NullPointer Exception while retrieving data from JSON
NetworkOnMainThreadException
Django model with 2 foreign keys from the same table I'm trying to install the  IDE in my Ubuntu and in the process it's asking for my root password which I don't remember. I know my  user password. How can I recover my root password? How does the Ready action work? So from reading the Player's Handbook, it seems that the Ready action is taken instead of any other action as it is an action in its own right. However, can you move on the same turn that you ready an action? For instance, (taking the example from the Player's Handbook):     If the cultist steps on the trapdoor, I’ll pull the lever that opens it   Presumably, when you ready this action, you would want to move near to the lever so you can pull it when the time is right. Likewise, with readying a spell, you would obviously want to move away from combat so you could concentrate on the spell.  Secondly, when the trigger goes off do you have to wait for your turn, or do you in effect get a bonus turn? For instance, the cultist starts running towards you, but on his way he steps on the trap door - so you immediately pull the lever, even though it wasn't your turn. I assume you then act as normal when your actual turn comes around? Does set difference distribute over set intersection? I am trying to figure out this:  c = 1 def f(n):     print c + n  def g(n):     c = c + n  f(1) # =&gt; 2 g(1) # =&gt; UnboundLocalError: local variable 'c' referenced before assignment   Thanks! I am flying to Tokyo in November, and I have the choice to go direct (paying extra) or transit via Seoul. Is 6 hours transit time enough to leave Incheon airport for a bit to see something of Seoul? It might make my trip more worthwhile to see something of South Korea too. I don't know much about the busyness of the airport around this time, and travel time between the airport and the city, so that's why I am asking. Scanf skips every other while loop in C How can Linux/Ubuntu be installed safely on ChromeBook? Is installing Ubuntu on my Chromebook potentially dangerous to anything on my Chromebook? I got it as a gift, so I don't want to destroy anything that is important on the laptop. Also, which is better for being able to safely install Ubuntu: ChrUbuntu or Crouton? I'm using the Samsung Chromebook 3 (as described by the quick-start manual). Does that make any other differences as well? Rich Wizards, Poor Muggles Using Mosfet with seperate Logic Converter and Arduino As the title say, I want to prove that  $C_c^{\infty}(\mathbb R^n)$ is dense in $W^{k,p}(\mathbb R^n)$  i.e.  $\displaystyle{ W^{k,p} (\mathbb R^n) = W_0^{k,p}(\mathbb R^n)  \quad (\star)}$. In a book I found that in order to prove it, we need the following claim:  Claim: Let $\displaystyle{\zeta \in C^{\infty} ([0, \infty)) }$ such that $\zeta (t)  =1 $ for $ t \leq 1 $ and $\displaystyle{ \zeta (t) =0 }$ for $ t \geq 2$. For $R&gt;0$ and  $x \in \mathbb R^n$ define $\displaystyle{ \eta_R (x) = \zeta \left( \frac{|x|}{R} \right)}$. If $ \displaystyle{ u \in W^{k,p} ( \mathbb R^n) }$ with $1 \leq p &lt; \infty $ then, $\displaystyle{ \eta_R u \to u }$ in $W^{k,p}(\mathbb R^n) $ as $ R \to \infty$.  If I prove the claim then the $(\star)$ follows using mollifiers. But unfortuently I have stuck, with the proof of the claim.  Any ideas? $ \lim_{x\to o} \frac{(1+x)^{\frac1x}-e+\frac{ex}{2}}{ex^2} $ $$ \lim_{x\to o} \frac{(1+x)^{\frac1x}-e+\frac{ex}{2}}{ex^2} $$   (can this be duplicate? I think not) I tried it using many methods  $1.$ Solve this conventionally taking $1^\infty$ form in no luck  $2.$ Did this, expand $ {(1+x)^{\frac1x}}$ using binomial theorem got $\frac13$ then grouped coefficients of $x^0$ and it cancelled with $e$ then took coefficient of $x$ cancelled with $\frac{ex}{2}$ and so on   very messy right ? at last I got $\frac13$ but that's not the expected answer!  I must have went wrong somewhere can anyone help me with this. Can I disable full-disk encryption? I recently installed Ubuntu 12.10 and it requires a passphrase to boot up (I installed it with an encrypted file system).  Do I have to reinstall to change to a standard unencrypted file system? Difference in meaning and use of future perfect forms Why use gradient descent with neural networks? When training a neural network using the back-propagation algorithm, the gradient descent method is used to determine the weight updates. My question is: Rather than using gradient descent method to slowly locate the minimum point with respect to a certain weight, why don't we just set the derivative $\frac{d(\text{Error})}{dw}=0$, and find the value of weight $w$ which minimizes the error? Also, why are we sure that the error function in back-propagation will be a minimum? Can't it turn out the error function is a maximum instead? Is there a specific property of the squashing functions that guarantees that a network with any number of hidden nodes with arbitrary weights and input vectors will always give an error function that has some minima? limit of $\lim\limits_{x \to \infty}((x+1)^a - x^a)$ Hello everybody, i couldn't figure out how to demonstrate this equation without L'Hopital i wonder if its possible.   $a \in (0,1)$ $\lim\limits_{x \to \infty}((x+1)^a - x^a) = 0$ I see more and more servers that have no domain defined in the /etc/resolv.conf file.  Only a search entry. In what cases is this setup used ? Are there any cases where it must not be used ?  nameserver xxx.xxx.xxx.xxx nameserver yyy.yyy.yyy.yyy nameserver zzz.zzz.zzz.zzz  search domain1 domain2 domain3 ... How do I install a .deb file via the command line? How do I install a .deb file via the command line? Lost my old passport for Schengen visa application One word for things that would be nice to have, but not required to have?