I tried to enter assertTrue into code and found that i need to import junit lib.   In this code,  import static org.junit.Assert.assertTrue; //import org.junit.Assert;   with this didnt worked  public class Person implements Serializable {        // some code there          assertTrue(p2.getAge() == p.getAge());         assertTrue(p2.getName().equals(p.getName())); }   So i tried with import org.junit.Assert; but that asserTrue didnt worked then I tried with import static org.junit.Assert.assertTrue; and then it works. I need explanation why need static ?
When used like this:  import static com.showboy.Myclass;  public class Anotherclass{}   what's the difference between import static com.showboy.Myclass and import com.showboy.Myclass?
Properties vs Methods Quick question: When do you decide to use properties (in C#) and when do you decide to use methods?  We are busy having this debate and have found some areas where it is debatable whether we should use a property or a method. One example is this:  public void SetLabel(string text) {     Label.Text = text; }   In the example, Label is a control on a ASPX page. Is there a principle that can govern the decision (in this case) whether to make this a method or a property.  I'll accept the answer that is most general and comprehensive, but that also touches on the example that I have given. What is the value of $\sum\limits_{i=1}^\infty\frac{1}{p_{p_i}}$ where $p_{i}$ is the $i$th prime? Hello [Comma?] John, The set of all finite subsets of the natural numbers is countable Expectation and variance of the geometric distribution How can one use memorylessness and the  and the  to find the expectation and variance of the geometric distribution?  I will post my own answer, but as always, that shouldn't stop anyone else from posting theirs. Find the number of natural solutions of $5^x+7^x+11^x=6^x+8^x+9^x$   It's easy to see that $x=0$ and $x=1$ are solutions but are these the only one? How do I demonstrate that?  I've tried to write them either:  $$5^x+7^x+11^x=2^x*3^x+2^{3x}+3^{2x}$$  or  $$5^x+7^x+11^x=(5+1)^x+(7+1)^x+(11-2)^x$$  and tried to think of some AM-GM mean inequality or to divide everything by $11^x$, but those don't seem like the way to go. Any hints? How do I print a double value with full precision using cout? In my  I was printing a double using cout that got rounded when I wasn't expecting it.  How can I make cout print a double using full precision? In Python, how do I determine if an object is iterable? Infinitely many primes of the type 5 mod 6. Problem: Prove that there are infinitely many primes of the type 5 mod 6.  My professor did the problem and the proof was horribly long. Can someone show me a shorter version of the proof of this problem. Emacs: Symbol's value as variable is void Top Down RPG Movement w/ Correction? The -k option (or --convert-link) will convert links in your web pages to relative after the download finishes, such as the man page says:     After the download is complete,   convert the links in the document to   make them suitable for local viewing.   This affects not only the visible   hyperlinks, but any part of the   document that links to external   content, such as embedded images,   links to style sheets, hyperlinks to   non-HTML content, etc.   So, if I didn't specify -k, can I run wget again after the download and fix that, and if so, what would be the proper command? My guess is wget -c [previous options used] [url] and run it in the same working directory as the file were downloaded to. Constraint the camera to look at an object In my scene I have a camera sitting at the origin. I would like to contraint it so that it always looks at the center of a given object. But the camera should not change its position.  I found some answers using a "TrackTo" or "LockedTrack" constraint but could not manage to make it work.  Could I probably use a Driver for this and if yes, how can I adjust it?  Thanks in advance! Success of Bernoulli trials with different probabilities When $\min_{x \in X,y \in Y} f(x,y) = \min_{x \in X} \min_{y \in Y} f(x,y)$? $_POST empty on utf-8 characters What is the formal definition of polynomial ring of several variables? Let's consider a polynomial ring of single variable. One can define them informally by saying $P(X)=\sum_{i=1}^n a_n X^n$ while $X$ is an indeterminate variable. However, since mathematics is based on first-order logic, one can only talk about something that actually exists (as a set). So as its name says, indeterminate variable is not a sentence in $ZFC$. Nevertheless, we can formally define a polynomial ring $R[X]$ as a subset of $R^\omega$ whose support is finite. ($R$ is a commutative ring with unity) Just like a single variable, I want to know what would be the formal definition of a polynomial ring of several variables. What would be a formal definition? === I have figured out a candidate. That is,  Candidate for a &quot;Definition of a polynomial ring $R[X_1,...,X_n]$&quot;. ($R$ is a commutative ring with unity) Let $R[X_1,...,X_n]$ be the set of all functions $f:\omega^n \rightarrow R$ whose support is finite. Define $(f+g)(a,b,c)=f(a,b,c)+g(a,b,c)$ and $(f•g)(a'',b'',c'')=\sum_{a+a'=a''} f(a,b,c)•g(a',b',c')$ (Note that in this way, $+,•$ are well defined.) Then, it can be checked that $(R[X_1,...,X_n],+,•)$ is a ring.  Is this a formal definition of a polynomial ring? Can virtual particle have mass? Do all virtual particle travel at light speed in a vacuum? else wouldn't that imply they should have rest mass however tiny? When they pop back out of existence do their mass disappear instantly? BTW what is the heaviest virtual particle ever found? Period character used for local computer name I'm wondering about the period character . used as a shortcut for the local computer name.  You can use it when logging into Windows 7, for example, to specify that the user account you're entering belongs to the local computer rather than to a domain:  .\MyLocalUserAccount   And you can use it within a Windows Management Instrumentation (WMI) query to indicate that the target is the local computer rather than a remote computer.  You can also use it when working with named pipes to for similar purposes.  However, you cannot use it as the UNC network name for the computer, like this:  \\.\MyShare   Does this character have an official name (e.g. "LocalHostToken") and when and where can it be used for this purpose? Can't understand a proof: Let $a,b,c$ be integers. If $a$ and $b$ divide $c$, then $lcm(a,b)$ also divides $c$  Proof I've been shown:  Since $c$ is a common multiple of $a,b$, it means that $lcm(a,b) \leq c$.  So: $c=q\cdot lcm(a,b)+r$, $q \in \mathbb Z$ and $0\leq r \leq lcm(a,b)$  Since $c$ and $lcm(a,b)$ are common multiples of $a,b$, then so is $r$. But $m$ is the least common divisor, then it means $r=0$.   [Proof taken from: http://www.math.utah.edu/~wood/4400/hw1sol.pdf]  I cannot understand the last step... Why does it imply that $r=0$?   Thank you!