Null pointer exception when trying to access method (java)
What is a NullPointerException, and how do I fix it?
...where each object also has references to other objects within the same array?  When I first came up with this problem I just though of something like   var clonedNodesArray = nodesArray.clone()   would exist and searched for info on how to clone objects in javascript. I did find a  on StackOverflow (answered by the very same @JohnResig) and he pointed out that with jQuery you could do  var clonedNodesArray = jQuery.extend({}, nodesArray);   to clone an object. I tried this though, this only copies the references of the objects in the array. So if I   nodesArray[0].value = "red" clonedNodesArray[0].value = "green"   the value of both nodesArray[0] and clonedNodesArray[0] will turn out to be "green". Then I tried  var clonedNodesArray = jQuery.extend(true, {}, nodesArray);   which deep copies an Object, but I got "too much recursion" and "control stack overflow" messages from both Firebug and Opera Dragonfly respectively.  How would you do it? Is this something that shouldn't even be done? Is there a reusable way of doing this in Javascript? how to prove that this positive sequence converges to 1 What would you call a person who doesn't want to learn anything new? According to Theorem 8.8 in Time Series A.W. van der Vaart an ARMA process $$\phi (L)X_t=\theta(L)\epsilon_t$$ has a  unique stationary solution $X_t=\psi(L)\epsilon_t$ with $\psi=\theta/\phi$ if $\phi$ has no roots on the complex unit circle. This would imply that the explosive process, with $\rho&gt;1$, is a stationary process $$X_t=\rho X_{t-1}+\epsilon_t$$ with stationary solution $X_t=\sum_{i=1}^\infty \rho^{-i}\epsilon_{t+i}$.  Now indeed $\sum_{i=1}^{\infty} \rho^{-i} &lt; \infty$ so that weak stationarity can be proved by using this representation.   However, here on stackexchange I see a lot of question/answers that suggest that the process above is not stationary (see for example , ). In particular, the accepted answer of the latter question claims that the process is non-stationary by simulating a series and showing it displays explosive trending behaviour.  I think the only way to reconcile the theorem I mention above and the plots in the accepted answer of () is the following: the explosive process is indeed stationary but non-ergodic, that is, we cannot find the statistical properties of $X_t$ such as $\mathbb{E}(X_t)=\mu$ by observing a single infinitely long sample path of the explosive process, mathematically: $$\lim_{t \to \infty}\frac{1}{t}\sum_{t=1}X_t \neq\mathbb{E}X_t$$  Is this reading correct? Let $S = \bigoplus_{n\ge 0} S_n$ be a graded commutative ring. Let $f$ be a homogeneous element of $S$ of degree $&gt; 0$. Let $S_{(f)}$ be the degree $0$ part of the graded ring $S_f$, where $S_f$ is the localization with respect to the multiplicative set $\{1, f, f^2,\dots\}$. Suppose $S$ is finitely generated algebra over $S_0$. Then $S_{(f)}$ is a finitely generated algebra over $S_0$. Conformal Maps onto the Unit Disc in $\mathbb{C}$ How to prove that a nilpotent operator has a basis representation that is strictly upper triangular? Normal Subgroup Counterexample Im having trouble with the second part of this question,  Let $H$ be a normal subgroup of $G$ with $|G:H| = n$,  i) Prove $g^n \in H$ $\forall g \in G$ (which i have done)  ii) Give an example to show that this all false when $H$ is not normal in $G$.(which I am having trouble with showing)  Any suggestions? Why can't I copy a 7 GB file to an external USB HD with 120 GB free? bash function cannot change the value of a local variable when called by $() The following code works differently depending on which way Parse_Short_Switches() is called.  After calling the function 'Parse_Short_Switches' by using result=$(Parse_Short_Switches), the value of $error_flag is NOT set to -1 as I would expect.  After calling the function 'Parse_Short_Switches' by simply using Parse_Short_Switches, the the value of $error_flag is set to -1 as I would expect.  Any help would be greatly appreciated.  Thanks  #!/bin/bash  function Parse_Short_Switches() { echo "error_flag inside of the function= $error_flag" 1&gt;&amp;2 error_flag="-1" echo "blah blah ..." }  # --- MAIN --- error_flag="999" echo "error_flag= $error_flag" #result=$(Parse_Short_Switches) Parse_Short_Switches echo "error_flag= $error_flag" Author information column wise I am using authblk package and I want to achieve following output using this package. How to download and use any other kernel than the one which is installed by default What are the odd of a single coin toss after many consecutive ones? I have little knowledge of probability and have recently been thinking of a math problem I am sure you guys could answer  If for example I tossed a coin ten times and got all heads, would the odds of the next coin toss beeing heads be 50 50 or s very low as the odds of getting 11 in a row is tiny?   Thanks DKIM sign outgoing mail from any domain (with Postfix and Ubuntu) I got DKIM setup on my mail server (postfix and ubuntu) so it signs outgoing emails.  I used these instructions:   However, I need it to sign emails from any domain (in the From address) and not just my own.  I'm building an email newsletter service and clients will be sending their own email through the server.  First I set "Domain *" in /etc/dkim-filter.conf.  This got it to include the DKIM headers in all outgoing emails, no matter what the domain.  However, the verification check fails on gmail because it is checking the domain in the from address, and not my domain (and dns record).  Does anyone know how to do this? Attack moving or Attack Canceling I watch streams sometimes and i see the high elo Ranged AD move between each shot. Do they gain anything with this? And if so whats a good way to practice it. I am a graduate student in economics who recently converted to R from other very well-known statistical packages (I was using SPSS mainly). My little problem at the moment is that I am the only R user in my class. My classmates use Stata and Gauss and one of my professors even said that R is perfect for engineering, but not for economics. He said that many packages are built by people who know a lot about programming, but not much about economics and therefore are not reliable. He also mentioned the fact that since no money is actually involved in building an R package, there is therefore no incentive to do it correctly (unlike in Stata for example) and that he used R for a time and got some "ridiculous" results in his attempts to estimate some stuff. Moreover, he complained about he random number generator in R which he said was "messy".  I've been using R for just a little more than a month and I must say I have fallen in love with it. All this stuff I am hearing from my professor is just discouraging me.  So my question is: "Is R reliable for the field of economics?". I upgraded my Nexus 4 to Lollipop a few days ago but I don't like it. I'll leave out my reasons because they're not relevant here. I wiped my phone and installed a clean stock 4.2.2 version instead. I'm happy with this.  Not long after, Android automatically downloaded the 4.3 upgrade and notifies me with the choices "Later" and "Install". I don't want to do this upgrade.  How do I:   get rid of the notification, and  remove the downloaded update (to free up precious storage space).     I have already tried choosing "Later" but the same notification immediately reappears.    Based on Google search results, I also tried going to Settings &gt; Apps &gt; All &gt; Google Services Framework and unticked "show notifications" but it still appears. Force stop or disable also doesn't seem to help, so I've re-enabled the service including notifications. I didn't see any other apps in this list that sounded relevant - did I just not see it? Why doesn't the UK ask for travel bookings for a tourist visitor visa? SaveAsActivity is not allowed with whatId that is not supported as a task whatId Is the EmDrive, or "Relativity Drive" possible?