java.lang.NullPointerException when reading from a text file
What is a NullPointerException, and how do I fix it?
Set a global policy for floats positioning I have a document with many floats (figures, specifically).  I want to be able to change the global floats positioning policy from htbp to just h (or even H with the floats package).  For my-own reasons, I don't want to do this by appending the [h] argument to each float env.  One option that I can think of is using a macro:  \newcommand{\mypos}{h} % or htbp \begin{figure}[\mypos]...   I also prefer not to do that - It is cumbersome.  Is there a way to set the global float positioning argument globally? Why choose a low latency kernel over a generic or real-time kernel? I have B1/B2 Visa. Can I travel for Business trip to US with this Visa? I have been given B1/B2 Visa, but first time when I had applied, it  was for vacation &amp; holiday. Now I need to go to US for business meetings. Is this Visa good enough or do I have to apply for a B1 Visa again?  Note: I originally applied for vacation purposes, but in my visa it is stamped "R b1/b2" $\mathbb{F}_p[X]/(X^2+X+1)$ is a field iff $p \equiv 2 \bmod 3$ Let $p$ be a prime. Prove that $\mathbb{F}_p[X]/(X^2+X+1)$ is a field iff $p \equiv 2\bmod3$.    So:   If $p \equiv 2 $ mod $ 3$, I have to show that every element of $\mathbb{F}_p[X]/(X^2+X+1)$ has an inverse.  If $\mathbb{F}_p[X]/(X^2+X+1)$ is a field I have to show $p \equiv 2 $ mod $ 3$. How does stuff glow in the dark? How long does it take for reputation on Stack Overflow Careers to be updated? Just curious how this works:  My Stack Overflow reputation on my Stack Overflow CV shows an amount X, which is less than my actual Stack Overflow reputation Y. It's been this way for a few days. In addition, some of my 'favorite answers' on my CV have a lower # of votes than they do in reality.  How long does it take for this (I assume cached) value to be updated? Finding the uniquely determined region of a PDE (a) Solve the equation $yu_x+xu_y=0$  with the condition $u(0,y) = e^{-y^2}$. (b) In which region of the xy plane is the solution uniquely determined?     I did the first part but I don't understand how to do part b.  I read   But I don't understand how the argument is based. A more clear explanation is appreciated Does "until [date]" mean "before that date"? What does until mean in the following?     You need to deliver this product within 2 days (until August 18, 2011)   to meet your deadline and get paid.   Does this mean that I have to deliver the product by 23:59 on 17 August 2011 or 23:59 on 18 August 2011? The order time is 21:04 on August 16 2011. Do these leaves signify anything? Why do I have blurred vision and how do I fix it? How do you persuade an organization to value UX? UX is such an underrated field in a lot of industries. I wonder how companies consider employing UX designers and even heavily valuing their suggestions. Some big companies happen to see the light and invest in UX, and that keeps them on top of others. However, UX people rarely make it to the top management. In Don Norman's talk (  ), out of so many UX people (I don't know exactly), only two were vice presidents. I assume that there are even less influential UX designers in developing countries, and that's what makes it even harder for people like me. In the same talk, Don Norman suggested that UX designers should approach their executives like marketing people, showing how investing in something will affect profit. Perhaps, it's the best thing to do but it has to be mastered for it to be executed successfully.   I'm a fresh grad and am looking for a job. I think, working for a company with a more conventional job description would be the way to go. When I'm already influential enough, I'll go up to the executives and show them how UX will improve sales (in whatever industry it is. I just want to do UX)  Do you do UX as consultants or are you employed? How do you persuade companies to invest in UX? Are you lucky enough to be employed by people who you didn't have to persuade to value UX? If $a_{ij}=\max(i,j)$, calculate the determinant of $A$ What happens when you target a "magical effect" with Dispel Magic? With Bash's source it is possible to execute a script without an execution bit set. This is documented and expected behaviour, but isn't this against the use of an execution bit?  I know, that source doesn't create a subshell. Can I still use a usb flash drive after spilling water on it? So a few months ago I accidentally spilled a little water on a few of my usb flash drives. I really want to test and see if they work, but before I do, I just want to make sure that there's no risk of damaging my computer. I'm pretty sure it's fine, but I just got a new laptop and would hate to ruin it over something stupid. Is there a sentence that begins with “them”? When do I need to invoke \phantomsection? Can a PC with the Alert feat alert his friends? Closed formula for the sums $\sum\limits_{1 \le i_1 < i_2 < \dots < i_k \le n} i_1 i_2 \cdots i_k $? I've worked out a few summation formulas, and I am hoping to find a pattern. Unless I have made a mistake somewhere, we have the following identities:  $$\sum_{1 \le i \le n} i = \frac{(n+1)n}{2} $$  $$\sum_{1 \le i &lt; j \le n} ij = \frac{(3n+2)(n+1) \, n \, ( n-1)}{24}$$   $$\sum_{1 \le i &lt; j &lt; k \le n} ijk = \frac{(n+1)^2 \, n^2 \, (n-1)(n-2) }{48}$$   It seems clear that $$p_k(n)= \sum_{1 \le i_1 &lt; i_2 &lt; \dots &lt; i_k \le n} i_1 i_2 \cdots i_k $$ is a polynomial in $n$ of degree $2k$. But is there a nice closed-form formula for it? Maybe in terms of its factorization?  Comment: I realize that what I am looking for is the coefficient of $t^k$ in the expansion $$(1+t)(1+2t) \dots (1+nt),$$ so maybe generating function techniques could be helpful. But the main way I know to extract the coefficient of $t^k$ is to take derivatives $k-1$ times and on the surface of things that looks like a huge mess. How can I use multiple accounts with Telegram? Is there a way to have two copies of  app in Ubuntu each with a different account?  It seems copying the app in another folder does not work.