Null Pointer Exception from a boolean array method So I have been viewing stack overflow to see if any questions have been answered referring to my problem, but I feel as if my array was indeed initialized. Currently I am attempting to make a simple card game but I continue to get the same error no matter what I do.   Main:  public class Main { public static void main(String[] args) {     Dealer deal = new Dealer();     User use = new User();     Player play = null;     Logistics log = new Logistics();      boolean[] initElementList = {false, false, false};     use.initElementList(initElementList);     deal.initElementList(initElementList);      while(play == null){         use.printDeck();         Card userChoice = use.chooseCard();         Card dealerChoice = deal.chooseCard();         **log.roundWinner(userChoice, dealerChoice);**         play = log.gameWinner();     }     System.out.println(play); } }   Logistics:  public Card roundWinner(Card user, Card dealer){     Dealer deal = new Dealer();     User use = new User();     String userChoiceE = user.getElement();     String dealerChoiceE = dealer.getElement();      int userChoiceS = user.getStrength();     int dealerChoiceS = dealer.getStrength();      **if(userChoiceE.equalsIgnoreCase("FIRE") &amp;&amp; dealerChoiceE.equalsIgnoreCase("ICE")){         use.setElementList(0);         return user;     }**   Player:  public abstract class Player {  private boolean[] hasElement; private Card[][] deck;  public boolean[] getElementList(){     return this.hasElement; } **public void setElementList(int index){     this.hasElement[index] = true; }  public void initElementList(boolean[] ElementList){     this.hasElement = ElementList; }** public void createDeck(){     CardGenerator cg = new CardGenerator();     this.deck =  cg.Deck(); } public Card[][] getDeck(){     return this.deck; } }
What is a NullPointerException, and how do I fix it? 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?
What commands (exactly) should replace the deprecated apt-key? My customers are eager to show news categorized in tabs.  I recently developed it for them.  In my experience in web designing, display:none is used widely in implementing tabs. I also know that it is not good for SEO.  Is there any way to have tabs but without hurting SEO factors? I've got a Windows 10 Computer (home edition), which has 4GB of Ram and an i5 processor. I need to run an old 32 bit accounting programme. The vendor said it won't release a 64 bit version (although a 64bit version exists, it's missing key features from the older version).  The programme installs fine, but when I click on the programme icon, it says the programme won't work on a 64 bit system.   What options do I have?    I've done a fair bit of research, but it seems to run up dead ends.   1) WoW64     Apparently, this is supposed to let you run 32 bits on 64 bit Windows. However, I am not sure how to install it. I think it's for web servers only. However,  says it can work on Windows 7, but doesn't explain how to set it up (or if it will work on Windows 10).  2) XP mode     A 32bit Windows XP emulator. However, it seems to be for Windows 7 only. Also according to this , you need Windows Professional.   3) Virtual Box Machine    Let's you emulate Windows. Seems overkill for my purposes. Plus I would need to buy a 32 bit Windows license. I think it would run slowly with 4GB of Ram.  4) Partition drive into 32bit and 64 bit versions Apparently, you can use the free tool  to split the drive into two and then install separate 32bit and 64 bit versions.   Again, seems overkill and it looks like I would need buy a 32 bit Windows 10 license.   Are these my only options?     Images  Installation    First run (From the error message I guess it's a 16-bit program)   Clicking on programme How to import a .max model into Blender? Computing $ \int_0^\infty \frac{\log x}{\exp x} \ dx $ java.lang.RuntimeException Cannot find FacesContext How to print paragraphs in twig template? I have a content type, basic, where i have added a Paragraph field field_pr that has two fields: field_text, field_color. I have a twig template node--basic--full.html.twig where I want to print the value of the paragraph field node.field_pr.   node.field_pr can have between one and ten paragraph values.   When I print the array for content.field_pr, I get a huge array. However, I only want the values from the field_pr.field_text and field_pr.field_color. How would I be able to do this from the node twig template?   I have tried the following but cannot seem to access the values. What am I missing?  {% for field in content.field_pr %}    {{ field[loop.index0].entity.field_text.value }}    {{ field[loop.index0].entity.field_color.value }} {% endfor %}  {% for field in content.field_pr %}    {{ field[loop.index0]['#paragraph'].field_text.value }}    {{ field[loop.index0]['#paragraph'].field_color.value }} {% endfor %}   Here is an image of the array that is printed for the node.field_pr field. # ~/.profile: executed by the command interpreter for login shells. # This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login # exists. # see /usr/share/doc/bash/examples/startup-files for examples. # the files are located in the bash-doc package.  # the default umask is set in /etc/profile; for setting the umask # for ssh logins, install and configure the libpam-umask package. #umask 022  # if running bash if [ -n "$BASH_VERSION" ]; then     # include .bashrc if it exists     if [ -f "$HOME/.bashrc" ]; then     . "$HOME/.bashrc"     fi fi  # set PATH so it includes user's private bin if it exists if [ -d "$HOME/bin" ] ; then     PATH="$HOME/bin:$PATH" fi   Can anyone explain the contents of the ~/.profile file? So when you enter into the ~/.profile file what does all the writing mean? I need to find the closure of these sets on the ordered square: $$A = \{(1/n)\times 0 | n\in \mathbb{Z}_+\}$$ $$B = \{(1-1/n)\times \frac{1}{2}| n\in \mathbb{Z}_+\}$$ $$C = \{x\times 0 | 0&lt;x&lt;1\}$$ $$D = \{x\times \frac{1}{2}| 0&lt;x&lt;1\}$$ $$E = \{\frac{1}{2}\times y | 0&lt;y&lt;1\}$$ I know that the closure is just the set itself united with its limit points. For $A$, the set of limit points, I imagine, are $\{&lt;1,0&gt;\}$, that is, the $x$ coordinate is $1$ and the $y$ is $0$. But  is says the reverse. What am I getting wrong? Following the same reasoning, $B' = \{&lt;1,\frac{1}{2}&gt;\}$ $C' = \{&lt;0,0&gt;,&lt;0,1&gt;\}$ What am I doing wrong? How can I sort a string of text followed by a number using LINQ Can I open Microsoft Word and Excel files? Is there a way of finding a formula for $\sum\limits_{k=1}^n k^k$? Maybe I'm missing something really obvious, but I've looked around a bit on the Internet and I haven't been able to find anything.  So, what I'm looking for is a formula in closed form to generate the sequence $1,5,32,288,3413,\dots$ Most efficient method to break Ubuntu Ways to update Ubuntu (debian-based distros) offline What is the easiest way to update/upgrade an offline Ubuntu machine with the help of a Windows machine that has internet access?  This question also applies to installing new packages offline and not only updates/upgrades.  The Linux system shall remain completely cut off from the Windows machine, meaning there should be no ethernet connection or the likes between the two computers.  Update:  Please have patience, since I haven't updated this since two weeks. There are some complications getting apt-offline to work properly on Lubuntu and all other methods seem to be too old and deprecated:  AptOff - last update 2006 AptMedium - last update 2007 Keryx - last update 2011, looks like this project was discontinued  I hope I will be able to somehow update the offline machine, finally.  While I was still not able to update/upgrade the offline system due to authentication errors, I accepted an answer, because it's taking too long. When does an expired domain become available for others to register? Class is not key value coding-compliant "What more" vs "what else" do you need? I am providing you with food, shelter, clothes.      What more do you need   or      what else do you need?   Which one's correct? I'm having this Error when I try to compile my .tex file with xelatex:  ! Package hyperref Error: Wrong DVI mode driver option `dvips', (hyperref)                because XeTeX is running.  See the hyperref package documentation for explanation.   This is my LaTeX header  \documentclass[10pt, a4paper, dvips,]{moderncv}  \moderncvtheme[grey, roman]{classic}  \usepackage{ifxetex} \ifxetex % only for xelatex \usepackage{xltxtra} % this should load both fontspec &amp; xunicode \usepackage{fontspec} \setromanfont{Helvetica Neue} \else % \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \fi % \ifxetex   Any ideas?  EDIT:  I removed the 'dvips', now I get:  ! Package hyperref Error: Wrong driver option `pdftex', (hyperref)                because pdfTeX in PDF mode is not detected.  See the hyperref package documentation for explanation.   Now my first latex line  \documentclass[10pt, a4paper]{moderncv}   Any clues ? How do you change the size of figures drawn with Matplotlib? How do you change the size of figure drawn with Matplotlib? How can I understand a Vortex Tube and its efficiency? A  takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. .  Both linked sources are scarce with information about how and why this works. Now, I have two questions:   Why does it work, specifically why should the situation in the vortex lead to a transfer of thermal energy from the inner stream to the outer one? How efficient can it be?  How do you define the efficiency of a device that may be closer to Maxwell's Demon than to a heat pump? My feeling is that any analysis should not only take into account the sum of input energy (thermal and mechanical energy instream) and sum output (thermal energies and pressures of both gas streams), but also the Temperature differential that is created - since that contains an ability to create work.* If course it's pointless to create heat from high grade 8mech.) energy to transform it back to mech. energy - but it gives an idea on the worth of the output.