clean this up slightly, but the real issue is still present. Short of some sort of functional programming (and java's inner classes are too ugly to be considered functional) I still have no obvious way of clearly expressing what variable is associated with each constant short of writing (and maintaining) it in the read/write methods. For instance I still need to write somewhere that the FOO_LOCATION specifies the location of foo.getValue(). It seems as if there should be a prettier, easier to maintain, manner for approaching this? Incidentally, I'm working in java at the moment, however, I am interested conceptually about the design approach regardless of language. Some library in java that does all the work for me is definitely welcome (though it may prove more hassle to get permission to add it to the codebase then to just write something by hand quickly), but what I'm really asking is more about how to write elegant code if you had to do this by hand.

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• Merging the Executive Committees

  - by Patrick Curran

  As I explained in this blog last year, we use the Process to change the Process. The first of three planned JSRs to modify the way the JCP operates (JSR 348: Towards a new version of the Java Community Process) completed in October 2011. That JSR focused on changes to make our process more transparent and to enable broader participation. The second JSR was inspired by our conviction that Java is One Platform and by our expectation that Java ME and Java SE will become more aligned over time. In anticipation of this change JSR 355: JCP Executive Committee Merge will merge the two Executive Committees into one. The JSR is going very well. We have reached consensus within the Executive Committees, which serve as the Expert Group for process-change JSRs. How we intend to make the transition to a single EC is explained in the revised versions of the Process and EC Standing Rules documents that are currently posted for Early Draft Review. Our intention is to reduce the total number of EC seats but to keep the same ratio (2:1) of ratified and elected seats. Briefly, the plan will be implemented in two stages. The October 2012 elections will be held as usual, but candidates will be informed that they will serve only a one-year term if elected. The two ECs will be merged immediately after this election; at the same time, Oracle's second permanent seat and one of IBM's two ratified seats will be eliminated. The initial merged EC will therefore have 30 members. In the October 2013 elections we will eliminate three more ratified seats and two elected seats, thereby reducing the size of the combined EC to 25 members (16 ratified seats, 8 elected seats, plus Oracle's permanent seat.) All remaining seats, including those of members who were elected in 2012, will be up for re-election in 2013; that election should be particularly interesting. Starting in 2013 we will change from a three-year to a two-year election cycle (half of all EC members will be up for re-election each year.) We believe that these changes will streamline our operations, and position us for a future in which the distinctions between desktop and mobile devices become increasingly blurred. Please take this opportunity to review and comment on our proposed changes - we appreciate your input. Thank you, and onward to JCP.next.3!

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• How to deal with checked exceptions that cannot ever be thrown

  - by ammoQ

  Example: foobar = new InputStreamReader(p.getInputStream(), "ISO-8859-1"); Since the encoding is hardcoded and correct, the constructor will never throw the UnsupportedEncodingException declared in the specification (unless the java implementation is broken, in which case I'm lost anyway). Anyway, Java forces me to deal with that exception anyway. Currently, it looks like that try { foobar = new InputStreamReader(p.getInputStream(), "ISO-8859-1"); } catch(UnsupportedEncodingException e) { /* won't ever happen */ } Any ideas how to make it better?

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• 1Z0-899/OCPJWCD 6 Preparation [closed]

  - by Msaleh

  I am preparing for the exam 1Z0-899/OCPJWCD 6 and I have some questions about the preparation: Book: the only good book I can find for now is the Head First Servlet JSP, Second Edition, but it's mostly for the Java EE 5, so are there any books for Java EE 6? Advises from the people passed the exam: can anyone from the people who passed the exams give me some feedback about the exam, and how he prepared for the exam?

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• ArrayList of Entites Random Movement

  - by opiop65

  I have an arraylist of entites that I want to move randomly. No matter what I do, they won't move. Here is my female class: import java.awt.Graphics2D; import java.awt.Image; import java.awt.Rectangle; import java.util.Random; import javax.swing.ImageIcon; public class Female extends Entity { static int femaleX = 0; static int femaleY = 0; double walkSpeed = .1f; Random rand = new Random(); int random; int dir; Player player; public Female(int posX, int posY) { super(posX, posY); } public void update() { posX += femaleX; posY += femaleY; } public void draw(Graphics2D g2d) { g2d.drawImage(getFemaleImg(), posX, posY, null); if (Player.showBounds == true) { g2d.draw(getBounds()); } } public Image getFemaleImg() { ImageIcon ic = new ImageIcon("res/female.png"); return ic.getImage(); } public Rectangle getBounds() { return new Rectangle(posX, posY, getFemaleImg().getHeight(null), getFemaleImg().getWidth(null)); } public void moveFemale() { random = rand.nextInt(3); System.out.println(random); if (random == 0) { dir = 0; posX -= (int) walkSpeed; } } } And here is how I update the female class in the main class: public void actionPerformed(ActionEvent ae) { player.update(); for(int i = 0; i < females.size(); i++){ Female tempFemale = females.get(i); tempFemale.update(); } repaint(); } If I do something like this(in the female update method): public void update() { posX += femaleX; posY += femaleY; posX -= walkSpeed; } The characters move with no problem. Why is this?

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• The term "interface" in C++

  - by Flexo

  Java makes a clear distinction between class and interface. (I believe C# does also, but I have no experience with it). When writing C++ however there is no language enforced distinction between class and interface. Consequently I've always viewed interface as a workaround for the lack of multiple inheritance in Java. Making such a distinction feels arbitrary and meaningless in C++. I've always tended to go with the "write things in the most obvious way" approach, so if in C++ I've got what might be called an interface in Java, e.g.: class Foo { public: virtual void doStuff() = 0; ~Foo() = 0; }; and I then decided that most implementers of Foo wanted to share some common functionality I would probably write: class Foo { public: virtual void doStuff() = 0; ~Foo() {} protected: // If it needs this to do its thing: int internalHelperThing(int); // Or if it doesn't need the this pointer: static int someOtherHelper(int); }; Which then makes this not an interface in the Java sense anymore. Instead C++ has two important concepts, related to the same underlying inheritance problem: virtual inhertiance Classes with no member variables can occupy no extra space when used as a base "Base class subobjects may have zero size" Reference Of those I try to avoid #1 wherever possible - it's rare to encounter a scenario where that genuinely is the "cleanest" design. #2 is however a subtle, but important difference between my understanding of the term "interface" and the C++ language features. As a result of this I currently (almost) never refer to things as "interfaces" in C++ and talk in terms of base classes and their sizes. I would say that in the context of C++ "interface" is a misnomer. It has come to my attention though that not many people make such a distinction. Do I stand to lose anything by allowing (e.g. protected) non-virtual functions to exist within an "interface" in C++? (My feeling is the exactly the opposite - a more natural location for shared code) Is the term "interface" meaningful in C++ - does it imply only pure virtual or would it be fair to call C++ classes with no member variables an interface still?

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• Java SE 7 Update 4??????·???????G1 GC??????“WebLogic+WebSocket”??????????????????????WebLogic Server 12c Forum 2012?????

  - by ???02

  2012?4?????????Java SE 7 Update 4????????·??????(GC)????G1 GC??????????GC???????????? ???????Web??????????????????HTML5??????/???????????????????WebSocket??????????????????WebLogic Server?????????????????????????????? 2012?8????????WebLogic Server 12c Forum 2012???????????·?????????????????????????(???) Java SE 7 Update 4??????G1 GC???????? 2012?8????????WebLogic Server 12c Forum 2012??????????????????·???????????????????????Java EE 6??????????????????????????????????????WebLogic Server????????????????????·???????????????????Java SE 7 Update 4???????GC??HTML5??????1????WebSocket??????????·????????????????????? ?????? Fusion Middleware?????? ?????????????? ???? 2012?4???????Java SE 7 Update 4?????Mac OS X????????????????????????G1 GC?????????? Fusion Middleware?????? ???????????????????????G1 GC???????????????? ????????GC???????????????????????????????????????????????????????????????????????????????????????????·??????????????????????????·??????????GC????????????????1??GC???????????????????????????????? GC????????????????????????????GC??????????????????????GC????GC???????????????????????????????GC??????????????????????????????????????????????????????????????? ???64????????????????????JVM?????64????????????64????JVM????GB???????·????????????????????????GC????????????????GC????????????????????????????·????????????????GC?????????????????????????????????????????????????????????????????SLA????????????????????·?????????????? ????????????????????????Java SE 7 Update 4????????GC?G1 GC?? G1 GC????????????????????????????????????????????????????????????GC???????????????????????????(????????)??????????????????????????????????????????????????????????????????????????????????????????? ??????G1 GC??????????????????????????????????????????? ??G1 GC?????????????????????????????????????????????????????????????????????????????????????????GC?????????????????????64????JVM????????·???????????????????????????????????????GC??????? ???????????????????????? ????????????????????????????????????????????OutOfMemory???????????????????????????????? WebLogic Server 12c?Java SE 7??????????????G1 GC???????????WebLogic Server 11g(10.3.6)??????????????????????GC????????JVM??????????-XX:+UseG1 GC????????????????? HTML5?Web????/?????????WebSocket?????????????????? ?????? Fusion Middleware?????? ?????????? ?????? ?????? Fusion Middleware???????WebLogic Server??????·???????????????????????·?????????Near future of WebLogic / ????WebLogic???????????????Web??????????HTML5???? ????????IT????????????????????1???????·?????????????????????????????????????????????????????????????HTML5?? HTML5???????HTML????????????HTML???Web????????????????????????HTML5???????????????????????????????????????????????HTML5????????/???????????????????????????????????WebWorker?????????????????????????????Web Storage???????API??????HTML5??????????????HTML??????????? ???HTML5??????????????????????WebSocket????????Web????/?????????????????????????? WebSocket????????????????????????(???????)?HTTP????????????????WebSocket????????WebSocket????????????????????????HTTP????????????????????????Web????/??????????????????? WebSocket??????????“??????Web”???????????????????????????????????????????????????????????????1???????????????????????HTTP???????????????????????????????????Comet????HTTP???????????????????????????????WebSocket???????????????????????????????????????????????????????????????? ?????????WebSocket????????????????????????????????????????????????????? WebSocket???????????????????????????? ?????? WebSocket???????(RFC 6455) ?????(Proposed Standard)??? WebSocket API(JavaScript)??(W3C) ????(Last Call Working Draft)??????2012?6?14???? WebSocket API Java EE??(JSR-356) Review Ballot??? ???? Web???? Google Chrome 16?Mozilla Firefox 11?Internet Explorer 10(PP5)?Safari 6??? ???·????? Jetty?jWebSocket?node.js?GlassFish 3.x????? ????????????????(RFC 6455)?????????JavaScript??????????????????????Java EE????????JSR-356?????????????????????????·????????????????????????????·??????????????? ??????????Java???????????????GlassFish????????????????????(JSR-356)??????????????·???·???????????????? ?WebSocket?WebLogic Server ??????????????WebSocket??WebLogic Server???????????????????? WebSocket????HTML5?????????????????????????????????HTML5?????????????????????Java EE?????????HTML5????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ???????HTML5?????????????????????????????????? ????????????? ?????????????????????????????????????????????????????????????????????????????????????????????????????HTML5???????????Java EE??????????????????????????(???) ???????????????????????????????????????????????????????????????????????????????????Java EE?WebLogic?????????????????????????????????????????????????????

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• Entity Framework 4.0 and DDD patterns

  - by Voice

  Hi everybody I use EntityFramework as ORM and I have simple POCO Domain Model with two base classes that represent Value Object and Entity Object Patterns (Evans). These two patterns is all about equality of two objects, so I overrode Equals and GetHashCode methods. Here are these two classes: public abstract class EntityObject<T>{ protected T _ID = default(T); public T ID { get { return _ID; } protected set { _ID = value; } } public sealed override bool Equals(object obj) { EntityObject<T> compareTo = obj as EntityObject<T>; return (compareTo != null) && ((HasSameNonDefaultIdAs(compareTo) || (IsTransient && compareTo.IsTransient)) && HasSameBusinessSignatureAs(compareTo)); } public virtual void MakeTransient() { _ID = default(T); } public bool IsTransient { get { return _ID == null || _ID.Equals(default(T)); } } public override int GetHashCode() { if (default(T).Equals(_ID)) return 0; return _ID.GetHashCode(); } private bool HasSameBusinessSignatureAs(EntityObject<T> compareTo) { return ToString().Equals(compareTo.ToString()); } private bool HasSameNonDefaultIdAs(EntityObject<T> compareTo) { return (_ID != null && !_ID.Equals(default(T))) && (compareTo._ID != null && !compareTo._ID.Equals(default(T))) && _ID.Equals(compareTo._ID); } public override string ToString() { StringBuilder str = new StringBuilder(); str.Append(" Class: ").Append(GetType().FullName); if (!IsTransient) str.Append(" ID: " + _ID); return str.ToString(); } } public abstract class ValueObject<T, U> : IEquatable<T> where T : ValueObject<T, U> { private static List<PropertyInfo> Properties { get; set; } private static Func<ValueObject<T, U>, PropertyInfo, object[], object> _GetPropValue; static ValueObject() { Properties = new List<PropertyInfo>(); var propParam = Expression.Parameter(typeof(PropertyInfo), "propParam"); var target = Expression.Parameter(typeof(ValueObject<T, U>), "target"); var indexPar = Expression.Parameter(typeof(object[]), "indexPar"); var call = Expression.Call(propParam, typeof(PropertyInfo).GetMethod("GetValue", new[] { typeof(object), typeof(object[]) }), new[] { target, indexPar }); var lambda = Expression.Lambda<Func<ValueObject<T, U>, PropertyInfo, object[], object>>(call, target, propParam, indexPar); _GetPropValue = lambda.Compile(); } public U ID { get; protected set; } public override Boolean Equals(Object obj) { if (ReferenceEquals(null, obj)) return false; if (obj.GetType() != GetType()) return false; return Equals(obj as T); } public Boolean Equals(T other) { if (ReferenceEquals(null, other)) return false; if (ReferenceEquals(this, other)) return true; foreach (var property in Properties) { var oneValue = _GetPropValue(this, property, null); var otherValue = _GetPropValue(other, property, null); if (null == oneValue && null == otherValue) return false; if (false == oneValue.Equals(otherValue)) return false; } return true; } public override Int32 GetHashCode() { var hashCode = 36; foreach (var property in Properties) { var propertyValue = _GetPropValue(this, property, null); if (null == propertyValue) continue; hashCode = hashCode ^ propertyValue.GetHashCode(); } return hashCode; } public override String ToString() { var stringBuilder = new StringBuilder(); foreach (var property in Properties) { var propertyValue = _GetPropValue(this, property, null); if (null == propertyValue) continue; stringBuilder.Append(propertyValue.ToString()); } return stringBuilder.ToString(); } protected static void RegisterProperty(Expression<Func<T, Object>> expression) { MemberExpression memberExpression; if (ExpressionType.Convert == expression.Body.NodeType) { var body = (UnaryExpression)expression.Body; memberExpression = body.Operand as MemberExpression; } else memberExpression = expression.Body as MemberExpression; if (null == memberExpression) throw new InvalidOperationException("InvalidMemberExpression"); Properties.Add(memberExpression.Member as PropertyInfo); } } Everything was OK until I tried to delete some related objects (aggregate root object with two dependent objects which was marked for cascade deletion): I've got an exception "The relationship could not be changed because one or more of the foreign-key properties is non-nullable". I googled this and found http://blog.abodit.com/2010/05/the-relationship-could-not-be-changed-because-one-or-more-of-the-foreign-key-properties-is-non-nullable/ I changed GetHashCode to base.GetHashCode() and error disappeared. But now it breaks all my code: I can't override GetHashCode for my POCO objects = I can't override Equals = I can't implement Value Object and Entity Object patters for my POCO objects. So, I appreciate any solutions, workarounds here etc.

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• Android threading and database locking

  - by Sena Gbeckor-Kove

  Hi, We are using AsyncTasks to access database tables and cursors. Unfortunately we are seeing occasional exceptions regarding the database being locked. E/SQLiteOpenHelper(15963): Couldn't open iviewnews.db for writing (will try read-only): E/SQLiteOpenHelper(15963): android.database.sqlite.SQLiteException: database is locked E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:1637) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1587) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:638) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:659) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:652) E/SQLiteOpenHelper(15963): at android.app.ApplicationContext.openOrCreateDatabase(ApplicationContext.java:482) E/SQLiteOpenHelper(15963): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:193) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98) E/SQLiteOpenHelper(15963): at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:158) E/SQLiteOpenHelper(15963): at com.iview.android.widget.IViewNewsTopStoryWidget.initData(IViewNewsTopStoryWidget.java:73) E/SQLiteOpenHelper(15963): at com.iview.android.widget.IViewNewsTopStoryWidget.updateNewsWidgets(IViewNewsTopStoryWidget.java:121) E/SQLiteOpenHelper(15963): at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:338) E/SQLiteOpenHelper(15963): at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:1) E/SQLiteOpenHelper(15963): at android.os.AsyncTask$2.call(AsyncTask.java:185) E/SQLiteOpenHelper(15963): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256) E/SQLiteOpenHelper(15963): at java.util.concurrent.FutureTask.run(FutureTask.java:122) E/SQLiteOpenHelper(15963): at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) E/SQLiteOpenHelper(15963): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) E/SQLiteOpenHelper(15963): at java.lang.Thread.run(Thread.java:1060) Does anybody have a general example for code which writes to a database from a different thread than the one reading and how can we ensure thread safety. One suggestion I've had is to use a ContentProvider, as this would handle the access of the database from multiple threads. I am going to look at this, but is this the recommended method of handling such a problem? It seems rather heavyweight considering we're talking about in front or behind Thanks in advance.

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• Using Repository and Unit of Work patterns with Entity Framework 4.0 and MVC 2

  - by Mr. D

  Hi, I'm following this article Using Repository and Unit of Work patterns with Entity Framework 4.0. I'm tying to implement the Repository and Unit of work pattern, using Asp.Net MVC 2 and Entity Framework 4. Please let me know if I'm doing it right... In the Models folder: Northwind.edmx Products.cs (POCO class) ProductRepository.cs (Did my product query) IProductRepository.cs NorthwindContext.cs IUnitOfWork.cs In the Controller folder: ProductController.cs (Retrieve from ProductRepository.cs and Pass it to the view) When I run the application, I'm getting error message: Mapping and metadata information could not be found for EntityType 'NorthwindMvcPoco.Models.Category'. I don't know what I'm doing wrong. I search through whole web and I couldn't resolve this issue. Please help me.

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• LRU cache design

  - by user297850

  Least Recently Used (LRU) Cache is to discard the least recently used items first How do you design and implement such a cache class? The design requirements are as follows: 1) find the item as fast as we can 2) Once a cache misses and a cache is full, we need to replace the least recently used item as fast as possible. How to analyze and implement this question in terms of design pattern and algorithm design?

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