23 February 2009


Use netstat to See Internet Connections | Linux Journal
$ netstat -tpe

The -t flag limits the output to show only TCP connections.
The -p flag displays the PID and name of the program making the connection.
The -e flag displays extra information, such as the user name under which each program is running.

package protected methods java puzzler

An excellent Java puzzler

comments by xeukun JOU

package m1;
public class M1 {
     void doIt() {System.out.println("M1");}

package m1;
public class M2 extends M1 {
    void doIt() {System.out.println("M2");}

package m2;
public class M3 extends M2 {
    void doIt() {System.out.println("M3");}

package m1;
public static void main(String[] args) {
     M1 m=new M3();

This will show "M2", not M3, even though M3's doIt() should be invoked, based on what a vtable would indicate.

It's not a common thing; I wouldn't have put main() in the m1 package, and if it's not local to M1 you won't see the behavior (it won't compile). But it's still an interesting corner case, and I think it's not obvious unless you've run into it.

20 February 2009

Add a Binary Payload to your Shell Scripts

Add a Binary Payload to your Shell Scripts | Linux Journal
Adding a binary payload to a shell script could, for instance, be used to create a single file shell script that installs your entire software package which could be composed of hundreds of files. You merely append the tar or gzip file of your package as a binary payload to the script file, when the script runs it extracts the payload and does its task with the extracted files.

17 February 2009

Popcorn Hour A-110

I'm getting tempted to buy a Popcorn Hour A-110 media server to replace my old xbox running XBMC. XBMC is great but the old xbox hardware isn't capable of display HD (1080p) content. Like XBMC, the Popcorn Hour A-110 can play just about any format.

15 February 2009

Delay the messages you send from Microsoft Outlook

Delay the messages you send from Microsoft Outlook | Workers' Edge - CNET News
Have you ever wished you had reconsidered sending that e-mail to your boss, explaining in detail his shortcomings as a manager? Or perhaps you regret complaining to a client about her unprofessional behavior for canceling a meeting at the last minute--before learning that the cab she was riding in hit a bus.

13 February 2009

Library to daemonize java processes on Linux and fork new processes

akuma: Embeddable daemonization library -
This library also lets you write a multi-process network server that listens on the same TCP/IP port. By forking multiple processes, you improve the robustness of your server --- a single destroyed process will not interrupt the service as other worker processes will take over the processing.

This is how Unix daemons have been traditionally written, such as Apache, yet it was impossible to do this in Java because it doesn't provide an API to let file descriptors to be inherited into children.

Building A Low Latency Infrastructure For Electronic Trading | A-Team Group

GC Performance Bug in LinkedBlockingQueue

Automation for the people: Deployment-automation patterns, Part 2

12 February 2009

Mysql diagnostics

You can see which queries are running and who is connected by running

mysqladmin processlist -i10 -u root -p

you can kill a listed connection by running

mysqladmin kill pid1,pid2 -u root -p

02 February 2009

Some Maven humour :)

Java Performance Tuning comments on ReadWriteLocks

Tips December 2008
Starvation with ReadWriteLocks (Page last updated October 2008, Added 2008-12-30, Author Dr. Heinz M. Kabutz, Publisher The Java Specialists' Newsletter). Tips:

* ReadWriteLock should only be used in cases where the critical section is at least 2000 code statements
* For most applications concurrency classes such as ConcurrentHashMap and ConcurrentLinkedQueue are more efficient than using ReadWriteLock.
* ReadWriteLock with many readers compared to writers can cause the write threads to be starved of access to the lock.
* Using fairness et to true in ReentrantLock reduces throughput significantly.
* You should probably never use ReadWriteLocks in Java 5. In Java 6, use ReadWriteLock when you are willing to wait for writers to get an opportunity to acquire the lock - they won't get locked out completely, but it might take some time before they are serviced.

Gmail offline mode

SQL Editor in IntelliJ IDEA

01 February 2009

Deleting unknown files in an svn workspace

svn status | grep \? | cut -c 8- | xargs rm -rf