java difference between "ClassName className" and "ClassName className = new Class(property)
What is a NullPointerException, and how do I fix it?
Moon photography Hi I am a photography hoobyist. At the moment I am using a Nikon D3100 with the standard kit lens (18-55mm). I am interested in taking photos of the moon. I am debating whether to buy a 55-200mm lens or a 55-300mm lens. Which one would be better?  P.S I am on a tight budget and I am looking for a lens for personal use, not commercial.  Would appreciate any answers!  Thank you! Why does the buffer take up whole screen? I am trying to create buffers around the Hurricane Sandy path I created in QGIS (points are lat/long).   I have both points from each day she was tracted and the line I created from it with Points2One.   When I go to make buffers around either the line or the points, the buffer takes up the whole screen. Its all just one color.   I have made buffers before but from data I did not create.   Right now all of my projections are set to WGS 84 EPSG 4326. How far does a rogue move when dashing twice using Cunning Action? A rogue receives a bonus Cunning Action, and one option is to Dash. My understanding is a Dash allows a player to move up to twice his speed for his turn.  If a rogue is using a regular action to Dash (hence, is already dashing) can he also use his cunning action as a bonus to Dash again — effectively moving 4 times normal speed in a turn? Difference between systemctl and service commands systemd gives us the systemctl commands suite which is mostly used to enable services to start at boot time. We can also start, stop, reload, restart and check status of services with the help of systemctl.  We can do, for example, sudo systemctl enable service_name, and service_name will automatically start at boot time. We can also disable services not to start at boot time.  Is the only difference between the service and systemctl commands that systemctl can be used to enable the start of services at run time? Can we use systemctl on any service? What other significant differences are there? 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. Prove: $\lim\limits_{n \to \infty} \int_{0}^{\sqrt n}(1-\frac{x^2}{n})^ndx=\int_{0}^{\infty} e^{-x^2}dx$ I'd like your help with the following claim to prove:  $$\lim_{n \to \infty} \int_{0}^{\sqrt n}\left(1-\frac{x^2}{n}\right)^ndx=\int_{0}^{\infty} e^{-x^2}dx.$$  I think I should use the claim:     Let $a,b$ two real numbers and $\{f_n\}$ a sequence of continuous functions on $\left[a,b\right]$  which converges uniformly to $f$ on $[a,b]$. Then    $$\lim_{n\to\infty}\int_a^bf_n(t)dt=\int_a^bf(t)dt.$$   But for this, I must prove that $(1-\frac{x^2}{n})^n$ uniformly converges to $e^{-x^2}$.  How do I do that? One of the hardest and trickiest things to do is to prove this uniformly converges.. every function has its own way. I believe that the more examples I'll see the easiest it will be. Thanks again! How to show $\sum_{i=1}^{n} \binom{i}{2}=\binom{n+1}{3}$? Show that $\,\displaystyle\sum_{i=1}^{n} \binom{i}{2}=\binom{n+1}{3}$.   I'm thinking right now (though not getting anywhere with it) that I want to expand out the summation portion to $i!/2!(i-2)!$ and simplify from there? Not sure if that will help, not to mention if I put $1$ in for $i$ I get $1/-2$ which I don't think is right.   Anyone care to shed some light on the subject?   Thanks. Are there any places to leave luggage in Brussels, for short and/or long periods of time? Consecutive spoiler blocks (>!) are shown as blockquotes The markdown &gt;! a  &gt;! b  &gt;! c  Will be shown as a blockquote with ! in front of it:   a    b    c  Instead of a spoiler for 3 paragraphs (or 3 spoiler blocks, whatever). What is the best way to give a C# auto-property an initial value? Mac OS X 10.6 executable not found without full path I just installed Apache via MacPorts. It seems that my Mac was absolutely confused about which version of the Apache executables to run.  After moving the Apache executables that ship with the Mac to a directory that is not listed in the PATH variable, trying to run the httpd built by MacPorts fails even though the correct directory (/opt/local/apache2/bin) is listed in the PATH variable.  If I navigate to the directory /opt/local/apache2/bin and type the command httpd I still get the error message     -bash: httpd: command not found   If I type the command with the full path /opt/local/apache2/bin/httpd it works fine.  I've run the command alias to see if something was clashing but the only thing listed is:  alias wget='curl -O'   How do I find what is intercepting the command and preventing the executable being found in the directory, even when I'm inside the same directory?  By the way, the httpd file is executable:  -rwxr-xr-x  1 root      admin  442496  9 May  2012 httpd Detect edits to add [SOLVED] or [RESOLVED] to the title and direct the user to add an answer Users often ask questions that they answer for themselves. Good for them. And good for us.  Symptom  The correct procedure seems to be:   Write new answer to own question  Wait two days Accept own answer   The incorrect, but fairly popular, procedure seems to be:   Edit the question to include the solution Put "[SOLVED] or [RESOLVED]" in the title   Proposed solution  Users should be warned when using the word "solved", delimited in any way, in a question title. This could be "[SOLVED]", "(solved)", or even "Solved - ". I imagine this:   The user tries to submit an edit that adds "solved" such that the word "solved is delimited. The user is brought to a warning page. If the only edit to the question was appending new lines (such as adding an "edit:" paragraph), that edit is copied into a text box The page mentioned in 1 is shown as follows:     $StackSite marks questions as answered when you accept an answer. You can accept an answer by clicking the green check mark next to that answer. There's no need to put "SOLVED" or "RESOLVED" in the title!      Are you answering your own question?      Create a proper answer to your question:         Move your edit to a new answer.   Write your answer.   If nobody writes a more correct or thorough answer after two days, come back and accept your answer.         By doing this, you remove your question from the Unanswered Questions list. You also allow other $StackSite users to vote your answer up. Thanks for helping out!      TEXT BOX WITH EDITS GOES HERE, FOLLOWED BY "POST YOUR ANSWER" BUTTON      Not answering your own question?      Sorry for slowing you down.      OVERVIEW OF EDIT, FOLLOWED BY "SAVE EDITS" BUTTON    Discussion  This would likely reduce the number of [RE]SOLVED questions that appear. However, it's unclear whether this should be a community moderation issue or a feature request issue. The increased engineering work required in building in the interstitial page is probably quite nontrivial, whereas this type of question makes up well under .  Note: Google also provides a . A list of inconveniences between quantum mechanics and (general) relativity? It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them?  E.g. relativity theory uses a space-time continuum, while quantum theory uses discrete states.  I am not merely looking for a solution or rebuttal of such opposites, more for a survey of the field out of interest. How do I remap the Caps Lock and Ctrl keys? I'd like to remap my keys such that Ctrl behaves as the Caps Lock key and vice-versa. Also, if possible I'd like the settings to be available only within the currently logged-in user. How can I achieve this?  I'm a vim user, unlike the other people who use this machine, so I'd like those settings only for my account. Basically I have a setup like the following:  Array (  [0] =&gt; Array ( [0] =&gt; stdClass Object ( [nid] =&gt; 1 [title] =&gt; title1 [uid] =&gt; 1 [parent] =&gt; 0 [weight] =&gt; -15 [name] =&gt; name1 [value] =&gt; 0 )                [1] =&gt; stdClass Object ( [nid] =&gt; 2 [title] =&gt; title2 [uid] =&gt; 1 [parent] =&gt; 0 [weight] =&gt; -7 [name] =&gt; name2 [value] =&gt; 100 )                [2] =&gt; stdClass Object ( [nid] =&gt; 3 [title] =&gt; title3 [uid] =&gt; 2 [parent] =&gt; 0 [weight] =&gt; -1 [name] =&gt; name3 [value] =&gt; 0 )                [3] =&gt; stdClass Object ( [nid] =&gt; 4 [title] =&gt; title4 [uid] =&gt; 2 [parent] =&gt; 0 [weight] =&gt; 1 [name] =&gt; name4 [value] =&gt; 80 )               )   )   What I need is a way to sort all the arrays inside the parent array by the [value] key in the Object. I've been trying for about 2 days now with usort and different methods but I just can't seem to get my head around it. The [value] key will range anywhere from 0 to 100 and I need all of the arrays sorted in decreasing order (IE: 100 down to 0). When are stopovers permitted on Japan Railways (JR) trains? How to insert strings containing slashes with sed? Proving the identity functions is continuous iff $\tau_1\supseteq\tau_2$ Exercise: Let $\tau_1$ and $\tau_2$ be two topological spaces on a  set $X$. Then $\tau_1$ is said to be a finer topology than $\tau_2$ if $\tau_1\supseteq\tau_2$. Prove the identity function $f:(X,\tau_1)\to (X,\tau_2)$ is continuous if and only if $\tau_1$ is a finer topology than $\tau_2$.  Attempted proof: Let $A\in\tau_1$. If $f$ is continuous then $\exists B\in\tau_2$ such $f(A)\subset B\implies A\subset B$ for any $A\in\tau_1$ such that all open sets of $\tau_1$ are open sets of $\tau_2$ hence $\tau_1\supseteq \tau_2$. If $\tau_1$ is a finer topology than $\tau_2$, for any $B\in\tau_2\implies B\in\tau_1$ which implies that $f^{-1}(B)=B$, then $B\in\tau_1$ which proves $f$ to be continuous. Questions: Is my proof right? If not. What is wrong? What are alternatives? Thanks in advance! An entire function whose real part is bounded must be constant. Greets  This is exercise 15.d chapter 3 of Stein &amp; Shakarchi's "Complex Analysis", they hint: "Use the maximum modulus principle", but I didn't see how to do the exercise with this hint rightaway, instead I knew how to do it with the Casorati-Weiestrass Theorem, here is my answer:  Define $g(z)=f(1/z)$ for $z\neq{0}$,then by the hypothesis we must have that for any $\epsilon&gt;0$ $g(D_{\epsilon&gt;0}(0)-\{0\})$ is not dense in $\mathbb{C}$, then the singularity at $0$ of $g$ is not essential, this implies $f$ must be a polynomial, but if $f$ is a non-constant polynomial, it is easy to see that its real part must be unbounded, so $f$ must be constant.  I would like to know an answer with the the maximum modulus principle.  Thanks How does the double strike mechanic interact with other mechanics like lifelink or trample? I understand that the double strike mechanic allows a creature to attack in both a first strike combat damage step and a normal combat damage step.  It's clear that when a creature with no other abilities aside from double strike is blocked that even if the defender has lethal damage marked in the first strike step that the additional damage does not carry forward to the player.  How does this view of double strike change with relation to trample and lifelink?  I believe the correct interpretations are (not accounting for other effects or abilities) that 2 times the attacker's power is marked as damage on the defender.  For trample this amount is reduced by the defender's toughness and additional damage carries forward as normal.  Similarly for lifelink the active player gains life equal to 2 times the attacker's power.  Thus a 10/10 trampling double striking life linker blocked by a 1/1 creature would deal 19 points of trample damage and the active player would gain 20 life.  Is this interpretation correct?