After searching, finally, I find out that I should use an interface to pass a list of objects from an activity to a fragment. before that, I made my object class Perceilable to send in as an argument to fragment, but it seems that it's not a good approach because I have to initiate my fragment for the first time without setting any argument and after my list of the object is ready I can pass it. So now I want to send my list via Interface but I get this error :  java.lang.NullPointerException: Attempt to invoke interface method 'void com.x.x.Interfaces.CurrenciesSync.syncCurrencies(java.util.List)' on a null object reference     at com.x.x.DashboardActivity$1.onResponse(DashboardActivity.java:124)   here is my interface file codes:  public interface CurrenciesSync {   public void syncCurrencies(List&lt;CurrencyModel&gt; currencies);  }   here is the way I set currencies List in DashboardActivity to syncCurrencies method:  public class DashboardActivity extends AppCompatActivity {         CurrenciesSync currenciesSync;   currenciesSync.syncCurrencies(currencies);     } And how I implement it's method :  public void syncCurrencies(List&lt;CurrencyModel&gt; currencies) {  // using currencies here }
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?
I am running an HP pavilion dv6000 dual boot win7 and Ubuntu 12.04. (well, up until today).  After a reboot, the boot process drops to the BusyBox shell and I end up at the prompt:  BusyBox v1.18.5 (Ubuntu 1:1.18.5-1ubuntu4) built-in shell (ash) Enter 'help' for a list of built-in commands.  (initramfs)   I've been researching others who have had this same problem, but haven't been able to find any of those solutions to work for me.  I tried the method described , and after the final command   mount -t ntfs-3g /dev/sda1 /root -o force   it does nothing and gives me another (initramfs) prompt.  I can boot to a live CD (USB) and get to a terminal, but it doesn't seem to do much good, as I can see the /dev/sda1 in the ls command, but it doesn't recognize it when I try to cd to it.  One more question: using the command fdisk -l how can I tell which mount point (sda1/sda2) is my windows partition and which one is Ubuntu? Windows 8 turns program sound volume down randomly I recently upgraded to Windows 8 from Win 7 64 bit and have started to encounter a strange issue. When I have any program running which plays sound, such as a game or spotify, after a random interval (usually around 5-10 minutes) the program sound will set itself really low.    If I Alt-Tab to the desktop and check the Mixer I can see that the Application volume has automatically set itself really low - the other volume levels (i.e. the Device speakers) stay the same.  I'm able to just set the application volume back to a reasonable level and it stays that way for another 5 - 10 minutes then goes quiet again.  My sound is Realtek High Definition Audio and my machine is an Acer Aspire 5738G if that helps in any way.  Any help much appreciated! Compactness of $A:=${$f \in C[0,1], |f|_\infty \le K, |f'|_\infty \le M$} Here we use infinity norm as metrics for $C[0,1]$. The professor claims that this set is compact. I can show this set is relative compact by Arzela Ascoli, i.e., for each subsequence there is a further sub-subsequence that uniformly converges to a continuous function on $[0,1]$. But it is not intuitive to me why this set is compact, i.e. the limiting function also satisfies $|f'|_\infty \le M$. Is it true that $A$ is close and therefore compact? Two paths that show that $\frac{x-y}{x^2 + y^2}$ has no limit when $(x,y) \rightarrow (0,0)$ What is probabilistic programming? For the past year, I've been hearing a lot about Probabilistic Programming (PP) frameworks like  and , and how great PP is. And today, someone shared this link with me:    However, I don't really follow what is special about it since it feels like whatever you can do in PP you can do in any other general purpose language. I'm sure there are technical aspects about PP that make it attractive (e.g. parallel computing), but this aside, is PP really any different from any other language?  Question: I was wondering if there was a consensus of what PP was and how it differs from other statistical-focused software like R, Matlab, Mathematica. It should be noted that PyMC3 and Stan are focused on more Bayesian analysis.  Doing a little research on Google, I came across the following two definitions. The first more abstract, and the second more about PP's technical characteristics.     1.2. Probabilistic Programming Is      Instead, probabilistic programming is a tool for statistical modeling. The idea is to borrow lessons from the world of programming languages and apply them to the problems of designing and using statistical models. Experts construct statistical models already—by hand, in mathematical notation on paper—but it's an expert-only process that's hard to support with mechanical reasoning. The key insight in PP is that statistical modeling can, when you do it enough, start to feel a lot like programming. If we make the leap and actually use a real language for our modeling, many new tools become feasible. We can start to automate the tasks that used to justify writing a paper for each instance.      Here's a second definition: a probabilistic programming language is an ordinary programming language with rand and a great big pile of related tools that help you understand the program's statistical behavior.      Both of these definitions are accurate. They just emphasize different angles on the same core idea. Which one makes sense to you will depend on what you want to use PP for. But don't get distracted by the fact that PPL programs look a lot like ordinary software implementations, where the goal is to run the program and get some kind of output. The goal in PP is analysis, not execution (added emphasis).   --   I'd like to know if the general statistical community agrees with these two definitions of PP, and if there are any other characteristics this definition may be missing. Selecting an ID with a colon in it with jQuery Where does the extra kinetic energy of the rocket come from? Consider a rocket in deep space with no external forces. Using the formula for linear kinetic energy $$\text{KE} = mv^2/2$$ we find that adding $100\ \text{m/s}$ while initially travelling at $1000\ \text{m/s}$ will add a great deal more energy to the ship than adding $100 \ \text{m/s}$ while initially at rest: $$(1100^2 - 1000^2) \frac{m}{2} \gg (100^2) \frac{m}{2}.$$ In both cases, the $\Delta v$ is the same, and is dependent on the mass of fuel used, hence the same mass and number of molecules is used in the combustion process to obtain this $\Delta v$. So I'd wager the same quantity of chemical energy is converted to kinetic energy, yet I'm left with this seemingly unexplained $200,000\ \text{J/kg}$ more energy, and I'm clueless as to where it could have come from. URLs are linked despite being inside a code span I am using longtable and I cannot find a way to adjust its column spacing. I want a table like this:    But I am getting this:    This is what I am doing for defining table size:   \begin{longtable}{p{.1\textwidth} p{.2\textwidth} p{.2\textwidth}p{.3\textwidth}}     xxxxx &amp; xxxxx &amp; xxx &amp; xxxxx\\     \end{longtable} Moved bin and other folders! How to get them back? List all columns for a specified table What Does it Really Mean to Have Different Kinds of Infinities? The spectral radius of normal operator Can we use media9 to show a video on a PDF but the video is not embedded to the PDF? I have video tutorials that I want to show in my presentation with beamer class. I don't want the video files get embedded to the PDF because they will make the PDF size very very huge.  If you know how the videos can be played on the HTML with a reference rather than embedding the video file to the HTML file, I want something like this to be applied to my PDF presentation. I just want to reference the video URL from my PDF presentation.   Shortly speaking, can we use media9 to show a video on a PDF but the video is not embedded to the PDF?  Uploading those videos to a web server might be difficult for me because internet connection is very slow and sometimes not available in the presentation room. :-) Regionalism or just bad English? I've encountered a particular type of writing occasionally and it being, derp, in writing, it's hard to tell whether there's an accent behind it. The English used seems to me to be simply incorrect, but I can't help but feel that the following features are part of a dialect or a regional style of English. One of the most glaring (and grating) features is the substitution of &quot;saw&quot; with &quot;seen&quot;.  He seen him at the shop the other day. I seen that you were looking for... etc.  The use of &quot;away (to)&quot; is also peculiar, if not incorrect.  He was away to open the door when... He was away to get what he had asked for. etc.  I haven't come across these forms very often, and even then it was accompanied by otherwise mostly correct English, which is what makes me wonder what the hell. This is more intellectual curiosity than anything else. How can I create a zip archive of a whole directory via terminal without hidden files? I have a project with lots of hidden folders / files in it. I want to create a zip-archive of it, but in the archive shouldn't be  any hidden folders / files. If files in a hidden folder are not hidden, they should also not be included.  I know that I can create a zip archive of a directory like this:  zip -r zipfile.zip directory   I also know that I can exclude files with the -x option, so I thought this might work:  zip -r zipfile.zip directory -x .*   It didn't work. All hidden directories were still in the zip-file. Im asked to prove that a polynomial of an odd degree has a root. Im going to use IVT to prove this, but I'm wondering if I can use the assumption that an odd degree polynomial has either two cases:  $$ \lim_{x\to\infty}h(x)=+\infty \\ \lim_{x\to-\infty}h(x)=-\infty \\ $$ $$and$$ $$ \lim_{x\to\infty}h(x)=-\infty \\ \lim_{x\to-\infty}h(x)=+\infty \\ $$ Then by this there exists numbers $a,b$ such that $$ h(a)&lt;0&lt;h(b) $$ $$or$$ $$ h(b)&lt;0&lt;h(a) $$ Which I think would prove that odd degreed $h(x)$ has at least a root. Or is there a more convincing way to show that there are numbers in $h(X)$ greater than zero and less than zero?  edit: (sorry about the bad limit notation) For example:  me$ FOO="BAR * BAR" me$ echo $FOO BAR file1 file2 file3 file4 BAR   and using the \ escape character:  me$ FOO="BAR \* BAR" me$ echo $FOO BAR \* BAR   I'm obviously doing something stupid.  How do I get the output BAR * BAR? I just bought a used  and it comes with regular rim brakes. I'm perfectly happy with them so far, but have been wondering if disc brakes would come handy when it rains.  What is involved in converting a bike from rim brakes to disc brakes (mechanical or hydraulic)?   Is this something that is feasible, or am I better off buying another bike that already has disc brakes? Are $\mathbb{Q}_p$ and $\mathbb{Q}_q$ homeomorphic?