Techsymphony's Blog

Remembering log4j levels

novice — Thu, 14 Jul 2011 11:01:25 +0000

A simple sentence to remember log4j levels in the descending order of severity.

On Friday Eve We Invited Doctor Toni.

O – Off

F – Fatal

E – Error

W – Warn

I -Info

D – Debug

T -Trace

Though I have been using log4j for years, most of the time confused with the order, this simple sentence helps me a lot.

Frequently confused whether to add ‘Table’ keyword or not in the sql query

novice — Tue, 05 Jul 2011 09:08:16 +0000

While writing sql query, I frequently get confused whether to add the keyword ‘table’ to the query or not.

Sometime I write the update query as ‘UPDATE TABLE EMPLOYEE….’, only after the sql exception I will realize that ‘TABLE’ keyword should not be added and now I found the pattern and never repeated such mistakes.

You too can correct that. As you know we have DDL and DML commands. The ‘TABLE’ keyword comes only for DML commands.

DDL commands:

create
alter
truncate
drop
comment
rename

DML commands:

select
insert
update
delete
merge

You may follow this link to know the complete list of ddl and dml commands.

How to fix missing right click option “Compile NSIS script”

novice — Tue, 28 Jun 2011 09:41:44 +0000

By default, NSIS files will open in notepad when double clicked and opened. Out of curiosity I changed that to notepad++, and from then I don’t see “compile NSIS script” option on right click of NSIS files. To bring that option back, I googled, tried several registry changes, stood upside down but no success. Finally, changed the file property(right click any NSIS file->Properties->General->Opens with->Change->Notepad) to open in notepad and it fixed and brought back the “compile NSIS script” option .

OO principles from Head First Design Pattern

novice — Fri, 04 Feb 2011 05:34:08 +0000

Encapsulate what varies
Favor composition over inheritance
Program to interfaces, not to implementations
Strive for loosely coupled design between objects that interact
Depend upon abstractions. Do not depend upon concrete classes

Difference between hiding and shadowing in java

novice — Sun, 23 Jan 2011 06:39:36 +0000

Hiding : Happens during inheritance (between superclass and subclass).

Shadowing : Happens within a class (between a member variable and local variable).

Examples :

Hiding :

class Parent {

String city = “Dallas”;

}

class Child extends Parent {

String city =”Zurich”;

}

“city” in Child hides the one in Parent.

Shadowing :

class Main {

String city = “Dallas”;

void method() {

String city = “Zurich”;

}

“city”, local variable shadows the member variable.

Stack and heap memory

novice — Sun, 23 Jan 2011 05:01:48 +0000

What is stored where?

Stack :

- local variables

Heap :

- instance variables

- static variables

- objects

Following snippet will help to understand better.

Difference between multitasking and multithreading

novice — Fri, 21 Jan 2011 04:21:31 +0000

MS word, Outlook, Spreadsheet, Browsers are some of the examples of heavy weight programs.

Multitasking:
Running the above programs concurrently.

Multithreading :
Let’s take Outlook. At the same time it allows to compose a mail, send/receives new mail while typing, prints some mail while typing and send/receiving the mail, this concept is called multithreading.

Reference link which explains with pictures.

Eclipse Helios – Install all your eclipse plugins from eclipse marketPlace

novice — Sun, 11 Jul 2010 06:49:31 +0000

No more remember eclipse plugins url. I know how difficult it is to find the url of each eclipse plugin and install it via ‘Install New Software’. Especially if you are behind office firewall you cannot install those plugins.

Eclipse Helios has resolved those problems introducing ‘Eclipse MarketPlace’.

Benefits of this feature (Eclipse MarketPlace) :

– No more remember the eclipse plugin url’s

- Find which plugins are popular all over the worls

- Trusted Plugins as millions install from here

- Install all those plugins even if you are behind a firewall (eclipse plugin url is not restricted by the firewall)

- Install multiple plugins in a single shot

- Switch to Yoxos catalog

Here is my video where I explained step by step guide to install plugins using eclipse marketPlace.

How to delete a windows service

novice — Sat, 10 Jul 2010 00:34:08 +0000

Quick Solution : Run the command – sc delete “serviceName”

Java Threads

novice — Sun, 16 May 2010 11:24:09 +0000