I have a jtable and it is returning a NullPointerException.  My code looks like this:       for( int i=0 ;i&lt;rows;++i){         if(Stats.getValueAt(i,2)!=null){           observed[i]=Double.parseDouble(Stats.getValueAt(i,2));        }       if(Stats.getValueAt(i,2).equals("  "))         break;      }   It still returns NullPointerException if not filled up. How can I stop this?
What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?
The Tree of Life in Evangelion I've noticed references to the Kabbalah in a couple of anime I've watched.  One of them is Neon Genesis Evangelion.  Neon Genesis Evangelion has it in the sky in both the opening credits and in the series itself:     I also remember it was on the ceiling at NERV, but the best screencap I could find of that was too tiny to be visible.  So, my question is, Is there any deeper meaning to the use of the Kabbalistic tree of life, or is it just used because it looks cool? What defines a PC's consciousness of self, memories and knowledge? Feynman diagram for attractive forces How to integrate $\int\sqrt{x^2+1}dx$ I have one site with two languages: English and Spanish for example. What would be the proper convention to name image files?  From my point of view it would be stupid to duplicate image and then name it according to on which site it will be uploaded. It would be waste of resources IMO and unnecessary job to do.  What do you think about this one? XCOPY still asking (F = file, D = directory) confirmation If I utilize the two columns of multicols for my Kurdish sequence of numbers, it arranges the items in column like the following figure:   But I want to arrange the items in rows splitted by some columns (two columns in this case) alike the following figure:   And for the case of "three columns", the output would be alike the following figure:   How may I achieve the functionality? And I don't want to use the sequence of the following commands:  \begin{multicols}{2}‎ \begin{enumerate}[$1)$,noitemsep] \item ‎ Yek \item ‎ Du \end{enumerate} \end{multicols}‎   Instead, I want to specify the split count of the columns and then have the items arranged in the desired arrangement automatically. For the record, I've check  post, but it's too generalized. I have a spawn area I am hoping to make a safe haven, so I have a command block on a clock that kills each hostile mob type. This works to keep the place free of any hostile mobs, however every night I see rotten flesh, bones, arrows, and string everywhere.  I would like to add something to my command blocks so that they are killed without dropping loot. How can I accomplish this?  Note that I want mobs to drop loot generally elsewhere in the world, so /gamerule doMobLoot false will not do the trick for me. I'm hoping for a command that only applies to the mobs killed by the command block, and not anything else. Does a wireless-N (802.11n) network have poor performance when in b/g "mixed" mode? It seems to be an "old" wives tale that, when using a wireless-N router in "mixed mode" to support legacy 802.11b or 802.11g devices, the performance of 802.11n clients will suffer.      claim that when running in mixed-mode, all (some?) N clients run at G speeds.   make the same claim, but say it only happens when a G client is connected.    say N clients run faster, but still run about 30% slower than if the router were in N-only mode, even if there are no legacy B/G clients connected.    claim there is no speed drop for N clients when running on a mixed-mode network.  They say the only issue is that overall network throughput will be lower, because only one client can be transmitting at any time, so some of that transmission time must be shared with the legacy B/G clients running at lower speeds, reducing the overall throughput from what it would be if there were only N clients connected.    So, which is it?  Will running in mixed-mode slow down my network, even if there are no B/G clients?  If I'm running N, will having another client connected at B/G slow me down substantially vs. if they were running N? How to find (and delete) duplicate files I have a largish music collection and there are some duplicates in there. Is there any way to find duplicate files. At a minimum by doing a hash and seeing if two files have the same hash.  Bonus points for also finding files with the same name apart from the extension - I think I have some songs with both mp3 and ogg format versions.  I'm happy using the command line if that is the easiest way. The new Chip credit cards are being introduced to provide better security to consumers, merchants and credit card vendors.    Sample Card:   (source: )    Card Reader &amp; PIN Entry:    Are they really better from a security point of view?  What are the advantages and disadvantages? Print floating point values without leading zero tag:* links incorrectly when using Save And Copy Profile To All Stack Exchange Accounts The  tag in my Stack Exchange profile links to different sites depending on where it's being viewed:  Profile on StackOverflow:  [tag:CSS] =&gt; https://stackoverflow.com/questions/tagged/css   Profile on StackExchange:  [tag:CSS] =&gt; https://stackexchange.com/questions/tagged/css   Profile on CodeReview:  [tag:CSS] =&gt; http://codereview.stackexchange.com/questions/tagged/css    I'd like to have these all link to https://stackoverflow.com/questions/tagged/css. You can ; why not add the ability to specify the site with tags? &lt;!-- tag: stackoverflow --&gt;[tag:css] &lt;!--tag: meta --&gt;[tag:feature-request]  The current behavior also cause a bug on my :    All tags send me to find a Panda aka 404 Page Not Found. Obtain the joint PDF of $\theta_{1} - \theta_{2}$ and $\theta_{1}$ where $\theta_{1}$ and $\theta_{2}$ are i.i.d $\text{Uniform}[0, 2\pi)$ I have 2 i.i.d Uniform random variables $\theta_{1}$ and $\theta_{2}$ on $[0, 2\pi)$. Here the problem pushes us to consider that all operations are made modulo $2\pi$. My question is how to obtain the joint PDF of $\theta_{1} - \theta_{2}$ and $\theta_{1}$ and then obtain the conditional PDF of $\theta_{1}$ given $\theta_{1} - \theta_{2}$??. For the second part It can be deduced from the first by writing it as the joint PDF divided by the PDF of $\theta_{1}$. But for the first part, A common idea that I saw is to derive the $\text{CDF}(x, y) = P(\theta_{1} - \theta_{2} \le x$, $\theta_{1} \le y$) and then perform derivations respect to $x$ and $y$. Is this a right approach? If yes, how to proceed with CDF especially with our uniform distribution restrictions? Table of Variables I have the following file:  abcde kwakwa &lt;0x1A&gt; line3 linllll   Where &lt;0x1A&gt; represents a byte with the hex value of 0x1A. When attempting to read this file in Python as:  for line in open('t.txt'):     print line,   It only reads the first two lines, and exits the loop.  The solution seems to be to open the file in binary (or universal newline mode) - 'rb' or 'rU'. Can you explain this behavior ? Why does everyone do 9-overlord, not 10-overlord? What is the advantage on saving the money for the overlord when you have 9 drones, and not filling your supply first and then getting the overlord?  In my theory, in the first case you get to wait the saving time with 9 drones, and get to wait almost the same time with 10 drones in the second case. Second case should be better, since 10 drones mine faster than 9? So why does everybody go with the first case?  All this is assuming you go 12 pool or something like that, where you will get more drones after the overlord. 6- and 8-pools are obviously different. WOL - Wake On Lan over internet Does the rank-nullity theorem hold for infinite dimensional $V$? How do I set up a "secure" open resolver? This is a  about securing public DNS resolvers   Open DNS servers seem pretty neat and convenient, as they provide IP addresses that we can use consistently across our company regardless of where they are located. Google and OpenDNS provide this functionality, but I'm not sure that I want these companies to have access to our DNS queries.  I want to set up something like this for use by our company, but I hear a lot about this being dangerous practice (particularly in regards to ) and I want to make sure that we do this right. What things do I need to keep in mind when building this type of environment?