Java load properties file java.lang.NullPointerException error
What is a NullPointerException, and how do I fix it?
On Linux can I keep a program running in background even after I disconnect? If I'm logged into a remote Linux machine, I know I can suspend a process (cntr-z) and move it to the background (bg 1) but if I disconnect from the machine, the process stops.  Is there a way I can leave it in the background and have it there when I log back in? This is a very long running process.  On Ubuntu, logged in via SSH. Let's say I want a way to display just the the center 50x50px of an image that's 250x250px in HTML. How can I do that. Also, is there a way to do this for css:url() references?  I'm aware of clip in CSS, but that seems to only work when used with absolute positioning. What can I do if a repository/PPA does not have a Release file? When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do? Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases?  I am aware of the advantages against one phase and two phase, namely the reduced amount of conductor needed, and that motors can provide torque when stalled (and less pulsation).  Is this solely due to diminishing returns, with only a small increase in smoothness of torque application, at the cost of increased complexity (increased number of wires (albeit of smaller CSA)).  To be clear, the phases are all evenly distributed, that is, five phases separated by 72 degrees. How do I check if a list is empty? How do I wrap a macro definition in an environment? Calculate the uncertainty in velocity of electron I got this question in one of my periodic test in coaching, I (seemingly) solved the question but later recognised what mess I did.  So, the question is :      Calculate the uncertainty in velocity of an electron. If the uncertainty in its position is ${10^ {-15}} \; \mathrm m$.   By simple calculations one can see that the answer would be ${5.79\times{10^{10}}} \; \mathrm{m/s}$. However, as one can see, the uncertainty in velocity is greater than the velocity of light then how is that possible or there is some other way to handle such problems.  P.S. I know the concept of dynamic mass but I am not very familiar with it. (I think that would work here, but don't know how?) todonotes: How to make multiple listoftodos? In this MWE, I made two commands to highlight parts of the text as a reviewer comment, while the comments are colored uniquely to indicate the author whose comment is typeset.  If I want to make two listoftodos, each has the comments entries of one author, how can it be done?  \documentclass{article} \usepackage{hyperref,lipsum}  \usepackage[textwidth=2.5cm,colorinlistoftodos]{todonotes} \setlength{\marginparwidth}{2.5cm}  \newcommand\stR[2]{% 1st reviewer comment     \todo[%     author=1st Reviewer,noline,caption={1st Reviewer #1 Comment},color=blue!20%     ]%     {#1 Comment}{\color{blue}{\bfseries#2}}}  \newcommand\ndR[2]{% 2nd reviewer comment     \todo[%     author=2nd Reviewer,noline,caption={2nd Reviewer #1 Comment},color=red!50!white%     ]%     {#1 Comment}{\color{red}{\bfseries#2}}}  \begin{document} \listoftodos[Reviewers Comments] \section{Section} Text \stR{2nd}{2nd comment of the 1st reviewer} another text\vspace{\baselineskip} \lipsum[1]\vspace{\baselineskip} Some text \ndR{1st}{1st comment of the 2nd reviewer} continue text \end{document} Understanding the proof for showing that there are infinitely many $n\in\mathbb{Z}^+$ such that $n!+1$ is divisible by at least two distinct primes There is another post pertaining to this question; however, the other post does not address some specifics that concern me in the proof. Proof: Let $n=p-1, p \geq 7$. Then $p|(p-1)!+1$. We will show that $(p-1)!+1=p^n$ has no solutions. Suppose not. Suppose $(p-1)! + 1 = p^n$ has a solution for $p\geq 7$. Then $(p-1)! =p^n-1  = (p-1)(p^{n-1}+\cdots+p+1)$. So $(p-2)!\equiv n (\mod p-1)$. Now suppose that $(p-1)|n$. Then $p-1\leq n$. So $(p-1)!+1&lt;p^{p-1}\leq p^n$. Hence, there are no solutions. It remains to show that $(p-1)|(p-2)!$. But $p-1=2m$ means $2m|(p-2)!$. QED  Questions:  My understanding is that at the start of the proof, Wilson's theorem is used to show that at least one prime divides $n!+1$.  Why do we want to show that $(p-1)!+1=p^n$ has no solutions? The way I see it is that $p^n$ is composite, and we are basically saying that $p^n\nmid (p-1)!+1$, so no composite number divides $n! +1$. But how and where in the proof do we actually show that another prime $q \neq p$ divides $n!+1$?    Thanks in advance. Equation numbers are shown in reverse parentheses I am using   \begin{equation} a = b \end{equation}   to write the equations in my paper. However, the problem is that the number related to each equation is not shown in the correct format like the picture   How can I fix this?  This is what I have at the first of my code:  \usepackage{graphicx} \usepackage[justification=centering]{caption} \usepackage{float} \usepackage{url}% typeset urls \usepackage{times} \usepackage{url} \usepackage{latexsym} \usepackage{fontspec} \usepackage{multirow} \usepackage{listings} \usepackage{setspace} \usepackage{listings} \usepackage{fontspec} \usepackage{amsmath} \usepackage{polyglossia} \usepackage{color} \usepackage{bidi} \newfontfamily\faFont[Script=Arabic]{Yas}  \newenvironment{Fa}{\begin{RTL}\faFont}{\end{RTL}} \newcommand{\fa}[1]{{\faFont\RL{#1}}} \newcommand\Mark[1]{\textsuperscript#1} \definecolor{backcolour}{rgb}{0.95,0.95,0.92} \definecolor{darkblue}{rgb}{0.95,0.95,0.92} \setmainlanguage{english} \setotherlanguage{farsi} \newfontfamily\farsifont[Script=Arabic]{Yas} SharePoint Migration 2007 to 2013 HTML element does not fade in using jquery Where does the word "torsion" in algebra come from? Failed to download repository information due to missing CDROM Let I and J be ideals of a ring R. Show by example that the set of products {xy | x ∈ I, y ∈ J} need not be an ideal Let I and J be ideals of a ring R. Show by example that the set of products {xy | x ∈ I, y ∈ J} need not be an ideal, but that the set of finite sums of products of elements of I and J is an ideal. This ideal is called the product ideal, and is denoted by IJ.   I want to check if my work on the first part makes any sense. I am not sure if I am picking the right example.  If I let R = Z and I = (2) and J = (3) then I has multiples of 2, and J has multiples of 3  6 will divide the product IJ if we add 2 and 3 though we get 5 in IJ, but I am not sure if 5 Divides IJ. How to use Whatsapp mobile application on Ubuntu Touch? In my Android I have "Whatsapp" application running. But mobile freak I am not, and specially the mobile keyboards.  So how can I run my same application, same account from my Ubuntu desktop PC?   Follow up:  Just to do keyboard routing, i have used . Which allows me to takeover the Android input fields access via web link to type in my PC keyboard, and then it re-route the keys to Mobile.  Features:   Allows me to copy and paste large texts to Android input fields without using the keyboard of Android but simply using my Desktop PC, via web link http://android.ip.address.goes.here:port/ Allows me to have key submit which is similar to key press of mobile set itself   At-least works without having mobile in rooted. Hope it helps you!! Windows shortcut (.lnk) parser in Java? I'm currently using Win32ShellFolderManager2 and ShellFolder.getLinkLocation to resolve windows shortcuts in Java. Unfortunately, if the Java program is running as a service under Vista, getLinkLocation, this does not work. Specifically, I get an exception stating "Could not get shell folder ID list".  Searching the web does turn up mentions of this error message, but always in connection with JFileChooser. I'm not using JFileChooser, I just need to resolve a .lnk file to its destination.  Does anyone know of a 3rd-party parser for .lnk files written in Java I could use?  I've since found unofficial documentation for the .lnk format , but I'd rather not have to do the work if anyone has done it before, since the format is rather scary. "In and of itself" is a phrase I find myself using all the time. But in and of itself, the phrase "in and of itself" has no meaning. That is, the individual words don't seem to contribute to the whole meaning of the phrase. Space ship manned by only AI returns home to a different earth, back in time I read this short story 30 years or more ago.  A space ship is returning home to Earth from a battle. There are no people on board this ship, only an AI and the ship's computer. When the ship tries to contact Earth it gets no immediate response. The ship attempts to make contact for some time and then is successful with Houston Control (I think).  The AI discovers that it is on a different Earth from the one it is from and that it has also traveled back in time. (The enemy the fleet that it fought still exists).  The space ship comes from an Earth were the Greek empire did not get destroyed.  In the end the AI crashes the ship on the Capitol and gets destroyed, but the computer survives so that the human race has the knowledge of how to build ships and defend against the enemy.  Does anyone know the name of this story? Can store bought salmon be used for sashimi? Is it safe to consume raw fish purchased at the fish counter of a typical suburban grocery store? If not, do you have any tips for finding sushi grade fish. Also, are there requirements for safe sushi/sashimi beyond the use of safe fish?