I was playing around with examples from .  What I find really confusing is that when I mistakenly put a wrong type into one of generics when forming Collectors, java compiler gives me a very misleading message:     Non-static method cannot be referenced from a static context   My error has nothing to do with static vs instance context in reality:  Map&lt;String, Map&lt;Integer, Integer&gt;&gt; mapOfStudents = list.stream().collect(Collectors.groupingBy(Student::getClassName,             Collectors.toMap(Student::getName, Student::getAge)));   My mistake is in generic return type. When I correct it and put:  Map&lt;String, Map&lt;String, Integer&gt;&gt; mapOfStudents   everything goes back to normal.  Can someone explain the reason behind such a confusing error message? I'm sure the is a good one, but I fail to grasp it.  EDIT:  ~$ java -version openjdk version "1.8.0_121" OpenJDK Runtime Environment (build 1.8.0_121-8u121-b13-0ubuntu1.16.04.2-b13) OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode)
The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message:     You can either make the non static method static or make an instance of that class to use its properties.   Why? I am not asking for solutions. I would be grateful to know what is the reason behind it. The very core reason!  private java.util.List&lt;String&gt; someMethod(){     /* Some Code */     return someList;             }  public static void main(String[] strArgs){                // The following statement causes the error. You know why..     java.util.List&lt;String&gt; someList = someMethod();          }
std::string formatting like sprintf Sorry, I'm still a newbie to blender, but why are some edges visible only in edit mode, but not in wireframe view? is it a bug or am I missing something here?  edit mode: Edges visible. Object mode, wireframe view: Pooff, they're gone. what can i do to fix this? / thanks Why can't I catch Pokemon in Pokemon Go anymore? Using the definite article before a country/state name The Punjab is a rich state.   Is it correct to use the before Punjab? I am a n00b to physics. What physics I know comes from high school and popular science books.  At school we were taught about atoms and what make up atoms, but we weren't actually told what the particles were!  So sure an atom has electrons orbiting around a nucleus made of protons and neutrons, but what exactly is an ?  And if we don't know, how can we fire them from guns, like they do in experiments ... etc  Any clarification on this would be great. Photon energy - momentum in matter $E = h\nu$ and $P = h\nu/c$ in vacuum. If a photon enters water, its frequency $\nu$ doesn't change. What are its energy and momentum: $h\nu$ and $h\nu/c$ ? Since part of its energy and momentum have been transferred to water, it should be less.  If water's refractive index is $n$, are the energy and momentum equal to $h\nu/n$ and $h\nu/c/n$ ? ASP.NET MVC Custom Error Handling Application_Error Global.asax? Offset a background image from the right using CSS When is it appropriate to use a hyphen? Why do eukaryotic organisms have introns in their DNA? We touched on introns and exons in my bio class, but unfortunately we didn't really talk about why Eukaryotes have introns. It would seem they would have to have some purpose since prokaryotes do not have them and they evolved first chronologically, but I could easily be wrong. Did the junk sections of DNA just evolve there by some sort of randomness or necessity as opposed to an actual evolutionary advantage? Why hasn't evolution stopped us from having introns since they seem to be a 'waste' of time and DNA? Why do prokaryotes not have introns? I had a problem with the laptop lid so I am using it with an external monitor. I was wondering if there is any way to power on the laptop without opening the lid, that is through ports.  Laptop: Dell Inspiron 1525 Password hash function for Excel VBA Qualitative variable coding in regression leads to "singularities" I want to make a logistic model from my survey data. It is a small survey of four residential colonies in which only 154 respondents were interviewed. My dependent variable is "satisfactory transition to work". I found that, of the 154 respondents, 73 said that they have satisfactorily transitioned to work, while the rest did not. So the dependent variable is binary in nature and I decided to use logistic regression. I have seven independent variables (three continuous and four nominal). One guideline suggest that there should be 10 cases for each predictor / independent variable (Agresti, 2007). Based on this guideline I feel that it is OK to run logistic regression.    Am I right? If not please let me know how to decide the number of independent variables? How can I recover my account? I tried to log into Minecraft today to find that my password isn't working. I tried to change it, but I can't login to my email because I forgot the answer to my security question. I tried changing the email to a different one, but that didn't work for some reason (it kept saying "invalid email"). I don't have my transation ID because I forgot which credit card I used.  Does this mean that I have to buy a new Minecraft account? Is it ever bad to use \left and \right? For mathematics, is it ever disadvantageous to use \left(  and \right)  in equations?  I can't see any way that doing this would hinder the typesetting, so why isn't () just converted into \left( \right) automatically? This would save a lot of typing.  Cheers! Does javascript use immutable or mutable strings? Do I need a "string builder"? Following on from this question:   It seems all feats carry over to your new form if your new form is capable of using them (so Mounted Combatant and Inspiring leader would usually be ruled as unusable in most circumstances). But what about Tough?     Your hit point maximum increases by an amount equal to twice your   level when you gain this feat. Whenever you gain a level thereafter,   your hit point maximum increases by an additional 2 hit points.   Would this increase your maximum HP by the same amount when in the form of a rat, or brown bear? Avoid footnotes from appearing before mark What can I actually do with a high credit score? I recently checked my credit score via two of my credit card providers. It seems to be hovering between 790 and 815. One service brands the score it provides as a FICO score and the other specifically says its score comes from Transunion.   What can I actually do to leverage this high credit score to my advantage?  The only new debt I might take on would be a small HELOC or car loan. Does a high score give me any negotiating power with the lender to get a better rate? Should I treat the score as a card in my hand or is it something I should show early in negotiations?  Does a high score make me eligible for any discounts on insurance?  Does a high score open up any options for earning more interest on savings accounts?  The typical advice I'm reading suggests refinancing a mortgage. That seems like good advice in general but it does not apply to my personal circumstances. I've got 3.5% on a 15 year note with 9 years left. A casual review of current rates suggest I could maybe scrape 0.5% off of that, hardly seems worth the effort and cost for half a percent.