Attempt to invoke virtual method 'void androidx.appcompat.widget.LinearLayoutCompat.setVisibility(int)
What is a NullPointerException, and how do I fix it?
I am using my school's computers and would like to use zsh instead of bash. I'd like to make it the default shell, but I cannot run a command such as $ chsh -s $(which zsh) because I don't have admin privileges.   Is there a way I can put something in my .bashrc or something that automatically calls zsh when it opens as a workaround?   To clarify, zsh is already installed. Explanation that air drag is proportional to speed or square speed? Your last flag was declined - no it wasn't I went to flag something, and in the flag dialog I got the message  "Your last flag was declined - please review it before flagging this post!"    That's all well and good, but when I went to review my flags, the statement is not accurate.  My last 5 flags were all marked 'helpful'.  The 6th down the list is marked 'declined', but that wasn't my last flag.  The message should probably be modified to correspond to the actual condition that triggers it.  Perhaps it should say     One of your flags was recently declined - please review it before flagging this post!   I'm going to guess that this message is triggered if, of all the flags of mine that have been handled by a moderator, the one that was most recently handled was declined. This isn't necessarily the last flag that I raised (the one I raised most recently), as moderators might handle them in a different order than I raised them, and it's not necessarily the flag at the top of the list.  Thus, calling it my "last" flag seems like it could cause confusion.  Yes, I realize this is extremely minor. Wulfgar won't teach me Unrelenting Force's final word after Arngeir accepts the Horn of Jurgen Windcaller Testing stored procedure scalability I have an email application that will be called upon to deliver to the UI the number of new messages for a given user on each page load. I have a few variations of things I am testing on the DB level but all are abstracted by the stored proc call.  I'm trying to slam the DB to see what the breaking point (# of requests per second) would be.   In a nutshell, I have a table such as this userId, newMsgCount with a clustered index on userId. SQL should be able to server hundreds or thousands of these responses per second. I think the laggard is my .NET app.  How can I make this a good test to achieve the test results based on SQL performance?  Is there a tool for this that i can give it a stored proc name and param for it to pund my  DB?  I want to see if the DB can return a min. of 250 responses per second. Studying for an exam, a review question...  Given $G=\langle x,y|x^4=y^4=e,xyxy^{-1}=e\rangle$.    Show $|G|\leq16$.   For this, I want to consider that $x^3=x^{-1}$ and $y^3=y^{-1}$ based on our assumptions. I am a little lost as to how to put the second part, $xyxy^{-1}=e$ to show there are no more than 16 elements.   If $|G|=16$, find the center of the group and find a group that is isomorphic to $G/\langle y^2\rangle$.   I'm pretty sure the group is centerless. How can I get more of this macro photo in focus? To turn off my system, I can use one of these three commands:  sudo halt   Or:  sudo poweroff   Or:  sudo shutdown -h now   What are the differences between these commands, or are they all just aliases of each other? When should I use a struct rather than a class in C#? When should you use struct and not class in C#? My conceptual model is that structs are used in times when the item is merely a collection of value types.  A way to logically hold them all together into a cohesive whole.  I came across these rules :   A struct should represent a single value. A struct should have a memory footprint less than 16 bytes. A struct should not be changed after creation.   Do these rules work? What does a struct mean semantically? How come such different methods result in the same number, $e$? What's an intuitive way to think about the determinant? In my linear algebra class, we just talked about determinants. So far I’ve been understanding the material okay, but now I’m very confused. I get that when the determinant is zero, the matrix doesn’t have an inverse. I can find the determinant of a $2\times 2$ matrix by the formula. Our teacher showed us how to compute the determinant of an $n \times n$ matrix by breaking it up into the determinants of smaller matrices. Apparently there is a way by summing over a bunch of permutations. But the notation is really hard for me and I don’t really know what’s going on with them anymore. Can someone help me figure out what a determinant is, intuitively, and how all those definitions of it are related? Difference between Simple Past and Past Perfect What is the difference in meaning between the two examples below?   When she returned home from office, she was shocked to see that her husband and daughter were missing. (Simple Past)  When she returned home from office, she was shocked to see that her husband and daughter had been missing. (Past Perfect)    FIRST QUESTION: For me example #1 gives only idea of Status of her missing husband and daughter and example #2 gives idea of completed action/situation of missing husband and daughter before she reached home. Is this right? SECOND QUESTION: Is example #2 past perfect or past perfect continuous? How to prove that $A_5$ has no subgroup of order 30? I need to show that $A_5$ has no subgroup of order 30. Any ideas? Sometimes when I'm making a sauce or soup that needs to be a bit spicy, I have no troubles spicing how I want to.  But if the dinner party is a bit late, or I made the sauce in advance to really draw out all the flavors of the spices, vegetables and meat, sometimes I end up with a way too spicy/hot dish.  You can always pour a bit water and try to dilute it a bit, but that also takes away all of the good flavor. So is there some trick that I'm missing I can use, when this happens to me (other than being more careful or using the spices later)? Is the distribution of an Ito diffusion at time t absolutely continuous wrt Lebesgue measure? Let $m$ be a natural number. Define $f(m) = m + \lfloor\sqrt{m}\rfloor$. Prove that at least one of the number among $m, f(m), f^2(m), \ldots$ is a perfect square. Here $f^k(m)$ denotes the composition of $f$ over itself $k$ times.  I tried the question, but the greatest integer along with square root is creating trouble. I don't have cd burner, so I want to install W7 on my 2nd computer via an USB-Drive. I just copied the files from the iso but it won't boot. So I installed ms-sys and did a ms-sys -7 /dev/sdb but it just says "Boot error".  How can I install it the right way? Tried many different tutorials by now but none worked. Limit of $\left(1-\frac{1}{n^2}\right)^n$ Wrong Java resource bundle loaded How can I pad a String in Java? Is there some easy way to pad Strings in Java?  Seems like something that should be in some StringUtil-like API, but I can't find anything that does this.