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Xml configuration versus Annotation based configuration In a few large projects i have been working on lately it seems to become increasingly important to choose one or the other (XML or Annotation). As projects grow, consistency is very important for maintainability.   My questions are: what are the advantages of XML-based configuration over Annotation-based configuration and what are the advantages of Annotation-based configuration over XML-based configuration? Difference between StringBuilder and StringBuffer What is the main difference between StringBuffer and StringBuilder? Is there any performance issues when deciding on any one of these? When do you use Java's @Override annotation and why? Why does $x$ divided by zero not equal $x$? Network booting couldn't find kernel image I have a problem with PXE booting. I followed  on the Ubuntu help wiki. But I get an error on client machine:  Could not find kernel image: vmlinuz-3.13.0-24-generic   And now, question. This image should be in pxelinux.cfg folder, am I right? I would like to solve the beginner's standard exercise which claims that a point of $\mathrm{Spec} \ R$ is closed iff it is a maximal ideal.  The reverse implication is easy. The direct one seems much subtler. If $P = V(I)$ then, since there exist a maximal ideal $M$ containing $P$, it would follow that $\{P, M\} \subseteq V(I) = P$, whence $P=M$. In order to show the existence of $M$ I applied Zorn's lemma to the set of ideals containing $P$.  The question is the following: is there any other proof of the above implication that does not (indirectly) use the axiom of choice? My concern is that I may be using a cannon to shoot a fly. Also, it would be the first time that I see closedness of points to require the axiom of choice. If the axiom is indeed needed in general, are there "nice" classes of rings for which we could get away without it? The set of all finite subsets of the natural numbers is countable How to create a torus with divided cuts that correspond to the direction of the torus As I understand it, anything created with an alloc, new, or copy needs to be manually released. For example:  int main(void) {     NSString *string;     string = [[NSString alloc] init];     /* use the string */     [string release]; }   My question, though, is wouldn't this be just as valid?:  int main(void) {     NSAutoreleasePool *pool;     pool = [[NSAutoreleasePool alloc] init];     NSString *string;     string = [[[NSString alloc] init] autorelease];     /* use the string */     [pool drain]; } How can I make a script (or make some changes) to allow me to turn the screen off in Ubuntu (12.04) whenever I want, the way thevscreen can be turned off in Cellphones?  And how can I make a combination of keys (a shortcut) to execute that script?  I want to conserve power.  I've seen this question    but there is no hotkey for it.  Moreover, in the answer, it is said that there are many ways to accomplish this so I'd like to know more. I am trying to incorporate a wms feed in the British national grid projection (EPSG:27700) into a openlayers 3 project. I initially had used this wms layer in an openlayers 2 application using the following syntax:  new OpenLayers.Layer.WMS(         "ukimage",         "http://www.linktowms",         {             "LAYERS": 'ukimage',             "STYLES": '',             format: state.image_format         }, {     buffer: 0,     displayOutsideMaxExtent: true,     isBaseLayer: true } );   But I am having trouble converting this over to openlayers 3. I first tried setting the map projection to British national grid (view: new ol.View({ projection: 'EPSG:27700'}) as I had in the openlayers 2 app, but this produced the error  TypeError: h.B is not a function    and a white map.   When I try and use proj4 to convert the projection to EPSG:3857 as described here:  I get the same error:   TypeError: h.B is not a function    and again a white map.   my wms request is generally a varient of:  new ol.layer.Image({       source: new ol.source.TileWMS({         url: 'http://www.linktowms',         params: {'LAYERS': 'ukimage'},       })     }),   (I tried adding projection but that didn't help)  I am trying to work out if the image is even getting loaded from the WMS feed, but the syntax seems to have changed significantly from openlayers 2, instead of the properties and functions that have rather descriptive names, there are a now lots of short functions with names like Ua and Ig, which leaves me a bit in the dark as to what's actually going on when I try and inspect the layer with firebug.  I don't mind what projection the application is in, as I can re-project my other layers to match the basemap, so basically any way of using this EPSG 27700 WMS layer in openlayers 3 would be great. Probability of correctly guessing 12 zodiac signs without replacement I just watched  where someone assigns a zodiac sign to twelve different individuals. There is one of each sign.  My question, Guessing at random, (this was not quite at random), what number of people are you expected to guess correctly? And with what probability are you expected to guess a given number of people correctly?  i.e. What are the odds of getting 1, 2, 3, 4, etc. correct. Viruses in wine? The Story  I installed wine some time ago, and after trying out some versions of Cinema 4D that were "free", I looked in the comments of the videos, and saw some people complaining about viruses. I got worried, downloaded and installed MalwareBytes, and scanned my "system". Of course, since MalwareBytes was runnning through Wine, it only scanned ~/.wine/C:. It found many viruses/trojans and I opted to delete them. I did so.  Questions:   Assuming there is any malware left, can this malware spread into my OS? Tell me the entire truth on what can happen. I deleted my entire .wine directory and am planning to uninstall wine later. I am the only user out of the three on this system that runs wine programs, but wine is installed for all. Is that enough, or must I do more? Please be specific on what I should do because I want to be 100% sure that there are no viruses.   I am sure that many others have these questions too, so please answer this question to the point.   Additional information:  Wine was installed with sudo-apt get. The exact commands can be found here:   Commands:  sudo add-apt-repository ppa:ubuntu-wine/ppa -y sudo apt-get update sudo apt-get install wine1.6 -y   I did try to install a font that was a ttf font. I tried to convert it to otf with no success. Then, I placed it in the fonts directory directly. I then saw that some people said it was malicious, and I removed it.  This question was flagged as  a duplicate of this question:  It is not the same. This question is more precise, as it specifies two scenarios involving viruses, not risks of viruses. The other question talked about Internet Explorer; this one does not mention the installation of any programs.  Note: wine was installed with sudo privileges, so does that mean it runs with sudo privileges? Geometric random variables $X_1:G(p_1)$ $X_2:G(p_2)$ $X_3:G(p_3)$ are independent, prove the following : At work we have a Domain Controller running Server 2008 R2. Our desktop support group has the ability to join computers to the domain using their network credentials. We are now running into a problem where if the name of the computer that is being joined is the same as an existing computer on the domain, the existing computer will get a "The trust relationship has failed..." error and will not authenticate at all unless someone logs in as a local admin, changes the computer name and rejoins it to the domain.  I want to make it so that Desktop Support can only join computers with unique names to the domain. If the name already exists on the domain the operation should fail. Looking through TechNet it looks like this functionality exists but I can't seem to find out how to enable it.  Any ideas? Setup Apache in Amazon AWS I tried to setup apache 2.2 in amazon aws using amazon ami. i did installed httpd and php and congirue http.conf to use /var/www/html.  Then put file index.html on that folder. But when i tried to use browser to browse my domain which is ec2-122-248-255-181.ap-southeast-1.compute.amazonaws.com, nothing was loaded.  I did start httpd by running apachectl start, and i can see it listening on port 80.  Does anybody know what is wrong? Are primes (ignoring $2$) equally likely to be $1~\text{or}~3\pmod 4$? For all primes $p\neq 2$, it's easy to see that $$p\equiv 1~\text{or}~3\pmod 4$$ I was wondering if it's equally likely ($50\%-50\%$) that prime modulo $4$ is $1$ or $3$. And if so, is there a simple proof? Tikz: setting options for pin I just found the pin option to drawing, and it looks useful in some of the things I want to draw. How do I format it though? I've tried pin=[red]60:{Hey!} and I get the error Cannot parse this coordinate.  \documentclass{standalone} \usepackage{tikz} \usetikzlibrary{shapes,arrows,positioning} \begin{document} \begin{tikzpicture}[node distance=2cm,&gt;=latex, every node/.style={     font=\sffamily\scriptsize     },       circtext/.style={draw,circle,minimum size=8pt,inner sep=2pt},     dot/.style={draw,circle,fill=black,minimum size=0.6mm,inner sep=0pt} ] { \node[rectangle, fill=green!10!white!90!black, minimum width=6cm, minimum height=3cm] at (2,0){}; \node[circtext, fill=yellow](A) at (0,0) {A}; \node[circtext, fill=yellow, right=of A](B){B}; \draw[-&gt;] (A) -- node[dot, pos=0.5, pin=[red]60:{Hey!}](C){}(B); } \end{tikzpicture} \end{document}     The default style looks like it's a gray thin arrow, and I want to change it to a black thin dotted line with no arrow.    update: I figured out how to add style to the pin node:  pin={[red]60:Hey!}]  But I can't figure out how to change the linestyle though. Why does editing posts on SO require a minimum of 6 charaters? I have just recently started editing the post on Stack Overflow.  I found some posts which only required 2-3 character changes like they had correct grammar but some mistakes in spelling.  When I tried to correct the spelling mistakes, and clicked on "edit", it said:  Edits must be at least 6 characters   I don't know why Stack Overflow added this limit. How can I edit only 3-4 characters in a post? I have just installed 12.04 LTS on my laptop and I'm kinda new in this. I am required to write some program in Fortran 77 and I need a Fortran 77 compiler. I have tried installing g77 as described in the Ubuntu website but was unable to do so. I have typed in the following in terminal:  sudo apt-get install g77   and get the following:  Reading package lists... Done Building dependency tree        Reading state information... Done Package g77 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'g77' has no installation candidate   May I know what is the problem? I have tried searching g77 in the software center but apparently it is not there. Does this mean it is not available for 12.04?  I'm currently using an Asus K43S laptop with Intel Core i5-2450M processor and my Ubuntu is installed alongside Windows.