Why I was unable to call the class member even after declaring the member as protected
What is the difference between public, protected, package-private and private in Java?
Define a new block environment in LaTeX beamer I have two kinds of examples in my document. I want to use different colors, say, red and blue. This is what I am doing now.  \documentclass[]{beamer} \usetheme{Madrid} \begin{document}  \begin{frame} \frametitle{Test} \setbeamercolor{block title}{fg=white,bg=red!75!black} \begin{block}{First Kind Example} This is example of the first kind. \end{block} \setbeamercolor{block title}{fg=white,bg=blue!75!black} \begin{block}{Second Kind Example} This is example of the second kind. \end{block} \end{frame}  \end{document}   I know this is kind of stupid. I want to define two new block environments, one for each color, so I don't need to use setbeamercolor every time I use them.   \begin{block1}{First Kind Example} ... \end{block1} \begin{block2}{Second Kind Example} ... \end{block2}   I know I need to define these two new environments in the preamble, but don't know how. Thanks for the help.  By the way, what is a good reference on these kinds of tricks in LaTeX/beamer? Any recommendations? What TV movie had lost space cadets who piloted yellow tripod robots, and a squid bad guy? File permissions and saving External hard drive and Recycle Bin behavior When my Seagate external hard drive is plugged in, its $RECYCLE.BIN folder automatically contains all the files contained in the Recycle Bin of the PC. Is it true that actually we don't have any Recycle Bin of external hard drive, rather it is the Recycle Bin of the PC? Why is it so? Why does my user number show up in the search box when clicking my profile information? I've only played one placement match so far and I won it because my opponents were less than stellar.  I'm afraid that if I get similar placement matches in the future and end up winning them all I might get put into a league beyond my skill.  How many different leagues are there?  Once placed in a league, is there any way to move to a different one?  How? Finding distance between points in two different layers along route in ArcMap? I need to find the distance between points in separate layers along a stream network. I have source sites for macro-invertebrates and sites where they are lacking. I need to find the distance between the source sites and the sites where they are not through the stream network.   I tried the linear referencing toolbox but the locate features along route tool can only use one layer of points and has not way to differentiate between sources and not source sites.  Any ideas?  I am using ArcMap 10.3? I am having Problems converting user rights. I want to assign the following rights to certain files/folders but dont know hat to translate them into a format which chmod will work with like chmod 755.  -rwxrwxrwx    will be?  And  drwxr-xr-x   will be?  And finally  -rw-r--r--   will be? Every package "has no installation candidate" While attempting to install openssh-server on Ubuntu 14.04 64-bit, I get the following error:  Package openssh-server is not available but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'openssh-server' has no installation candidate   I see the same error when trying to install any package.  This is the sources.list file:  deb http://archive.canonical.com/ubuntu hardy partner deb-src http://archive.canonical.com/ubuntu hardy partner According to the well ordering theorem "". Whenever we have a well ordering on a set, it is not difficult to construct a new well ordering with a largest element. My question is:     For a given infinite set, can we find a well ordering on it such that there is no largest element? Are there areas of mathematics (current or future) that cannot be formalized in set theory? I often read that ZFC can formalize "most" of everyday mathematics, but I could never find an example which it cannot. The closest I got is differential geometry (DF), where some article mentions that the translation from concepts of DF into set theory would render it almost "meaningless", in the sense that any intuitions one could have would be lost in the translation. So, if I didn't misunderstand, at least in theory, the translation could be done, so that a future AI machine could prove theorems of differential geometry using set theory. On the other hand, the Stanford Encyclopedia of  Philosophy states that "all of mathematics can be reduced to a formal system of set theory"().   So, the questions are:    Is there any current area of mathematics that could be not formalized within set theory? If so, which ones? and  Is there any reason to think that every math of the future will be always formalizable in set theory? any references to read on the subject are welcomed!   Clarification: by set theory I am not restricting to ZFC, but to any flavor of it, including all additional axioms you want (about large cardinals or any kind) I've grown quite fond of HTTP reverse proxies in our development environment and found the DNS based virtual host reverse proxy quite useful. Having only one port (and the standard one) open on the firewall makes it much easier for management.  I'd like to find something similar to do SSH connections but haven't had much luck. I'd prefer not to simply use SSH tunneling since that requires opening port ranges other than the standard. Is there anything out there that can do this?  Could HAProxy do this? Unfair 3 Sided Die Question Say you have an unfair 3-sided die.  Side 1 will be rolled with probability $P_1.$ Side 2 will be rolled with probability $P_2.$ Side 3 will be rolled with probability $P_3.$  Find a formula for the probability that the 8th 3 will be rolled on the 10th roll.  Here is how I started:  $$ \sum_{i=8}^{10}P(T_8 = i) $$  Im just having trouble with that expansion? How to prove that any idempotent matrix is diagonalizable? Where can I find some guidance on index strategies? For groups $A,B,C$, if $A\times B$ and $A\times C$ are isomorphic do we have $B$ isomorphic to $C$? The motivation for this question is in my answer to this post :       (1) If I take $A$, $B$ and $C$ three groups such that $A\times B$ is isomorphic to $A\times C$ then do we have $B$ is isomorphic to $C$ ?   In the post a counter example is given when $A$ is an infinitely generated group. However I cannot get a counter-example when $A$, $B$ and $C$ are assumed to be finite groups. Note that there is no reason a priori if $\phi$ is an isomorphism from $A\times B$ to $A\times C$ that $\phi(A\times\{1_B\})=A\times\{1_C\}$.   In the case of finite groups it is true because of the Krull-Schmidt theorem : .  A slightly more general question is the following :     (2) If $B$ and $C$ are two finitely generated groups, can I always find a finitely generated group $A$ such that $A\times B$ is isomorphic to $A\times C$?   If $A$ is not assumed to verify any property but to be a group we can take :  $$A=B^{\mathbb{N}}\times C^{\mathbb{N}} $$  Furthermore replacing :$ \prod_{\mathbb{N}}$ by $\bigoplus_{\mathbb{N}}$ (or more likely the restricted product for groups but I am not sure of a well known notation, it is the subgroup of the product with all but a finite number components being trivial) will give you the same result for countably infinite groups.   $\underline{\text{Edit}}$ : To be clear about what I am asking. (1) is kown to be true for finite groups whereas (2) is known to be true when we are considering groups without restriction (even just for countably infinite groups). Let us pretend we are working on the smaller class of groups : the finitely generated groups. Is there any counter example to $(1)$? Is there any counter example to $(2)$?   $\underline{\text{Edit 2}}$: Here is a partial answer, from the classification of finitely generated abelian groups $(1)$ is always true if all groups are assumed to be abelian finitely generated groups. Now assume that $A\times B=G=A\times C$. Then you have (derived groups) :  $$D(G)=D(A)\times D(B)=D(A)\times D(C) $$  So the abelianizations verify :  $$A^{ab}\times B^{ab}=A^{ab}\times C^{ab}$$  Because we are now in the realm of finitely generated abelian groups we get :  $$B^{ab}=C^{ab} $$  So $(2)$ cannot be true in general for instance you can take $B:=\mathbb{Z}$ and $C=\mathbb{F}_5$, those two groups have different abelianizations.   The new question can be found here : What is an ultra-wide lens? What is the point at which a lens is considered "ultra-wide angle" vs just wide angle? I just read a book "Linear Algebra and Its Applications 4E" by David C. Lay. The book is (should be) LaTeX typeset. The matrix and equations are so nice, please see the following 3 examples:        It's so beautiful, so I want get the same effect inside my paper. Here is my code:   \usepackage{amsmath} \usepackage{colortbl} \newcommand\y{\cellcolor{clight2}} \definecolor{clight2}{RGB}{212, 237, 244}%  %%% \[A=\left[ \begin{array}{ccccc} \y 0 &amp; -3 &amp; -6 &amp; 4 &amp; 9 \\    -1 &amp; \y -2 &amp; -1 &amp; 3 &amp; 1 \\ -2 &amp; -3 &amp; 0 &amp; \y 3 &amp; -1 \\ 1 &amp; 4 &amp; 5 &amp; -9 &amp; -7      \end{array} \right]\]  \[A=\left[\begin{array}{cccccc} \rowcolor{clight2} 3 &amp; -9 &amp; 12 &amp; -9 &amp; 6 &amp; 15\\ 0 &amp; 2 &amp; -4 &amp; 4 &amp; 2 &amp; -6 \\ 0 &amp; 3 &amp; -6 &amp; 6 &amp; 4 &amp; -5 \end{array} \right]\]   And the result:     But how to add these arrows?? Intuitive Explanation of Tippe Top Effect? Why didn't Dumbledore show his memory of Barty Crouch Jr's confession to Cornelius Fudge to confirm his point that Voldemort returned? Wouldn't that just prevent all the mumbo-jumbo happening in the 5th book?