I am a beginner in Spring Security, so I coded a controller with two methods like this :  @RestController public class EtudiantRestService {      @Autowired     private EtudiantReository etudiantReository;      @Secured(value = {"ROLE_ADMIN","ROLE_SCOLARITE"})     @RequestMapping(value = "/saveEtudiant",method = RequestMethod.GET)     private Etudiant saveEtudiant(Etudiant etudiant){         System.out.println(etudiant.getNom());         System.out.println(etudiant.getPrenom());         return etudiantReository.save(etudiant);     }      @Secured(value = {"ROLE_ADMIN","ROLE_SCOLARITE","ROLE_PROF","ROLE_ETUDIANT"})     @RequestMapping(value = "/etudiants")     public Page&lt;Etudiant&gt; listEtudiant(int page,int size){         return etudiantReository.findAll(new PageRequest(page,size));     } }   The configurations of spring security is :  @Configuration @EnableWebSecurity @EnableGlobalMethodSecurity(securedEnabled = true) public class SecurityConfig extends WebSecurityConfigurerAdapter {      @Autowired     public void globalConfig(AuthenticationManagerBuilder auth) throws Exception{         // Type d'authentification (Base de données, LDAP, Mémoire)         auth.inMemoryAuthentication()                 .withUser("admin").password("123456")                 .roles("ADMIN","PROF");         auth.inMemoryAuthentication()                 .withUser("prof").password("123456")                 .roles("PROF");         auth.inMemoryAuthentication()                 .withUser("etudiant1").password("123456")                 .roles("ETUDIANT");         auth.inMemoryAuthentication()                 .withUser("scolaritel").password("123456")                 .roles("SCOLARITE");     }      @Override     protected void configure(HttpSecurity http) throws Exception {         // Pattern builder         http             .csrf().disable()             .authorizeRequests()                 .anyRequest()                     .authenticated()                         .and()             .formLogin()                 .loginPage("/login")                 .permitAll()             .defaultSuccessUrl("/index.html")             .failureUrl("/error.html");     } }   Mon contrôleur fonctionne bien mais lorsque j'utilise la annotation @Secured et j'authentifier j'avais l'exception :  java.lang.NullPointerException: null     at com.upsys.sec.service.EtudiantRestService.saveEtudiant(EtudiantRestService.java:29) ~[classes/:na]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_102]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_102]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_102]     at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_102]     at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]     at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]     at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]     at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapt     ....
What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?
Numbered list in rows in tables I want to have numbered listing in each row, I've tried with \rownumber, but it doesn't work. I wrote a number at the beginning, but Could it be automatically?  Can you help me? This is my code:  \documentclass[10pt, a4paper]{article}  \usepackage{fontspec} \setmainfont{Arial}  \usepackage{color, colortbl} \definecolor{Gray}{gray}{0.9}  \begin{document}  \begin{table}[h!] \tiny \begin{tabular}{|&gt;{\raggedright\arraybackslash}m{30mm}|&gt; {\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|&gt;{\raggedright\arraybackslash}m{5mm}|} \hline \multicolumn{1}{|&gt;{\centering\arraybackslash}m{30mm}|}{\rowcolor{Gray}\textbf{Text}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 1}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 2}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 3}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 4}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 5}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 6}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 7}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 8}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 9}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 10}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 11}} &amp; \multicolumn{1}{|&gt;{\centering\arraybackslash}m{5mm}|}{\textbf{Sem 12}}\\ \hline 1. Text text text text text text text text text text text text text &amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;\\\hline 2. Text text text text text text text text text text text text text &amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;\\\hline 3. Text text text text text text text text text text text text text  &amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;\\\hline 4. Text text text text text text text text text text text text text &amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;\\\hline  \hline \end{tabular} \end{table}  \end{document} iPhone 4 water damage - how to recover data? Slow leak on front cruiser tire I ride my cruiser to the supermarket and back, using either a trailer or a basket over the front wheel for carrying groceries. The bike has developed a persistent slow leak on the front wheel, and I've replaced the tube without it helping. I can't see anything puncturing the tire, and the spokes aren't poking through the rim tape that I can see.   These are 26" wheels with low pressure (around 40 - 50 psi). What else can I look for that might be causing this? I have read several introductory texts about LSTM online, but none of them give a rigorously mathematical explanation of what the model actually does. For instance, why does the forget gate forget any more than any of the other gates in the LSTM unit?  Which papers and/or books should I read if I want to get a deeper understanding of LSTM? Does increasing voltage increase the torque of a brushless motor? 1.) I have a brushless motor with testing data at 12V. I want to know if I increase the voltage supply, will this increase the torque?   In my research I keep seeing "current controls torque, and voltage controls speed." But that doesn't seem quite right. Let's say I have a theoretical electrically powered unicycle that is weighted. With a 5V source and 2A, the motor can't move the unicycle. But now I increase the voltage to 10V, and I believe current will also increase by x2 if resistance is constant (V = IR). So now the torque increases and the unicycle can move itself. It that a reasonable sequence of events? Can I say that increasing voltage increases torque?   2.) A similar question: if P = VI = tau*omega, then P/omega = tau, so:  2*(P/omega) = 2*tau, which means increasing power will increase torque, correct? And since P = VI, increasing V will increase P, which will in turn increase torque. Is this accurate at all? Switching to HTTPS - redirect question If $\mathrm{Tr}(A)=0$ then $T=R^{-1}AR$ has all entries on its main diagonal equal to $0$ I was solving a few problems from a textbook and I came across this one:     Find the tangent lines to the graph of $x^2+4y^2 = 36$ that go through   the point $P=(12,3)$   I could find the tangency points $$ but my solution was completely messy (I had four equations that I had to go back-and-forth with.  Is there an elegant/simple solution to that?  Tangency points:  $$P_1 = (0,3)$$ $$P_2 = \left( \frac{24}{5} , 3-\frac{24}{5} \right)$$ What's wrong with this .desktop file? Black screen after suspend-after moving to the nvidia official drivers (not priority) So, when I used the priority drivers, the suspend worked normal. But the official drivers works better, so I installed the official driver. Then suspend won't work.  Should I change any text/documants to make it work? Any solution will be aprreciated, thanks you all! How to add a custom icon or symbol to a flag link? I'm working on a 'sample request' implementation for a commerce site using , , sessions and a little custom code.  I'd like to add an icon or a symbol to let people know that an item they are viewing has been flagged.  I'm not sure exactly how to approach this, I can imagine perhaps adding a conditional field that displays an image or check box that is then changed by  or ajax, or perhaps something more complicated in JavaScript?  It could really be as simple as adding a checkbox that is checked or unchecked as the flag link is clicked or maybe even changing the css/html on click to be identified as marked.   Anyway, grateful for any advice here. Can I travel to the UK unaccompanied on an accompanied child visa now that I am over 18? Delete all but top n from database table in SQL What's the best way to delete all rows from a table in sql but to keep n number of rows on the top? Let $f(x)$ and $g(x)$ be two continuous functions on $[0,1]$ and  $$\int_{0}^{1}f(x) dx= \int_{0}^{1}g(x)dx = 1$$   Show that there exist  $[a,b]\subset [0,1]$, such that  $$\int_{a}^{b}f(x) dx= \int_{a}^{b}g(x)dx = \frac{1}{2} $$  The question can be solved by considering the fundamental group of $S^1$, now I am wondering if we can solve it by real-analysis.  Here is the topological solution:  Assume that for any $[a,b]\subset[0,1]$, we always have  $$(\int_{a}^{b}f(x) dx\neq \frac{1}{2}) \quad \vee \quad(\int_{a}^{b}g(x)dx \neq \frac{1}{2}) $$ Consider mapping $$\phi:D\rightarrow\mathbb{E}^2\backslash\{(\frac{1}{2},\frac{1}{2})\},\,\,(x,y)\mapsto(\int_{y}^{x}f(t) dt,\int_{y}^{x}g(t) dt)$$ where $D=\{(x,y)|0\leq x\leq y\leq 1\}$.  Let $a$ be path from $(0,0)$ to $(0,1) $in $D$ and $b$ be path from $(0,1)$ to $(1,1) $in $D$, then $ab$ is a path from $(0,0)$ to $(1,1) $in $D$ and $$\phi\circ (ab):[0,1]\rightarrow\mathbb{E}^2\backslash\{(\frac{1}{2},\frac{1}{2})\} $$ Notice that $$(\phi\circ (ab))(0)=(\phi\circ (ab))(1)=(0,0)$$  so $\phi\circ (ab)$ is a loop based on $(0,0)$ in $\mathbb{E}^2\backslash\{(\frac{1}{2},\frac{1}{2})\}$.  For any $t\in [0,\frac{1}{2}]$, it's not hard to get that $$(\phi\circ (ab))(t+\frac{1}{2})=(1,1)-(\phi\circ (ab))(t)$$ is equivalent to $$(\phi\circ (ab))(t+\frac{1}{2})-(\frac{1}{2},\frac{1}{2})=-((\phi\circ (ab))(t)-(\frac{1}{2},\frac{1}{2}))$$  Define retraction  $$r:\mathbb{E}^2\backslash\{(\frac{1}{2},\frac{1}{2})\}\rightarrow S^1,\quad (x,y)\rightarrow\ \frac{(x,y)-(\frac{1}{2},\frac{1}{2})}{||(x,y)-(\frac{1}{2},\frac{1}{2})||}$$  Then $r\circ \phi\circ (ab)$ is a loop on $S^1$, such that $$(r\circ \phi\circ (ab))(t+\frac{1}{2})=-(r\circ \phi\circ (ab))(t),\quad\forall t\in [0,\frac{1}{2}]$$  So $&lt;r\circ \phi\circ (ab)&gt;$ is not trivial in $\pi_1(S^1)$.   However, $ab$ is path homotopic to $c$ in $D$, where $c$ is the path between $(0,0)$ and $(1,1)$ in $D$. In this case, $r\circ \phi\circ (ab)$ is a point-path in $S^1$ by $$(\phi\circ c)(t)=\phi(t,t)\equiv (0,0)$$  which leads to contradiction. How to interpret a QQ plot I am working with a small dataset (21 observations) and have the following normal QQ plot in R:     Seeing that the plot does not support normality, what could I infer about the underlying distribution? It seems to me that a distribution more skewed to the right would be a better fit, is that right? Also, what other conclusions can we draw from the data? Often in fantasies involving magic casting spells requires a certain physical or mental toll on the caster. I don't recall any mention of spells being physically or mentally taxing in the Harry Potter universe.  Does this mean they can cast an unlimited number of spells in a given day without any negative effect to themselves? I don't know why but now, when i go in material preview or rendered (in solid mode it works fine), my object is entirely gray, or invisible idk, because it has the same color of the background. I've been working for days on this project without having this issue, it suddenly showed up. I tried opening other old projects and suddenly they all do the same so i guess it is some blender program setting that applies for all the projects, but idk how it happened cuz i didn't change anything :/, anyone got any tips? Calculate battery life I would like to know how to calculate battery life when using an LED strip. The LED strip is powered by 8 AA batteries in series. LED Current Draw = 260 mA. LED power consumption: 3.1 W. LED Operating Voltage range: 9-14.8 VDC. Please see attached images for battery datasheet.  This is my calculation, but I'm not sure if it's correct:     Battery Life = (Battery Capacity)/(Load Current) = 2000 mAh /260 mA = 7.7 Hours   This is for one battery, and the lights are powered by 8 batteries, so is the total battery life = (7.7)x(8) = 61.6 hours ? Given, $\{x_n\}$ and $\{y_n\}$ are two real valued sequences such that $\lim_{n\to\infty} (x_{n}^{3}-y_{n}^{3})=0 $ Then is it always true that $\lim_{n\to\infty} (x_n-y_n) =0 $ ? I tried by splitting $ (x_{n}^{3}-y_{n}^{3}) $, but that didn't help as $\lim_{n\to \infty} (x_{n}^{2}+x_{n}y_{n}+y_{n}^{2}) $ can be $0$ or non zero or doesn't exist. Why is my iron ore disappearing when mined with a wooden pickaxe? I am on Peaceful mode, and I am using a Wooden Pickaxe. Whenever I mine Iron Ore, it just disappears. Am I doing something wrong?