I'm trying to make a soundboard and I wanted to add a class to make it run easier and I get more points with a class if I use it.  However I get a NullPointerException and I would like to know why the problem happened. If someone can explain it to me that would be perfect.  The NullPointerException occurs when calling `sound1.run().  import ddf.minim.*; import ddf.minim.analysis.*; import ddf.minim.effects.*; import ddf.minim.signals.*; import ddf.minim.spi.*; import ddf.minim.ugens.*;  PImage soundboard; PImage [] array= new PImage[0];  sound sound1;  Minim minim;  AudioPlayer player; Boolean player1= false;  void setup() {     size(451,385);     minim = new Minim(this);     player = minim.loadFile("deadmau5.mp3");     soundboard = loadImage("sb.png"); }  void draw() {     image(soundboard,1,CENTER);     sound1.run(); }  void mousePressed() {     player1=!player1;     if (player1) {         player.play();     } else {         player.pause();     player.rewind();     } }  class sound {      float x = 1;     float y = 1;      void run() {         draw();     }      void draw() {         rect(x,y,100,100);          }   }     One more question that I must ask: when I rewrite code, sometimes it overwrites on my current code and I want to know how to stop that, even if I use space it still overwrites the code.   Thank you guys!
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?
How to change inside background color of UISearchBar component on iOS Cardinality of a set of closed intervals What is the cardinality of the set S of all closed intervals on the real number line with rational (positive) lengths?  I believe the number of intervals with a specific fixed length but varying start points is |R|, and the number of intervals with a fixed start point but varying lengths is |Q| = |N|. I think the answer to the question would then be |S| = |R x N| = |R|? I'm not quite sure how to prove the last equality though. Would I have to define a bijective function that maps elements of (R, N) to R? How would I approach doing so? I decided to make sure that I know this important difference between American and British English, so I wrote what I have found out so far and I would be grateful to anyone who reads this and tells me whether I am wrong, or not.  In British English when people say  to hospital or in hospital when  talking  about somebody being there as a patient they don't use the definite article : "I had to go to hospital", "She spent two weeks in hospital". And the meaning is that somebody was there as a patient.   If then for some other reasons British English speakers  will use the definite article which will change the meaning itself, I noticed that, in American English, native speakers often use the  the and if they need to show that somebody is in church to pray,  in school as a student, in hospital as a patient, in prison as a prisoner, they use 'in' and not 'at'. Do American English speakers use 'at' like British English speakers use 'the' to give the sentences a different meaning?    Are my sentences correct? Do they show American English usage?   He is in the school. (enrolled as a student) He is at the school. (for some different reasons) He is in the hospital. (as a patient) He is at the hospital. (visiting somebody) He is in the church. (to pray) He is at the church. (for some different reasons) He is in the university. (as a student) He is at the university. (not as a student) He is in the college. (as a student) He is at the college. (Not as a student) He is in the prison. (as a prisoner) He is at the prison. (not as a prisoner) How were bullets able to dent Captain America's Shield? Just after Captain America's shield was introduced in Captain America: The First Avenger, Peggy Carter shot few bullets at it which created few minor distortions on it.                                  From  page of Marvel.Wikia,     Proto-Adamantium   This is the original Adamantium created by Dr. MacLain. Proto-Adamantium is the official name for the metal that makes up Captain America's Shield. It has never been recreated and is the absolute most invulnerable item in all of existence.    From  page of Marvel.Wikia:     The true shield was once slightly dented by an enraged Odinforce empowered Thor, using Mjolnir, but he later reconciled and pounded out the small dent.    How were few bullets able to dent Captain America's shield then? How to properly unwrap my mesh? Is there a way to automatically unwrap my character? If not, is there a tutorial or something? Say there are $m+n$ elements split into two groups ($m$ and $n$). The variance of the first group is $\sigma_m^2$ and the variance of the second group is $\sigma^2_n$. The elements themselves are assumed to be unknown but I know the means $\mu_m$ and $\mu_n$.  Is there a way to calculate the combined variance $\sigma^2_{(m+n)}$?   The variance doesn't have to be unbiased so denominator is $(m+n)$ and not $(m+n-1)$. What damage will powering down instead of shutting down do? I am getting these warnings every time I update my initramfs image(-s) with  on my Dell PowerEdge T20 server running    10.0. Is there a fix?    W: Possible missing firmware /lib/firmware/i915/bxt_dmc_ver1_07.bin for module i915 W: Possible missing firmware /lib/firmware/i915/skl_dmc_ver1_27.bin for module i915 W: Possible missing firmware /lib/firmware/i915/kbl_dmc_ver1_04.bin for module i915 W: Possible missing firmware /lib/firmware/i915/cnl_dmc_ver1_07.bin for module i915 W: Possible missing firmware /lib/firmware/i915/glk_dmc_ver1_04.bin for module i915 W: Possible missing firmware /lib/firmware/i915/kbl_guc_ver9_39.bin for module i915 W: Possible missing firmware /lib/firmware/i915/bxt_guc_ver9_29.bin for module i915 W: Possible missing firmware /lib/firmware/i915/skl_guc_ver9_33.bin for module i915 W: Possible missing firmware /lib/firmware/i915/kbl_huc_ver02_00_1810.bin for module i915 W: Possible missing firmware /lib/firmware/i915/bxt_huc_ver01_07_1398.bin for module i915 W: Possible missing firmware /lib/firmware/i915/skl_huc_ver01_07_1398.bin for module i915 How to append something to an array? How do I append an object (such as a string or number) to an array in JavaScript? How do I limit the number of rows returned by an Oracle query after ordering? I am currently using a MacBook Pro 13&quot; Mid 2018 with Touch Bar. Today macOS Big Sur was released and I tried to download it but it's getting stuck at 484.4 MB. Initially, it shows 16-17 minutes left, but as soon as it reaches 484.4 MB it's stuck and the timer goes till 10 hours! My Wi-Fi is totally stable with a speed of 100 Mbps. I tried to restart my Mac but it still gets stuck. Earlier there were similar issues in the App Store (even now they are). The issue was I was not able to download an app unless I connect to the US VPN. I even contacted support but they were not able to help out. It wasn't a big deal as a VPN could be used. But now even with VPN, it gets stuck. Killing thread after some specified time limit in Java let $a,b,c$ be postive real numbers ,and such $$ab+bc+ac=3$$   show that   $$\dfrac{a^2}{a+2b^2}+\dfrac{b^2}{b+2c^2}+\dfrac{c^2}{c+2a^2}\ge 1$$   This problem is from Secrets In Inequalities volume 1  page 30,example 1.24. the comment.the  author this case is a bit more diffcult,But this author can't post solution.Thank you About $\lim \left(1+\frac {x}{n}\right)^n$ How to know if a time series is stationary or non-stationary? How to draw Venn diagrams (especially: complements) in LaTeX Detecting unused packages in LaTeX document I have quite a bad habit of copy-and-pasting my packages from one LaTeX document to another. Is there any way we can detect unused packages (i.e. \usepackage commands) so that they can be removed from the LaTeX document? What is "function*" in JavaScript? How does Ubiquity determine the required disk space before installation? This question intends to demystify  the desktop installer for Ubuntu, on how the required disk space before installation is being determined.  From this dated post :     [When installing] Ubuntu 12.04 alongside with Windows 7 using the Ubuntu installer, [the user] wasn't able to give Ubuntu less than 32 GB [...] and as the guide states, "Ubuntu needs about 4.5 GB to install, so add a few extra GB to allow for your files".   The required disk space was previously about 5 GB (Ubuntu 12.04), 8 GB (Ubuntu 16.04), and has since increased to 25 GB (Ubuntu 18.04), as per . In practice, the absolute minimum for required disk space may differ by installation media and machine.  The design spec via  describes the installer mockup and nothing else about how the required disk space is determined (top half screenshot).    I have clarified that Ubuntu 16.04 will require at least 8 GB disk space only on a physical machine, but the minimum changes to 8.3 GB when installing to a virtual machine (bottom half screenshot).  So how does Ubiquity determine the required disk space? Proving that $m+n\sqrt{2}$ is dense in $\mathbb R$ I am having trouble proving the statement:     Let $$S = \{m + n\sqrt 2 : m, n \in\mathbb Z\}$$ Prove that for every $\epsilon &gt; 0$, the intersection of $S$ and $(0, \epsilon)$ is nonempty.