Android Sqlite Nullpoint Exception --- java.lang.NullPointerExceptio
What is a NullPointerException, and how do I fix it?
A sequence includes $a_p=\sqrt2$, $a_q=\sqrt3$, $a_r=\sqrt5$ for some $1\leq p<q<r$. Can these be terms of an arithmetic progression? harmonic? What does the '!' really do when it's added to an ex command (:wq! | :w! | :q! )? I understand that it means force to do something.  When doing $ vim -R file I enter in read-only mode, but this works as preventive mode only   -R  Readonly mode.  The 'readonly' option will be set for all the     files being edited.  You can still edit the buffer, but will     be prevented from accidentally overwriting a file.  If you     forgot that you are in View mode and did make some changes,     you can overwrite a file by adding an exclamation mark to     the Ex command, as in ":w!".  The 'readonly' option can be     reset with ":set noro" (see the options chapter, |options|).     Subsequent edits will not be done in readonly mode.  Calling     the executable "view" has the same effect as the -R argument.     The 'updatecount' option will be set to 10000, meaning that     the swap file will not be updated automatically very often.   But what I can't get yet is why it makes the instruction to skip permissions even if the file's owner is root user, besides it also change owner &amp; group. Non constant analytic function from $\{z\in\mathbb{C}:z\neq 0\}$ to $\{z\in\mathbb{C}:|z|>1\}.$ C# difference between == and Equals() Check if a class is derived from a generic class I have a generic class in my project with derived classes.  public class GenericClass&lt;T&gt; : GenericInterface&lt;T&gt; { }  public class Test : GenericClass&lt;SomeType&gt; { }   Is there any way to find out if a Type object is derived from GenericClass?  t.IsSubclassOf(typeof(GenericClass&lt;&gt;))   does not work. It didn't fixed the error. So, how do I fix my GUI update?  For every software I have to install it from command line because I got same error when install software from Ubuntu Software Center. Given fields $M/E/F$, why does $[M:F] = [M:E][E:F]$? Let $M$ be a finite extension of $E$ and let $E$ be a finite extension of $F$. Then $M$ is a finite extension of $F$ and $[M:F] = [M:E][E:F]$.   Is there an easy explanation and/or proof for this theorem? My instructor gave an incomplete proof in class but got stuck and I'm kind of confused of what's going on. Why don't Death Eaters always use Avada Kedavra? When the Death Eaters attacked Hogwarts, why did the Death Eaters not just use Avada Kedavra and kill everyone? First quick glance at a dataset Please pardon my ignorance, but...  I keep finding myself in a situation, where I'm faced with a bunch of new data I managed to find. This data usually looks something like this:  Date     Number1  Number2  Category1  Category2 20120125      11      101        Dog      Brown 20120126      21       90        Cat      Black 20120126      31      134        Cat      Brown (...)   Usually at first glance I can't really tell if there are any trends here. The correlations between the various columns may not be very significant, but I would be delighted if I didn't have to manually create a plot for every possible combination of columns/categories.  Is there a tool out there which would accept a table of data along with information which columns should be treated as numbers, dates and categories and then proceed to plot:   correlations between each two numerical columns correlations between each two numerical columns, with separate trend lines for each category each number column as a time series, each number column as a time series, separated by category, etc.   In the end this would generate a large number of plots, most of which would show only noise. Ideally, the tool could score the plots by correlation and in the end display a slideshow starting with the highest scoring plots. This would be a very imperfect, but useful first glance at the dataset.  So? Is there a tool everyone uses for this and I just don't know about it, or is this something we need to make? Do megapixels matter with modern sensor technology? Extended Euclidean Algorithm: backward vs. forward I'm confused about how to do the extended algorithm. For example, here's the gcd part gcd(8000,7001)  $$\begin{align}8000 &amp;= 7001\cdot1 + 999\\ 7001&amp;=999\cdot 7+8\\ 999&amp;=8\cdot 124+7\\ 8&amp;=7\cdot 1+1\\ 7&amp;=1\cdot 7+0\\ \gcd(8000,7001)&amp;=1\end{align}$$    Now, the extended algorithm  $$\begin{align}1 &amp;= 8 - 1\cdot7\\ &amp;= 8 - 1\cdot(999 - 8\cdot124)\\ &amp;= -1\cdot999 + 8\cdot125\end{align}$$  How do you get this 8*125 from the previous line? Firefox: Downloading files with drag and drop When to use LinkedList over ArrayList in Java? I've always been one to simply use:  List&lt;String&gt; names = new ArrayList&lt;&gt;();   I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code.    When should  be used over  and vice-versa? This is a very simple question but I believe it's nontrivial.  I would like to know if the following is true:      If $R$ and $S$ are rings and $R[x]$ and $S[x]$ are isomorphic as rings, then $R$ and $S$ are isomorphic.    Thanks!  If there isn't a proof (or disproof) of the general result, I would be interested to know if there are particular cases when this claim is true. Intuition for why the sum of Bernoulli trials is a sufficient statistic via cancellations on numerator and denominator? Suppose that $X_1, \ldots, X_n$ are iid Bernoulli trials with parameter $p$, and that $Y = \sum_{i=1}^nX_i$. Then, we have that $Y$ is a sufficient statistic by the following condensed proof:  $$ P(X_1 = x_1,  ... , X_n = x_n |Y = y) = \frac{p^y(1-p)^{n-y}}{\binom{n}{y}  p^y(1-p)^{n-y}} =\frac{1}{\binom{n}{y}}   \text{ if } \sum_{i=1}^{n}x_i = y $$  I am trying to see why this is the case. My reasoning is that there is some cancellation property on top and bottom that "kills" off the parameter $p$. In that whatever is on top through $p$ is perfectly matched by whatever is on the bottom minus scaling factors (in this case $\binom{n}{y}^{-1}$).   However, I am wondering what the deeper meaning behind this is, that the numerator of the joint distribution of the data and the sufficient statistic has its EXACT form on the bottom, except for constants which are only multiplicative (to facilitate cancellations). Am I onto something bigger and deeper here? Recently I began studying machine learning, however I failed to grasp the intuition behind .   The following are the facts about logistic regression that I understand.   As the basis for hypothesis we use . I do understand why it's a correct choice, however why it's the only choice I don't understand. Hypothesis represents the probability that the appropriate output is $1$, therefore the domain of our function should be $[0,1]$, this is the only property of sigmoid function I found useful and appropriate here, however many functions satisfy this property. In addition, sigmoid function has a derivative in this form $f(x)(1-f(x))$, but I don't see the utility of this special form in logistic regression.   Question: what so special about sigmoid function, and why we cannot use any other function with domain $[0,1]$? The cost function consists of two parameters ${\rm Cost}(h_{\theta}(x),y)=-\log(h_{\theta}(x))$ if $y=1, {\rm Cost}(h_{\theta}(x),y)=-\log(1-h_{\theta}(x))$ if $y=0$. In the same was as above, I do understand why it's correct, however why is it the only form? For example, why couldn't $|h_{\theta(x)}-y|$ be a good choice for the cost function?  Question: what is so special about the above form of cost function; why cannot we use another form?   I would appreciate if you could share your understanding of logistic regression. How to "shuffle" an array? Display Custom Fields in a SharePoint 2010 Content Query Web Part Using SharePoint 2010, Having Custom List With 4 Columns, Now I am Using Content Query Web-part To Display List Data ,But Currently It Display Only First Column, SO How to Display Custom Fields in a SharePoint 2010 Content By Query Web Part Prove that $(n-1)! \equiv -1 \pmod{n}$ iff $n$ is prime [Wilson's Theorem] How can I show that $(n-1)!\equiv-1 \pmod{n}$ if and only if $n$ is prime? Thanks. How to find windows 10 activation Key Where can it be find?  At activation panel i can only find option to change the activation key. The current key is not presented on this screen.