Access Array From another class error in Code
What is a NullPointerException, and how do I fix it?
Undergraduate/High-School-Olympiad Level Introductory Number Theory Books For Self-Learning Does a correlation matrix of two variables always have the same eigenvectors? I had to immediate shut down, and I lost about 20 unsaved tabs, is there any way to recover these? Nginx rewite rules 403 error I am having trouble with converting .htaccess files to nginx. I have 3 .htaccess files. The first .htaccess file is located in the document root and is as follows:  Options +FollowSymLinks RewriteEngine On RewriteRule ^img-(.*)\.html img.php?id=$1 [L] RewriteRule ^slide-(.*)\.html slider.php?id=$1 [L] RewriteRule ^page-(.*)\.html page.php?name=$1 [L] RewriteRule ^contact\.html$ contact.php [QSA,L,NC]   The second .htaccess file is located in a folder called upload:  RewriteEngine On RewriteCond %{HTTP_REFERER} !^http://(.+\.)?foo\.com/ [NC] RewriteCond %{HTTP_REFERER} !^$ RewriteRule .*\.(jpe?g|gif|bmp|png)$ nohotlink.gif [L] &lt;Files ~ "\.(php|sql|php3|php4|phtml|pl|py|jsp|asp|htm|shtml|sh|cgi)$"&gt;   order allow,deny   deny from all &lt;/Files&gt;   And the third and final .htaccess file is found in a subdirectory of the upload folder named "small":  RewriteEngine Off   Now I have created a folder in /etc/nginx called includes and made 3 seperate .access files with these rewrite rules:  For the first .htaccess file located in the document root directory I have created an file in /etc/nginx/includes called root.access. In this file I have:  # nginx configuration   location /img {  rewrite ^/img-(.*)\.html /img.php?id=$1 break;  }  location /slide {      rewrite ^/slide-(.*)\.html /slider.php?id=$1 break;  }  location /page {      rewrite ^/page-(.*)\.html /page.php?name=$1 break;  }  location /contact {      rewrite ^/contact\.html$ /contact.php break;  }   For the second file located in the "upload" folder I have crated a file in /etc/nginx/includes called upload.access. This file contains the following:  # nginx configuration   location /upload {  if ($http_referer !~ "^http://(.+\.)?foo\.com/"){  rewrite .*\.(jpe?g|gif|bmp|png)$ /nohotlink.gif break;  }  }  location ~ \.(php|sql|php3|php4|phtml|pl|py|jsp|asp|htm|shtml|sh|cgi)$ {  deny all;  }   And for the third and final file I have created a file in /etc/nginx/includes names small.access. The contents of this file are as follows:  # nginx configuration   location /upload/small {  }   In the server block configuration file I have:   location / {               try_files $uri $uri/ /index.php;               include /etc/nginx/includes/root.access;      }   location /upload {               include /etc/nginx/includes/upload.access;      }   location /upload/small {               include /etc/nginx/includes/small.access;      }   Now with this configuration when trying the site I receive 403 errors. Nginx error log reports:  [error] 18156#0: *7 access forbidden by rule, client: 111.**.**.**, server: foo.com, request: "POST /upload.php HTTP/1.1", host: "foo.com", referrer: "http://foo.com/"   Now under apache everything works no problems. But I can not see why I am getting 403 errors. I am also worried that the rewrite rules as I have stated them, beyond the 403 error will not function properly at all. Can anyone help me with this? I can not see what is wrong here. What is the result of $ \lim_{n \to \infty} \frac{ \sum^n_{i=1} i^k}{n^{k+1}},\ k \in \mathbb{R} $ and why? How do I disable this:    after taking screenshot? Let $R$ be a ring, where $a^{3} = a$ for all $a\in R$. Prove that $R$ must be a commutative ring. How to boot from a USB drive in VirtualBox? The question is simple and straight forward:  How to boot from an USB drive in VirtualBox?  EDIT:  I have attached usb to VirtualBox as shown in the screenshot.    But it is not possible to boot from an USB drive even when attached  .  So I would like to know if there is any other possiblity to boot from an USB drive? Prove $a^\alpha b^{1-\alpha} \le \alpha a + (1 - \alpha)b, \; a,b > 0,\; 0 < \alpha < 1$ I have no idea how to do this. Any help would be appreciated. The chapter I'm on is about differentiation and the mean value theorem.  Prove $a^\alpha b^{1-\alpha} \le \alpha a + (1 - \alpha)b, \; a,b &gt; 0,\; 0 &lt; \alpha &lt; 1$ From : In calculus and other branches of mathematical analysis, an indeterminate form is an algebraic expression obtained in the context of limits. Limits involving algebraic operations are often performed by replacing subexpressions by their limits; if the expression obtained after this substitution does not give enough information to determine the original limit, it is known as an indeterminate form.    The indeterminate forms include $0^{0},\frac{0}{0},(\infty - \infty),1^{\infty}, \ \text{etc}\cdots$   My question is can anyone give me a nice explanation of why $1^{\infty}$ is considered to be an indeterminate form? Because, i don't see any justification of this fact. I am still perplexed. Why do some questions not start with an auxiliary verb? When I learned English, my teachers told me that all questions must have an auxiliary verb at the beginning, just like Are you mad? or Is she playing? do.  But when watching some movies or talking with people who speak English, they just ask using things like You mad? and She’s playing?   Of course, the kind of intonation let me know they are asking a question, but why this happen? Sample query/DDL for producing page locks on a clustered index in SQL Server (without hints) We currently have some indexes where ALLOW_PAGELOCKS is set to off. This presumably was done in order to reduce deadlocks. However I doubt that it would really had an effect back then.   Now I am trying to understand WHEN SQL Server actually chooses to start locking pages rather than keys in a clustered index. I asked Jonathan Keyhaisas recently and he told me that this could happen if I am touching rows on several subsequent pages. However I didn't manage to get any exclusive page locks by updating rows in a clustered index with a sample query.   Could you help me understand page locks better with a sample query and table? I am running SQL Server 2008 SP4.  Thanks in advance  Martin Why is echo a shell built in command? $ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat   Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons? I got my dad a Logitech LS21 system for Christmas. It's a 2.1 system, but it's recognized in Windows 8 as a 2.0 system (it says there is no subwoofer connected).    How would I go about getting the sub recognized?  It plays some sound now, but it's so quiet you can't hear it without putting your ear right next to it. How to configure preferred network for internet? I am connected to a LAN network and wireless network. Both provide access to internet.  Sometimes when the internet on LAN is not working, the browser simply throws an exception instead of switching to Wireless. (Wireless is on and local peer computers on wireless are connectible).  Apparently it is giving more priority to LAN. How do I increase the priority of Wireless or set it as an automatic fall back? Single-word synonym for "immensely valuable"? I am looking for some (may be rarely know to nonnative English speakers) synonyms for  "immensely valuable" or "extremely valuable". Will reformatting my hard drive fix bad sectors on it? NVMe PCIe x4 SSD on M.2 PCIe x2 slot? i'm about to get a new SSD for my PC, and before spending the money i have some doubts about my decision i would like to clarify First, my mobo is a B450 Aorus Pro Wifi, it has 2 M.2 slots, one of them full length (22110) compatible with PCIe 3.0 x4 and the other one standard length (2280) and support only for PCIe 3.0 x2 About the drive, i'm aiming for a 1tb XPG SX8200 Pro , which is a PCIe 3.0x4 SSD My first M.2 slot is already taken by the main SSD, which i use for the OS and other stuff, i can't really use it. Will a PCIe x4 SSD work on a PCIe x2 slot? How much performance will be lost if it does? Will it be worth it? Several lines of formulas to the left of one curly brace pointing to equation number How to make several lines of equations under one curly brace from the left side, such that it point to a reference number.  Now I do something like this:  \begin{align} \left. \begin{array}{ll} a = b + c \\ &amp; \dots  \\ a = b + c \\ &amp; \dots  \\ a = b + c  \end{array} \right\} \label{formulas}\\ \end{align}   But equation number appears in the bottom of curly brace. Are the Night's Watch still required?