What I would like to do is loop through all of the classes that are extending a class i have called Cmd.  For instance, what I'd like to be able to do is something like this:  for (Class&lt;?&gt; c : classesExtendingSuperclass) {     cmds.put(c, c.getName()); }   Thanks.  Edit: I can't use reflections in my project, if I do it will complicate everything when using the program. I can't use Reflections due to the performance downsides in the project.
How does one go about and try to find all subclasses of a given class (or all implementors of a given interface) in Java? As of now, I have a method to do this, but I find it quite inefficient (to say the least). The method is:    Get a list of all class names that exist on the class path Load each class and test to see if it is a subclass or implementor of the desired class or interface   In Eclipse, there is a nice feature called the Type Hierarchy that manages to show this quite efficiently. How does one go about and do it programmatically?
What is the variance of Y = AX where A is a matrix? Here $X,Y$ are vector of length $n$ and $A$ is  a $n\times n$ matrix. Suppose the covariance matrix $D(X)$ is known? Do potions use concentration for their effects? I'm wondering how it is correct to structure sentence and what punctuation should be used. In particular, is the next sentence correct:     I was wondering if there's any progress on the issue.    Or should I put a question mark in the end of it. Also, can it be restructured to:     I was wondering: is there any progress on the issue? Invoking makeindex for nomencl I have spent many many hours failing to implement nomencl for my PhD thesis. The problem seems to be with invoking makeindex and creating the .nls file  I keep reading that I must invoke makeindex or write a Unix command:  makeindex filename.nlo  -s nomencl.ist -o filename.nls   But I don't know how to do this. I would be grateful for some instructions i.e. where do I type the command?    I am using TeXShop 2.43. How do I display 2 sections side-by-side? Matrix doesn't shrink when put in fraction. How do I change my username? Some time ago, when I installed Ubuntu, I chose a rather stupid username for my account that I do not want to use anymore. How do I change this (including the name of my home directory, and the name in the terminal) without losing settings for applications? How do I keep permissions and my keys for various authentification (e.g. email, SSH, GPG and more)? What settings could possibly get lost if I changed my username? Deleted comments are persisting in the global inbox I realise that there is other questions out there about the  (First open one I found is ), but this is marked .  I often get the below issue where it will notify me about comments on my  (in this case what appears to be the user re-writing after deleting their comment) that no longer exist.  Also, occasionally, I see comment snippets with text that doesn't match what is on the page when I view it.  Let me know if I should be trying to edit that one to remove the tag indicating that it has been fixed, and add the above as another answer. Finite group for which $|\{x:x^m=e\}|\leq m$ for all $m$ is cyclic. MacBook Pro never goes to sleep How does a battery ( primary cell ) work? I'm having an hard time understanding primary cells. There are plenty of videos and explanations about the reactions that happen inside the battery, but you must have a strong background in chemistry to really understand them. Instead, I would love to have a description that abstracts from the chemicals details, and still manages to explain its basic working princeples! I would like it to address the following questions/doubts:     Electrons flow form higher potential to lower potential so, when you buy a  battery, is an electric field already there, before connecting it to a wire? (I presume yes) So,How is this field created? Are the electrons at the top and the protons at  the bottom, or just electrons at the top and the bottom is neutral? How are electrons kept together in the same place before connecting the battery  to the wire? What does prevent them to flow inside the battery? How does the battery pump up the electrons? and at which rate? What makes it burn out? and after many cycles does it burn out?       I know there are a lot of questions but my mind is exploding. I don't expect everything to be abstracted from the chemicals but as long as you can through analogies, or intuitive principles, i'd love that. Anyway the main intent of the answer must be addressing the doubts listed. What does env x='() { :;}; command' bash do and why is it insecure? There is apparently a vulnerability (CVE-2014-6271) in bash:   I am trying to figure out what is happening, but I'm not entirely sure I understand it. How can the echo be executed as it is in single quotes?  $ env x='() { :;}; echo vulnerable' bash -c "echo this is a test" vulnerable this is a test     EDIT 1: A patched system looks like this:  $ env x='() { :;}; echo vulnerable' bash -c "echo this is a test" bash: warning: x: ignoring function definition attempt bash: error importing function definition for `x' this is a test   EDIT 2: There is a related vulnerability / patch:  which uses a slightly different test:  $ env 'x=() { :;}; echo vulnerable' 'BASH_FUNC_x()=() { :;}; echo vulnerable' bash -c "echo test"   unpatched output:  vulnerable bash: BASH_FUNC_x(): line 0: syntax error near unexpected token `)' bash: BASH_FUNC_x(): line 0: `BASH_FUNC_x() () { :;}; echo vulnerable' bash: error importing function definition for `BASH_FUNC_x' test   partially (early version) patched output:  bash: warning: x: ignoring function definition attempt bash: error importing function definition for `x' bash: error importing function definition for `BASH_FUNC_x()' test   patched output up to and including CVE-2014-7169:  bash: warning: x: ignoring function definition attempt bash: error importing function definition for `BASH_FUNC_x' test   EDIT 3: story continues with: Change hanging indent in description list I'm trying to get a description's list hanging indent to lie flush with the first line of text.  I have a description list such as the following:  \begin{description}  \item[Label the first] Lorem ipsum dolor sit amet, consectetur adipisicing                         elit, sed do eiusmod tempor incididunt ut labore et                         dolore magna aliqua.  \item[The longest label] Ut enim ad minim veniam, quis nostrud exercitation                           ullamco laboris nisi ut aliquip ex ea commodo                           consequat.  \item[Shrtlbl] Duis aute irure dolor in reprehenderit in voluptate velit esse                 cillum dolore eu fugiat nulla pariatur. \end{description}   This produces the following output:    I would like to have each paragraph indented so that the following lines are flush with the first letter of the list item's text, the way it's laid out in my TeX.  For instance, the "s" of "sectetur" should be right under the "L" of "Lorem".  I've tried looking through the documentation of , but I can't seem to find a good option.  I tried specifying [leftmargin=3cm, style=sameline], but this results in the following:    This isn't quite right: I'm trying to get each item lined up differently, so that the "L" of "Lorem" is not necessarily flush with the "U" of "Ut" or the "D" of "Duis".  Does anybody know a good way to do this? If a set of parentheses lies between a subject and its verb, and the parentheses contain an substitutive subject whose singularity/plurality disagrees with the original subject, whose singularity/plurality should be chosen for the verb?  In other words, in the following example, should "questions" (and its verb "are") be singular, or should they remain plural as shown?     Many (if not every) questions on this StackExchange are answered.   My intuition tells me that the two words in question should remain in plural forms, since the text in parentheses only interrupts the sentence (and the sentence would be grammatically incorrect if everything in parentheses were removed and the words were in singular form).  On the other hand, when read aloud (assuming one reads the text in parentheses), this has an uncomfortable sound to it, and I've seen others write in what would be the above example's singular-form case, so I'm curious to find out which is correct.  And, thinking about it, I suppose the same question would apply when commas are used in place of parentheses. How do I recreate this color overlay layer effect in Photoshop? I would like to use the overlay effect used on the screenshot(s) below.    I've tried experimenting with several Blending modes but keep missing the mark. I'm sure this has a very easy answer but I'm having trouble recreating the effect on my own.  Here are a few more images for further context:        Thanks in advance for your help. Is there a way to capture the viewport in Blender the same way as it is on 3DS Max? I know that by default I can render the viewport and everithing that is in the viewport to be the same as in the render. But, when comparing 3DS Max to Blender, I have certain limitations. In Blender I can render the view-port with vertices/edges/faces to be shown, to be selected, but not the reflections, shadows and such.  Is there a way to render the viewport in Blender as it is in 3DS Max?  Here's how I can do it in 3DS Max:  Viewport look    Render result of the viewport    Here is how I can do it in Blender:  Viewport look:      Render result of the viewport How to support different screen size in android find all the members of A4/K Let K={(1),(12)(34),(13)(24),(14)(23)} show that K is a normal subgroup of the alternating group of degree A4 and find all the members of A4/K and write down the group table for A4/K.   i know that K is the Klein four group and i have already proven it is a normal subgroup but i need a start on approaching the A4/K part of this question no direct answers are necessary,just ideas thank you! :) How can I hire a professor to answer my advanced technical questions in a niche area? In short, How does one go about hiring a professor or someone really well established in their field for a private tutoring session?  I tried looking online but can’t find much, mainly websites for tutors that are practitioners or “experts” as in with with n years of experience at best. This doesn’t cut it at my level as I am a researcher with a PhD and already have published papers on my topic.   However, I am very passionate about my subject and always looking to grow. So I do have questions, very technical (in my case computer science) and would happily pay a fee for consulting with a professor in the field.  Any advice? How to stop iPhone users from sending iMessages and send SMS instead I used to have an iPhone, but I changed to an android (shock, horror!). Unfortunately Apple refuses to let me go and whenever friends message me the messages get sent as iMessages (unless they remember to specifically chnge the format). I never get these messages. They never get resent as SMSs automatically as is supposed to happen. How can I get my phone number deleted from the iMessage list. I've turned off iMessage on the old iPhone.