Null pointer Exception Error Using getters and setters
What is a NullPointerException, and how do I fix it?
A formula for the roots of a solvable polynomial Let $F$ be a field and $p(x)\in F[x]$ a separable polynomial, denote $K$ as the splitting field of $p$ and assume that $K/F$ is Galois with a solvable Galois group.  I don't understand if this imply of any formula (in radicals) for the roots of $p$ (however, I do understand how a formula would imply that $p$ is solvable by roots).  Is there some kind of a way to obtain the roots of a solvable polynomial ? cant install or remove anything on 18.04 cause of DPKG error Word or Phrase for "Easily Swayed" What word or phrase best communicates the idea that a human (or other sentient being) is easily swayed, particularly between moral good and evil? Words I have found that are close are:   Impressionable - Easily influenced because of a lack of critical ability.   Implies that the subject lacks critical skills, and misses the concept of good and evil.  Gullible - Easily persuaded to believe something   Misses the concept of good and evil    I created a typical angels and demons scenario to demonstrate the polar extremes of the the spectrum. In this scenario, I lack the word to describe the humans, who can be influenced towards either end of the spectrum if impressed upon by an external entity.     The angels are devoted to good, and are immovable in their ideals. The demons are wicked, and will feign morality only to manipulate others. Both prey upon the humans, who are ____________.   I think that the key here is the spectrum of good an evil. Here are examples of other spectra and their associated words, for comparison.   Easily pushed from calm to angry: Temperamental Easily moved from determined to hopeless: Weak-willed Easily influenced by propaganda: How can I verify a Google authentication access token?  I need to somehow query Google and ask: Is [given access token] valid for the [example@example.com] Google account?  Short version: It's clear how an access token supplied through the  can be used to then request data from a range of Google services. It is not clear how to check if a given access token is valid for a given Google account. I'd like to know how.  Long version: I'm developing an API that uses token-based authentication. A token will be returned upon provision of a valid username+password or upon provision of a third-party token from any one of N verifiable services.  One of the third-party services will be Google, allowing a user to authenticate against my service using their Google account. This will later be extended to include Yahoo accounts, trusted OpenID providers and so on.  Schematic example of Google-based access:    The 'API' entity is under my full control. The 'public interface' entity is any web- or desktop-based app. Some public interfaces are under my control, others will not be and others still I may never even know about.  Therefore I cannot trust the token supplied to the API in step 3. This will be supplied along with the corresponding Google account email address.  I need to somehow query Google and ask: Is this access token valid for example@example.com?  In this case, example@example.com is the Google account unique identifier - the email address someone uses to log in to their Google account. This cannot be assumed to be a Gmail address - someone can have a Google account without having a Gmail account.  The Google documentation clearly states how, with an access token, data can be retrieved from a number of Google services. Nothing seems to state how you can check if a given access token is valid in the first place.  Update The token is valid for N Google services. I can't try a token against a Google service as means of verifying it as I won't know which subset of all Google's services a given user actually uses.  Furthermore, I'll never be using the Google authentication access token to access any Google services, merely as a means of verifying a supposed Google user actually is who they say they are. If there is another way of doing this I'm happy to try. Address is invalid on local machine [on windows 8 only] How to add an image to a JPanel? I have a  to which I'd like to add JPEG and PNG images that I generate on the fly.  All the examples I've seen so far in the , specially in the  use ImageIcons.  I'm generating these images as byte arrays, and they are usually larger than the common icon they use in the examples, at 640x480.   Is there any (performance or other) problem in using the ImageIcon class to display an image that size in a JPanel? What's the usual way of doing it? How to add an image to a JPanel without using the ImageIcon class?   Edit: A more careful examination of the tutorials and the API shows that you cannot add an ImageIcon directly to a JPanel. Instead, they achieve the same effect by setting the image as an icon of a JLabel. This just doesn't feel right... popping to root view in navigation controller Does assigning objects to null in Java impact garbage collection? Merging two incoming broadband lines for faster Internet Why do some badges appear white in color and others are dark? How can I press "Insert" on a keyboard without that key? Unloading classes in java? I have a custom class loader so that a desktop application can dynamically start loading classes from an AppServer I need to talk to. We did this since the amount of jars that are required to do this are ridiculous (if we wanted to ship them). We also have version problems if we don't load the classes dynamically at run time from the AppServer library.  Now, I just hit a problem where I need to talk to two different AppServers and found that depending on whose classes I load first I might break badly... Is there any way to force the unloading of the class without actually killing the JVM?  Hope this makes sense I'm trying to convert some LaTeX into HTML but my code listings don't preserve their code coloring. Why is that and how do I fix it?  This is what it looks like:    Side note: I'm also wondering why the caption on the table was removed.  Edit  Here is an example listing with colors:  \documentclass{article} \usepackage{color} \usepackage{listings} \lstset{     basicstyle=\footnotesize\ttfamily,     language=[Sharp]C,      keywordstyle=\color[rgb]{0,0,1.0}\bfseries,       commentstyle=\color[rgb]{0.133,0.545,0.133}\bfseries, }  \begin{document} \begin{lstlisting} int x = 10;  // This is a comment string str = "hello"; \end{lstlisting} \end{document}   This produces the following HTML when doing: htlatex myfile.tex:  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"     "http://www.w3.org/TR/html4/loose.dtd"&gt;   &lt;html &gt;  &lt;head&gt;&lt;title&gt;&lt;/title&gt;  &lt;meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"&gt;  &lt;meta name="generator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"&gt;  &lt;meta name="originator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"&gt;  &lt;!-- html --&gt;  &lt;meta name="src" content="LaTeX4.tex"&gt;  &lt;meta name="date" content="2012-07-20 12:30:00"&gt;  &lt;link rel="stylesheet" type="text/css" href="LaTeX4.css"&gt;  &lt;/head&gt;&lt;body  &gt;    &lt;!--l. 12--&gt;    &lt;div class="lstlisting" id="listing-1"&gt;&lt;span class="label"&gt;&lt;a   id="x1-2r1"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;int&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;x&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;=&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;10;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-3r2"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-4r3"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;//&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;This&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;is&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;a&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;comment&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-5r4"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;string&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;str&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;=&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;"&lt;/span&gt;&lt;span  class="cmtt-8"&gt;hello&lt;/span&gt;&lt;span  class="cmtt-8"&gt;"&lt;/span&gt;&lt;span  class="cmtt-8"&gt;;&lt;/span&gt;     &lt;/div&gt;  &lt;/body&gt;&lt;/html&gt;   Which looks like this:    I would want the HTML result to look like this: Homomorphism between compact Hausdorff spaces. I'm currently working on building a predictive model for a binary outcome on a dataset with ~300 variables and 800 observations. I've read much on this site about the problems associated with stepwise regression and why not to use it.  I've been reading into LASSO regression and its ability for feature selection and have been successful in implementing it with the use of the "caret" package and "glmnet".   I am able to extract the coefficient of the model with the optimal lambda and alpha from "caret"; however, I'm unfamiliar with how to interpret the coefficients.    Are the LASSO coefficients interpreted in the same method as logistic regression? Would it be appropriate to use the features selected from LASSO in logistic regression?   EDIT  Interpretation of the coefficients, as in the exponentiated coefficients from the LASSO regression as the log odds for a 1 unit change in the coefficient while holding all other coefficients constant. I'm working on a VAR model and am doing a log transformation of the raw data.   x = log(x)   After differencing, running various tests and running a VAR(2) model, I add the predicted differences cumulatively to the original time series (logged) like this:  prd.diffs &lt;- as.ts(prd$mean$d.x1) U &lt;- tail(undiff,2) cumu &lt;- cumsum(prd.diffs) + U[1]   However, while the output now looks as it should, it is still in logged values.  My question is as follows:  How does one return the logged output to original values? I'm under the impression that using exp() will not give the correct results, and having tried some variations it hasn't worked for me.   Does the fact that it is a VAR($p$) model (and possibly what lag it has) influence the method, and how should that be implemented to get the correct output?  P.S. I realise that the above code does not constitute a replicable example as I didn't deem that necessary for the question, but should that be desired I can add some more code. What is the name of an 80s TV movie where a man acquires endurance powers and quick self-healing ability after a crash with a vehicle containing radioactive material? Regular expression to match balanced parentheses Product of binomial coefficient as a basis What does outputting to /dev/null accomplish in bash scripts?