I hope you can help me. I get an NullPointerExeption when I want to Put the NodeList / Node to my Map:  Map &lt;String, NodeList&gt; config = null;   public void loadConfiguration() {     helper helper = new helper();     NodeList nodes = null;     nodes = helper.getXPathFromFile("/root/*", "conf/config.xml");      if (nodes.getLength() &gt; 0) {         for (int i = 0; i &lt; nodes.getLength(); i++) {             String NodeName = nodes.item(i).getNodeName();             NodeList NodeItem = (NodeList) nodes.item(i);             System.out.println(NodeName); // Here the right Name puts out             System.out.println(helper.nodelistToString(NodeItem)); // here right inside XML-Code put out             config.put(NodeName, NodeItem); // Here comes the NullPointerEx.         }     } }
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?
I block everything Google, including Google APIs, as I don't like to to have Google tracking all of my usage on the Internet. Is there any way to use Stack Exchange without Google APIs?  I usually am browsing with Windows 7 and Firefox, but of course not Firefox with StackExchange. How can I deactivate Bluetooth on system startup? How can I deactivate Bluetooth on system startup? Simultaneously merge multiple data.frames in a list When do I use "I" instead of "me?" To show that $2$ | $x^{2n} - x^n$, $n \in \mathbb{Z^+}$ is the following adequate? What are some good ways to showcase someone's portfolio work online? Generalized Euler sum $\sum_{n=1}^\infty \frac{H_n}{n^q}$ I found the following formula   $$\sum_{n=1}^\infty \frac{H_n}{n^q}= \left(1+\frac{q}{2} \right)\zeta(q+1)-\frac{1}{2}\sum_{k=1}^{q-2}\zeta(k+1)\zeta(q-k)$$  and it is cited that Euler proved the formula above , but how ?  Do there exist other proofs ?  Can we have a general formula for the alternating form   $$\sum_{n=1}^\infty (-1)^{n+1}\frac{H_n}{n^q}$$ ${a^2}{\mid}({b^3} + 1)\;$and$\;{b^2}{\mid}({a^3} + 1)$ "Battery Health" in macOS Catalina 10.15.5? I have just installed the macOS Catalina 10.15.5 update on my 11" Mid 2013 MacBook Air. The update is working fine.  The MacBook Air specifications on the Wikipedia page says that this model has a lithium-ion battery, 'tho I haven't unscrewed the case to look. But the new Battery Health controls in System Preferences → Energy Saver don't appear.  Not a lithium-ion battery? Or perhaps other differences in this model prevent Battery Health from showing up? Something else? Prediction in Cox regression I am doing a multivariate Cox regression, I have my significant independent variables and beta values. The model fits to my data very well.   Now, I would like to use my model and predict the survival of a new observation. I am unclear how to do this with a Cox model. In a linear or logistic regression, it would be easy, just put the values of new observation in the regression and multiply them with betas and so I have the prediction of my outcome.  How can I determine my baseline hazard? I need it in addition to computing the prediction.  How is this done in a Cox model? Why isn't smoke flowing with the shape of the domain? I created this Smoke domain.    Then When I added smoke, it didn't stay within the domain, it went through the hole. Align equation left Here is my split equation:  \documentclass{article} \usepackage{amsmath} \begin{document} \begin{equation} \begin{split} a_{ijk} =&amp; \frac {Pr(M_{I} =2  \&amp;  M_J=1 \&amp; M_K =1 | I=i , J=j , K=k)}{Pr (M_I =1 \&amp; M_J =1 \&amp; M_K=1 | I=i , J=j)} \\             =&amp; \frac {\mu_{ijk211}}{\mu_{ijk111}}\\ \end{split} \end{equation} \end{document}   I want to align this equation to the left. Is this possible in an equation environment? Proofs involving limsup and liminf I've been working with proofs involving $\limsup$ and $\liminf$, and I'm a bit confused regarding their general methodology. More specifically, I'm unsure about whether my approach to the following problem makes sense.  Problem. Let $(s_n)$ and $(t_n$) be sequences and suppose that there exists $N_0$ such that $s_n \leq t_n$ for all $n &gt; N_0$. Show that $\liminf s_n \leq \liminf t_n$ and that $\limsup s_n \leq \limsup t_n$.   The way I approached it was as follows:   Let $N &gt; N_0$. Then $\limsup_{N \rightarrow \infty} \{ s_n : n &gt; N \} \leq t_n$ as $s_n \leq t_n$, and $\limsup s_n $ is the largest possible limit of a subsequence of $s_n$. As $t_n : n &gt; N$ is (by definition) less than $\limsup_{N \rightarrow \infty} \{ t_n : n &gt; N \}$, the proof is complete.  I'm pretty sure this is incorrect, however, and I'm generally unclear about the method behind such a proof. Any help is appreciated! Can all real polynomials be factored into quadratic and linear factors? Why isn't temperature frame dependent? Russian SE has a slightly longer and more storied history than Japanese SO Looking for an intuitive explanation why the row rank is equal to the column rank for a matrix Why don't metals bond when touched together? Yesterday, I've listened to a song called "Fear not this night". I find the syntax unusual (as a foreigner, I have never encountered it). Is it the same meaning as "Don't fear this night" ? What's the slight difference between these 2 ?  Thank you for your time. No feedback when comment fails to post on Android 2.3.5 In the mobile theme on Android 2.3.5, comments that do not meet the minimum length will fail to post but no feedback message is displayed to the user.  The submit button changes to its active state, but nothing else happens.