I've been trying to get this working for far too long. I am to use an array of strings to construct an array of "sentence" classes by using the string as part of the constructor. Can anyone help me out?     public class FileConverter {  private final String input; private final String output; private boolean inputEncrypted; private ArrayList&lt;Sentence&gt; y;  public FileConverter(String input, String output, boolean inputEncrypted) {                     this.input = input;     this.output = output;     this.inputEncrypted = inputEncrypted; }  // this method creates an array of sentences from input public boolean readInput() {     String[] x = input.split("\\.");             for(String x1:x){        Sentence a = new Sentence(x1);         y.add(a);    }     return false; }   y.add(a) is giving me a null pointer exception. I've tried a few different ways to do this and I can't seem to figure it out.
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?
In the Tiny Tina DLC "The Beard Makes the Man" quest, the objectives are (1) Crush five drunk dwarves, (2) Pick up five beards, and (3) Get five dwarves drunk. (The last one's optional.) I found the miner dwarves in the mine on the minimap, but they won't follow me into the crusher machine. How do I lure them? Does it have to do with getting them drunk, and how can I do that with no alcohol around? I thought getting drunk was optional? Trying to hide spam/offensive deletions on user profiles announces them How to make `sudo` preserve $PATH? I have a program that is installed in a custom directory under /opt. To make it easier to run it, I edited my bashrc to add said directory to my path: export PATH=$PATH:/opt/godi/bin:/opt/godi/sbin  This works fine if I want to run the program without sudo. However, if I try to run it with sudo it fails with a &quot;command not found&quot; error. $ sudo godi_console sudo: godi_console: command not found  Inspecting the PATH variable after using sudo reveals that its not including the same PATH I have as a normal user: $ sudo sh # echo $PATH                  /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin  Why is the PATH not the same? Am I doing something wrong? I'm on Debian Jessie, if it makes a difference. One thing I tried was to invoke /opt/godi/sbin/godi_console directly, passing the absolute path to the executable. Unfortunatelly, that didn't help in this particular case because godi_console itself depends on the PATH being correctly set. Definitionally, we have that  $$ \int_\gamma f\ \overline{dz} = \overline{\int_\gamma \overline{f}\ dz} $$  Now let $\int_\gamma f\ dz = w = x +yi$.  Question 1: Is it not the case that $\int_\gamma \overline{f}\ dz = \bar{w} = x - iy$?  Question 2:  Assuming that $\int_\gamma \overline{f}\ dz = \bar{w} = x - iy$, then is it not the case that  $$ \overline{\int_\gamma \overline{f}\ dz} = \overline{x - iy} = x+iy = \int_\gamma f\ dz? $$  Basically, I'm failing to see how $\overline{\int_\gamma \overline{f}\ dz}$ isn't just $\int_\gamma f\ dz$. Take most recent (or concatenate) edit comments when editing during grace period Cardinality and infinite sets: naturals, integers, rationals, bijections VirtualBox 5.0.40 crashes the whole host since update to kernel 4.13.0-26-generic Java equivalent of unsigned long long? In C++, I enjoyed having access to a 64 bit unsigned integer, via unsigned long long int, or via uint64_t. Now, in Java longs are 64 bits, I know. However, they are signed.  Is there an unsigned long (long) available as a Java primitive? How do I use it? Keeping the time stamp when syncing with Ubuntu One? I would like to keep the original time stamp of a file when synchronizing with Ubuntu One.  Now Ubuntu One is messing with my time stamps, and I no longer know when I last worked on the file.  Ubuntu One also seem to mess up time stamps on the original source host.  This really is a show stopper, and we are just about to implement Ubuntu One across the many users in the organization. Gravitational waves and time Second law of Newton for variable mass systems Frequently I see the expression  $$F = \frac{dp}{dt} = \frac{d}{dt}(mv) = \frac{dm}{dt}v + ma,$$ which can be applied to variable mass systems.  But I'm wondering if this derivation is correct, because the second law of Newton is formulated for point masses.   Furthermore if i change the inertial frame of reference, only $v$ on the right side of the formula $F = \frac{dm}{dt}v+ma$ will change, meaning that $F$ would be dependent of the frame of reference, which (according to me) can't be true.   I realize there exists a formula for varying mass systems, that looks quite familiar to this one, but isn't exactly the same, because the $v$ on the right side is there the relative velocity of mass expulsed/accreted. The derivation of that formula is also rather different from this one.   So my question is: is this formula, that I frequently encounter in syllabi and books, correct? Where lies my mistake. Replace values which obey certain criteria Clicking on tags in global search results is broken Each time I changed and saved .config/user-dirs.dirs, and after restarted the system, the XDG_DOWNLOAD_DIR are reverted:  diff --git a/.config/user-dirs.dirs b/.config/user-dirs.dirs index 8f6e2db..dcff34e 100644 --- a/.config/user-dirs.dirs +++ b/.config/user-dirs.dirs @@ -7,11 +7,9 @@  #   XDG_PUBLICSHARE_DIR="$HOME/public"  XDG_TEMPLATES_DIR="$HOME/public/template" -  XDG_DESKTOP_DIR="$HOME/private/desktop"  XDG_DOCUMENTS_DIR="$HOME/private/doc"  XDG_PICTURES_DIR="$HOME/private/picture"  XDG_MUSIC_DIR="$HOME/private/music"  XDG_VIDEOS_DIR="$HOME/private/video" - -XDG_DOWNLOAD_DIR="$HOME/var/downloads" +XDG_DOWNLOAD_DIR="$HOME/"   How to make my changes permanent? List of tables, db schema, dump etc using the Python sqlite3 API How do I run a Perl script from within a Perl script? I've got a Perl script that needs to execute another Perl script. This second script can be executed directly on the command line, but I need to execute it from within my first program. I'll need to pass it a few parameters that would normally be passed in when it's run standalone (the first script runs periodically, and executes the second script under a certain set of system conditions).  Preliminary Google searches suggest using backticks or a system() call. Are there any other ways to run it? (I'm guessing yes, since it's Perl we're talking about :P ) Which method is preferred if I need to capture output from the invoked program (and, if possible, pipe that output as it executes to stdout as though the second program were invoked directly)?  (Edit: oh, now SO suggests some related questions.  is close, but not exactly the same as what I'm asking. The second program will likely take an hour or more to run (lots of I/O), so I'm not sure a one-off invocation is the right fit for this.) When I have .txt files or .py files, I can Quick Look those files in Finder. I have .jl files that are codes written in the Julia Language. Of course they are text files. They will open in a text editor like Sublime Text. How can I Quick Look these .jl files in Finder? In some papers or documents, "linear times series" seems to refer to a time series that can be modeled as a linear AR (auto-regressive) model.   In other places, "linear time series" seems to refer to a time series with a linear trend.   When someone just drops "linear time series" out of the blue without any context, what do they mean usually? How can I make the Logitech Wingman Formula Force steering wheel work in Vista and 64 bit Windows 7? Possible Duplicate:          Is there anywhere or anyone to complain to about the behaviour of moderators? I've been "spoken" to offensively by a moderator, and I'm unhappy about it.