i am getting java.lang.NullPointerException in Automation testing selenium
What is a NullPointerException, and how do I fix it?
Windows of an application have minimum size and I can't find the window anymore I had an application (in case it matters: LibreOffice Calc] in full-size mode. I then clicked the middle of the three buttons of the top right to adjust the size. When I did that, the window became minimum size, literally a vertical line. I panicked and alt-tabbed, and now I can't even find the vertical line anymore. Opening new windows in that application opens all of them hidden to me, and closing/reopening or even restarting the OS doesn't help. I don't know how to resize my invisible windows anymore. Here's the preview of the windows in the application launcher: a vertical line (that I don't find on my screen anywhere if I click this). Suppose the default shell for my account is zsh but I opened the terminal and fired up bash and executed a script named prac002.sh, which shell interpreter would be used to execute the script, zsh or bash? Consider the following example:  papagolf@Sierra ~/My Files/My Programs/Learning/Shell % sudo cat /etc/passwd | grep papagolf [sudo] password for papagolf:  papagolf:x:1000:1001:Rex,,,:/home/papagolf:/usr/bin/zsh # papagolf's default shell is zsh  papagolf@Sierra ~/My Files/My Programs/Learning/Shell % bash # I fired up bash. (See that '%' prompt in zsh changes to '$' prompt, indicating bash.)  papagolf@Sierra:~/My Files/My Programs/Learning/Shell$ ./prac002.sh  Enter username : Rex Rex # Which interpreter did it just use?   **EDIT : ** Here's the content of the script  papagolf@Sierra ~/My Files/My Programs/Learning/Shell % cat ./prac002.sh  read -p "Enter username : " uname echo $uname Confidence bands for QQ line This question doesn't specifically pertain to R, but I   chose to use R to illustrate it.  Consider the code for producing confidence bands round a (normal) qq-line:  library(car) library(MASS) b0&lt;-lm(deaths~.,data=road) qqPlot(b0$resid,pch=16,line="robust")   I'm looking for an explanation of (or alternative a link to a paper/online document explaining) how these confidence bands are constructed (I have  seen a reference to Fox 2002 in the help files of R  but sadly I don't have this book handy).   My question will be made more precise with an example.  Here's how R computes these particular CI's (I've  shortened/simplified the code used in car::qqPlot)  x&lt;-b0$resid good&lt;-!is.na(x) ord&lt;-order(x[good]) ord.x&lt;-x[good][ord] n&lt;-length(ord.x) P&lt;-ppoints(n) z&lt;-qnorm(P) plot(z,ord.x,type="n") coef&lt;-coef(rlm(ord.x~z)) a&lt;-coef[1] b&lt;-coef[2] abline(a,b,col="red",lwd=2) conf&lt;-0.95 zz&lt;-qnorm(1-(1-conf)/2) SE&lt;-(b/dnorm(z))*sqrt(P*(1-P)/n)     #[WHY?] fit.value&lt;-a+b*z upper&lt;-fit.value+zz*SE lower&lt;-fit.value-zz*SE lines(z,upper,lty=2,lwd=2,col="red") lines(z,lower,lty=2,lwd=2,col="red")   The question is: what is the justification for  the formula used to compute these SE (e.g. the line SE&lt;-(b/dnorm(z))*sqrt(P*(1-P)/n)).   FWIW this formula is very different from the formula of the usual How to create a good glass reflection with Principled BSDF I read on the wiki that people will move in under the following conditions:   You do something to please them An empty house is available with a light source, table, and chair (also with walls).   I have a house which is about 7x8, then a roof space above that; about half the area. I could put furniture up there too, but will anyone move in? Integral $\int_{1}^{2011} \frac{\sqrt{x}}{\sqrt{2012 - x} + \sqrt{x}}dx$ Evaluate:  $$\int_{1}^{2011} \frac{\sqrt{x}}{\sqrt{2012 - x} + \sqrt{x}}dx$$  Using real methods only.  I am not sure what to do.  I tried finding a power series, which was too ugly.  I just need some hints, not an answer to do this integral, this is from the MIT Integration bee 2012. I am running Ubuntu Gnome 16.10 (64bit). Gnome-shell version 3.20.4.   When I start my computer, I eventually see GDM3 offering a login prompt, as expected.   After I login, my monitors flash a little (like they're unplugged and then replugged in), and then I am brought to the gnome 3 desktop.   However, if I hit  CTRL + ALT + F1, I am brought back to GDM3, offering a login prompt.   If I then hit CTRL + ALT + F2,  I am brought back to my Gnome 3 desktop.  So it seems like GDM3 continues to run in TTY1 while the desktop runs in TTY2.   Questions   Is this how things are supposed to work? I thought the desktop was supposed to use the same TTY (or whatever you call it) as the display manager.  Am I using more graphical resources by having things setup this way? Is there a way to have GDM3 pass off the display to Gnome Desktop after I login? Is there any advantage do doing #3? Are there fixed size integers in GCC? On the MSVC++ compiler, one can use the __int8, __int16, __int32 and similar types for integers with specific sizes. This is extremely useful for applications which need to work with low-level data structures like custom file formats, hardware control data structures and the like.  Is there a similar equivalent I can use on the GCC compiler? Minkowski Metric Signature When I learned about the Minkowski Space and it's coordinates, it was explained such that the metric turns out to be $$ ds^{2} = -(c^{2}dx^{0})^{2} +(dx^{1})^{2} + (dx^{2})^{2} + (dx^{3})^{2}   $$ where $ x^0,x^1,x^2,x^3 $ come from $ x^{\mu} : \mu = 0,1,2,3 $, and $ c $ is the speed of light. The first resource I had access to--I have to do a bit of digging for the exact paper--of course addressed that this invariant takes the tensor form: $$ ds^2 = g_{\mu \nu}dx^{\mu}dx^{\nu} $$ as well. This two things I've seen in all of my texts and online resources regarding resources. The element in question that varies between authors, is the time coordinate, $ x^0 $. When it was first explained to me, it was using the standard Cartesian representation for the spatial portion of the coordinates, and the time coordinate was labeled as $ x^0 = ict $. Squaring gives $ (x^0)^2 = -c^2t^2 $, and applying differential calculus, we get $ (dx^0)^2 = -c^2dt^2 $. Sensible and expected to have the tensor formula spit out the Minkowski Metric. The author then later explicitly states the coordinates are $ x^0 = ict, x^1=x,x^2=y,$ and $x^3 = z$.  My questions is then, why is it most authors on the subject omit the imaginary unit on the time coordinate? For example, .   The only reason I can fathom omission is if the author is using metric signature $ [+,-,-,-] $, where I started off learning the theory with signature $ [-,+,+,+] $ which may be the reason seeing the time coord with no imaginary unit seems dissonant to me. All help appreciated!  Edit: After reading the other answers, my questions is now one of why and how (mathematically) do we obtain the Minkowski Metric Signature. More specifically the one element with a different sign. Set "older" kernel as default grub entry I installed a mainline kernel for testing purposes. I would like to set grub to boot from the older kernel by default.  I know I can set the GRUB_DEFAULT=0 setting for the first page of grub but how do I set it to boot by default from one kernel in the second page (Advanced page)?  I would prefer doing this without installing other software (ex. grub-customizer).     Related Questions: Putting char into a java string for each N characters Proving question on sets I am unable to understand this question. I have to say whether its true of false and then prove it but I can't proceed with the question unless I understand it.     Let $S$ be the set of stars in our galaxy. There is exactly the same   number of subsets of stars in our galaxy as there are functions   $f:S\rightarrow\{\alpha,\beta\}$ Did she judge him "wrong" or "wrongly"? Which one is the correct use?  She judged him wrong. She judged him wrongly.  Or, are both correct, but have slightly different meanings? I've just got my first follower, and I'm wondering if I can get a second person to follow me. Is the game limited to one or two follower(s) or does it allow for a large number of followers? It really seems handy to me to have some followers protect me when I draw attention from a larger group, or when I try to steal something where I really shouldn't... Original  The remainder provided by polynom.sty is NOT complete (as shown in the following figure).      My Objective  When I was in senior high school, my teacher made the diagram like below. :-)  Thus the final step must show the TOTAL remainder and mark it with L-shaped curve.  NOTE  I am sorry. The previous post I forgot to put back -1/4 in the original position. It have made you confused. Now there is no mistake anymore. :-)      Minimal Code  \documentclass{article} \usepackage{polynom,array} \usepackage[table]{xcolor}   \makeatletter \def\pld@ArrangeResult#1{%     \ifx\pld@remainder\@empty         \@tempcnta\pld@maxcol\relax         \pld@InsertItems@do\pld@lastline             {\pld@firsttrue\pld@PLD{\pld@R{0}{1}}}%     \fi     \ifnum\pld@currstage&gt;\z@         \pld@Extend\pld@allines{\pld@lastline\cr}%     \else         \pld@InsertFake\pld@lastline     \fi     \pld@iftopresult         \def\pld@lastline{\pld@PrintPoly\pld@divisor%         %====================================================================================         \quad\smash{{\color{red}\rule[-6pt]{\arrayrulewidth}{17pt}}}\kern-\arrayrulewidth&amp;}%         %====================================================================================     \else         \let\pld@lastline\@empty         \ifx B\pld@style\else             \def\pld@lastline{\pld@leftdelim\strut\pld@rightxdelim&amp;}%         \fi     \fi     \expandafter\pld@AR@col\expandafter\pld@PLD                            \expandafter\pld@lastline#1+\relax+%     \pld@SplitQuotient     \pld@iftopresult         \let\pld@currentline\@empty         \expandafter\pld@AR@col\expandafter\pld@PLD                                \expandafter\pld@currentline                                            \pld@quotient+\relax+%         \expandafter\pld@AR@col\expandafter\pld@XPLD                                \expandafter\pld@currentline                                            \pld@shadow+\relax+%         \edef\pld@subline{%             \noexpand\cline{\tw@-\pld@maxcol}%             \noalign{\vskip\jot}}%         \pld@Extend\pld@currentline{\expandafter\cr\pld@subline}%     \else         \@tempcnta-\@tempcnta         \advance\@tempcnta\pld@maxcol\relax \advance\@tempcnta\@ne         \edef\pld@span{\the\@tempcnta}%         \ifx B\pld@style           \pld@AddTo\pld@lastline{%             &amp;\multispan\pld@span${}=%             \pld@PrintPolyWithDelims\pld@divisor             \expandafter\pld@IfSum\expandafter{\pld@divisor}{}{\cdot}%             \expandafter\pld@IfSum\expandafter{\pld@quotient}\pld@true                                                              \pld@false             \pld@if \pld@leftdelim                     \pld@PrintPolyShadow                     \pld@rightdelim               \else \pld@PrintPolyShadow \fi             \pld@firstfalse             \expandafter\pld@PrintRemain\expandafter{\pld@remainder}$}%         \else           \pld@AddTo\pld@lastline{%             &amp;\multispan\pld@span$\pld@leftxdelim\strut\pld@rightdelim             \pld@div             \pld@PrintPolyWithDelims\pld@divisor=             \pld@PrintPolyShadow             \ifx\pld@remainder\@empty\else                 +{}%                 \setbox\z@=\hbox{$\displaystyle                   \frac{\let\strut\@empty\pld@firsttrue \expandafter                         \pld@PrintRemain\expandafter{\pld@remainder}}%                        {\let\strut\@empty\pld@PrintPoly\pld@divisor}$}%                 \dp\z@=\z@\box\z@             \fi             $}%         \fi     \fi \expandafter\pld@AR@\pld@allines\relax} \makeatother   \arrayrulecolor{red} \arrayrulewidth=0.8pt \def\strut{\rule[-6pt]{0pt}{12pt}}  \begin{document} \polylongdiv[style=A]{\frac{3}{7}x^9+x^2-\frac{1}{4}}{\frac{9}{5}x^4-1}  \vspace{1cm} \polylongdiv[style=A]{x^4-1}{x^2-1} \end{document} I have a raster image (Sentinel-2 band 4) and a shapefile covering the same area than the image (same projection and extension). The shapefile has different polygons which are agricultural fields.   I want to create a new file where, for each polygon, the mean value of the pixels that are inside it is calculated.  Could you please help me to find an appropriate R code for that? Prove that a polynomial is irreducible or the field contains a $p$th root An exercise from Lang:  Let $k$ be a field. Let $n$ be a nonnegative integer. Consider the polynomial $x^{p^n}-a \in k[x]$. Assume that $\text{char}(k) = p &gt; 0$. Prove that either the polynomial $x^{p^n}-a$ is irreducible over the field $k$ or there exists a $b\in k$ such that $a = b^p$.  How to prove this statement? I am a little bit confused with this statement. Blaise Pascal's famous wager was that even if the existence of God cannot be determined through reason, a rational person should wager as though God exists, because living life accordingly has everything to gain, and nothing to lose.  What logical flaws and/or fallacies (if any) are committed in making this argument? Google Maps API v3, jQuery UI Tabs, map not resizing How can I translate CMYK to Pantone colors? In particular, how do I translate CMYK 90C 85M 80Y 63K to a Pantone color?