Java Generic Object Null Pointer Check Throwing Null Pointer Exception
What is a NullPointerException, and how do I fix it?
Limit of derivative is zero. Does it imply a limit for f(x)? The proof of shrinking coefficients using ridge regression through "spectral decomposition" I have understood how ridge regression shrinks coefficients towards zero geometrically. Moreover I know how to prove that in the special "Orthonormal Case," but I am confused how that works in the general case via "Spectral decomposition." Where did they go / do they went? Where did they go?   Where do they went?   Can you please advise which of above forms is correct?  I'm pretty sure that first one is fine but wondering about second one.   Can I use a second form as well or it's incorrect? One form of Jensen's inequality is     If $X$ is a random variable and $g$ is a convex function, then   $\mathbb{E}(g(X))\geq g(\mathbb{E}(X))$.   Just out of curiosity, when do we have equality? If and only if $g$ is constant? In LWC am trying to iterate over a list and show the details from the list, this is working correctly , but as a header want to show the record number in a displayed order, below is desired outcome and simplified sample code.  Desired OutCome:   Employee Record 1: A  Employee Record 2: B  Employee Record 3: C   JavaScript:  Var empNames = ["A" , "B" , "C"];   HTML:  &lt;template for:each={empNames} for:item="employee" for:index="index"&gt; Employee Record{index} {employee} &lt;/template&gt;    Actual outcome  Employee Record 0: A  Employee Record 1: B  Employee Record 2: C   I understand as i am using {index} which indicated the position of element in an array which starts from 0 my actual outcome also starts like Employee Record 0 instead of Employee Record 1, but is there a simple way without writing much logic on JS to handle this in html and to make my headers starts from 1 instead of 0? Clarification on maps in Salesforce I know this might be a very basic question but i'm pretty confused by this:  Map&lt;Id,Account&gt; accountWithOpportunities =      new Map&lt;Id,Account&gt;([SELECT Id,(SELECT Id FROM Opportunities) FROM Account]);   I have no clue on to where the Opportunities are relevant at all in this map and how they are stored or can be accessed?   Can anyone clear this out for me? How to write a while loop with the C preprocessor? tl;dr  Due to the special nature of Meta and the high rate of "lost souls", should we try out the Ask a Question Wizard here on Meta Stack Exchange too?  General idea  In case anyone doesn't know yet, . It guides new users towards writing better questions.  I think that such a question wizard would be useful on Meta Stack Exchange too, for three main reasons:   . There are four types of questions on Meta, each represented by the different required tags: , ,  and . Especially bug reports can often be split into a certain structure (what's wrong, how to reproduce, why I think it's wrong, examples). The same holds true for feature requests. Such a structure is ideal for a question wizard. Quite a few users  and . While the Meta community is well prepared to deal with these posts quickly, they lead to an less-than-ideal first impression by the new users and they distract the community from more important issues. Site-specific questions are often off-topic. This  since nowhere is it hinted at in the help pages (and there are a lot of old, not-yet-closed SO-specific questions from a prior era of this site) and can lead to unnecessary drama. If we add an honeypot into the wizard to catch this case (and ideally redirect them to the proper meta site), we could prevent this.   As Sonic said, there's an  new users need to read and confirm. However this doesn't really prove effective right now and we might need to try stronger tools (e.g. question wizard).  Therefore I think that we should test the Ask Question Wizard here on Meta too.  Implementation details (help welcome)  I think the wizard should have six main entry points:   I want to discuss a specific post or action from any Stack Exchange site. (-> honeypot, redirects to the appropriate per-site meta) I have a question regarding the use of Stack Exchange sites (-> support mode) I think I found a bug while using the Stack Exchange sites  (-> bug mode) I have an idea for improving the Stack Exchange sites  (-> feature request mode) I have a discussion I want to start about Stack Exchange communities or their rules  (-> discussion mode) I have some other (e.g. programming) question  (-> honeypot, redirects to )   Coming from these choices, the user would either be redirected to a landing page explaining, why this is not the right community and offering some alternative choices or they would follow the guided assistant.  For 1. the user might be asked on which site the post/action is. Maybe the system could show the three sites where the user was recently active/has the highest reputation on.  support mode would ask the user for these details:   what do you want to achieve? what have you tried? what is your current problem?   bug mode would ask the user for these details:   bug description how to reproduce the problem why do you think that this is wrong? (possibly) examples   feature request mode would ask the user for these details:   what is your goal? how do you think could this be achieved? why will the community benefit from this change? (possibly) details   discussion mode would ask the user for these details:   which rule do you want to propose/clarify (optionally) examples/why is this rule required?   Note: the above implementation details probably require some revision. Feel free to edit/suggest improvements for both wording and details. What is role-playing, and where do I start? I have been told that roleplaying is great fun. I've looked and looked and it all seems so complicated. Could anyone tell me a good place to start, and what sort of things you end up doing in roleplaying? In The Winter Soldier, who did Peggy Carter say she married? When Steve Rogers visits Peggy Carter, she has a family photo on her nightstand and says that she married someone after Cap disappeared. Who did she marry? How can I create light trails without a blurry subject? I love the subset of collective nouns known as the terms of venery. These are collective nouns specific to a particular group of animals. Some of the more inventive examples are: a murder of crows, a crash of rhinos, a mischief of mice, and a puddling of ducks (specifically swimming ducks).  Is there a standard for these group names and is there a central reference for them as with other zoological taxonomy?  I can see in the Wikipedia articles that the practice has its origins in Medieval Hunting tradition, but the Kangaroo (Mob), for instance would have been unknown at that time, so how do new collections come into being? Replace strings in a file based on a list of strings and a list of corresponding replacements Does it look good to edit the question you're answering? I have a question about editing practices:  Does it look good to edit a question you have just answered?  For example: say I had just answered a question, then saw that the question had some minor formatting issues. Should I edit it? Does it turn up voters off when they see that I am answering a question I changed, possibly to better suit my answer? Let $R$ be a commutative ring with finitely many maximal ideals $\mathfrak m_1,\ldots,\mathfrak m_n$. Let $M$ be a finitely generated module. Then there exists an element $x\in M$ such that $\frac{x}{1}\not\in\mathfrak m_iM_{{\mathfrak m}_i}$ for every $i=1,\dots,n$.    I cannot prove that such an element there exists. I was trying to prove it by induction on $n$. If $n=1$ it is true by Nakayama, so suppose it is true for $n-1$. Then for every $i$ I can find an $x_i\in M$ such that $\frac{x_i}{1}\not\in \mathfrak m_jM_{\mathfrak m_j}$ for every $j\neq i$. If $\frac{x_i}{1}\not\in \mathfrak m_iM_{\mathfrak m_i}$ for some $i$ we are done, so suppose $\frac{x_i}{1}\in\ m_iM_{m_i}$ for every $i$. I don't know how to go on, could you help me? I'm trying to create an item that can break certain blocks, but also has a colored name in 1.13.2   Here's the command I'm using.  /give iAugust minecraft:shears{display:{Name:"[{\"text\":\"Arcane Shears\",\"color\":\"aqua\",\"italic\":false,\"bold\":false}]CanDestroy:[minecraft:iron_bars]"}}   But it only has a colored name, and it can't break specific blocks. Short story about interstellar travel gone wrong Trying to find a story I read a couple of years ago in an anthology, not sure when the story dates from but likely to be recent - the last decade or so.   The story has passengers travelling between stars via a series of jumps. The calibration of the drive is affected by a special metal, any of which has to be stored in a shielded compartment (I think the jumps were measured in 'degrees'). One of the passengers unwittingly takes some of this metal on board, which throws off the calculations for the jumps, and they jump into an alternative universe where there are no signs of any humans ever existing. They start to try to reverse their steps to get back to the known universe, but the reverse calculation seems impossible.  That's as much as I read of the story before I lost the book. After many dreams (feverish nightmares!) re-living this story, I need to know how it ends. I know it's not much to go on. The story name, author, or the anthology it appears in would be fantastic. Why did Voldemort take the wand of one of his most loyal servants? In Harry Potter and the Deathly Hallows, chapter one The Dark Lord Ascending, Voldemort believes he must use a wand other than his own in order to kill Harry, when Harry is moved from Privet Drive. He demands Lucius Malfoy's wand, and gets it.   My question is, why did Voldemort take the wand of one of his most loyal servants, rendering Lucius Malfoy useless if a battle was to occur?  If I remember correctly, he had Ollivander at his disposal, and he was the one who told him to use another wand in first place. Why not ask Ollivander to create another wand, or just use ones that he had ready to sell in his shop at Diagon Alley? He could even have taken Ollivander's own wand. If my memories are correct, a wand's importance was compared to that of a limb. I've got a very small coefficient (-0.04) and R-squared (0.028) but a significant P value (&lt;0.0001). My question is:   Is my result still meaningful? How to interpret it?   The result is from a linear regression model in a big database in R.  The independent variable (B) has more than 200 values, whereas the dependent variable (A) has 13 values.   The potential correlation is below:   So, I ran a linear regression model between A and B and the result is:  &gt;mod1&lt;-lm(A~B)          Call:         lm(formula = A ~ B)           Residuals:              Min      1Q  Median      3Q     Max           -63.174 -11.816  -1.651  10.184 118.001            Coefficients:                        Estimate Std. Error t value Pr(&gt;|t|)              (Intercept) 132.274547   0.303723 435.511  &lt; 2e-16 ***          B            -0.036675   0.009052  -4.052 5.13e-05 ***          ---         Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1          Residual standard error: 18.52 on 8093 degrees of freedom            (123 observations deleted due to missingness)         Multiple R-squared:  0.002024,  Adjusted R-squared:  0.001901          F-statistic: 16.42 on 1 and 8093 DF,  p-value: 5.134e-05   As you can see, the coefficient of B is only -0.03 and adjusted R squared is only 0.1% but with a p value &lt;0.0001. Is my result reasonable and countable? Surely, my database is larger (8000 records) and even a very small effect size will show a significant P value. But how would I interpret this? Was Philip K. Dick able to watch a complete version of Blade Runner before his death or just unedited material?  The Blade Runner release date according to  and IMDb was 25 June, 1982. Philip K. Dick died a few months before, on March 2, 1982.