Hi guys i have a NullPointerException when i run this code ,and its pointing on the model = (DefaultTableModel) DbUtils.resultSetToTableModel(rs) , and i have imported the net.proteanit.sql.DbUtils , any ideas ?  public void setTableValues(){          try {              cn.start();              String sql = "select id,first_name as Firstname,last_name as Lastname,email,phone,description as AllergyInfo from clients where isDeleted=0";              rs = cn.executeSelect(sql);              model = (DefaultTableModel) DbUtils.resultSetToTableModel(rs);              jTable1.setModel(model);              rowSorter = new TableRowSorter&lt;&gt;(jTable1.getModel());              jTable1.setRowSorter(rowSorter);              cn.stop();          } catch (SQLException ex) {              Logger.getLogger(Clients.class.getName()).log(Level.SEVERE, null, ex);          }     }
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?
Neatest proof that set of finite subsets is countable? How can I search for a keyword with special characters in Google Search? I want to search for what += means, but Google won't return any documents.  Also when I come across some PHP code I don't understand I can't search for the keywords as written.  How can I search for these special characters or include these special characters in a search. How does new shield system work? After the upgrade I can't figure out how the new shield system works. I have the option to discard the shield, and I notice I have a new potion in the inventory.  More importantly, I got attacked (and lost) twice in a short amount of time and don't have a shield. When do you now get shield? Reprojecting MODIS Swath data to WGS84 using GDAL Prove that the sum to $n$ terms of a sequence:  $$\frac{1^2}{1\times 3}+\frac{2^2}{3\times 5}+\frac{3^2}{5\times 7}+\cdots $$ is  $$ \frac{n(n+1)}{2(2n+1)} $$ How do I install Skype? I want to install Skype, but I can't locate it in Software Center or by using Synaptic Package Manager. Can anyone help me? RegEx for Javascript to allow only alphanumeric I need to find a reg ex that only allows alphanumeric. So far, everyone I try only works if the string is alphanumeric, meaning contains both a letter and a number. I just want one what would allow either and not require both. How to prove or disprove statements about sets Prove or disprove:  The set: $\{ \emptyset\}^{\Bbb N}$ has only one element.  The set $\emptyset^{\Bbb N}$ is empty.    I'm pretty sure both are true, for 1. all the natural numbers go to the empty set and that is the only element. Where as 2. all the natural numbers go to nothing so that's why it's empty. (Same as $ {\Bbb N}^{\emptyset} $ nothing goes to something is nothing (I think)). The problem is I have no idea how to show this so advice would be appreciated.  Edit: My defintion of a function is: $f:B\to A$ if  $(a_1,b),(a_2,b)\in f \ \Rightarrow \ a_1=a_2$ So for 2. I can simply say that: $(1,\emptyset),(2,\emptyset)\in f \Rightarrow a_1\neq a_2$  ? I use youtube-dl to download videos for watching later offline. Usually, it works fine. However, due to frequent changes on the video sites, it sometimes requires a quick update. It wasn't a problem before on 13.04 but after upgrading to 13.10, I get  # youtube-dl -U It looks like you installed youtube-dl with a package manager, pip, setup.py or a tarball. Please use that to update.   I tried updating it via apt-get but there is no new package. So the app's update mechanism has been disabled and the maintainers aren't keeping up, what is the solution? How do I update it?  And why was it changed at all? It was updating a package manager version just fine in raring.   I'm already running into compatibility problems.   $ youtube-dl "http://vimeo.com/55784152" [vimeo] 55784152: Downloading webpage [vimeo] 55784152: Extracting information ERROR: Unable to extract info section; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type  youtube-dl -U  to update.   QUICK UPDATE:  As requested,  # type youtube-dl youtube-dl is hashed (/usr/bin/youtube-dl)  # apt-cache policy youtube-dl youtube-dl:   Installed: 2013.08.29-1   Candidate: 2013.08.29-1   Version table:  *** 2013.08.29-1 0         500 http://pl.archive.ubuntu.com/ubuntu/ saucy/universe amd64 Packages         100 /var/lib/dpkg/status Is it possible to show a screensaver on a secondary monitor while using the primary monitor? I have an iMac with a large format display set up as a secondary monitor that we use as a television for watching movies.  When I am just using the iMac, I would like for the secondary display to display something interesting rather than just the wallpaper.  Is it possible to set up a screensaver that appears on the second monitor (I really like the iPhoto slideshow) while allowing me to use the primary iMac monitor?  I would even be happy if it wasn't technically a screen saver, but just any sort of slideshow that could be displayed on one monitor while I work on the other.  Currently if I play a slideshow in iPhoto, the other monitor goes blank. :( I want to enable gzip compression for acethehimalaya.com. Can anybody please tell me what is the best way of achieving compression in an Apache Webserver? What makes the number of neutrons the number of proton similar? In basic chemistry, we are taught that an atom has roughly the same number of neutrons and number of protons, this doesn't seems to hold for larger atoms, but it is always roughly proportional (i.e. you seldom find an atom with 100 protons but 1 neutron, that just does not happen). Why is that? A question I'm struggling with is to prove or disprove that the automorphism group of a finite cyclic group must be cyclic. I think the statement is false but have not been able to come up with a counterexample.  Thank you for any assistance you can provide. Why does my Mac's list of "Open with" applications start listing the apps twice and sometimes three times? Difference between "little" and "small" Is there a difference between them? If so, how and when are they used?  For example:     I fixed a little/small typo. Java conditional compilation: how to prevent code chunks from being compiled? Over the years I have slowly developed a  that validates MOST email addresses correctly, assuming they don't use an IP address as the server part.  I use it in several PHP programs, and it works most of the time.  However, from time to time I get contacted by someone that is having trouble with a site that uses it, and I end up having to make some adjustment (most recently I realized that I wasn't allowing 4-character TLDs).  What is the best regular expression you have or have seen for validating emails?  I've seen several solutions that use functions that use several shorter expressions, but I'd rather have one long complex expression in a simple function instead of several short expression in a more complex function. This is a follow-up question to the discussion about the finite axiom of choice .  Suppose we have a countable collection of non-empty sets $\{A_1, A_2, A_3,\cdots\}$ Reasoning as indicated in that discussion, we can prove the existence of a choice function $c_n$ such that $c_n(i)$ belongs to $A_i$ for $i = 1,\cdots,n$  Again reasoning as suggested and using induction, we can prove the existence of a function $C$ defined over $\{1, 2, \cdots\}$ such that $C(n)$ is a choice function defined for $i=1,\cdots,n$ with $C(n)(i)$ an element of A_i. We can require in addition that $C(n)(i)$ and $C(n-1)(i)$ are equal for $i=1,\cdots,n-1$.  Now it would it seem that we can prove the countable axiom of choice by taking the union of $C(1)$, $C(2)$, $\cdots$  The question is as follows: why is that proof wrong? I suspect the answer may have something to do with the axiom of union. pgfplots fillbetween with multiple curves List contents of tarball in tree format Per the answers  I'm able to list the contents of my tarball in ls format. However, I'd like to be able to list them in tree format, i.e. something like the latter instead of the former:  With tar:  $ tar -tf foo.tar  foo/ foo/baz/ foo/baz/qux/ foo/baz/qux/hisfile.txt foo/bar/ foo/bar/myfile.txt foo/bar/yourfile.txt   With tree:  $ tree foo foo ├── bar │   ├── myfile.txt │   └── yourfile.txt └── baz     └── qux         └── hisfile.txt   Is it possible to do this without extracting the tarball? I'd prefer to have to avoid extracting the tarball due to their size.