I have the following code:  public static void main(String[] args)      throws ParserConfigurationException, SAXException, IOException {      DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();     dbFactory.setNamespaceAware(true);     DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();     Document document = dBuilder.parse("NewFile.xml");     String usr = document.getElementsByTagName("username").item(0).getTextContent();     System.out.println(document);  }   This is causing a NullPointerException at String usr line. Any ideas why? The new file is placed in the workspace project folder and i also tried to give the absolute path with no success.  XML file:      &lt;?xml version="1.0"?&gt; &lt;tudorTestUser&gt;     &lt;propertySet&gt;         &lt;property name="username"&gt;TudorTest123&lt;/property&gt;            &lt;property name="firstName"&gt;Ion&lt;/property&gt;         &lt;property name="lastName"&gt;Vasile&lt;/property&gt;         &lt;property name="password"&gt;Tester123&lt;/property&gt;         &lt;property name="passwordAgain"&gt;Tester123&lt;/property&gt;     &lt;!-- &lt;property name="location"&gt;Bucharest&lt;/property&gt; --&gt;         &lt;property name="email"&gt;tester@test.com&lt;/property&gt;         &lt;property name="Status"&gt;active&lt;/property&gt;         &lt;property name="thirdParty"&gt;No Third Party&lt;/property&gt;         &lt;property name="agentID"&gt;Tester&lt;/property&gt;         &lt;property name="switch"&gt;on&lt;/property&gt;         &lt;property name="position"&gt;Web Master&lt;/property&gt;         &lt;property name="clone"&gt;&lt;/property&gt;         &lt;property name="overrideCode"&gt;&lt;/property&gt;        &lt;/propertySet&gt; &lt;/tudorTe
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?
KeyboardViewer app is saved from this AppleScript.  on run {input, parameters}     if application "KeyboardViewer" is running then         quit application "KeyboardViewer"     else          activate application "KeyboardViewer"     end if     return input end run   Dock toggle save. Adding shortcut to above, needs some work...   Syntax error Can’t set application "KeyboardViewer" to some object. Access not allowed.  tell application "System Events"     set application "KeyboardViewer" to (keystroke "K" using control down) end tell Tabs in output file written by xelatex and pdflatex are different In Windows 8 I can reset everything and reinstall Windows. I assume this will clear my drive and start from scratch? Is that right? Does this create a Windows.old folder?  I see this dialog, but aren't my settings and preferences saved in the cloud? If I screw up my settings and reset like this, are my settings also refreshed back to defaults?  Since I use SkyDrive to sync my files, my personal files are safe, right?    Also, in Windows 8 I can refresh my PC without affecting files. Are my desktop and/or Windows store apps uninstalled when I refresh my PC?  I see this dialog, but I still am not sure. For example, when it says apps are "kept" does that mean I don't have to buy them again or are they installed after the refresh is over for me? I assume "from disk" means desktop apps? Or maybe corp apps?    What would motivate a user to choose between these two? Column line overshooting the horizontal line in table \begin{tabular}{|m{3.5cm}|m{5.5cm}|m{4.5cm}|} \hline \emph{Category of Benefits} &amp; \emph{General Benefit} &amp; \emph{Operational Advantages} \\ \hline \multirow{3}{*}{\pbox{3.5cm}{Robust operational performance}} &amp; \multirow{3}{*}{\pbox{5.5cm}{One sensor can contribute information while other are unavailable, denied(jammed), or lack coverage of a target or event}} &amp; -Allows continued operation despite jamming \\ &amp;  &amp; -Graceful degradation \\ &amp;  &amp; -Increased probability of detection \\ \hline  \multirow{2}{*}{\pbox{3.5cm}{Extended spatial coverage}} &amp; \multirow{2}{*}{\pbox{5.5cm}{One sensor can look where another cannot}} &amp; -Increased survivability \\ &amp;  &amp; -Probability of detection increased  \\ \hline \label{tab1.1} \end{tabular}   For the LateX code mentioned above the table which comes looks like this ![enter image description here][1]   In the resulting table, column 1 vertical line overshoots the last horizontal line.  What is the problem? I'd like to declare some new operators using \DeclareMathOperator and some of the names are already taken by other commands (that I do not want to use). Is there an equivalent to the \renewcommand command for \DeclareMathOperator or a different way to overwrite the commands using \DeclareMathOperator? I know it existed as sort of a folder in Windows Explorer in at least Windows XP, but I just can't seem to find it in Windows 7...  How can I take a picture with my webcam in Windows 7 without using any 3rd party tools? Today 4/30/20 my seemingly worthless USO call option increased in value.   Specifically: USO1 $2.5 Call 5/8  On 4/29 it was valued at $.04 and stayed there.   4/30 I checked after hours and now it’s up to $.08? Which was wasn’t even the highest it went to today.  So who is buying this contract?  Who is allowed to buy this contract? Bc I’m only able to sell and from what I understood, nobody is able to buy it.   I have screenshots and will post if requested. Thank you How to remove local (untracked) files from the current Git working tree Why can't variable names start with numbers? I have a script in file bla.sh and it is executable. When I click on it, the script is executed and the window is closed. I'd like the window to stay open.  Something like command cmd /k** command in Windows.  P.S. I don't want to use pause, but I want to able to write more commands after the script was executed. Can't execute terminal commands: "the command 'sudo' is available in '/usr/bin/sudo'" Let $x \in \mathbb R$  Find a closed form of $\int_0^\infty\dfrac{\cos(xt)}{1+t^2}dt$ .   Let me give some context: this is an exercise from an improper integrals course for undergraduates. My teacher was not able to give a valid solution without  resorting to Fourier series.   He actually wanted to prove first that the function is a solution of the ODE $$ y-y'' =0$$ without succeeding in proving it.   Anyway the result sould be $\dfrac{\pi}{2}e^{-x}$  Thanks for any help on this subject. How do ability score improvements improve modifiers? First time player in a group figuring out things as we all go.  I just hit level four as a Ranger, and I get to improve one ability score of my choice by 2, or I can increase two ability scores of my choice by 1.  My first thought was Strength, as I've been rocking a score of 11 with a mod of +0 so far. But I read that Rangers use (wisdom mod + 10) for their spell casting modifier. Currently my wisdom is 13, with a mod of +1. If I increase either STR or WIS, will the modifier increase as well? How and why?  A Monk in our party went from 9 CON to 11 during their ability score improvement, and by doing so their modifier went from −1 to 0.  We're all pretty new, so between eight people we're currently sharing one book, and all trying to locate our own copies for later campaigns. That's making it… inefficient for us to learn these things quickly. No room for a new \dimen A book suggests that we should not interchange "so" and "so that". "So" means "therefore", and "so that" means "in order that". However, it seems to me that in many cases they don't actually have a difference. For example:     Alice got up at 5:00 A.M., so that she could drive her son to school.   If I substitute "so that" with "so", this sentence presents the exact same causal relation to me:     Alice got up at 5:00 A.M., so she could drive her son to school.   I must have missed something here, since English is my second language. Could somebody explain the difference? Debian : Verify disk encryption password for already mounted system What is the different between an Normal and Admin account? What is the different between an Normal user account and the Admin account in Ubuntu?  You must always enter your password if you want do something. Can you give a Normal account  "limitations" to do not install or remove anything or to not open any program? Can you also "hide/deactive" the terminal and console for a normal user? Why does chmod +w not give write permission to other(o) When I run chmod +w filename it doesn't give write permission to other, it just gives write permission to user and group.  After executing this command  chmod +w testfile.txt   running ls -l testfile.txt prints  -rw-rw-r-- 1 ravi ravi 20 Mar 10 18:09 testfile.txt   but in case of +r and +x it works properly.  I don't want to use chmod ugo+w filename. How do I change my profile picture, or avatar? Where does the image come from? How do I change my profile picture, or avatar? How do I change my profile picture on all SE sites at once? How can I use different avatars on different SE sites? How do avatars work? How do the SE sites know when I changed my Gravatar? Why do SE sites show a different Gravatar identicon than other sites where I use the same email address? How can I use a Gravatar image after logging in to facebook.stackoverflow.com? I changed my picture but am still seeing the old one    See also: What is wrong with my date regex?