Finding nullpointerException
What is a NullPointerException, and how do I fix it?
Comparing values between two tables How to compare values between two different tables?  I have two tables as shown below:   Table 'A' sql_id       OPERATION       OPTIONS  63kf3an2j0pk SELECT STATEMENT 63kf3an2j0pkc TABLE ACCESS FULL  Table 'B' sql_id       OPERATION     OPTIONS 63kf3an2j0pk SELECT STATEMENT 63kf3an2j0pkc INDEX UNIQUE SCAN IDX_THU   I need to compare the values in Table 'A' and Table 'B' for the given sql_id. My question is how to find the changed values.  In this case in Table 'A' the second line is TABLE ACCESS FULL. Table 'B' the the second line is INDEX UNIQUE SCAN IDX_THU. So here the value has changed. How can I find that using query? Something like when matched then "matched" when not changed "value changed".  I'm looking for output something like below:     sql_id           comaparion outcome dmqb1hzrf5uxh   No change in the plan 74anujtt8zw4h   plan changed   Can I do something like this?  select sql_id,case when ( select sql_id,OPERATION,options  from  a where sql_id='dmqb1hzrf5uxh' minus  select sql_id,OPERATION,options from  b where sql_id='dmqb1hzrf5uxh') is null then 'matched'  else 'changed' end as status;   I am comparing the explain plans before and after patch. The table 'A' is before patch result of the sqlid and table 'B' is after patch result. Now I want to compare the plans in both the tables. I want to compare the plan by using a query. Calendar month view is unresponsive on iOS 9 How do I divide a circle into equal parts like a pie chart with Adobe Illustrator? Is there a fairly simple way to divide a circle into equal parts using Adobe Illustrator CC? How can I pad an integer with zeros on the left? Possible Duplicate:          The FAQ specifies that:     Use your downvotes whenever you encounter an egregiously sloppy, no-effort-expended post, or an answer that is clearly and perhaps dangerously incorrect.   But if I find a correct question, closed (or not yet) as duplicate, is downvote a correct behavior for Stack&nbsp;Overflow policy? "In and of itself" is a phrase I find myself using all the time. But in and of itself, the phrase "in and of itself" has no meaning. That is, the individual words don't seem to contribute to the whole meaning of the phrase. Move iTunes folder outside Music folder iTunes by default stores its settings, the iTunes Library.itl file, and the music library audio tracks, inside the \Users\username\Music\iTunes folder.  I don't want my Music folder polluted with program settings, especially because I'm synchronizing that folder on the cloud. Via the settings panel I can only change the path of the audio tracks, but the settings remain in the default position.  Is there a way to completely move the iTunes folder to another path?  PS: I've looked at the answers to , but the focus there is on moving the media library only, not the whole iTunes directory. how do you prove that $A\times (B\setminus C) = (A\times B) \setminus (A\times C)$? This is what I have come up with so far, but I am rather lost at lines 3-4...  $$\begin{align} (a,b)\in A\times (B\setminus C)\iff&amp; a\in A \land b\in (B\setminus C)\\ \iff&amp; a\in A \land (b\in B \land \lnot(b\in C))\\ \iff&amp; (a\in A \land b\in B) \land (a\in A \land b\notin C)\\ \iff&amp; (a\in A \land b\in B)\setminus (a\in A \land b\in C)\\ \iff&amp; (a,b)\in (A\times B)\setminus ((a,b)\in A\times C)\\ \iff&amp; (a,b)\in (A\times B)\setminus (A\times C) \end{align}$$ Anything similar in javascript to ruby's #{value} (string interpolation) Is there any option with 'ls' command that I see only the directories? Sometimes, I need to check only the directories not files. Is there any option with the command ls? Or is there any utility for doing that?  EDIT: I'm using Mac OS X, and ls -d gives me . even though I have directories. How to track the number of tag wikis I edited? I want to see the number of tag wiki that I edited till now. Also I want to see which are accepted and which are rejected with the detail of all those tags. How can I know that? Also I want to know the progress for Research Assisstant badge. How to calculate Area Under the Curve (AUC), or the c-statistic, by hand I am interested in calculating area under the curve (AUC), or the c-statistic, by hand for a binary logistic regression model.  For example, in the validation dataset, I have the true value for the dependent variable, retention (1 = retained; 0 = not retained), as well as a predicted retention status for each observation generated by my regression analysis using a model that was built using the training set (this will range from 0 to 1).  My initial thoughts were to identify the "correct" number of model classifications and simply divide the number of "correct" observations by the number of total observations to calculate the c-statistic. By "correct", if the true retention status of an observation = 1 and the predicted retention status is > 0.5 then that is a "correct" classification. Additionally, if the true retention status of an observation = 0 and the predicted retention status is &lt; 0.5 then that is also a "correct" classification. I assume a "tie" would occur when the predicted value = 0.5, but that phenomenon does not occur in my validation dataset. On the other hand, "incorrect" classifications would be if the true retention status of an observation = 1 and the predicted retention status is &lt; 0.5 or if the true retention status for an outcome = 0 and the predicted retention status is > 0.5. I am aware of TP, FP, FN, TN, but not aware of how to calculate the c-statistic given this information. Link Google Form responses To Already Existing Google Spreadsheet Tab I have a Google Form. I had all of my Google Form responses linked to a specific tab in my Google Spreadsheet. Somehow my form responses were unlinked from my tab. When I go to re-link my form responses to my already existing tab it only gives me the option to create a new tab in my spreadsheet.   How do I simply re-link my Google Form responses to my already existing tab in my Google Spreadsheet? In an ideal circuit, How can there be a current b/w points a &amp; b, when there is no potential difference and thus no electric field between a &amp; b? If there is no current, then where does current across the resistor come from, because that means no charge is coming from the battery (?). Is it possible to install Windows from an external hard drive?  I have Windows XP installed on my laptop, and I want to remove it and install Windows 7.  My Windows 7 installation is in an .iso format on an external USB hard drive.  Is it possible to install it or will I need to put in a DVD before I start installing? Biblatex-apa style is missing a comma in the references. why? I have been trying to solve this problems for hours, but there is no solution in sight.  Until a few weeks ago, my biblatex-apa style was working like a charm. Although, after installing the updates and Biber, the reference section became a problem. It should display a journal article by two authors with a comma after the first author, but it doesn't:     Weber, M. &amp; Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   it should look like this:     Weber, M., &amp; Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   This is how my document looks like:   \documentclass[12pt, onecolumn]{apa6}   \usepackage[utf8]{inputenc} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[style= apa, backend=biber]{biblatex} \bibliography{testbib} \DeclareLanguageMapping{american}{american-apa}   \begin{document}  Some text \parencite{Weber2012}.  \printbibliography \end{document}   And the BibTeX file:  @article{Weber2012, abstract = {}, author = {Weber, M. and Ruch, W.}, doi = {10.1016/j.adolescence.2012.06.002}, file = {}, issn = {1095-9254}, journal = {Journal of adolescence}, number = {6}, pages = {1537--1546}, pmid = {22749517}, publisher = {Elsevier Ltd}, title = {{The role of character strengths in adolescent romantic relationships: An initial        study on partner selection and mates' life satisfaction.}}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22749517}, volume = {35}, year = {2012} }    I have tried various things so far, but none of it helped: e.g,   \renewcommand*{\finalnamedelim}{ \finalandcomma}   or  \renewcommand\finalandcomma{\addcomma}   Even in the biblatex manual, the reference examples of two authors is without the comma (it works for three or more authors). There should be a comma, according to . Why is that comma not there? And how could I insert that into my references? How does dark matter halo outside a galaxy help to explain galaxy rotation curve? How does a   outside a galaxy help to explain a ?  Suppose for simplicity we use a model of a star rotating about a more massive star in a fixed circular orbit. For another star at larger radius, the velocity should be smaller but observationally for spiral galaxies, the opposite happens (moves at even more speed or at least at the same speed as the closer star).  People hypothesize that dark matter halo may be present “surrounding” the system (i.e., halo exists outside the system) to account for such observation. I feel that exactly the opposite should be the case that is, dark matter halo should be inside the galaxy rather than outside. Reason being, if dark matter is outside the galaxy then the effective gravitational pull on the rotating star towards the center will be reduced due to outward attraction on the star exerted by dark matter existing outside. Thus, its speed of rotation should be reduced; but we observe the opposite. So how does dark matter halo "surrounding" a galaxy help to explain galaxy rotation curve? Where am I making mistake in argument? I would like to know if there is a word or phrase for a systematic campaign to annihilate every descendant of a particular ancestor.   We have the word 'genocide' for killing off an entire race, and plenty of words for killing people based on how they are related to you (fratricide, filicide, et. al.), but looking over the  and the , I couldn't find a term for systematically killing an entire bloodline.   My question is prompted by a US news story about the horrific murder of 8 members of the same family, but those murders are not an example of what I'm thinking of because the children of the victims were left alive, so the motive for the killings was not to kill off the bloodline. The sense that some group had coordinated an attack against just one family is what made me wonder what the "not an entire race, just one bloodline" version of 'genocide' would be called.   Searching the Internet for "kill off" and bloodline sends me straight into the land of vampires, Illuminati, reptilian overlords, and, naturally, Priory of Sion nonsense so I haven't had much luck finding a thread to pull.   It may be that there is no word for it in the sense of murdering a human bloodline, because we just don't attempt kill off our royals down to the last heir often enough to coin a term for it. Maybe there is a scientific term for culling a line from a test population as part of biological research? I am trying to show that: \begin{equation} \frac{n}{\phi(n)} = \sum_{d \mid n} \frac{\mu^2(d)}{\phi(d)} \end{equation} where $\phi(n)$ is  and $\mu$ is the .  The identity clearly holds for $n=1$, so if we write $n=p_1^{a_1} \cdots p_k^{a_k}$ for the prime decomposition of $n$, the left-hand side becomes: \begin{eqnarray*} \frac{n}{\phi(n)} &amp; = &amp; \frac{p_1^{a_1} \cdots p_k^{a_k}}{\phi(p_1^{a_1}) \cdots \phi(p_k^{a_k})} \\ &amp; = &amp; \frac{p_1^{a_1} \cdots p_k^{a_k}}{(p_1^{a_1-1})(p_1-1) \cdots (p_k^{a_k})(p_k-1)} \\ &amp; = &amp; \frac{p_1 \cdots p_k}{(p_1-1)\cdots (p_k-1)} \end{eqnarray*}   Whereas the right-hand side becomes:  \begin{eqnarray*} \sum_{d \mid n} \frac{\mu^2(d)}{\phi(d)} &amp; = &amp; \sum_{\substack{d \mid n \\ p^2 \nmid d}} \frac{1}{\phi(d)} \\ &amp; = &amp; 1 + \frac{1}{\phi(p_1)} + \dots + \frac{1}{\phi(p_k)} + \frac{1}{\phi(p_1 p_2)} + \dots + \frac{1}{\phi(p_{k-1}p_k)} \\ &amp; + &amp; \dots + \frac{1}{\phi(p_1 \cdots p_k)} \\ &amp; = &amp; 1 + \frac{1}{p_1 - 1} + \dots + \frac{1}{p_k - 1} + \frac{1}{(p_1 - 1)(p_2 - 1)} + \dots + \frac{1}{(p_{k-1}-1)(p_k-1)} \\ &amp; + &amp; \dots + \frac{1}{(p_1 - 1) \cdots (p_k - 1)} \end{eqnarray*}  I am unsure of how to proceed from this point however. Any help would be much appreciated. I've heard you can start with pikachu in pokemon go instead of the 3 standard starters. How would one do this? Is this even possible?