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• Why doesn't java.util.Set have get(int index)?

  - by Marty Pitt

  I'm sure there's a good reason, but could someone please explain why the java.util.Set interface lacks get(int Index), or any similar get() method? It seems that sets are great for putting things into, but I can't find an elegant way of retrieving a single item from it. If I know I want the first item, I can use set.iterator().next(), but otherwise it seems I have to cast to an Array to retrieve an item at a specific index? What are the appropriate ways of retrieving data from a set? (other than using an iterator) I'm sure the fact that it's excluded from the API means there's a good reason for not doing this -- could someone please enlighten me? EDIT: Some extremely great answers here, and a few saying "more context". The specific scneario was a dbUnit test, where I could reasonalby assert that the returned set from a query had only 1 item, and I was trying to access that item. However, the question is more valid without the scenario, as it remains more focussed : What's the difference between set & list. Thanks to all for the fantastic answers below.

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• structDelete doesn't affect the shallow copy?

  - by Travis

  I was playing around onError so I tried to create an error using a large xml document object. <cfset XMLByRef = variables.parsedXML.XMLRootElement.XMLChildElement> <cfset structDelete(variables.parsedXML, "XMLRootElement")> <cfset startXMLShortLoop = getTickCount()> <cfloop from = "1" to = "#arrayLen(variables.XMLByRef)#" index = "variables.i"> <cfoutput>#variables.XMLByRef[variables.i].id.xmltext#</cfoutput><br /> </cfloop> <cfset stopXMLShortLoop = getTickCount()> I expected to get an error because I deleted the structure I was referencing. From LiveDocs: Variable Assignment - Creates an additional reference, or alias, to the structure. Any change to the data using one variable name changes the structure that you access using the other variable name. This technique is useful when you want to add a local variable to another scope or otherwise change a variable's scope without deleting the variable from the original scope. instead I got 580df1de-3362-ca9b-b287-47795b6cdc17 25a00498-0f68-6f04-a981-56853c0844ed ... ... ... db49ed8a-0ba6-8644-124a-6d6ebda3aa52 57e57e28-e044-6119-afe2-aebffb549342 Looped 12805 times in 297 milliseconds <cfdump var = "#variables#"> Shows there's nothing in the structure, just parsedXML.xmlRoot.xmlName with the value of XMLRootElement. I also tried <cfset structDelete(variables.parsedXML.XMLRootElement, "XMLChildElement")> as well as structClear for both. More information on deleting from the xml document object. http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSc3ff6d0ea77859461172e0811cbec22c24-78e3.html Can someone please explain my faulty logic? Thanks.

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• Career day in kindergarten

  - by Péter Török

  I was invited to the kindergarten group of my elder daughter to talk and answer the kids' questions about my profession. There are 26 kids of age 4-6 in the group, plus 3 teachers who are fairly scared of anything related to programming and IT themselves, but bold enough to learn new tricks. I would have about 20-30 minutes, without projector or anything. They have an old computer though, which by its look may be a 486, and I am not even sure if it's functioning. My research turned up excellent earlier threads, with lots of good tips: How would you explain your job to a 5-year old? Career Day: how do I make “computer programmer” sound cool to 8 year olds? What things can I teach a group of children about programming in one day? My situation is different from each of the above though: the latter ones are concerned with older children, while the first one is about talking to a single kid (or elder person)—a group of 20 is a whole different challenge. How can I teach the kids and their teachers about programming in a fun way?

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• SQL Server INSERT, Scope_Identity() and physical writing to disc

  - by TheBlueSky

  Hello everyone, I have a stored procedure that does, among other stuff, some inserts in different table inside a loop. See the example below for clearer understanding: INSERT INTO T1 VALUES ('something') SET @MyID = Scope_Identity() ... some stuff go here INSERT INTO T2 VALUES (@MyID, 'something else') ... The rest of the procedure These two tables (T1 and T2) have an IDENTITY(1, 1) column in each one of them, let's call them ID1 and ID2; however, after running the procedure in our production database (very busy database) and having more than 6250 records in each table, I have noticed one incident where ID1 does not match ID2! Although normally for each record inserted in T1, there is record inserted in T2 and the identity column in both is incremented consistently. The "wrong" records were something like that: ID1 Col1 ---- --------- 4709 data-4709 4710 data-4710 ID2 ID1 Col1 ---- ---- --------- 4709 4710 data-4709 4710 4709 data-4710 Note the "inverted", ID1 in the second table. Knowing not that much about SQL Server underneath operations, I have put the following "theory", maybe someone can correct me on this. What I think is that because the loop is faster than physically writing to the table, and/or maybe some other thing delayed the writing process, the records were buffered. When it comes the time to write them, they were wrote in no particular order. Is that even possible if no, how to explain the above mentioned scenario? If yes, then I have another question to rise. What if the first insert (from the code above) got delayed? Doesn't that mean I won't get the correct IDENTITY to insert into the second table? If the answer of this is also yes, what can I do to insure the insertion in the two tables will happen in sequence with the correct IDENTITY? I appreciate any comment and information that help me understand this. Thanks in advance.

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• wordpress generating slow mysql queries - is it index problem?

  - by tash

  Hello Stack Overflow I've got very slow Mysql queries coming up from my wordpress site. It's making everything slow and I think this is eating up CPU usage. I've pasted the Explain results for the two most frequently problematic queries below. This is a typical result - although very occasionally teh queries do seem to be performed at a more normal speed. I have the usual wordpress indexes on the database tables. You will see that one of the queries is generated from wordpress core code, and not from anything specific - like the theme - for my site. I have a vague feeling that the database is not always using the indexes/is not using them properly... Is this right? Does anyone know how to fix it? Or is it a different problem entirely? Many thanks in advance for any help anyone can offer - it is hugely appreciated Query: [wp-blog-header.php(14): wp()] SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 6 id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE wp_posts ref type_status_date type_status_date 63 const 427 Using where; Using filesort Query time: 34.2829 (ms) 9) Query: [wp-content/themes/LMHR/index.php(40): query_posts()] SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.ID NOT IN ( SELECT tr.object_id FROM wp_term_relationships AS tr INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy = 'category' AND tt.term_id IN ('217', '218', '223', '224') ) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 6 id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY wp_posts ref type_status_date type_status_date 63 const 427 Using where; Using filesort 2 DEPENDENT SUBQUERY tr ref PRIMARY,term_taxonomy_id PRIMARY 8 func 1 Using index 2 DEPENDENT SUBQUERY tt eq_ref PRIMARY,term_id_taxonomy,taxonomy PRIMARY 8 antin1_lovemusic2010.tr.term_taxonomy_id 1 Using where Query time: 70.3900 (ms)

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• Removing "Using temporary; Using filesort" from this MySQL select+join+group by query

  - by claytontstanley

  I have the following query: select t.Chunk as LeftChunk, t.ChunkHash as LeftChunkHash, q.Chunk as RightChunk, q.ChunkHash as RightChunkHash, count(t.ChunkHash) as ChunkCount from chunksubset as t join chunksubset as q on t.ID = q.ID group by LeftChunkHash, RightChunkHash And the following explain table: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subsets ref PRIMARY,IDIndex,SubsetIndex SubsetIndex 767 const 522014 "Using where; Using temporary; Using filesort" 1 SIMPLE subsets eq_ref PRIMARY,IDIndex,SubsetIndex PRIMARY 771 sotero.subsets.Id,const 1 "Using where; Using index" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 "Using where" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 note the "using temporary; using filesort". When this query is run, I quickly run out of RAM (presumably b/c of the temp table), and then the HDD kicks in, and the query slows to a halt. I thought it might be an index issue, so I started adding a few that sort of made sense: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment chunks 0 PRIMARY 1 ChunkId A 17796190 NULL NULL BTREE chunks 1 ChunkHashIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 IDIndex 1 Id A 1483015 NULL NULL BTREE chunks 1 ChunkIndex 1 Chunk A 243783 NULL NULL BTREE chunks 1 ChunkTypeIndex 1 ChunkType A 2 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 2 ChunkId A 17796190 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 2 ChunkType A 261708 NULL NULL BTREE chunks 1 chunkHashByIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByIDIndex 2 Id A 17796190 NULL NULL BTREE But still using the temporary table. The db engine is MyISAM. How can I get rid of the using temporary; using filesort in this query? Just changing to InnoDB w/o explaining the underlying cause is not a particularly satisfying answer. Besides, if the solution is to just add the proper index, then that's much easier than migrating to another db engine.

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• Two entities with @ManyToOne should join the same table

  - by Ivan Yatskevich

  I have the following entities Student @Entity public class Student implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; //getter and setter for id } Teacher @Entity public class Teacher implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; //getter and setter for id } Task @Entity public class Task implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne(optional = false) @JoinTable(name = "student_task", inverseJoinColumns = { @JoinColumn(name = "student_id") }) private Student author; @ManyToOne(optional = false) @JoinTable(name = "student_task", inverseJoinColumns = { @JoinColumn(name = "teacher_id") }) private Teacher curator; //getters and setters } Consider that author and curator are already stored in DB and both are in the attached state. I'm trying to persist my Task: Task task = new Task(); task.setAuthor(author); task.setCurator(curator); entityManager.persist(task); Hibernate executes the following SQL: insert into student_task (teacher_id, id) values (?, ?) which, of course, leads to null value in column "student_id" violates not-null constraint Can anyone explain this issue and possible ways to resolve it?

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• Saving an active record, in what order are the associated objects saved?

  - by Bryan

  In rails, when saving an active_record object, its associated objects will be saved as well. But has_one and has_many association have different order in saving objects. I have three simplified models: class Team < ActiveRecord::Base has_many :players has_one :coach end class Player < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end class Coach < ActiveRecord::Base belongs_to :team validates_presence_of :team_id end I expected that when team.save is called, team should be saved before its associated coach and players. I use the following code to test these models: t = Team.new team.coach = Coach.new team.save! team.save! returns true. But in another test: t = Team.new team.players << Player.new team.save! team.save! gives the following error: > ActiveRecord::RecordInvalid: > Validation failed: Players is invalid I figured out that team.save! saves objects in the following order: 1) players, 2) team, and 3) coach. This is why I got the error: When a player is saved, team doesn't yet have a id, so validates_presence_of :team_id fails in player. Can someone explain to me why objects are saved in this order? This seems not logical to me.

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• JQuery UI drag and drop doesn't notice DOM changes happening during the dragging ?

  - by user315677

  Hi everybody, I have a html table in which each line (<tr>) represents a group of client computers. Each line can be expanded to show the clients belonging to the group. The <tr> containing the clients are always generated but hidden and showed when clicking the plus button at the beginning of each line. The clients themselves (they are <div>) can be dragged and dropped in another group as long as this group is already expanded. So far it works fine. What I am trying to achieve now is that the client can be dragged to a collapsed group and after a second or so hovering the group it will be expanded and the client can be dropped amongst the other clients of the group. I programmed the hover using the in and outevents of the droppable and it expands the group all right, but (and now it starts to be hard to explain with words ;) the behavior of the droppable (the client) is still as if the table line that appeared were not there : the in out and drop events of the droppable are fired on the old position of the elements, and the in out and drop events of the newly appeared <tr> are never fired. It looks as if JQuery memorizes the position, size etc. of the elements when the drag starts, and these values are not updated if there is a change in the DOM before the drop happens... Can someone confirm this behavior is normal, or can it be caused by another problem in my own code ? Any workaround ? (the question is quite bloated already so I don't include any code but I'll gladly upload it if required)

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• Code Golf: Find the possible ways on a numpad

  - by ikar

  I was bored today at school and so I tried to amuse myself using my calculator and a "game" I've invented which isn't really a game but keeps the boringness away. Also some time has passed since the last real code-golf here, so I decided to create this one. Imagine a simplified numpad like you know it from your phone (I'll leave the 0 out for this code-golf as it kinda destroys all the fun) 1 2 3 4 5 6 7 8 9 Now the rules of the game were always: At the end every digit must have been visited exactly once You can start at any digit you want You can always move one digit up, down, left or right. You can't move diagonally! There a quite a lot of possible ways (or not; I haven't found out yet), here some trivial examples: > > v v < < > > | The output of the golf-program should look something like the above, I'll try to explain: Symbols: Go right < Go left ^ Go up v Go down | End of the way Example solutions: (Program output can either be the numbers pressed in the right order from beginning point to end, or an (ASCII) picture like above) 147852369 569874123 523698741 So if we speak out the example above it would be: Start at 1, move right to 2, move right to 3, go down to 6, go left to 5, go left to 4, go down to 7, go right to 8 then go right to 9 and we are finished! Now there are many different ways possible: You could as well start at 5 and go around it in a circle. So the task would be: Write a program that can compute (using brute-force or whatever) the possible solutions for the numpad problem described above. (Friendly rethorical question with smiley removed because it made some people think that this is homework)

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• MUD (game) design concept question about timed events.

  - by mudder

  I'm trying my hand at building a MUD (multiplayer interactive-fiction game) I'm in the design/conceptualizing phase and I've run into a problem that I can't come up with a solution for. I'm hoping some more experienced programmers will have some advice. Here's the problem as best I can explain it. When the player decides to perform an action he sends a command to the server. the server then processes the command, determines whether or not the action can be performed, and either does it or responds with a reason as to why it could not be done. One reason that an action might fail is that the player is busy doing something else. For instance, if a player is mid-fight and has just swung a massive broadsword, it might take 3 seconds before he can repeat this action. If the player attempts to swing again to soon, the game will respond indicating that he must wait x seconds before doing that. Now, this I can probably design without much trouble. The problem I'm having is how I can replicate this behavior from AI creatures. All of the events that are being performed by the server ON ITS OWN, aka not as an immediate reaction to something a player has done, will have to be time sensitive. Some evil monster has cast a spell on you but must wait 30 seconds before doing it again... I think I'll probably be adding all these events to some kind of event queue, but how can I make that event queue time sensitive?

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• Is there any danger in committing to a component library such as SmartGwt or Swing?

  - by Banang

  Since February this year I have been working on an app that's built using SmartGWT components. Generally, I find the components very nice to work with, and the fact that they're open source and free to use is just fantastic. However, I can't seem to shake the feeling that it's not a durable way of developing, but I can't quite explain why. Maybe it's because I know that any minute now the team developing it could decide to stop, which would leave me and my team in a bit of a pickle, but I'm sure there must be something more. I have been trying to find ways of explaining this feeling to myself, but to no avail. Therefore I turn to you, dear community, to ask if you can come up with a good reason why committing to building your app (that's supposed to be around for many more years to come) using a component library such as SmartGWT is a bad idea? Is there any reason I should just have developed the components myself? Or did I make the right choice when deciding not to reinvent the wheel and just go for what was readily available?

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• escape sequence in c

  - by prp

  int main() { char *arr="\\0\1\8234\0"; int i=0; while(arr[i]) { switch(arr[i]) { case '0': printf("is no"); break; case '00': printf("is debugging\n"); break; case 0: printf("It is Avishkar\n"); break; case '\\': printf("This "); break; case '\1': printf("t s"); break; case '8': printf("o s"); break; case '2': printf("imp"); break; case '3': printf("le as"); break; case 2: case 3: case 4: case 8: printf("This "); break; default: printf(" it seems\n"); break;} i++; } } please explain the o/p ? i am not able to get it..

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• How to keep confirmation messages after POST while doing a post-submit redirect?

  - by MicE

  Hello, I'm looking for advise on how to share certain bits of data (i.e. post-submit confirmation messages) between individual requests in a web application. Let me explain: Current approach: user submits an add/edit form for a resource if there were no errors, user is shown a confirmation with links to: submit a new resource (for "add" form) view the submitted/edited resource view all resources (one step above in hierarchy) user then has to click on one of the three links to proceed (i.e. to the page "above") Progmatically, the form and its confirmation page are one set of classes. The page above that is another. They can technically share code, but at the moment they are both independent during processing of individual requests. We would like to amend the above as follows: user submits an add/edit form for a resource if there were no errors, the user is redirected to the page with all resources (one step above in hierarchy) with one or more confirmation messages displayed at the top of the page (i.e. success message, to whom was the request assigned, etc) This will: save users one click (they have to go through a lot of these add/edit forms) the post-submit redirect will address common problems with browser refresh / back-buttons What approach would you recommend for sharing data needed for the confirmation messages between the two requests, please? I'm not sure if it helps, it's a PHP application backed by a RESTful API, but I think that this is a language-agnostic question. A few simple solutions that come to mind are to share the data via cookies or in the session, this however breaks statelessness and would pose a significant problem for users who work in several tabs (the data could clash together). Passing the data as GET parameters is not suitable as we are talking about several messages which are dynamic (e.g. changing actors, dates). Thanks, M.

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• What caused the rails application crash?

  - by so1o

  I'm sure someone can explain this. we have an application that has been in production for an year. recently we saw an increase in number of support requests for people having difficulty signing into the system. after scratching our head because we couldn't recreate the problem in development, we decided we'll switch on debug logger in production for a month. that was june 5th. application worked fine with the above change and we were waiting. then yesterday we noticed that the log files were getting huge so we made another change in production config.logger = Logger.new("#{RAILS_ROOT}/log/production.log", 50, 1048576) after this change, the application started crashing while processing a particular file. this particular line of code was RAILS_DEFAULT_LOGGER.info "Payment Information Request: ", request.inspect as you can see there was a comma instead of a plus sign. this piece of code was introduced in Mar. the question is this: why did the application fail now? if changing the debug level caused the application to process this line of code it should have started failing on june 5th! why today. please someone help us. Are we missing the obvious here? if you dont have an answer, at least let us know we aren't the only one that are bonkers.

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• Help me write my LISP :) LISP environments, Ruby Hashes...

  - by MikeC8

  I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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• Need some help understanding this problem

  - by Legend

  I was wondering if someone could help me understand this problem. I prepared a small diagram because it is much easier to explain it visually. Problem I am trying to solve: 1. Constructing the dependency graph Given the connectivity of the graph and a metric that determines how well a node depends on the other, order the dependencies. For instance, I could put in a few rules saying that node 3 depends on node 4 node 2 depends on node 3 node 3 depends on node 5 But because the final rule is not "valuable" (again based on the same metric), I will not add the rule to my system. 2. Execute the request order Once I built a dependency graph, execute the list in an order that maximizes the final connectivity. First and foremost, I am wondering if I constructed the problem correctly and if I should be aware of any corner cases. Secondly, is there a closely related algorithm that I can look at? Currently, I am thinking of something like Feedback Arc Set or the Secretary Problem but I am a little confused at the moment. Any suggestions? PS: I am a little confused about the problem myself so please don't flame on me for that. If any clarifications are needed, I will try to update the question.

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• No idea how to solve SICP exercise 1.11

  - by Javier Badia

  This is not homework. Exercise 1.11: A function f is defined by the rule that f(n) = n if n<3 and f(n) = f(n - 1) + 2f(n - 2) + 3f(n - 3) if n 3. Write a procedure that computes f by means of a recursive process. Write a procedure that computes f by means of an iterative process. Implementing it recursively is simple enough. But I couldn't figure out how to do it iteratively. I tried comparing with the Fibonacci example given, but I didn't know how to use it as an analogy. So I gave up (shame on me) and Googled for an explanation, and I found this: (define (f n) (if (< n 3) n (f-iter 2 1 0 n))) (define (f-iter a b c count) (if (< count 3) a (f-iter (+ a (* 2 b) (* 3 c)) a b (- count 1)))) After reading it, I understand the code and how it works. But what I don't understand is the process needed to get from the recursive defintion of the function to this. I don't get how the code formed in someone's head. Could you explain the thought process needed to arrive at the solution?

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• Generic version control strategy for select table data within a heavily normalized database

  - by leppie

  Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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• Getting User input with Scanner

  - by Giannis

  I am trying to have a scanner take input in a loop. Once the user wants to finish he can exit this loop. I have tried many different ways to do it but there is always some problem. This is the code: Scanner sc = new Scanner(System.in); System.out.println("Continue?[Y/N]"); while (sc.hasNext()&& (sc.next().equals("Y"))) { System.out.println("Enter first name"); String name = sc.nextLine(); System.out.println("Enter surname"); String surname = sc.nextLine(); . . . System.out.println("Continue?[Y/N]"); } } The problem with the code above, which also happens on different methods I tried, is that when the user types Y, the scanner will skip the first input for first name,and jump to the surname. If the user types N the loop stops correctly. Someone can explain the reason this happens, and how to overcome using scanner class? p.s: Doing something like while(sc.nextLine().equals("Y")), will cause the loop to terminate before getting input from user after first run of the loop.

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• Problems breaking out of nested loops

  - by user1040281

  I have problems breaking out off these nested loops correctly. What the code is trying to do is to indicate that a customer has rented a certain movie. Both the movie and customer are compared to properties of arraylist objects and then if all checks out the name property and ID property of a movie object are added as a string to another arraylist. All this works correctly as long as I use the first movie (from movies) and the first customer (from customers) but if I try renting other movies further down my arraylist with other customers then it adds the rented movie to the customerRentedMovies arraylist but prints out the "else message". I figure I need to break out of the foreach(blabla) loops aswell? or could goto be used? Comments was removed (looked kinda messy, can explain further if needed) public void RentMovie(string titel, int movieID, string name, int customerID) { foreach (Customer customer in customers) { if (name == customer.Name && customerID == customer.CustomerID) { foreach (MovieInfo movie in movies) { if (titel == movie.Titel && movieID == movie.MovieID) { movie.rented = true; string rentedMovie = string.Format("{0} ID: {1}", movie.Titel, movie.MovieID); customer.customerRentedMovies.Add(rentedMovie); break; } else { Console.WriteLine("No movie with that titel and ID!"); } } break; } else { Console.WriteLine("No customer with that ID and name"); } } }

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• Android OS 2.2 Permissions: I have absolutely no idea why this simple piece of code doesn't work. Wh

  - by Kevin

  I'm just playing around with some code. I create an Activity and simply do something like this: long lo = currentTimeMillis(); System.out.println(lo); lo *= 3; System.out.println(lo); SystemClock.setCurrentTimeMillis(lo); System.out.println( currentTimeMillis() ); Yes, in my AndroidManifest.xml, I've added: <uses-permission android:name="android.permission.SET_TIME"></uses-permission> <uses-permission android:name="android.permission.SET_TIME_ZONE"></uses-permission> Nothing changes. The SystemClock is never reset...it just keeps on ticking. The error that I'm getting just says that the permission "SET_TIME" was not granted to the program. Protection level 3. The permissions are there...and in the API for 2.2 it says that this feature is supported now. I have no idea what I'm doing wrong. If android.content.Intent; comes into play, please explain. I don't really understand what the idea behind intents! Thanks for any help!

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• How do I implement configurations and settings?

  - by Malvolio

  I'm writing a system that is deployed in several places and each site needs its own configurations and settings. A "configuration" is a named value that is necessary to a particular site (e.g., the database URL, S3 bucket name); every configuration is necessary, there is not usually a default, and it's typically string-valued. A setting is a named value but it just tweaks the behavior of the system; it's often numeric or Boolean, and there's usually some default. So far, I've been using property files or thing like them, but it's a terrible solution. Several times, a developer has added a requirement for a configuration but not added the value to file for the live configuration, so the new release passed all the tests, then failed when released to live. Better, of course, for every file to be compiled — so if there's a missing configuration, or one of the wrong type, it won't get past the compiler — and inject the site-specific class into the build for each site. As a bones, a Scala file can easy model more complex values, especially lists, but also maps and tuples. The downside is, the files are sometimes maintained by people who aren't developers, so it has to be pretty self-explanatory, which was the advantage of property files. (Someone explain XML configurations to me: all the complexity of a compilable file but the run-time risk of a property file.) What I'm looking for is an easy pattern for defining a group required names and allowable values. Any suggestions?

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• Type errors when using same name

  - by lykimq

  I have 3 files: 1) cpf0.ml type string = char list type url = string type var = string type name = string type symbol = | Symbol_name of name 2) problem.ml: type symbol = | Ident of string 3) test.ml open Problem;; open Cpf0;; let symbol b = function | Symbol_name n -> Ident n When I combine test.ml: ocamlc -c test.ml. I received an error: This expression has type Cpf0.name = char list but an expression was expected of type string Could you please help me to correct it? Thank you very much EDIT: Thank you for your answer. I want to explain more about these 3 files: Because I am working with extraction in Coq to Ocaml type: cpf0.ml is generated from cpf.v : Require Import String. Definition string := string. Definition name := string. Inductive symbol := | Symbol_name : name -> symbol. The code extraction.v: Set Extraction Optimize. Extraction Language Ocaml. Require ExtrOcamlBasic ExtrOcamlString. Extraction Blacklist cpf list. where ExtrOcamlString I opened: open Cpf0;; in problem.ml, and I got a new problem because in problem.ml they have another definition for type string This expression has type Cpf0.string = char list but an expression was expected of type Util.StrSet.elt = string Here is a definition in util.ml defined type string: module Str = struct type t = string end;; module StrOrd = Ord.Make (Str);; module StrSet = Set.Make (StrOrd);; module StrMap = Map.Make (StrOrd);; let set_add_chk x s = if StrSet.mem x s then failwith (x ^ " already declared") else StrSet.add x s;; I was trying to change t = string to t = char list, but if I do that I have to change a lot of function it depend on (for example: set_add_chk above). Could you please give me a good idea? how I would do in this case.

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• MySQL "OR MATCH" hangs (very slow) on multiple tables

  - by Kerry

  After learning how to do MySQL Full-Text search, the recommended solution for multiple tables was OR MATCH and then do the other database call. You can see that in my query below. When I do this, it just gets stuck in a "busy" state, and I can't access the MySQL database. SELECT a.`product_id`, a.`name`, a.`slug`, a.`description`, b.`list_price`, b.`price`, c.`image`, c.`swatch`, e.`name` AS industry, MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) AS relevance FROM `products` AS a LEFT JOIN `website_products` AS b ON (a.`product_id` = b.`product_id`) LEFT JOIN ( SELECT `product_id`, `image`, `swatch` FROM `product_images` WHERE `sequence` = 0) AS c ON (a.`product_id` = c.`product_id`) LEFT JOIN `brands` AS d ON (a.`brand_id` = d.`brand_id`) INNER JOIN `industries` AS e ON (a.`industry_id` = e.`industry_id`) WHERE b.`website_id` = %d AND b.`status` = %d AND b.`active` = %d AND MATCH( a.`name`, a.`sku`, a.`description` ) AGAINST ( '%s' IN BOOLEAN MODE ) OR MATCH ( d.`name` ) AGAINST ( '%s' IN BOOLEAN MODE ) GROUP BY a.`product_id` ORDER BY relevance DESC LIMIT 0, 9 Any help would be greatly appreciated. EDIT All the tables involved are MyISAM, utf8_general_ci. Here's the EXPLAIN SELECT statement: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY a ALL NULL NULL NULL NULL 16076 Using temporary; Using filesort 1 PRIMARY b ref product_id product_id 4 database.a.product_id 2 1 PRIMARY e eq_ref PRIMARY PRIMARY 4 database.a.industry_id 1 1 PRIMARY <derived2> ALL NULL NULL NULL NULL 23261 1 PRIMARY d eq_ref PRIMARY PRIMARY 4 database.a.brand_id 1 Using where 2 DERIVED product_images ALL NULL NULL NULL NULL 25933 Using where I don't know how to make that look neater -- sorry about that UPDATE it returns the query after 196 seconds (I think correctly). The query without multiple tables takes about .56 seconds (which I know is really slow, we plan on changing to solr or sphinx soon), but 196 seconds?? If we could add a number to the relevance if it was in the brand name ( d.name ), that would also work

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