client_server chat app using JFrame form .. initializing server's socket
What is a NullPointerException, and how do I fix it?
# and ## in macros How to change language of a specific application? Editing Photoshop (PSD) files on Ubuntu? I was wondering that is it possible to edit PSD files on Ubuntu (like with Gimp). Actually, I need to edit layers. I haven't managed to do it. It would be nice if there is a chance! :) How can I see my progress for different badges? I am trying to obtain more badges on Stack Overflow. For example, to gain Archaeologist I need to edit 100 inactive posts but I am not keeping track of the number of posts I've edited. For Deputy I need to raise 80 helpful flags, etc. How can I view all my statistics about the badges, such as how many more edits I need to do, etc. I'm not doing it for badges, but I can spend a bit more effort if I'm close to getting a badge. Why doesn't hydrogen gas exist in Earth's atmosphere? The root mean square velocity of hydrogen gas at room temperature is: Gas constant: $R=8.31\ \mathrm{J\ K^{-1}\ mol^{-1}}$ Molar mass of hydrogen gas: $M=2.02\times10^{-3}\ \mathrm{kg/mol}$ $$\begin{align} v &amp;= \left(\frac{3\times8.31\ \mathrm{J\ K^{-1}\ mol^{-1}}\times300}{2.02\times10^{-3}\ \mathrm{kg/mol}}\right)^{\frac12}\\ &amp;= 3356.8377\ \mathrm{m/s}\\ &amp;= 3.356\ \mathrm{km/s} \end{align}$$ The escape speed of Earth is $11.2\ \mathrm{km/s}$, which is larger than the root mean square velocity of hydrogen gas. But still, hydrogen gas doesn't exist in Earth's atmosphere. Why? Have I made any mistakes in my calculations? I get the following error in my log files every time I try to upload a large file.  a client request body is buffered to a temporary file /var/lib/nginx/body/0000000001   Although the file uploads successfully, I always get the above error.  I increased the client_body_buffer_size to 1000m which is what I expect the largest file uploaded to be. However, this is was just a guess and although I don't get that error anymore I am wondering if this is an appropriate value to set for the client_body_buffer_size?  I would appreciate it if anyone can shed some light on this directive and how it should be used. Multiple disks vs single disk on virtualized environment We're planning to install a SQL Server on this physical architecture:  A hyper-v cluster based on windows server 2019 A cluster shared volume where all VMs live A full-flash SAN that contains the CSV  I've always read that is a common best practice to have multiple disks for data files, log files, temp db files ect... But that best practice is referred to a bare-bone installation. So, what I'm asking is: what are the actual benefits of doing so on the above described architecture (if any)? When I boot in GRUB2 and press c, I have access to GRUB shell.  How to change the keyboard layout (language) of this GRUB shell?  Note that I'm booting an Ubuntu VM inside Virtualbox. What is the difference between 'git pull' and 'git fetch'? What are the differences between git pull and git fetch? For whatever reason, we do no longer need to be root (or using sudo) to run /sbin/shutdown, /sbin/reboot etc.  This seems to be because those executables are now symlinks to /bin/systemctl which handles everything as normal user.  However, what if I want shutdown and reboot to require root authentication again? How can I achieve this? What is wrong with "Where should this car be parked?"? Rotation and translation of a conic-section I tried to solve the following exercises, so I want to ask you if my answers are correct.     1) Given the coordinates system $(O'; X'' Y'')$ asociated to the    basis $B=[{b_1=\frac{1}{\sqrt{2}}; \frac{1}{\sqrt{2}};  &gt; b_2=\frac{-1}{\sqrt{2}}; \frac{1}{\sqrt{2}}}]$ with origin in    $O'=(2;5)$ and the system $(O;XY)$ asociated to the standar basis, find the intersection between $Q: y''^2=-4 \sqrt{2} x''$    and the straight line in $(O,XY)$ $V=(0;5)+t(-1;1) t\epsilon R$    Well, first I tried to write $Q$ in terms of $X$ and $Y$, and not in terms of $X''$ and $Y''$. I used the formula:  $(\begin{matrix}  X''\\  Y'' \\  \end{matrix})$ =$(C)_B$ × $(\begin{matrix}  X-2\\  Y-5 \\  \end{matrix})$   Then I replaced those values in the equation of $Q$ and I got $Q: \frac{(-x+y-3)^2}{2}=-4 \sqrt{2} \frac{(x+y-7)}{\sqrt{2}}$   After that, I found the intersection between $Q$ and $V$ using equations and I got that the intersection points in $(O;XY)$ are $P_1(3;2)$ and $P_2(-1;6)$      2)Given the coordinates system $(O,X'Y')$ asociated to the basis    $B=[{b_1=\frac{1}{\sqrt{2}}; \frac{1}{\sqrt{2}};  &gt; b_2=\frac{-1}{\sqrt{2}}; \frac{1}{\sqrt{2}}}]$ with origin in    $O=(0;0)$ and the ellipse $9X'^2+5Y'^2-3X'+2Y'-10=0$ find the    coordinates of the centre of the ellipse in $(O,XY)$    So, here I found the centre of the ellipse in $(O,X'Y')$ and it was $(\frac{1}{6}; - \frac{1}{5})$, then, doing something similar to what I've done before I found out that the centre in $(O,XY)$ was $( \frac{11}{30 \sqrt{2}};$ $\frac{-1}{30 \sqrt{2}}$) Pgfplots with custom axis markers Assume you have a trigonometric function, say for simplicity sin(x). When plotting the function, how can one place the x-axis markers on 0, pi/2, pi, 3pi/2, 2pi, instead of the default numeric values that pgfplots uses? Should the top navigation be frozen (optional)? In Excel, the window can be frozen in place in such a way that you can always see the name of the column even though you go way down below the 'fold' of the screen.  On SE, when you scroll, the whole page goes up (or down). This means the top navigation bar is scrolled off screen. I'm not sure if it would be a good idea or not to fix the top navigation to the top of the screen and let the rest of the content scroll.  What do you think about this, in terms of pros and cons?  [Update]  With the new Top navigation bar, kudos to the design team, I think this question becomes relevant again. I'm aware of the busload of downvotes, but still.  The top navigation bar doesn't occupy much space and has two notification areas:   Inbox Achievements   Having these two notifications visible at all times would be nice, IMO.  [Update]  I've just noticed that I haven't used the word "optional" in this discussion... My bad. In Excel, the Freeze function is controlled by the user. You can optionally Freeze part of the interface, and you can eliminate the Freeze at will. Conditional formatting of an entire row based on multiple cells I'm trying to make a conditional formatting rule in Google Spreadsheet that would highlight a row green based on text in multiple cells.   If cells L2, M2, and N2 = APPROVED; and cell O2 = X; then row 2 = highlighted green. The lines wrap so much on v1.0.85 that only a few items can be displayed.  Edit: This is on the world's most low end tablet, Azpen A727.  Screenshots of the old:    and new, showing loss of quality Valid US visa on expired passport. Can I travel to the US? Determine which of $N$ points is not on $\sin(ax + b)$, where $a$ and $b$ are unknown. Suppose $N$ points ($(x_1,y_1), (x_2,y_2), ... (x_N,y_N)$) are given from a curve $y=\sin(ax+b)$ where $a, b$ values are unknown. Before giving these $N$ points to you, $y$ coordinate of one point is randomly tampered so that it does not lie on the curve.  Write a program to determine which point among $N$ points is NOT on the sinusoidal curve, whose $a$, $b$ values are unknown.  Any logic on how to approach this question, would be highly appreciate would be very thankful! Extract, convert, store and reuse (x,y) coordinate components Bootcamp: The startup disk does not have enough space to be partitioned When clicking continue on the first Boot Camp screen,  I am presented with a dialog that displays:     The startup disk does not have enough space to be partitioned.   You must have at least 39 GB of free space available.     This is despite "About this Mac" reporting 271GB of free space:    And "Disk Utility" reporting 268GB of free space:    Searching online I found  which suggested it was the result of Time Machine which i recently enabled and suggests to run sudo tmutil thinlocalsnapshots / 999999999999 which I did, it ran sucessfully, and I restarted, yet to no avail.  What is the solution to this instance of Apple's poor engineering?  Running macOS High Sierra 10.13.4 (17E202)