JAVA, null is converted to int, but has exception in running
What is a NullPointerException, and how do I fix it?
Shell with better editing capabilities Shells (at least what I know) have really bad command editing capabilities.  For example:    I can't point the cursor to any point of the command. I can't select and backspace/delete/replace text in the command.   Currently these are so distracting, I use gedit to edit commands before pasting them to the terminal.  Is there any solution that's good for these? Let $C$ be the class of all real-valued continuously differentiable functions $f$ on the interval $[0,1]$ with $f(0)=0$ and $f(1)=1$. How to show that $$\inf_{f\in C}\int_0^1|f'(x)-f(x)|dx=\frac{1}{e}?$$  I have been able to show that $1/e$ is a lower bound. Indeed, $$\begin{align*} \int_0^1|f'(x)-f(x)|dx &amp;= \int_0^1|f'(x)e^{-x}-f(x)e^{-x}|e^xdx \\ &amp;\geq \int_0^1\left(f'(x)e^{-x}-f(x)e^{-x}\right) dx \\ &amp;= \int_0^1 \frac{d\left(f(x)e^{-x}\right)}{dx}dx  \\ &amp;= f(1)e^{-1}-f(0)e^{0}\\ &amp;=\frac{1}{e}. \end{align*}$$ But how to show this is the infimum? Is there a function $f\in C$ such that we get $\int_0^1|f'(x)-f(x)|dx=1/e$? How is this command legal? "> file1 < file2 cat" Assuming file2 already exists, the command   &gt; file1 &lt; file2 cat   appears to be copying the content of file2 to file1.  But I cannot understand this structure.  I understand that "Nothing" is being directed to file1 (creating or erasing its content). Then the content of file2 is being directed to file1.  Why is cat after file2? How does it know to cat file2 if the operands are not in the correct order? Does the sequence $\{\sin^n(n)\}$ converge? Does the sequence $\{\sin^n(n)\}$ converge?   Does the series $\sum\limits_{n=1}^\infty \sin^n(n)$ converge? How can I put the computer to sleep from Command Prompt/Run menu? I know that almost everything on Windows, like opening any sort of application, can be done from the command prompt or from the Run menu.  How can I put my computer to sleep or shut it down? What is the command for that? Detect the Internet connection is offline? How to detect the Internet connection is offline in JavaScript? How do I tackle this combinatorics problem about married couples around a table? How to configure a firewall that only allows a few webpages and dropbox and U1 services? I am trying to identify a sci-fi movie from the 80's or 90's, with the following parameters:  Setting:    Scenes of a red desert planet   Culture:    Either people roam fairly solo and try to acquire resources to survive, or you live in a weird society where if a stranger is captured he needs to play in a game of fight to the death.  Mobility:      One foil character has a giant battle-bot-looking tank as his form of transportation through the desert. Protagonist has a car that has a plastic half bubble on top to look out from.   Robot:      The protagonist runs around in the beginning of the film with a female robot/android whose face is melted off after it has acid touch its face.(This scene happens next to the protagonist's rover)  Love interest:      Somehow protagonist comes across female protagonist in desert. She smells really bad and is hungry. They sleep outside, and he tells her to sleep away from him. He uses a thermal blanket(the first I ever saw in my life). She wakes up next to him, smelling horrible. He bathes her in some water hole they find(as if water were not scarce and they could just waste water.)   Pupa monsters:      Scene where they are in a building and they are trying to get out. They come across a room that is white, in which multiple giant, white, snot, pupa are hanging securely from the ceiling. Through curiosity, they disturb them, and now they have to get out of that room fast.  Boss Antagonist:      Pervert bionic man, that is actually attached to a giant robotic arm, as only form of movement. He is in black and has a pale bald head as his most human looking part. Solve for $x$ in $6x^2-25x+12+\frac{25}{x}+\frac{6}{x^2}=0$ Do electrons really perform instantaneous quantum leaps? This is not a duplicate, non of the answers gives a clear answer and most of the answers contradict.  There are so many questions about this and so many answers, but none of them says clearly if the electron's change of orbitals as per QM can be expressed at a time component or is measurable (takes time or not), or is instantaneous, or if it is limited by the speed of light or not, so or even say there is no jump at all.  I have read this question:      where Kyle Oman says:     So the answer to how an electron "jumps" between orbitals is actually the same as how it moves around within a single orbital; it just "does". The difference    is that to change orbitals, some property of the electron (one of the ones described by (n,l,m,s)) has to change. This is always accompanied by emission or absorption of a photon (even a spin flip involves a (very low energy) photon).   and where DarenW says:     A long time before the absorption, which for an atom is a few femtoseconds or so, this mix is 100% of the 2s state, and a few femtoseconds or so after the absorption, it's 100% the 3p state. Between, during the absorption process, it's a mix of many orbitals with wildly changing coefficients.      where annav says:     A probability density distribution can be a function of time, depending on the boundary conditions of the problem. There is no "instantaneous" physically, as everything is bounded by the velocity of light. It is the specific example that is missing in your question. If there is time involved in the measurement the probability density may have a time dependence.   and where akhmeteli says:     I would say an electron moves from one state to another over some time period, which is not less than the so called natural line width.     where John Forkosh says:     Note that the the electron is never measured in some intermediate-energy state. It's always measured either low-energy or high-energy, nothing in-between. But the probability of measuring low-or-high slowly and continuously varies from one to the other. So you can't say there's some particular time at which a "jump" occurs. There is no "jump".     where annav says:     If you look at the spectral lines emitted by transiting electrons from one energy level to another, you will see that the lines have a width . This width in principle should be intrinsic and calculable if all the possible potentials that would influence it can be included in the solution of the quantum mechanical state.   Experimentally the energy width can be transformed to a time interval using the Heisneberg Uncertainty of   ΔEΔt>h/2π   So an order of magnitude for the time taken for the transition can be estimated.     So it is very confusing because some of them are saying it is instantaneous, and there is no jump at all. Some are saying it is calculable. Some say it has to do with probabilities, and the electron is in a mixed state (superposition), but when measured it is in a single stable state. Some say it has to do with the speed of light since no information can travel faster, so electrons cannot change orbitals faster then c.  Now I would like to clarify this.  Question:   Do electrons change orbitals as per QM instantaneously? Is this change limited by the speed of light or not? What do I do now if I contributed to Roth IRA in 2012-2013 and my MAGI exceeded the limit? In 2013 I opened a Roth IRA for year 2012, contributing $4000 for year 2012.   In 2014 I contributed $5500 to that same Roth IRA for year 2013.  In 2015, I realized I was not eligible to contribute to a Roth IRA in 2012 and 2013 due to MAGI exceeding the limit. I opened a new account (Traditional IRA), deposited $5500, then immediately did a conversion to a new Roth IRA. (This is the "backdoor" approach as I understand it, is perfectly legal, and what I should have done in previous years). So I believe my Roth IRA account #2 (for tax year 2015) is in good standing  So now, what exactly should I do with the first Roth IRA account that I contributed to (incorrectly) for years 2012-2013? Luckily (?) there is only about $500 of gain in the account at this time.  If I re-characterize it as "Traditional IRA", have I missed the opportunity to do the conversion to Roth IRA for years 2012 and 2013?  Out of curiosity: Had I not caught this error, what would be the implications at Retirement time when I tried to take money out of the Roth IRA? Would the funds be treated as ordinary income (plus penalty?)   Lastly, with all this seemingly "fancy footwork" opening Traditional IRA and converting to Roth IRA, what documents (if any?) do I need to hold on to when it comes time to withdraw from the Roth IRA at retirement time to ensure the tax-free benefit? I need to show the following: $$\lim_{k\rightarrow \infty} \left(1 + \frac{z}{k}\right)^k=e^z$$  For all complex numbers z. I don't know how to start this. Should I use l'Hopitals rule somehow? Evaluate $\lim_{n\rightarrow\infty} \int_0^1 f(x^n) dx$ Is it appropriate to put a comma before "which"? On Server Fault, we were discussing  in chat. There are non-native speakers in the chat and somehow we got on the topic of grammar and proper use of commas.   The sentence of interest:     I have just got a new Ubuntu LAMP VPS server, which I am trying to configure.   Some people thought that the comma was superfluous. Others did not.   When is it appropriate for a comma to preceed the word which, and is the example sentence above correct?    Also, before you vote to close this question as a dupe of , please consider the differences between the two questions and ignore the similarity of the titles. The OP's example sentence was restructured in that question instead of addressing the proper use of commas. Set same icon for all my Forms Is there any way to set the same icon to all my forms without having to change one by one? Something like when you setup GlobalAssemblyInfo for all your projects inside your solution. What is the point of isomorphism concept? 17.10 Super key to open applications I'm writing a sports management simulation game. Like most sport management games, it makes heavy use of statistics. I would like to use real players, teams and league names.  i) Am I running the risk of getting into legal battles if I should use the real names? ii) Also what about team colours and emblems etc?    Update Much thanks for all the input! Help with Spivak Calculus Ch3 Problem 6a Yet again I find myself stuck on a Spivak question. This time it is simply the question that isn't clear to me. It states:  If $x_1, ..., x_n$ are distinct numbers, find a polynomial function $f_i$, of degree $n-1$ which is 1 at $x_i$ and 0 at $x_j$ for $j\neq i$. Hint: the product of all $(x-x_j)$ for $j\neq i$, is 0 at $x_j$ if $j\neq i$. This product is usually denoted by: $$\prod_{\begin{smallmatrix}{j=1}\\ {j\neq i} \end{smallmatrix}}^n(x-x_j)$$  To be honest I don't know where to begin. I understand how to create a polynomial equation for a given set of results but this is quite strange. I'm not sure exactly what the author is expecting.  The answer book shows:  $$f_i(x)={\prod_{\begin{smallmatrix}{j=1}\\ {j\neq i} \end{smallmatrix}}^n(x-x_j)}/{\prod_{\begin{smallmatrix}{j=1}\\ {j\neq i} \end{smallmatrix}}^n(x_i-x_j)}$$  Which I have expanded out just fine but don't know what to do with.