I have used db=this.getWritableDatabase(); in the constructor itself, so I havent used a specific open or close function. Should I?   public void changeCabLocation(String to_loc, String cab_id2) {     // TODO Auto-generated method stub     ContentValues val=new ContentValues();     val.put(cab_location, to_loc);     db.update(TB_cabs, val, cab_id+"="+cab_id2, null); }  public void changeDriverLocation(String to_loc, String driver_id2) {     // TODO Auto-generated method stub     ContentValues val=new ContentValues();     val.put(driver_location, to_loc);     db.update(TB_drivers, val, driver_id+"="+driver_id2, null); }
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?
If a group satisfies $x^3=1$ for all $x$, is it necessarily abelian? I know that any group satisfying $x^2=1$ for all $x$ is abelian. Is the same true if $x^3=1$? I don't think it is, but I can't find a basic counterexample. What's the bad magic number error? SQL Coalesce in WHERE clause I'm trying to implement optional parameters in a stored procedure that I have but I am running into a problem. Here's a simplified query to illustrate the issue:  SET ANSI_NULLS OFF  DECLARE @MiddleName VARCHAR(20); SET @MiddleName = NULL;  SELECT * FROM [Customer] WHERE [LastName] = 'Torres' AND [MiddleName] = COALESCE(@MiddleName, [MiddleName])   When I run this query I need to get one row back because one Torres has NULL in the [MiddleName] column. But the query returns zero rows. Using IFNULL() produces the same result. From researching COALESCE, I was under the impression that NULL would be returned if all expressions are NULL. As I am not a SQL expert I assume that I am missing something, but what is it.....  Thanks in advance for any help. Prevent direct access to a php include file I have a php file which I will be using as exclusively as an include. Therefore I would like to throw an error instead of executing it when it's accessed directly by typing in the URL instead of being included.  Basically I need to do a check as follows in the php file:  if ( $REQUEST_URL == $URL_OF_CURRENT_PAGE ) die ("Direct access not premitted");   Is there an easy way to do this? Show some indication that account is banned from asking new questions Show that $$\int_{0}^{\infty} \frac{x - \sin(x)}{x^3} \, dx = \frac{\pi}{4}$$   My attempt is as follows: Let $$f(z) = \frac{z - i e^{iz}}{z^3}$$ and consider the contour on $[\epsilon, R]$ followed by a semicircular arc in the counter clockwise direction, then on $[-R, -\epsilon]$, then the semicircular clockwise contour avoiding the origin. We have, then, that  $$0 = \int_{\Gamma} f(z) dz = \int_{[\epsilon, R]} f(t) dt + \int_{C_R}f(Re^{it})Rie^{it}dt + \int_{[-R, -\epsilon]}f(t)dt + \int_{C_{\epsilon}}f(\epsilon e^{-it})\epsilon i e^{-it} dt$$  Then the first and third integrals ( $I_1$ and $I_3$) combine so that  $$I_1 + I_3 = 2\int_{\epsilon}^R \frac{t - \sin{t}}{t^3}\,dt$$  Further,   $$|I_{C_R}| \leq \int_0^\pi \left|\frac{Re^{it} - ie^{-R\sin{t}}e^{iRcos{t}}}{R^2 e^{2it}} \right|dt \rightarrow 0 \text{ as } R\rightarrow \infty$$  (I've omitted the details, it isn't too bad to bound)  However, I'm having trouble computing the limit  $$\lim_{\epsilon \rightarrow 0}\int_{C_{\epsilon}} f(\epsilon e^{-it})\epsilon i e^{-it} dt$$  No matter which way I look at it, it seems like this limit does not exist. Perhaps I'm seeing something wrong or have I chosen a bad $f(z)$? I have a package (fcl) in my PPA  in my launchpad PPA and it depends on another package (libccd) which is in another PPA ppa:imnmfotmal/libccd. fcl has both build and run dependency in libccd. So i added libccd as a PPA dependency in launchpad and both are successfully build. but when i am trying to install fcl package after adding the fcl PPA, its throwing an error Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  fcl : Depends: libccd but it is not installable E: Unable to correct problems, you have held broken packages.  but its successfully getting installed after adding the libccd PPA also. I want fcl to install libccd automatically without adding its PPA. how can i achieve it ?? Output of apt-cache policy fcl fcl:   Installed: (none)   Candidate: 1.0-0ppa5   Version table:      1.0-0ppa5 0         500 http://ppa.launchpad.net/imnmfotmal/fcl/ubuntu/ trusty/main amd64 Packages This question led to a new package:      I'm giving my students an old exam and barely remembered to change the date at the top. A colleague and I joked about how long we could reuse the same exam, and it made me wonder if I could use LaTeX to create an exam that looked like it was written in 1963 on a typewriter.  Here's what I'd like to see:   Typewriter font even in math mode. (Several ways to accomplish this; is there a "best" way?) Slight inconsistencies in the printing of each letter. I attempt this below adapting code taken from . Each word has a random vertical shift, though I'd like to see it reduced to each letter having its own vertical shift. Other typewriter-like irregularities would be great. It would be great if math-mode delimeters \left(, \right}, etc., can be created in a piece-meal fashion as they did in days of old. Fraction bars, tops of square-root symbols -- any horizontal line, really -- is made up of a series of en-dashes that don't quite match up.   Here is what I've come up with so far:  \documentclass[10pt]{article}% This is a document class providing more font size options \usepackage{graphicx} \usepackage{ifthen} \usepackage[textwidth=7.5in,textheight=9.5in]{geometry} \pagestyle{empty}  % thanks to Bruno Le Floch: https://tex.stackexchange.com/q/9331/4012 % and in his comments to https://tex.stackexchange.com/a/29458/4012 \usepackage[first=-1,last=1]{lcg}% you can play around with these values \makeatletter \newcommand{\globalrand}{\rand\global\cr@nd\cr@nd} \makeatother  \newcommand{\randomvshift}[1]{\globalrand\raisebox{\value{rand}pt}{#1}}  %%% thanks to Martin Scharrer: https://tex.stackexchange.com/q/11598/4012 \makeatletter \def\typewriter#1{%     \@typewriter#1 \@empty } \def\@typewriter#1 #2{%    \randomvshift{#1}\space    \ifx #2\@empty\else     \expandafter\@typewriter    \fi    #2% } \makeatother \begin{document}\tt  \typewriter{Math 101 Fall 1963}  \begin{enumerate} \item   \typewriter{$\frac{\texttt{d}}{\texttt{dx}}\texttt{(x)}^2$}  \item \typewriter{State the Fundamental Theorem of Calculus.}  \end{enumerate}  \end{document} How to install H.265 / HEVC codec on Ubuntu Linux? I have seen that the new  shows off H.265/HEVC playback, the successor of H.264. I wonder how I may get this support in Linux. Is there a need to install a codec specific for this format? How? How did Harry, Ron and Hermione buy presents for each other? I have been re-reading the Harry Potter books again and I noticed that Harry, Ron and Hermione have been giving each other Christmas presents each year at Hogwarts. How have they been able to buy each other presents if they are not allowed to go out of Hogwarts?   From their third year on they could visit the village and buy presents there, but what about the first two years? Did they give their personal belongings? Or did they just happen to have boxes of chocolates or books to give each other? Change bounding box of math glyphs in LuaTeX I'm trying to use the Garamond-Math font in LuaTeX (despite the documentation saying I should use it with XeTeX only :-). It's working more or less OK with LuaTeX, except for some unfortunate glyph combinations, mostly at the end of inline math, such as “where $T$ is the period”.  I used \fbox to draw the bounding box of the glyph and noticed that the bounding boxes are different in LuaTeX:        and in XeTeX:        In XeTeX the glyph fits almost entirely in the bounding box, but in LuaTeX it overshoots far too much.  I'm not a font guy, so I have no idea why this happens. I thought the bounding box was a property of the font, so in my imagination the result should be the same. Thus the first question is: what actually happens that the bounding boxes are different?  The second question, in the title, is: can I change the bounding box of specific glyphs (using LuaTeX) so that the output looks more like XeTeX's?  I tried manually adding some spacing after the glyphs, but this looks hideous and will go down the drain if I happen to change the font or engine, so I'd really like not to do that. I also tried using the italic correction \/ but it seems to have no effect in math.  Here's the code to produce the pictures above:  \documentclass{standalone} \usepackage{unicode-math} \setmathfont{Garamond-Math.otf} \begin{document} \fboxrule=1sp \fboxsep=0pt In Lua\TeX{} this \fbox{$T$} looks horrible, but the \fbox{$X$} looks OK. \Huge\fbox{$T$}\quad. \end{document}   I'm using TL 2018:  This is LuaTeX, Version 1.07.0 (TeX Live 2018)  (format=lualatex 2019.3.29)  13 APR 2019 12:43  restricted system commands enabled. **test.tex (./test.tex LaTeX2e &lt;2018-12-01&gt; Lua module: luaotfload-main 2019-02-14 2.96 luaotfload entry point How do I get AMD/Intel Hybrid Graphics drivers to work? On Ubuntu 12.04 my Sony Vaio VPCSE with Intel® HD Graphics 3000 and AMD Radeon™ HD 6630M worked fine with the Catalyst Control Center version 12.6. Also the switching between integrated and discrete graphic card was working.  In both cases, I followed this .  But it is not working on Ubuntu 12.10.   I tested the tutorial with the Catalyst Control Center from the Ubuntu Software Center, the version 12.8 and version 12.9. Always the same problem: After installation process I am able to boot in the login-screen. But after entering the password for my username, only the background-image appears. Unity seems not to be starting. I am only able to reach the context-menu by right clicking the mouse button.  I also tried , but is also does not work for me.  Any ideas what to do to fix this problem?   Update: Same problem on Ubuntu 13.04!  Update: Solution for 13.04 ist not working on Ubuntu 13.10! Assume $f$ and $g$ are differentiable at $x$. Prove that $(fg)^{(n)} = \sum_{k=0}^n \binom{n}{k}f^{(k)}(x)g^{(n-k)}(x)$   I am assuming here $fg = f(x) g(x)$. Then we can prove this via induction. If $n = 0$ we have $1 = 1$ which is true. Now assume it is true for some $m$ we need to show it is possible for $m+1$. We have $(fg)^m = \sum_{k=0}^m f^{(k)}(x)g^{m-k}(x)$. How do we show that? Unwanted behaviour from dict.fromkeys Let, $X$ be a countable set. Which of the following are true?   There exists metric $d$ on $X$ so that $(X,d)$ is complete. There exists metric $d$ on $X$ so that $(X,d)$ is not complete. There exists metric $d$ on $X$ so that $(X,d)$ is compact. There exists metric $d$ on $X$ so that $(X,d)$ is not compact.   4 is true as we can take discrete metric. Then $\{\{x\}:x \in X\}$ is an open cover containing no finite subcover.  If there exists a compact metric then it would automatically become complete also. Hence if 3 is true, so is 1.  What about 2? Any other comment? How much can a grappler with reach move a grappled creature inside its reach? Create line graph with ggplot2, using time periods as x-variable How can I replace end line with fixed text when the next line begins with a defined set of characters? I have several big files with some measurements.   It looks this way:  N 12344;PE 9.9999999;... #S 0 0 31 44 75 130 165 196... #S_+ "2 5 2 3 3 1 1 2 3 1 2 2...  N 12345;PE 9.9999999;... #S 0 0 34 57 84 133 152... #S_+ "1 0 1 1 2 3 0 0 0...  N 12346;PE 9.9999999;... #S 0 0 31 44 73 140 169... #S_+ "3 3 4 0 0 2 1 2 4...  N 25104;PE 9.9999999;... #S 0 0 36 52 102 108 145... #S_+ "1 1 0 1 0 0 3 0 1...  N 25105;PE 9.9999999;... #S 0 0 32 58 88 130 143...   Sample is here:   The file is much bigger but I replaced part of the data with "..." to make it shorter.  I need to somehow replace the line ends before "#S" - in fact simply merge the "N" line with the following two ones into one line (or with the following three ones so I can get rid of the blank lines). Expect output like this:  N 12344;PE 9.9999999; #S 0 0 31 44 75 130 165 196 #S_+ "2 5 2 3 3 1 1 2 3 1 2 2... N 12345;PE 9.9999999; #S 0 0 34 57 84 133 152 #S_+ "1 0 1 1 2 3 0 0 0... N 12346;PE 9.9999999; #S 0 0 31 44 73 140 169 #S_+ "3 3 4 0 0 2 1 2 4... N 25104;PE 9.9999999; #S 0 0 36 52 102 108 145 #S_+ "1 1 0 1 0 0 3 0 1... N 25105;PE 9.9999999; #S 0 0 32 58 88 130 143...   Is this possible to achieve using some command-line utility in linux?   My knowledge is quite limited in this area so I would appreciate any help.  thanks Blender 2.80 system Req + GPU req Can someone please let me know the minimum system requirements and GPU requirement to run blender 2.80 and eevee smoothly?   Also please let me know the optimum system requirements for the purpose of    environment modeling Game development charachter modelling and animation   Also if someone can suggest me a good desktop/laptop for personal use that is compatible with blender 2.80 in a low budget.  Any help will be much appreciated.  Thanks in advance! How to create an index map of atlas features in QGIS 3? I realise that this question has been asked before (), however I am still unable to figure out how to create an index map of atlas features in the QGIS map composer.  Basically, I have a line and I have five atlas maps showing the extent of the line, and to show where which map corresponds to the line a I need five overviews on a map with numbers on them, which will look similar to below:    I've created five overviews, but as all of these must be set to correspond to the main map frame, all of them show the overview for which ever atlas feature is selected at the time, rather than appearing as separate index tiles.  Can anyone tell me where I am going wrong?