Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException in GUI?
What is a NullPointerException, and how do I fix it?
I have a Minecraft 1.8.1 vanilla server and would like to reward certain users. I would like to /give some users a 99999/99999 durability renamed Diamond Pickaxe (with all enchantments on it). How do I use commands to change/repair the durability of items? If possible, using only one command and use /give. How to encrypt individual folders? Given two sets $A$ and $B$, what is the difference between $A + B$ and $A \cup B$? For example, if $A = \left\{ a, b, c \right\}$ and $B = \left\{ d, e, f \right\}$, what are $A + B$ and $A \cup B$, respectively? From the third week ( when does it actually begin) This describes a certain natural process that takes 15 weeks  It describes what a certain component looks like at some point in time during a naturallly occurring process  What I don't get is if it means it appears this way starting in the third week or after ?  Here's the full sentence  "The malleus first appears as a cartilage model from the third week"  Thanks again for you support guys Includepdf causes an error message from pgfplots externalization I have a file test.pdf which I include in a document containing also an externalized pgfplots picture.  When I compile the following code, I get the error message Sorry, the system call pdflatex ... did NOT result in a usable file.  In order to make my code work, I first need to remove the includepdf statement, compile (to create the externalized figures) and then compile again with the includepdf statement.  I suppose that it is a bug, or is there any possibility to solve it ?  Of course, the file test.pdf is totally independent from the externalized pictures from pgfplots.  \documentclass{scrbook}   \usepackage{pgfplots}  \pgfplotsset{compat=1.8}  \usepgfplotslibrary[external]  \tikzexternalize[shell escape=-enable-write18]  \usepackage{pdfpages}   \begin{document} \includepdf{report_test-figure44}   \begin{tikzpicture}  \begin{axis}[  xlabel=Cost, ylabel=Error]  \addplot[color=red,mark=x] coordinates {  (2,-2.8559703) (3,-3.5301677) }; \end{axis}  \end{tikzpicture}   \end{document} Why would I want to use Interfaces? I understand that they force you to implement methods and such but what I cant understand is why you would want to use them. Can anybody give me a good example or explanation on why I would want to implement this. Matrices A+B=AB implies A commutes with B Disappointed to see that the 18.04 installer no longer offers the option to encrypt the home directory. According to  bug report referenced in the installer, the recommended method for encryption these days is full-disk with LUKS, or fscrypt for directories. Full-disk encryption seems a bit overkill for my needs, and all the bugs and caveats mentioned on the  don't make it a very attractive option. All I really want is to protect my home directory from someone accessing my documents, photos, etc. if my laptop were to get stolen, making fscrypt the option for me.  The  has some examples on how to set it up, but I can't find any documentation aimed at encrypting the home directory on Ubuntu. The old ecryptfs tool is still available, but after setting it up Ubuntu would sometimes freeze at the login screen.  So my question is: How do I setup fscrypt to encrypt my /home directory and decrypt when I log in? I also liked how ecryptfs allowed decrypting the folder manually (eg. from disk images).  (A similar question was posted  and was unfortunately closed for being an "off-topic" bug report. To clarify, this is not a bug report. The fact that the encrypt home directory option was removed from the installer was intentional. All I'm asking here is how to setup fscrypt.) Why do damaged hard drives freeze the entire system? Algebraic Property inherited by a "lift"? Suppose $K$ is a field, and $K\subset E$ is an algebraic extension, and $K\subset F$ is any extension.  Suppose that $L$ is some field which contains both $F$ and $E$ as subfields.  I want to show that $FE$ (the smallest subfield of $L$ containing both $F$ and $E$) is algebraic over $F$.  Lang mentions that the result is true because an element remains algebraic under lifting, but I can't prove the claim with this.  I interpret his comment to mean that if $x\in E$ is algebraic over $K$, then $x\in FE$ is algebraic over $F$.  This is certainly true.    But this doesn't seem enough if I start with any element of $FE$. Is there a possibility to make reference to the line in the lstlisting environment? I was wondering if it is possible to refer to the lines of the code enclosed in lstlisting environment rather than just manually write a number of the line I want to describe. I have never met with this feature, is this available? Can I get SSD rw performance while keeing data security if I combine SSD & HDD in btrfs RAID1 I have 2 storage devices; classical slow HDD (750GB, /dev/sda) and faster SSD (128GB, /dev/sdb). Currently I have installed Ubuntu &amp; Mint on same btrfs partition on SSD (/dev/sdb5). My btrfs pool consists of /dev/sdb5.  What I want to achieve is data replication on HDD while keeping SSD performance: Something like this:  For read case it would be ideal for procedure to go like this:   read from SSD check checksum if it verifies.. awesome, give me the data if not, fetch data from HDD and perform error correction through duplicate data   I'd manually run (some tool I'm not sure which one... btrfs check --repair perhaps?) every month or so to check HDD checksums and correct them via SSD data against bitrot.  For write case:   write to SSD sync to HDD when write requirements are low, thus not slowing down the system.   Is this possible and how would I do it?  Bottom line is, I like btrfs and would like it to duplicate data across HDD &amp; SSD drive automatically while keeping SSD excellent performance.   Using SSD as write cache is not an option since it's missing data duplication and security. List comprehension with expensive computation Mortarboard badges being awarded as a result of bounties after recalc How to deal with "java.lang.OutOfMemoryError: Java heap space" error? How do you create a daemon in Python? reveals x2 code snippets. The first result is to  which has a lot of documentation and explanation, along with some useful discussion underneath.   However, , whilst not containing so much documentation, includes sample code for passing commands such as start, stop and restart. It also creates a PID file which can be handy for checking if the daemon is already running etc.  These samples both explain how to create the daemon. Are there any additional things that need to be considered? Is one sample better than the other, and why? For primes $p≡3\pmod 4$, prove that $[(p−1)/2]!≡±1\pmod p$. I know to use Wilson's Theorem and that each element in the second half is congruent to the negative of the first half, but I'm not sure how to construct a proof for it. SSH login without password with kerberos Firstly my main goal is to try and get FTP files recursively in Centos.  However the actual FTP login contains an @ which ruins the syntax.  Is there some way to place the username in "double quotes" or some such equivalent such that I can use @in the username? If I have the following state:  $$ \left| \varphi \right&gt;=\frac{1}{\sqrt{2}}\left(\left(\frac{1+i}{\sqrt{2}} \right)\left| 0 \right&gt; + \left| 1\right&gt;\right) $$  How can I find the $\theta$ and $\phi$ values of this qubit on the Bloch sphere?