Am using this code for deleting the specific file in all directories and sub directorates in a drive but its not working. please help me in this regard. If i want to delete the specific file in all drives how to do.      static String refile= "input.txt";       public static void deletemyfile(File directory) {     if (directory.exists()) {            File[] files = directory.listFiles();            if (null != files) {                  for (int i = 0; i &lt; files.length; i++) {                         System.out.println(files[i].getName());                         if (files[i].isDirectory()) {                                deletemyfile(files[i]);                          } else  {                               String temp ;                             temp = files[i].getName();                                                           if (temp==refile){                              System.out.println("name matched and about to delete");                              (files[i]).delete();                           } else{                              System.out.println("name not matched");                         }                            }                  }            }     } else {System.out.println("wrong path");     }   }
I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?
Suppose that $y_1(x)$ and $y_2(x)$ are solutions of the differential equation $y''+py'+qy=0$ on $I$. How can I show that if $y_1$ and $y_2$ vanish at the same point then they are not linearly independent?   Here is my attempt to prove the problem. Since $y_1(x)$ and $y_2(x)$ are solutions of the differential equation $y''+py'+qy=0$ on $I$, it is enough for me to show that the Wronskian of $y_1$ and $y_2$ denoted by $W(y_1,y_2)$ is zero. Now since $y_1$ and $y_2$ vanish at the same point say $p$ we have $y_1(p)=0$ and also $y_2(p)=0$.   Solving for $W(y_1,y_2)(p)$ we have: $y_1(p)y_2'(p)-y_2(p)y_1'(p)=0$ since $y_1(p)=0$ and also $y_2(p)=0$.   Am I correct? Thanks we all study mathematics , and all of us learn mathematical methods to solve problems , we learn how to prove , how to think mathematically   but the question is, what is mathematics ? how can we define it as a branch of science ? I've encountered a particular type of writing occasionally and it being, derp, in writing, it's hard to tell whether there's an accent behind it. The English used seems to me to be simply incorrect, but I can't help but feel that the following features are part of a dialect or a regional style of English. One of the most glaring (and grating) features is the substitution of &quot;saw&quot; with &quot;seen&quot;.  He seen him at the shop the other day. I seen that you were looking for... etc.  The use of &quot;away (to)&quot; is also peculiar, if not incorrect.  He was away to open the door when... He was away to get what he had asked for. etc.  I haven't come across these forms very often, and even then it was accompanied by otherwise mostly correct English, which is what makes me wonder what the hell. This is more intellectual curiosity than anything else. Why does my procedure run slowly until I update statistics? Nature of the quantum degeneracy pressure Integral of Sinc Function Squared Over The Real Line I am trying to evaluate $$\int_{-\infty}^{\infty} \frac{\sin(x)^2}{x^2} dx $$ Would a contour work? I have tried using a contour but had no success. Thanks.  Edit: About 5 minutes after posting this question I suddenly realised how to solve it. Therefore, sorry about that. But thanks for all the answers anyways. Is adjoint of singular matrix singular? What would be its rank? Let $A$ be a square and singular matrix of order $n$.  Is $\operatorname{adj}(A)$ necessarily singular? What would be the rank of $\operatorname{adj}(A)$? Does the sum of reciprocals of primes converge? Is this series known to converge, and if so, what does it converge to (if known)?  Where $p_n$ is prime number $n$, and $p_1 = 2$,  $$\sum\limits_{n=1}^\infty \frac{1}{p_n}$$ Does there exist a $1$-form $\alpha$ with $d\alpha = \omega$? How to apply a texture to only one side of a plane How can you have an image as a texture (in this case on cloth) that is only applied to one side of a plane?  I would like the reverse side to be a solid color.  Please see below image where the cloth has the image texture on both sides. Do you have to take the second leg of a domestic flight? Say I want to book a flight from Fort Lauderdale to Chicago.  Say the airline also flies to St. Louis from Fort Launderdale but has a connecting flight through Chicago.  If I book that flights from FLL->ORD->STL and just get off in Chicago, what possible problems can I run into, assuming I didn't check any bags and only have carry on?  This scenario exist for Southwest, but I wanted this be more of a general question that would apply to all airlines. How to do selective-color in Photoshop? How to make the single color in a photography to be color and other parts changed to B&amp;W?.  Don't know exactly the name of the effect, to be more clear in the following photo I want the green part to be green and other parts( leg and sandal) in B&amp;W..    How to achieve that effect in Photoshop? How to debug a Custom Timer Job in SharePoint 2010? About finding the function such that $f(xy)=f(x)f(y)-f(x+y)+1$ Editing photo dimensions in large batches If I had the time, I would go through each and every photo to make sure that the dimensions and quality are pixel perfect. However, I'm in a time crunch, and need to make the couple hundred photos that are 4320 x 3240 into 950x630.   now I could- 1. Upload them into WordPress, uses native image reducing components and J query go from there. 2. Go through each and every photo, reduce file size, and proportion and bring it to Yahoo's PNG processing script.  However, maybe I'm missing a choice or alternative workflow that would allow for processing all of these photos in a clear manner without losing quality or perspectives. Any workflow suggestions? How can I check for an empty/undefined/null string in JavaScript? How can I attach a file to a question? How to identify predatory publishers/journals What are the best strategies for assessing if a journal is a &quot;vanity&quot; or &quot;predatory&quot; journal that should be avoided (both for publishing in and reviewing for)? For example, how would one go about determining if a journal/publisher belongs on ? I don't know what I've done, but all of a sudden I am unable to compile any document which uses the geometry package. Minimal (non)-working example:     \documentclass[11pt]{article}      \usepackage{geometry}  \begin{document} test \end{document}   doesn't produce any output, and this is what I see in my error summary screen in TeXnicCenter:    The red arrow points to what seems to be the problem: something about the bundle "oberdiek" and its package "ifvtex" is causing pdflatex.exe (which, while I don't really know what it does, sounds pretty important) to "not be initialized". I , and it's relevance here is a mystery to me.  I've confirmed that all of my files without the geometry package compile just fine; however, that doesn't mean that the problem is with the geometry package - what seems more likely is that there is some hidden cause of the error, and geometry happens to be one way to induce that. By the way, I've tried compiling a document which includes the ifpdf and ifvtex packages separately, and they do just fine; it's only when I include the geometry package (which for some reason requires these ifpdf and ifvtex packages) that the error occurs.  I've tried the only things I can think of:   going into MiKTeX Package Manager (by the way I am using 2.8), and removing + reinstalling both geometry and oberdiek refreshing the file name database ("FNDB") deleting all automatically generated files, as well as simply starting over in a new document   So I'm stuck now. I've considered attempting to just get rid of all traces of MiKTeX and TeXnicCenter from my computer and starting over, but that seems a bit excessive - after all, the geometry package was working for me . I honestly am not sure what I did to cause this; I've spent today trying to make a better template file for myself, and so I've been trying out new packages, but if I'm not loading these new packages there shouldn't be any conflicts, right?   Actually, I've just now thought of something that I think I did between the last time it worked and now, so is a possible candidate for the cause: I had to install some package manually, as it wasn't available on MiKTeX, and so I created a folder and pointed MiKTeX to it (i.e. the second option ). The package didn't do what I wanted, so I deleted the folder and removed it from the list of folders I told MiKTeX to check. Perhaps it's still trying to reach it for some reason? How to find a global minimum for $\frac{1}{2}x^tQx-b^tx$