Java: Splitting CSV file that contains multiple lines
Java - Splitting a CSV file into an Array
Evaluate $ \int_{0}^{\frac{\pi}2}\frac1{(1+x^2)(1+\tan x)}\:\mathrm dx$ How to make an alias permanent? I have created an alias:  alias shh='sqlplus hfdora/hfdora@hfd1"     After creating this alias I was able to enter my database only by typing shh.  But after closing my shell, I wasn't able to find the alias next time. Even after typing only alias, shh was not showing in the list.  Is there any file to make an alias permanent so that it will not be erased? Is it possible to install an old version of Mac OS on a new Mac? How can I recover a deleted file on Android? return statement vs exit() in main() Should I use exit() or just return statements in main()? Personally I favor the return statements because I feel it's like reading any other function and the flow control when I'm reading the code is smooth (in my opinion). And even if I want to refactor the main() function, having return seems like a better choice than exit().  Does exit() do anything special that return doesn't? "Interested with the course" or "interested in the course"? Interested in/with the course   Which preposition is correct? in or with, or both. IBM Slack links broken Does anyone know where I can find working Slack invite links to any of IBM's Slack pages? The Slack links on  are all broken. Thank you. Beryllium Vacuum Sphere Boat/Aircraft Is it possible to make a solid rigid evacuated "balloon" out of Beryllium or other elements or alloys?  The critical buckling pressure at which an evacuated sphere is given as $$ P_1=\frac{2E\cdot\left(h/R\right)^2}{\sqrt{3\left(1-\nu^2\right)}} $$ where $E$ is , $h$ the shell's thickness, $R$ the radius to the midsurface shell, and $\nu$ is .  Of course this is theoretical and experimental and literature values for submersibles hover around 1/4 of the theoretical pressure.  Beryllium has the following properties:   Density=1.85 g/cm$^3$ Young's Modulus=287*10$^9$ Pa Poisson Ratio=0.032   Calculating the upward force, buoyancy at 101.3 kPa atmospheric pressure and Radius of 10m gives 4.24*10$^8$ N. The weight of this sphere with shell thickness 1mm has 2.32*10$^7$ N downward force of Beryllium material, so it will theoretically float at ground level.   Calculating the critical buckling stress of this beryllium sphere is 331.57 kPa, which is 3.27 times the atmospheric pressure of 101.3 kPa, so theoretically it won't buckle. But in experimentation done in earlier experiments as stated before, due to construction/material non-ideal situations, the critical buckling formula predicts about 4 times stronger than actual, so it would need about 400 kPa, not 331 kPa as Beryllium sphere with this specification would hold. Increasing the strength capability also increases weight and therefore lowers it's ability to float, but Beryllium is the closest element with this situation I have calculated that could work if ideal (I have only been using periodic table elements and household materials)  Is it possible with an alloy of elements? Using the equations for buckling and buoyancy, the following is needed. What alloys/materials come to your mind?  Material considerations:   Material with larger Poisson ratio Material with larger Young's Modulus Less dense material Construction (is it possible)   Material considerations affect on lift   Thickness can be larger, increases strength by the squared. But also increases weight. If a material with lower density with similar structural properties as Beryllium is used, it would help. Radius can be lower for same reason, but also lowers buoyancy (volume)   My other designs (don't worry about these just yet, just if you are curious is a vacuum sphere with a pressurized "outer tube" with spokes in tension (carbon fiber nanotubes maybe) to keep the 2 spheres in position. Another is a spherical truss out of carbon fiber nanotubes with a light membrane around. The truss prevents the outer membrane from collapsing due to the atmospheric pressure  The "point" of this if you ask, as to why not use a traditional balloon is it can be used as a boat by filling the sphere with air, and then used as a aircraft at will by evacuating the sphere. An alternative mode of transportation for sea vessels etc. Space which is connected but not path-connected I have some lines. I want to draw perpendicular lines at the start and end of the lines, on both sides of the lines.  Can somebody help me in Python?  I am using ArcGIS. Random plot based on a specific random seed How can I set desktop defaults for new users? How can I set up desktop defaults, much like most distributions do, for every new user? (ex. default wallpaper, apps, etc) .NET String.Format() to add commas in thousands place for a number I want to add a comma in the thousands place for a number.     String.Format()? Precedence of user and group owner in file permissions I just ran into something unexpected (for me) regarding file permissions on Linux (Arch Linux). Basically I have:   userX in groupX fileX userX:groupX ---rwx----   What puzzles me: I cannot perform any action (rwx) on fileX. Is this right? Can someone please confirm this is indeed the expected behaviour?  The only actions I can perform are mv and rm because I have write permissions on the parent directory.  The thing is, I always thought these permissions collapse on each other, starting with the most general one (other -> group -> user). In other words, if o=rwx who cares what the persmissions for group and user are? Apparently this is not the case but it doesn't make much sense to me; it seems counterintuitive. The only thing this approach seems to be useful at, is to easily exclude a very specific person / group, which doesn't seem like a smart way to go at it (imho). Besides, the owner (and group?) should be able to chmod anyway right? Any thoughts on this matter? My book uses the argument that the multiplicities of a few macrostates in a macroscopic object take up an extraordinarily large share of all possible microstates, such that even over the entire lifetime of the universe, if each microstate had an equal chance of being accessed, fluctuations away from equilibrium would never occur.  My question to this statistical proof is this: In the real world, is there really an infinitesimal but nonzero chance that macroscopic systems could access some of the more unlikely macrostates (e.g. heat transfer from a cold object to a hot object)? How do I get from Terminal 1 to Terminal 5 in Fiumicino Airport? How has the age of the Universe been derived from the observations made by the Planck mission? Would NAT be eliminated transformed in ipv6? NAT is a wonderful concept used in ipv4. It is the major reason for the existence on internet, in my concerns. There are no networks in the world that doesn't work without employing NAT.  All I seek to know is that, would NAT be required if after ipv6 is implemented, would NAT be eliminated or be used in a different way(Transformed or Upgraded into a new version with some added abilities to tackle any situations or problems that the network specialists or researchers foresee). I have to find an easy ring which this ring is isomorphic with.  I can prove that $5 = (2+i)(2-i) \in (2+i)$ but this doesn't help me further.  My book says the answer is $\mathbb {Z_5} $ Convergence of $\int\limits_1^{\infty}x^\alpha\sin(x^\beta)dx$