Fixing Eclipse in Ubuntu 9.10 Karmic Koala

The fix is relatively simple. Create a file in your home folder (or wherever you want) called eclipsefix.sh – open it and add the following lines:


export GDK_NATIVE_WINDOWS=true
/opt/eclipse/eclipse


(where /opt/eclipse/eclipse is the location of your eclipse application file).

SOURCE: http://mou.me.uk/2009/10/31/fixing-eclipse-in-ubuntu-9-10-karmic-koala/

Fix Nvidia card resolution problem in Ubuntu (works in 9.10 too)

Sometimes the nvidia x server fails to recognize all the resolution combinations. This is how you fix it: 

Add Option "ModeValidation" "AllowNon60HzDFPModes, NoVertRefreshCheck, NoEdidMaxPClkCheck, NoHorizSyncCheck"

Under device section in the xorg.conf in /etc/X11/xorg.conf

Source: http://ubuntuforums.org/showthread.php?t=444960

JSTL taglib declaration reminder

Watch out for what specific JSTL version you're taglib-ing in your JSP's
If you put <%@ taglib uri="http://java.sun.com/jstl/core" prefix="c" %> and perform a basic <c:forEach> (you know... with attributes "var" for indexing and "items" for specifying the collection to loop) you might get a dumb error like this:

org.apache.jasper.JasperException: /index.jsp(65,0) According to TLD or attribute directive in tag file, attribute items does not accept any expressions
	org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
	org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)
	org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:148)
	org.apache.jasper.compiler.Validator$ValidateVisitor.checkXmlAttributes(Validator.java:1174)
	org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:821)
	org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1530)
	org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361)
	org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2411)
	org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2417)
	org.apache.jasper.compiler.Node$Root.accept(Node.java:495)
	org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361)
	org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1736)
	org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:183)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:332)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:312)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:299)
	org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:586)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

WTF ? you can't do a <c:forEach> without an "items" ... I've googled around and found out that you must include an updated JSTL version in your taglib i.e. <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> for it to work. Reason for this error is version incompatibility between JSP, Servlet and JSTL. Matching versions are listed below.

• JSP 1.2 , Servlet 2.3 , JSTL 1.0
  
• JSP 2.0 , Servlet 2.4 , JSTL 1.1

"Un taran la Bucuresti tot taran cauta" - Marin Preda

Groovy & Grails for Java

Some cool and easy tutorials of Groovy and Grails written in Eclipse IDE
Groovy tutorial: http://www.vogella.de/articles/Groovy/article.html
Grails tutorial: http://www.vogella.de/articles/Grails/article.html

have fun

Disable Your PC Speaker in Ubuntu

You know that annoying, shrill beep that comes not from your speakers, but rather inside the depths of your computer called a system beep? I hate it, but Ubuntu likes to use it when, for example, I'm searching for text in Firefox and I get to the point where the text doesn't match anything. In Windows, this invokes a fairly annoying noise. In Ubuntu, it's the system beep, which is even worse. Here's how to disable it:

Stop it for now by doing the following:

sudo modprobe -r pcspkr

Stop it forever by blacklisting the module.  Edit /etc/modprobe.d/blacklist and add this line:

blacklist pcspkr

That's it

Ubuntu screen resolution problem

It happens from time to time that ubuntu doesn't recognize multiple screen resolutions in my Nvidia x server settings so i'm stuck with 1024x768 (excuuuse me for wanting more from my Nvidia 9800 card). This problem suddenly appears and disappears randomly after a certain number of reboots. A solution i found is to use the following command and then reboot (you will have to reconfigure the Nvidia x server again using "sudo nvidia-xconfig"

sudo dpkg-reconfigure xserver-xorg

[Java] Mixing Generic with Legacy Code

This is kinda weird and troublesome. Even though as of Java 5 introduced generics to create type-safe collections, mixing this new kind of code with older non-generic one can be very tricky. Sun obviously did not want to make pre-Java 5 code redundant so it created a few ways to make these two types of code play nicely. For example:
List<String> l = new ArrayList<String>();  seems to create a type-safe arraylist polymorphically but mind you the JVM doesn't see the generic declaration at runtime; Using generics is ONLY a type of compile-time protection. But why ? Why did they do this ? The answer is simple - to mix this new code with legacy code; so at runtime the JVM only sees List l = new ArrayList(); . Look what happens if a developer is high and isn't careful when tampering with older code in the following example:

import java.util.*;

public class TestBadLegacy {
    public static void main(String[] args) {
          List<Integer> myList = new ArrayList<Integer>();
          myList.add(4);
          myList.add(6);
          Inserter in = new Inserter();
          in.insert(myList); // pass List<Integer> to legacy code
         
          /*
          for (int i=0;i<myList.size();i++){
              System.out.println(myList.get(i));
          }
          */
         
         
          for(Integer i:myList){
              System.out.println(i);
          }
         
         
       }
}
/*
this is the supposedly generic type-safe class, but check out below the legacy Inserter class which has a method that doesn't know
that a type-safe collection is being passed to it
*/

class Inserter {
      // method with a non-generic List argument
      void insert(List list) {
         list.add(new String("42")); // adds to the incoming list
    }
}

The result of running TestBadLegacy is:
4
6
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at TestBadLegacy.main(TestBadLegacy.java:18)

Surprised ? you shouldn't. even though a String element has been added to an integer-only collection the compiler didn't complain because the adding took place in the legacy code but at runtime when we did the foreach we assigned at one poin an Integer reference to a String object so this resulted in a complete meltdown.

Bollocks!