Yesterday this Question asked by Interviewer what is the output for that line.  public class StringTest {    public static void main(String[] args) {       String s1 = "abc";       String s2 = "abc";       String s3 = s1+s2;       String s4 = s1+s2;        //check s1 == s2       System.out.println(s1==s2);        //check s3 == s4       System.out.println(s3==s4);   } }   when i looked at this question then thinking how the easy question asked by interviewer. I told him output s1==s2 and s3==s4 will return true and trueand i was very confident. Suddenly he said no thats the wrong output then i thinking he might be joking or trying to loosing my confidence, but till the end he said its wrong. When i checked the output was true and false . I also thinking how it is possible please solve my confusion by giving a appropriate answer. thanks in advance.
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?
Insert result of a parallellized select query into a table, in Postgresql According to ,      "Even when it is in general possible for parallel query plans to be   generated, the planner will not generate them for a given query if any   of the following are true:       The query writes any data or locks any database rows. If a query contains a data-modifying operation either at the top level or within   a CTE, no parallel plans for that query will be generated. This is a   limitation of the current implementation which could be lifted in a   future release."   Indeed, when I try to insert result of a parallel SELECT query into a table (either by SELECT.. INTO either by WITH..SELECT..INTO, the query is not executed as parallel query.  My question is: Is there any way to trick the Postgresql so that a SELECT query is executed as parallel query and then its result inserted into a table? How do I enumerate the properties of a JavaScript object? Is there any canon information in Harry Potter that proves one way or another whether a wizard always owns only one wand as a matter of routine?  What I am talking about is a wizard buying and owning one wand and also a second wand (for backup, or simultaneous use, or separate purpose, or ceremonial+work wand), akin to people buying more than one pair of boots, guns or hammers.  A proof would be either canon info showing someone owning 2 wands simultaneously; or a statement showing why that does not happen except in rare exceptions (see below).    NOTE: I am discounting special situations such as winning an extra wand in a duel ala Harry (e.g. the second wand's obtainment wasn't intended/planned), or someone winning a Death Stick from prior owner (in which case it was intended as a replacement wand and not an extra one); or taking another's wand for a time being, ala Voldemort and Lucius Malfoy (since it was more of a "temporary replacement because main wand was useless for the purpose due to paired cores" - far from a normal situation).  Also, I meant wands intended for use - e.g. if Malfoy would have a (imagined by me) collection of rare antique wands, that's as irrelevant as someone having flintlocks in a display case. Writing ISO 19139 compliant XML metadata from spreadsheet? I am looking at a way to migrate the metadata from a spreadsheet into ISO 19139 compliant XML metadata documents for a collection of shapefiles. I can parse the data out of the spreadsheet into strings without issue however I am getting lost on how to take those strings and use them to populate the elements.   This example:  covers most of what I want to do, however I would need to generate the tree beforehand based on the ISO 19139 schema. PyXB seems to have schema bundles for OpenGIS but I would like some insight on how to connect everything. How to Regex search/replace only first occurrence in a string in .NET? It seems the .NET Regex.Replace method automatically replaces all matching occurrences.  I could provide a MatchEvaluator delegate that returns the matched string after the first replacement, rendering no change, but that sounds very inefficient to me.  What is the most efficient way to stop after the first replacement? I'm writing a linguistics paper that uses a large amount of linguistic examples from a wide variety of languages, using the gb4e package. I want to be able to label each example with information about the language it comes from, as I've seen in some texts, sort of like this:   Language (family, citation, etc.)      (1) example text          glosses        'translation'    gb4e is great at formatting the examples themselves, but I can't seem to get the label placed where I want it, that is, placed immediately before the example and without an indent. Here's some example code:  \documentclass{article} \usepackage{gb4e} \usepackage{lipsum}  \begin{document} \lipsum[2]  Hungarian (Finn-Ugric, \emph{reference})   \begin{exe}   \ex \gll    J\'anos h\'aza\\               John house.his\\       \glt    `John's house'   \end{exe}  \lipsum[3] \end{document}   If the label text is outside the exe environment, it's treated like a regular paragraph, but if I try to put it inside, it gives me an error. How can I make it look the way I want? I've looked at other packages that do numbered examples, but they don't seem to have solutions either, and they also don't have the same functionality as gb4e that I need.  Any help would be greatly appreciated. When should a Test Case be marked as "No Apply"? How to identify unused CSS definitions from multiple CSS files in a project A bunch of CSS files were pulled in and now I'm trying to clean things up a bit. How can I efficiently identify unused CSS definitions in a whole project? Is it considered rude if you only ask Questions but almost never answer one yourself I have used the websites of SO a lot the past few months because I am busy with a large scale web project. I feel I get better answers here on SO than when I just do a Google search, maybe because I can be more specific here with my problem, and the responses are really fast.  Occasionally when I am not working I try to answer some questions, but the question almost always has an answer which is 'as good as' or 'better' than the answer I would supply.  So my question/answer ratio is about 20/1 something, if not more. When I look at my profile page I see a bucket-load of questions and almost nothing I answered myself.  Is this considered bad behaviour? I can see that this looks a little egoistic.  : One devoted to one's own interests and advancement. I've played around in the past of the 2D Flash fan-made version of the popular Valve game Portal.  It has basically the exact same mechanics, but as a 2D side-view flash game.  Lately I've toyed around with creating a simplified flash version of some of my favorite franchises (such as Zelda, Mario, Splinter Cell, etc.).  Of course, nothing is "stopping" me from just using the same mechanics and just changing the name to something not copyrighted.  I have witnessed projects that have tried to directly port a 3D game into a 2D simplified version, with the exact same plot and puzzles (Ocarina of Time in 2D comes to mind), and I have seen them being shut down.  But I am not likely going to exactly duplicate any game...just borrow some of the source material and basic underlying mechanics.  For example, if I were to make a Zelda-influenced fan game, I would have items such as the Hookshot, Boomerang, and all other sorts of ones from the Gameboy Zeldas; just with a custom plot and dungeons.  With likely the same mechanics.  What are the legal issues involved in this?  I used to think it was a "Don't do this ever; it's a bad idea."  But then I've seen the Portal clone, and now I'm curious. What is the maximum or minimum tire width I can fit on my bicycle We often get questions on bicycles.stackexchange about fitting wider or narrower tires to bicycles. We have a large number of these with answers suiting the specific bike or style of bicycle in question, but I have been unable to find one that provides a generic answer covering off all things that need to be considered. For most bicycles, the answer is the same regardless of the specific style and sizes of tires in question.   This is intended as a canonical question that we can point closed questions to. How do you compute the earth's radius at a given geodetic latitude? Python interpreter error, x takes no arguments (1 given) Are there any clones/alternatives for running a Stack Exchange style Q&A site? Why is 'that' sometimes optional before dependent clauses? Prove that $A+I$ is invertible if $A$ is nilpotent Possible Duplicate:          Given $A^{2012}=0$ prove that $A+I$ is invertible and find an expression for $(A+I)^{-1}$ in terms of $A$. ($I$ is the identity matrix). So I tried deleting a question, my question. I'm not a mod, but I have reputation above 10k. I received this message after hitting delete, asking me to make sure I wanted to:    But after clicking Delete Question, I saw this:    It turns out that because the question has answers, I'm prohibited from deleting it. If I can't actually delete this question at all, could it just tell me immediately, and only show me the warning if I can actually delete it?  This is akin to the following analogy.     You see a flyer in your local paper stating there's a new burger shop   opening.  Great, you think to yourself, and rush over to get yourself   some burgers.  On your way into the parking lot, you see a huge banner   proclaiming one of their newest burgers. You see some employees walk   in and out of the restaurant, with T-Shirt with pictures of burgers on   them.  Great, you think to yourself, and walk in.   You get in line,   and after what seems like ages, you finally make it to the front.  You   look up at the menu.  You see that they also sell sandwiches. No, you   tell yourself, I'm looking for burgers.  You see that they also sell   burritos! No, you tell yourself, I'm looking for burgers.  Then you   see that they sell burgers. Great! You pick out a burger, then tell   the employee at the register, "Sir, I'd like to get a regular burger   please." Immediately, the employee looks up, with a quizzical look on   his face, saying "Sir? We don't sell burgers here.".   It's the same situation. I've come to that prompt so that I can delete a question.  After repeated messages and windows letting me know the consequences of deleting, what will happen after I have it deleted, I am told that the option of having it deleted by my own hand never existed in the first place. Java Strings: "String s = new String("silly");" I am trying to prove that any conjugate of $a$ has the same order as $a$.  Let $G$ be a group and let $a \in G$.  An element $b \in G$ is called a conjugate of $a$ if $b=xax^{-1}$.  My professor gave us a hint.  Prove $a^k=e$ iff $b^k=e$ for all $k \in \mathbb{Z}$ implies $o(a) = o(b)$.  My first move is to $b^k = (xax^{-1})^k = (x^{-1})^ka^kx^k = (x^{-1})^kex^k = (x^{-1})^kx^k=x^{-k+k}=x^0$  I am not sure that I am doing this correctly?  I am trying to get $b^k=e$.  However when I raise $(xax^{-1})^k$, I am not sure if I what I have done is correct?  I am kind of confused here. I´m having some trouble with my udev rule. At the moment, I had my udev rule setup to execute a script whenever a Android phone is connected to any USB port on the computer. But I don´t want the script to be executed from every USB port. I just want that the script to be execute in example when the phone is connected to the 4th USB port and nothing should happen when it is connected to 1st, 2nd or 3rd USB port.  How can I achieve that and how can I determine the for example 4th USB Port?  I would highly appreciate your help.  My current udev rule:  KERNELS="1-2:1.1", ACTION=="add", ENV{DEVTYPE}=="usb_device", ATTRS{idVendor}!="1d6b", ATTRS{idVendor}!="203a", ATTRS{idVendor}=="****", ATTRS{idProduct}=="****", RUN+="/usr/local/bin/tmp.sh $attr{serial}"