Error Exception in thread "main" java.lang.NullPointerException with .xlsx file
What is a NullPointerException, and how do I fix it?
What is the point of the Red Thread/Tape around evidence or newspaper clippings? I have seen in a lot-lot of movies that the person who searches for a crime or another person creates a web of red tape or wire around the newspapers and evidence he acquires. I never guessed its usefulness and am therefore asking why do they do it?  Here is an illustration I created: Explanation of Spikes in training loss vs. iterations with Adam Optimizer I am training a neural network using i) SGD and ii) Adam Optimizer. When using normal SGD, I get a smooth training loss vs. iteration curve as seen below (the red one). However, when I used the Adam Optimizer, the training loss curve has some spikes. What's the explanation of these spikes?   Model Details:  14 input nodes -> 2 hidden layers (100 -> 40 units) -> 4 output units  I am using default parameters for Adam beta_1 = 0.9, beta_2 = 0.999, epsilon = 1e-8 and a batch_size = 32.  i) With SGD  ii) With Adam Why does "ls -all" show time for some files but only year for others? If you issue ls -all command some files or directories have the year and some have the time? Why do some show the year while others show the time? Is the time representative of the time the file was created? I found this animal, which I suspect it's an insect, on the floor of a kitchen in Spain some days ago. It's about 8-10 mm long. I don't think I've ever seen it before. What is it? Google Analytics: How can I track between http:// and https:// profiles for a domain? MySQL: How to retrieve a random row or multiple random rows? Flag apron shows superfluous closing anchor tag I awoke this morning to a spam flag on a site I moderate, and noticed this when I went to read the post.    Notice answered&lt;/a&gt;, which I imagine isn't meant to have the &lt;/a&gt; there.  I also confirmed that this displays asked&lt;/a&gt; for other types of flags (namely, closed without comment).   I looked around for a duplicate of this but can't seem to find it, so maybe it's a recent change? Minecraft jar not marked as executable Unable to locate package There are many  about Unable to locate package.  For example : if user try to install package by using apt-get then the following error shown. (Here package is used only as example for displaying error message):  sudo apt-get install package Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package package   What does this error mean? How do I solve it?    provided General solution to understand and how to solve such type of error (which is helpful for new users that may unaware of repository-apt install mechanism)  Note : For resolving unmet-dependencies, visit: . Display data from geoserver on click map with openlayers I tried to display data with popup from Geoserver or Postgres to my map, but it dosen't work at all. Can anyone please help me? I used this code:      function Info(e)          {                 if (e.features &amp;&amp; e.features.length)                  {                      //console.log(e.features[0].attributes);                     var popupId = e.xy.x + "," + e.xy.y;                     var popup = popups[popupId];                     if (!popup || !popup.map) {                     popup = new OpenLayers.Popup.FramedCloud(                     popupId,                      map.getLonLatFromPixel(e.xy),                     null,                     " ",                     null,                     true,                     function(e) {                         delete popups[this.id];                         this.hide();                         OpenLayers.Event.stop(e);                     }                 );                 popups[popupId] = popup;                 map.addPopup(popup, true);                 }                popup.setContentHTML(popup.contentHTML + "nom_user:" +e.features[0].attributes.nomservice +" region_user :"+ e.features[0].attributes.region);             popup.show();                                    }       selectcltr = {         click: new OpenLayers.Control.WMSGetFeatureInfo({             url: 'http://localhost/geoserver/wms',              title: 'Identify features by clicking',             layers: [ser],             queryVisible: true         }),         hover: new OpenLayers.Control.WMSGetFeatureInfo({             url: 'http://localhost/geoserver/wms',              title: 'Identify features by clicking',             layers: [ser],             hover: true,             // defining a custom format options here             formatOptions: {                 typeName: 'projet',                  featureNS: 'http://www.openplans.org/topp'             },             queryVisible: true         })     } How to combine array items with string substitution? Want to install Ubuntu on Chromebook Should an adverb go before or after a verb? For example:     The word rarely turns up outside of those contexts.      The word turns up rarely outside of those contexts.   Which one is correct and why? Recursively list files with file names, folder names and permission Convergence in Distribution in Order Statistics Let $X_1, X_2, \ldots$ be iid from Exp$(\theta)$ with density function $f(x) = \frac{1}{\theta}e^{-\frac{x}{\theta}}$. (a) Find the limiting distribution of $M_n = Y_1 - \theta\ln(n)$ and $T_n = nY_n$, where $Y_1$ and $Y_n$ represent the first and last order statistics (among $n$ observations) respectively. Answer: I have obtained the CDF of X to be: $$F_x(x) = 1 - e^{-\frac{x}{\theta}}$$ the CDF of $Y_1$ to be: $$F_{Y_1} = 1 = e^{-\frac{xn}{\theta}}$$ the CDF of $M_n$ to be: $$F_{M_n}(x) = \left[1 - \frac{1}{n}e^{-\frac{x}{\theta}}\right]^n$$ with limiting distribution $$e^{-e^{-\frac{x}{\theta}}}$$ the CDF of $T_n$ to be: $$F_{T_n}(x) = 1 - e^{-\frac{x}{\theta}}$$ which is also the limiting distribution. (b) Show that $M_n$ and $T_n$ are asymptotically independent. Answer: I've tried finding the joint PDF for ordered statistics by using the equation $$g_{ij}(y_i, y_j) = \frac{n!}{(i - 1)!(j - i - 1)!(n - j)!}[F(y_i)]^{i - 1}[F(y_j) - F(y_i)]^{j - i - 1}[1 - F(y_j)]^{n - j}f(y_i)f(y_j)$$ however, it is a mess based on my CDFs. Any suggestions on a different approach? How can I modify the advanced search form when my hook runs too early? Have a look at   One of the bolds works, and the other one just turns up as ** in the actual post.  This is the string that isn't working: **x**ml n**ib**  Which renders as: xml nib Please warn about exceeding 50 question limit prior to asking a new question This is difficult for me to explain, but how do I put words over a symbol? For instance, I want to add words over an equal sign. Anyone know the command/syntax for that?  Also adding ^ doesn't cut it..., I want the text to appear ON TOP. Brand new laptop, two years in storage, will the battery be ok? I have an opportunity to buy a brand new (sealed box) EliteBook 8470p laptop for a good price.  The date of manufacture goes back to around March 2013, which is bang on two years ago.  Given that it's been two years, what state will the supplied Lithium-Ion battery be in? Still usable?