Buttons not working in android alert view?
What is a NullPointerException, and how do I fix it?
Background process of subshell strange behaviour I wonder why some similar bash commands behave the way they do.  I have a bash script foo:  #!/usr/bin/env bash  while true do     echo "reading"     read data     echo $data     echo "stderr msg" &gt;&amp;2     sleep 1 done   It's an infinite loop which reads one line at a time from stdin and outputs that same line. I also have a bash script bar:  #!/usr/bin/env bash  ./foo &amp;   The following commands were run in bash (v. 4.4.19) in a terminal on Ubuntu 18.04 (let's assume the scripts reside in the working directory):   ./foo &amp;   Stops when it tries to read from stdin, in accordance with . Killed when controlling terminal is killed, as expected.  (./foo &amp;)   Appears to be automagically continuously fed with new input from stdin. Shouldn't it too stop when attempting to read from stdin? Whatever it's getting it doesn't show when echoed, thus I'm guessing it's EOF characters.  Continues running even after the controlling terminal is killed. Looking at the output of ps, the controlling terminal changes from pts/x to ?. How did this happen without the use of either disown or nohup? (However, after killing the originally controlling terminal, it yields a "write error: Input/output error" on every write, which I suppose is because its stdout was tied to the now closed terminal. Correct?)  bash -c "./foo &amp;"  Appears to behave exactly like 2). ./bar  Appears to behave exactly like 2) and 3). Adding bash -c "~/foo" (no &amp;) as a startup application  Behaves similarly to 2), 3) and 4), with the differences:   Its controlling terminal is the desktop ttyx. You can't (can you?) kill its controlling terminal.   None of those differences seem odd to me, just the fact that it's continuously fed with new input.   My guess is that 2) - 5) all use a subshell of sorts whose stdin is redirected to something like /dev/null, though I'm very unsure and seek a more exact answer. Why isn't reflexivity redundant in the definition of equivalence relation? An equivalence relation is defined by three properties: reflexivity, symmetry and transitivity.  Doesn't symmetry and transitivity implies reflexivity? Consider the following argument.  For any $a$ and $b$, $a R b$ implies $b R a$ by symmetry. Using transitivity, we have $a R a$.  Source: Exercise 8.46, P195 of Mathematical Proofs, 2nd (not 3rd) ed. by Chartrand et al Reading the extension of files in a directory with Java? I plan on buying Windows 7 Ultimate Edition to run on an old Pentium 4. I also want to run Windows 7 virtual machines inside Windows 7. My question is two fold:   Do I need a license for each Virtual Machine? Does the answer change if I use a third party virtualization platform (e.g. , , , etc) as opposed to ? After booting I ran systemd-analyze blame and here are the results:       21.596s systemd-journal-flush.service      18.658s dev-sda8.device      15.099s dev-loop33.device      15.034s dev-loop19.device      15.012s dev-loop34.device      14.989s dev-loop21.device      14.877s dev-loop15.device      14.866s dev-loop26.device      14.773s dev-loop27.device      14.684s dev-loop30.device      14.677s dev-loop32.device      14.649s dev-loop35.device      14.590s dev-loop25.device      14.267s dev-loop23.device      14.192s dev-loop24.device      14.156s dev-loop29.device      14.133s dev-loop16.device      14.065s dev-loop31.device      14.059s dev-loop28.device      13.821s dev-loop20.device      13.531s dev-loop22.device      13.495s dev-loop14.device      13.364s dev-loop18.device   What are these dev-loopxx.device (xx denotes numbers) services and why are they taking so much time? Are they related to the mounting of snaps? Can I reduce the boot time by disabling them? I'm running Ubuntu 18.04 alongside Windows 10. Could someone please check if I'm saying something that make sense? I am trying to check the following:     If $f$ is a measurable function, then $\text{supp}(f)$ is measurable set?   Is it simply because, if we consider $E_1 = (0,\infty)$ and $E_2 = (-\infty,0)$, since they are open, they are measurable. So their union $\mathbb{R}-\{0\}$ is measurable as well. Since $f$ is measurable, then the preimage $f^{-1}(\mathbb{R}-\{0\})$ is measurable. But the preimage is just the support? "In a while" vs. "for a while" I am seeing quite a few conversions which have as source "accounts.google.com" (almost 40%).  AFAIK, in the new Universal Analytics as soon as a user has a Referrer set a new session is started. So if a user is getting on my page, and creates an account using social auth (e.g. Google accounts) when being redirected back, will this create a new session? I guess this would explain that there are many conversions coming from accounts.google.com - is it safe to enter accounts.google.com into the Referral Exclusion List? And more - what about Facebook logins, those would show up as facebook.com, but i probably don't want to exclude facebook.com as referrer?  Any ideas how to deal with UA referrers and social logins? Types of things vs. types of thing This was talked about a few podcasts ago. And they referenced some other site that does this.  Currently location is a string but adding a country dropdown (and for the usa a state drop down) could be a great addition to the site.  Then allow for user filtering by country / state. I have my own AppleID ("Bob") but I don't use this email addy "Bob" anymore. I want to add my current, daily used email addy ("Jim") to my ID, or better yet, make it my only AppleID and delete "Bob". BUT... I already used "Jim" for an AppleID for an older friend who had no email address, so set it up for him on mine, "Jim".  My older friend now has an email address ("Ivan") so can I   add "Ivan" to his AppleID, make it the primary email address, and then delete "Jim" from it? Or... delete his AppleID and create a new one for him "Ivan" knowing he would lose his minor purchases   And most importantly, this would all be pointless unless: - will deleting/removing "Jim" as linked to my friend's AppleID then make "Jim" available for me and no longer registered to another account? For a simple circuit with a battery supplying a voltage $V$ to a capacitor, let us assume that the charge on the capacitor is $Q$. Now, the work done by the battery or the energy supplied is given by the relation:  $$W=QV$$  But the energy stored in the capacitor is given by:  $$U = \tfrac12 QV$$  The value of $Q$ as well as that of $V$ should be the same in both the equations.  Now my question is, where is the other half of the energy that the battery supplied? Family name pluralization When pluralizing family (last) names that also happen to be common English words, does the pluralization follow the same rules as the common word?  For example, "the Smith family" can be pluralized as "the Smiths", but what if the family name is "Wolf" or "Fish"?  Would the correct pluralization be "the Wolfs" or "the Wolves"? I just wrote an answer to , which was trying to find numeric strings with or without commas (e.g. 1,234,567.89). I wanted to be thorough because I've seen this problem a lot, both on SO and in real-world code.   When I finished, I found 7 other new answers waiting for me, mostly variations on each other. Which would be fine, except for one thing: They're garbage answers. Unless I'm severely mistaken, every answer but mine (so far) is deeply flawed, and I want to downvote all of them. Yeah, I'm a stickler on regex, but IMHO if your pattern lets stuff like  ...,.,,.,,..9 or even ... pass as "numeric input," then you've failed to meet even the bare minimum requirements.  Enough venting. The reason I'm whining to Meta about this is that I'm about to do something that'll REALLY look like tactical downvoting, and I'm mildly concerned about the consequences. If I answer a question and then rain downvotes on every competing answer, will I get flagged for abuse? That would certainly seem like suspicious behavior to me.  More of an opinion question: At what point does a semi-correct answer deserve a downvote? Obviously, if it were just a typo, I'd edit it myself. Where's the line between "close enough" and "this answer sucks?"  Basically, is it just me? You've seen the question; am I right that these answers deserve downvotes? Seven people thought that [0-9,.]+ was good enough to declare something a number, so why am I the only one who doesn't?    Note: I found some related questions, but nothing that seemed like a duplicate:    - More of an etiquette question, plus the voter hadn't posted his own answer.  - I guess this pretty much covers my second question.   Also, as some have noted, my answer ended up pretty long and thorough. I put in a lot of effort because, with all this talk about how the other answers sucked, I wanted to be extra sure mine didn't. I don't expect pages of detail in a normal SO answer. I currently trying to join two rigged (and animated) models, which both has separate meshes, separate bones and separate animations. The first mesh is the horse while the second mesh is human:   So I am interested to join human model onto horse model to make a rider:   I think the best way would be to make horse as a parent and human as a child during the join process. In that case I would like that all horse animations (there are 3 of them - idle, walk and run) would remain as they are, while I can lose human animations, as I will need different ones for it. I was also thinking to make human root bone as a child of one horse back bones, that when horse moves up and down it would move entire human mesh together. It would be also good to keep the same weights that human bones would not start deforming horse mesh and vice versa.  I tried to use Ctrl+J by selecting various combinations between bones and meshes in object mode, however, I noticed that it messes up scaling and rotation of the child object. So I was wondering how it would be possible to properly join these models to create a rider? $\sqrt{c+\sqrt{c+\sqrt{c+\cdots}}}$, or the limit of the sequence $x_{n+1} = \sqrt{c+x_n}$ Unable to locate package kubuntu-plasma5-desktop on 14.04 I am attempting to install kubuntu-plasma5-desktop on Kubuntu 14.04 amd64, following    sudo apt-add-repository ppa:neon/kf5 sudo apt update sudo apt install project-neon5-session project-neon5-utils project-neon5-konsole  sudo apt-add-repository ppa:kubuntu-ppa/next sudo apt-add-repository ppa:ci-train-ppa-service/landing-005 sudo apt update sudo apt install kubuntu-plasma5-desktop   Unable to locate package kubuntu-plasma5-desktop  How can I fix this error? There was the following paragraph in the article that came under the title, “GOP and the rise of Anti-knowledge” written by  (October 29, 2015):     “English unfortunately doesn’t have a precise word for the German   “Fachidiot,” a narrowly specialized person accomplished in his own   field but a blithering idiot outside it. In any case, a surgeon is   basically a skilled auto mechanic who is not bothered by the sight of   blood and palpitating organs. We need the surgeon’s skills on pain of   agonizing death, and reward him commensurately but that does not make   him a Voltaire.”    In Japanese we have a word, 専門バカ, of which literal translation is “specialist idiot” meaning exactly same as defined the above - a narrowly specialized person accomplished in his own field but a blithering idiot outside it.  I’m really curious about the absence of short descriptions of the specialist who knows nothing more than his specialty area in English like German “Fachidiot,” and Japanese "専門バカ."  Isn’t there really any short word counterpart to “Fachidiot,” specialist’s ignorance, for instance, in English?  P.S.  I found "narrow-minded specialisit" as a German-to-English translation of "fachidiot" in the web site, Interglot translation dictionary. Intuitive explanation of the bias-variance tradeoff? I am looking for an intuitive explanation of the bias-variance tradeoff, both in general and specifically in the context of linear regression. I've compiled a java project into a Jar file, and am having issues running it.  When I run:  java -jar myJar.jar   I get the following error  Could not find the main class: myClass   The class file is not in the root directory of the jar so I've tried changing the path of the main class to match the path to the class file and I get the same issue.  Should I be flattening the file structure? if so how do I do this. I'm using Ant to build the Jar file if thats of any use.  UPDATE   Here is the contents of the jar and the relevant Ant sections, I've changed the name of the firm I work for to "org":  META-INF/ META-INF/MANIFEST.MF dataAccessLayer/ dataAccessLayer/databaseTest.class org/ org/eventService/ org/eventService/DatabaseObject.class org/eventService/DatabaseObjectFactory.class org/eventService/DbEventClientImpl$HearBeatMonitor.class org/eventService/DbEventClientImpl.class org/eventService/EmptyQueryListException.class org/eventService/EventHandlerWorkItem.class org/eventService/EventProcessor.class org/eventService/EventTypeEnum.class org/eventService/EventWorkQueue$MonitorThread.class org/eventService/EventWorkQueue$PoolWorker.class org/eventService/EventWorkQueue.class org/eventService/FailedToLoadDriverException.class org/eventService/IConnectionFailureListener.class org/eventService/InvalidEventTypeException.class org/eventService/JdbcInterfaceConnection.class org/eventService/NullArgumentException.class org/eventService/OracleDatabaseObject.class org/eventService/ProactiveClientEventLogger.class org/eventService/ProactiveClientEventLoggerException.class org/eventService/PropertyMap.class org/eventService/SQLServerDatabaseObject.class org/eventService/TestHarness.class org/eventService/Utilities.class   And the ant target:  &lt;target name="compile" depends="init" description="compile the source "&gt;     &lt;javac srcdir="src" destdir="bin" classpathref="project.class.path"/&gt; &lt;/target&gt; &lt;target name="buildjar" description="build jar file" depends="compile"&gt;     &lt;mkdir dir="dist"/&gt;     &lt;jar destfile="dist/myJar.jar" basedir="bin" includes="**/*.class" &gt;         &lt;manifest&gt;             &lt;attribute name="Main-Class" value="org.eventService.ProactiveClientEventLogger"/&gt;         &lt;/manifest&gt;      &lt;/jar&gt; &lt;/target&gt;