Java String Initialization

Java String Initialization - Null vs ""

In a code review, I got a comment which asked me why I initialized with a null instead of a ""

Reason #1
When you use String s = null it will create variable "s" on stack only and no object will exists on heap,but as soon as you declare things as like String s=""; what it will does is like it will create "" object on heap.As we know that Strings are immutable so whenever u wil assign new value to string varible everytime it will create new Object on heap...So I think String s=null is efficient than String s = "";

Reason #2
When we initialize a string as "",we are actually supressing a possible exception that will be automatically raised when we have it initialized to null. Yes Java has inbuilt exception handler for treating nulls - remember NUllPointerException (the buggy exception)...So if we have used this string somewhere on our webpage and it doesn't get inialized properly at runtime, if we had it initialized to null, java would shout "NullPointerException" if not we will have to work more towards catching this exception...

Comments

wget error–“zsh: parse error near &”

There is no doubt that I prefer wget way over any other type of downloads…Syntax: wget <DOWNLOAD_URL>If you get this error “zsh: parse error near &” then its probably because your download URL has a “&” so you should try giving your DOWNLOAD_URL in double quoteswget “<DOWNLOAD_URL>”If you are trying to download from a site which needs you to give your credentials then you can try giving it this waywget --http-user=<UserName> --http-password=<Password> “<DOWNLOAD_URL>”Hope this helps

How to check if my xpath is valid using firebug?

Yes, you can verify if your xpath is pointing to the right source on the web application under test using FireBug. Here is how:

Go to the Web Application under test We'll take Google for simplicity reasons
Open FireBug - Go to the Console Console can also be seen at the bottom of the page, so don't worry they both are the same. They can be switched as follows:

Type in $x("Your xpath here") on the command line prompt as shown below:

Hit Enter/RunYou will get to see the element which was filtered out with your XPath expression

How to Unpack a tar file on Windows?

On Windows:
You can download a simple command line tool to do this.
You can download the tool from here Usage can be found on the website but pasting it here too for convenience: C:\>TarTool.exe
Usage :
C:\>TarTool.exe sourceFile destinationDirectory
C:\>TarTool.exe D:\sample.tar.gz ./
C:\>TarTool.exe sample.tgz temp
C:\>TarTool.exe -x sample.tar temp
TarTool 2.0 Beta supports bzip2 decompression for files with extensions like tar.bz2 and .bz2.
TarTool -xj sample.tar.bz2 temp
or
TarTool -j sample.bz2
Download TarTool 2.0 Beta from here
Unpack a .txz file on Windows
Use the 7zip tool to unpack a .txz file on windows

On Linux:
You can use the bzip2 and tar combined to do this…
for ex: bzip2 –cd <tar.bz_fileName> | tar –xvf -
This will unpack the contents of the tar.bz file

Happy Un-Tar-ing

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