I am a begginer in Android. I am a PLC programmer, but I would like to write application for my mobile phone. I would like to remote control RGB led via Arduino. But when I make any changes I have the error, and I don't know what is this.     E/AndroidRuntime: FATAL EXCEPTION: main                     Process: com.led.led, PID: 7790                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.led.led/com.led.led.ledControl}:   java.lang.NullPointerException                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2412)                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2470)                         at android.app.ActivityThread.access$900(ActivityThread.java:174)                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1307)                         at android.os.Handler.dispatchMessage(Handler.java:102)                         at android.os.Looper.loop(Looper.java:146)                         at android.app.ActivityThread.main(ActivityThread.java:5593)                         at java.lang.reflect.Method.invokeNative(Native Method)                         at java.lang.reflect.Method.invoke(Method.java:515)                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)                         at dalvik.system.NativeStart.main(Native Method)                      Caused by: java.lang.NullPointerException                         at com.led.led.ledControl.onCreate(ledControl.java:121)                         at android.app.Activity.performCreate(Activity.java:5458)                         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2376)                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2470)                          at android.app.ActivityThread.access$900(ActivityThread.java:174)                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1307)                          at android.os.Handler.dispatchMessage(Handler.java:102)                          at android.os.Looper.loop(Looper.java:146)                          at android.app.ActivityThread.main(ActivityThread.java:5593)                          at java.lang.reflect.Method.invokeNative(Native Method)                          at java.lang.reflect.Method.invoke(Method.java:515)                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)                          at dalvik.system.NativeStart.main(Native Method)
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?
Short circuit evaluation and side effects I keep getting an error in line 38 saying "Extra alignment tab has been changed to \cr." \documentclass [12pt]{article} \oddsidemargin=0pt \topmargin=0pt \textwidth=6.5in \textheight=8.5in \begin{document} \begin{center} {\large\bf\LaTeX\ Example 6} \end{center} We can typeset array structures \begin{equation} \mathbf{A}\times \mathbf{B}=\left| \begin{array}{ccc} \mathbf{i} &amp; \mathbf{j}  &amp; \mathbf{k} \\      a_1  &amp;      a_2        &amp; a_3 \\       b_1  &amp;      b_2        &amp; b_3  \end{array}  \right| \end{equation} \begin{quote} \begin{verbatim} \begin{equation} \mathbf{A}\times \mathbf{B}=\left| \begin{array}{ccc} \mathbf{i} &amp; \mathbf{j}  &amp; \mathbf{k} \\  a_1  &amp;  a_2   &amp; a_3 \\  b_1  &amp;  b_2   &amp; b_3 \end{array} \right| \end{equation} \end{verbatim} \end{quote} Or \begin{equation} \mathbf{A}=\left( \begin{array}{ccc} a_{11} &amp; a_{12} &amp; \cdots &amp; a_{1n} \\ a_{21} &amp; a_{22} &amp; \cdots &amp;  a_{2n} \\ \vdots &amp; \vdots &amp; \ddots &amp; \vdots \\ a_{n1} &amp; a_{n2} &amp; \cdots &amp; a_{nn} \end{array} \right) \end{equation} \end{document} How do I use filenames that start with a dash "-" as command arguments? This may be a simple question, but how do I use files starting with "-" with command line programs?   For example,  I am trying to use pdfgrep on a file named -2013-01-01.pdf but it complains that there are no options defined for 2, 0, 1, 3 and so on.  Changing the filename to something that does not start with "-" solves it, but this is not an option since the files aren't created by me. I simply want to check for a specific change I know is coming. bash chained logical operator execution order, lazy evaluation How to use CDF and PDF statistics for analysis This may be too much of a general question but I hope I can find help here. I am starting a RA job in my university and my topic will be related to Internet Traffic Analysis. I am fairly new to the world of analysis but I guess in the world of research this is what I have to do a lot of.  I've been through a few papers and in a lot of them I find they use Probability Density (PDF), CDF, CCDF etc to explain the results they've obtained. For example, PDF of user session duration, CDF of bytes transferred each day etc. I have taken probability and statistics class so I understand what they are but I am still confused to the cases in which such representation would be chosen.  So, if there is anyone out there who does such graphs and analysis (in any other topic in general or this) could you tell me simply in what situation would I use one or the other of these representations I tried sudo yum update but it just keeps java "1.7.0_75". I need 1.8 for it to work with another application but can't figure out how to upgrade it. Do I need to manually install it somehow? There's not much information on this on the internet as far as I can see. Specs:   java version "1.7.0_75" OpenJDK Runtime Environment (amzn-2.5.4.0.53.amzn1-x86_64 u75-b13) OpenJDK 64-Bit Server VM (build 24.75-b04, mixed mode)   When I try update now:     [ec2-________]$ sudo yum update Loaded plugins: priorities, update-motd, upgrade-helper amzn-main/latest                                         | 2.1 kB     00:00 amzn-updates/latest                                      | 2.3 kB     00:00 No packages marked for update   Is there anything else I need to do? Thanks. How do I install pillow in Ubuntu 16.04 LTS? When should you push variables in quotes in boolean conditions? Are the following two boolean expressions the same?  if [ -n $1 ] ; then  if [ -n "$1" ] ; then   If not - When should you put a variable in quotes? I am solving the TOEIC workbook, by the way, I faced conflict that doesn't match meaning I knew.  The problem is     The newest branch of the library is located in/on Pine Street.   I think either 'in' or 'on' have the same meaning. But the commentary said that 'be located in' is mainly writing in front of building name and city name.   I don't know what is correct? Stopping to eat is tedious, is there any way to automate the process? While I've managed to optimize and automate almost everything, constantly having to stop and eat is annoying (I run around a lot, so I get hungry quickly). Is there any device or tool that will keep me well fed at all times without having to stop and feed? How to design a product table for many kinds of product where each product has many parameters Mass Lead Conversion - Programmatically or Using Data Loader Completion of rational numbers via Cauchy sequences Can anyone recommend a good self-contained reference for completion of rationals to get reals using Cauchy sequences? Does "She had a brother" mean that her brother is dead? My Friend has sent me this riddle to solve:     "If you solve this, then you are a genius. Mr.Smith has 4   daughters🙍‍♀🙍‍♀🙍‍♀🙍‍♀ and each daughter had a brother.  How many   children does Mr. Smith have now?"   He said the answer is not 5, but 4 only as in the riddle it is mentioned as each daughter had a brother. So their only brother is dead.     Is he right? How to simulate from a Gaussian copula? Suppose that I have two univariate marginal distributions, say $F$ and $G$, which I can simulate from. Now, construct their joint distribution using a , denoted $C(F,G;\Sigma)$. All the parameters are known.  Is there a non-MCMC method for simulating from this copula? Add Appendix with correct page to ToC App keeps crashing & rendering error since update to 1.0.68 I can reproduce that every time now, I go to a site, open an article, then to the next site, open another article. The Feed page pops up for a second, the article page lays over this with some some transparent areas (see picture). The same app-version is ok on a Smartphone with Android 4.4.2. I also sent in some bug reports.    Edit  1.0.71 isn't the solution yet. I go to Meta SE, then to an article. When I want back to Meta SE again, it crashes. Much earlier than before. I already sent in a bug report for this.  Another Edit  I can describe it better now. From the questions-page of a site I go to a post. When I use the back button, everything is ok, I can go to the next site. When I try to go to the next site directly from the post, it crashes. This only happens on the Nexus 10 with Android 5.1.1, App version 1.0.71. Hope this helps.  Edit3  This is fixed in 1.0.73 now. Thanks again. I am on a Mac with MacTex 2020 and ran into a strange problem with Biber. Working on a document all was fine, I did not change the bibliography (says my git) and only fixing typos (not even adding cites) and suddenly latexmk stopped working after a Biber run, while that looked like  INFO - This is Biber 2.14 INFO - Logfile is 'doc.blg' INFO - Reading 'doc.bcf' INFO - Found 31 citekeys in bib section 0 INFO - Processing section 0 INFO - Globbing data source 'literature.bib' INFO - Globbed data source 'literature.bib' to literature.bib INFO - Looking for bibtex format file 'literature.bib' for section 0 INFO - LaTeX decoding ... INFO - Found BibTeX data source 'literature.bib'   so harmless in my view. Then with --debug I additionally get in the end.  INFO - LaTeX decoding ... warning: overriding existing definition of macro "jun" warning: overriding existing definition of macro "jul" warning: overriding existing definition of macro "sep" warning: overriding existing definition of macro "jan" [...] warning: overriding existing definition of macro "nov" INFO - Found BibTeX data source 'literature.bib' Unicode::UCD: failed to find unicore/version in /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc/lib /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc CODE(0x7fd026aeb5a8) CODE(0x7fd026aebb90) at /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc/lib/Biber/Input/file/bibtex.pm line 1011.   It seems unrelated to the library itself since deleting a few entries (going through deleting one half, then the other), the problem persists. It does not happen for an empty literature, but as soon as a first entry is added (just author/journal/title/year/volume/pages - no utf8-only chars) this error message appears.  what does this last error message mean?  How can I solve this? Unity: How do I revert Alt-tab behavior to switch between windows on the current workspace? Enabling Bias alt-tab sorting to prefer windows on the current viewport as described  made no difference. How can I get back the exact same behavior as 11.04, so that alt-tab only switches between windows on the current workspace?  Simply disabling the alt-tab and shift-alt-tab keybindings on the unity switcher seems to have helped, but it still switches workspaces on me sometimes.  For example, if I give a terminal window focus then press alt-tab, it switches to another terminal window on any workspace before trying to switch on the same workspace. Also, the Unity switcher still shows up when I alt-tab then hold alt even though I removed its alt-tab keybinding. We know that continuous version of $\sum$ is $\int$, but, can there be a continuous version of $\Pi$?