Null Exception Error while returning values to driver
What is a NullPointerException, and how do I fix it?
Display keyboard without animation How can I check if a package is installed (no superuser privileges)? At our university we can get almost any ubuntu package installed we want, but we are not superusers ourselves (we need to request packages being installed).  With some libraries it is not always easy to know whether the package is already installed or not. Is there a simple way/command to check this? Current sensing nA to mA I need to sense the current of a target  through various periods of its on/sleep/off state and then need to send this data back to another interface MCU to read out the value. They will be both on the same board, powered by 5&nbsp;V USB.  However these are the requirements I have:   5&nbsp;V USB PSU Must be able to sense currents in the range of nA to mA with high    accuracy/precision. (I figure 1&nbsp;nA to 500&nbsp;mA) Only measure the current of the target MCU and not the interface. Must output maximum 3.3&nbsp;V interface MCU   I have looked at available options and current sense amplifiers by Texas Instruments can't sense nA due to higher bias currents. So therefore I feel I would need a precision amplifier.  However I am stuck on how to proceed with this because, I need to somehow have a automatic dynamic current range and I am fairly new to current sensing and am not really sure on all the specifics. Any way to send a personal message to another user? Order of an element in a finite cyclic group I would like AUCTeX (that is, Emacs with auctex loaded) to suggest more LaTeX macros when using completion (M-Tab or C-Ret) than it does by default. I would like to have macros from packages I have downloaded on CTAN and macros I have written. I would also like it if it would complete \section or other macros that can be accessed via C-c C-s, C-c C-e etc.  Solution: I could not make the code quoted by  work. i get an error on loading emacs but did not looked much further in because I ca bear the nuisance of appending a few lines to my files.  The link given by Ben ( contains a working solution, thus I accept his answer. I had come across this page in my researchs but somehow messed up things. What eventually worked for me was using TeX-auto-generate TEX AUTO to create a bunch of .el files in the ~/.emacs.d/auctex/auto direcoty. Note that this directory must be created beforhand. For some reasons TeX-macro-private did not achieve the wanted result. How to "flatten" a multi-dimensional array to simple one in PHP? It's probably beginner question but I'm going through documentation for longer time already and I can't find any solution. I thought I could use implode for each dimension and then put those strings back together with str_split to make new simple array. However I never know if the join pattern isn't also in values and so after doing str_split my original values could break.  Is there something like combine($array1, $array2) for arrays inside of multi-dimensional array? Using "that" and "this" interchangeably Learning and using English I'm always confused about what word to use for referring to things that have been described by me a few sentences earlier: "that" or "this".   Confusion comes from the fact that only the equivalent of "this" is always used in my native language for such referring. But I've noticed that in English for such referring "that" is used as often as "this" (or maybe even more often).  Some examples for illustrating (just tried to google something appropriate to convey my idea better):     We assess local... the demographics of the local population. What are the natural traffic drivers in the area. Things like cinemas and pubs and retail and office and all that type of things and we now put together a bit of a matrix and actually give a weighted score to each of the things we know help our business. That helps us decide in a more scientific fashion.   or:     The problem of Cervantes' origin became after that into a tough matter. Some experts believed that the Cervantes from Alcázar, in the times of the Lepanto Battle, was in the age of a child, more concerned about gathering nests and that type of things than about fighting as a soldier.   and for "this":     I believe lot of people who involved fishery industries in Mexico Gulf are suffering now but as for economic issues, U.S government and other countries will support them and give an utmost response to it. Important thing is that we learn from this mistake and make sure this type of things will never happen in the future and protect nature environment thus we have to take this technology to get energy from water very seriously. I really hope this technology will be available and used for everybody as soon as possible.   Is there a rule describing proper usage of these words in cases like this? (or should I have written "..in cases like that"?) Steps for going from Polyakov action to low-energy effective action (SUGRA?) in String Theory A lot of string-theory questions have been asked here. This one is, hopefully, different in that this inquiry is specific and the expected answer would be more mathematical than philosophical in character.  To give some context, I'm familiar with LQG, QFT etc. I'm a beginner in CFT and string-theory. On reading papers on AdS/CFT and String Theory the following sentence often appears: "The low-energy effective action for $x$ dimensional ST of type $y$ reduces to that of supergravity (SUGRA) in $z$ dimensions with matter fields of types $a$, $b$ and $c$".  The $64,000 dollar question any noob, such as me, wants answered is what are the mathematical/technical steps or arguments which lead us from the fundamental action of string-theory (the Polyakov/Nambu-Goto action) to a low-energy effective description. Of course, I might be asking a question for which the only concise answer is: "go read GSW". Here's hoping otherwise ;) How run a .jar file with a double-click? I have a problem running .jar files by double-clicking them. When I go to the Properties dialogue I can't find Java--only Archive Manager in the list of programs. But java -jar somefile.jar opens the program. Why $SU(3)$ and not $U(3)$? How to automount a partition on login? I have my musics in another partition of the HD, and I would like that, on login, the partition to be auto-mounted, so I can just open the media player and listen to my music. Is there a way? How to map inherited entities in EF code-first Run MySQLDump without Locking Tables From the command line is it possible to open a package installer window (not install the application).  I understand I could run the application using sudo installer -pkg ..... -target ....... Instead i would like to open the package in a similar way to if I double clicked the package within the Finder. Does a multiple-entry Schengen visa allow visiting other Schengen countries later, without going via the issuing country? How to create a chrome texture? Is it possible to get that typical chrome-like angled look using the Shader Editor? I see a lot of tutorials making chrome on all types of surfaces but not on a knob geometry like the one in the following image:  Q: Is there any way to get that chrome-like surface appearance procedurally or should I just use a texture to fake it? Why is ScreenToWorldPoint always giving same coordinates with mouse position? Whenever I use ScreenToWorldPoint(Input.mousePosition) and display the output in console this always gives me the same coordinates. MyCode: Vector3 screenToWorld;  void Update() {     screenToWorld = Camera.main.ScreenToWorldPoint(Input.mousePosition);     Debug.Log(screenToWorld); } How to get my 4yo daughter's fixation on my belly button under control? I don't know where to begin with this question. It's awkward and to be honest, it makes me feel rather uncomfortable. Simply put, I'm led to believe that my four year old daughter is obsessed with my belly button. It all started one day during the summer when she was three. I decided to take my family to the pool, and I guess I didn't see my daughter follow me into the changing room. Mind you, she's still at the age where it's appropriate to see her parents naked, so I wasn't surprised when, after I finished changing into my bikini, I turned around to see her staring at me.  I followed her gaze and saw her looking directly at my belly button. I asked her what she was looking at and she screamed "mommy, I can see your belly button!" which made me giggle. I picked her up and kissed her forehead, telling her that everyone has a belly button.  I think I might have accidentally given her a green light, because over the next year she constantly asks me if she can stick her finger in my belly button, and if I don't let her, she begins to scream.  For her fourth birthday, she requested that I wear nothing but a sports bra and underwear (in toddler speak. It sounded like "mommy, show your belly button for my birthday!" I could have simply worn a crop top but i didn't want to risk her throwing a temper tantrum)  My husband obviously doesn't mind, because he gets to look at my belly button all the time but it really upsets me that my daughter's finger is constantly in my belly button.  Tomorrow is her fifth birthday and I want to discuss with her that it's not appropriate to always be poking my belly button. Any ideas on how i can talk to her without her throwing a screaming fit? What are the limitations of a typical kit lens as a general purpose lens? I have a Canon EOS 550d with the 18-55mm IS kit lens. I have done  (portraits, nature, night shots etc), and find the image quality to be pretty good. In fact most of the reviews have also been positive (at least in terms of image quality):   Quote:     indeed Canon's main concern may   ultimately become whether users have   as much incentive to upgrade to more   expensive optics as they did before       So, what are the key limitations of this lens (or any other similar kit lens) that would compel one to upgrade to a more expensive general purpose zoom lens (apart from the wanting to upgrade the zoom range)?