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• Problems Expanding an Array in C++

  - by dxq

  I'm writing a simulation for class, and part of it involves the reproduction of organisms. My organisms are kept in an array, and I need to increase the size of the array when they reproduce. Because I have multiple classes for multiple organisms, I used a template: template <class orgType> void expandarray(orgType* oldarray, int& numitems, int reproductioncount) { orgType *newarray = new orgType[numitems+reproductioncount]; for (int i=0; i<numitems; i++) { newarray[i] = oldarray[i]; } numitems += reproductioncount; delete[] oldarray; oldarray = newarray; newarray = NULL; } However, this template seems to be somehow corrupting my data. I can run the program fine without reproduction (commenting out the calls to expandarray), but calling this function causes my program to crash. The program does not crash DURING the expandarray function, but crashes on access violation later on. I've written functions to expand an array hundreds of times, and I have no idea what I screwed up this time. Is there something blatantly wrong in my function? Does it look right to you? EDIT: Thanks for everyone's help. I can't believe I missed something so obvious. In response to using std::vector: we haven't discussed it in class yet, and as silly as it seems, I need to write code using the methods we've been taught.

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• Unit Tests Architecture Question

  - by Tom Tresansky

  So I've started to layout unit tests for the following bit of code: public interface MyInterface { void MyInterfaceMethod1(); void MyInterfaceMethod2(); } public class MyImplementation1 implements MyInterface { void MyInterfaceMethod1() { // do something } void MyInterfaceMethod2() { // do something else } void SubRoutineP() { // other functionality specific to this implementation } } public class MyImplementation2 implements MyInterface { void MyInterfaceMethod1() { // do a 3rd thing } void MyInterfaceMethod2() { // do something completely different } void SubRoutineQ() { // other functionality specific to this implementation } } with several implementations and the expectation of more to come. My initial thought was to save myself time re-writing unit tests with something like this: public abstract class MyInterfaceTester { protected MyInterface m_object; @Setup public void setUp() { m_object = getTestedImplementation(); } public abstract MyInterface getTestedImplementation(); @Test public void testMyInterfaceMethod1() { // use m_object to run tests } @Test public void testMyInterfaceMethod2() { // use m_object to run tests } } which I could then subclass easily to test the implementation specific additional methods like so: public class MyImplementation1Tester extends MyInterfaceTester { public MyInterface getTestedImplementation() { return new MyImplementation1(); } @Test public void testSubRoutineP() { // use m_object to run tests } } and likewise for implmentation 2 onwards. So my question really is: is there any reason not to do this? JUnit seems to like it just fine, and it serves my needs, but I haven't really seen anything like it in any of the unit testing books and examples I've been reading. Is there some best practice I'm unwittingly violating? Am I setting myself up for heartache down the road? Is there simply a much better way out there I haven't considered? Thanks for any help.

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• Manipulate method functionality call

  - by danrichardson

  Hello, is it possibly in c# to have some sort of base class functionality which is manipulated slightly based on the class. For instance say i have the following code (which will quite obviously not compile it's meant to only be for demonstrative purposes) class BaseFunctionality { public virtual bool adminCall public static string MethodName(int id, string parameter) { if (adminCall) return dbcall.Execute(); else return dbcall.ExecuteMe(); } } class Admin : BaseFunctionality { override bool adminCall = true; } class Front : BaseFunctionality { override bool adminCall = false; } Now what i would like to be able to do is; string AdminCall = Admin.MethodName(1, "foo"); string FrontCall = Front.MethodName(2, "bar"); Is their any way to do something like this? I'm trying to do everything with static methods so i do not have to instantiate classes all the time, and have nice clean code which is only being manipulated in one place. The idea behind this is so that there is minimal code repeating and makes things easier to expand on, so for instance another class could implement the BaseFunctionality later on. Thanks Dan

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• Abstract Design Pattern implementation

  - by Pathachiever11

  I started learning design patterns a while ago (only covered facade and abstract so far, but am enjoying it). I'm looking to apply the Abstract pattern to a problem I have. The problem is: Supporting various Database systems using one abstract class and a set of methods and properties, which then the underlying concrete classes (inheriting from abstract class) would be implementing. I have created a DatabaseWrapper abstract class and have create SqlClientData and MSAccessData concrete class that inherit from the DatabaseWrapper. However, I'm still a bit confused about how the pattern goes as far as implementing these classes on the Client. Would I do the following?: DatabaseWrapper sqlClient = new SqlClientData(connectionString); This is what I saw in an example, but that is not what I'm looking for because I want to encapsulate the concrete classes; I only want the Client to use the abstract class. This is so I can support for more database systems in the future with minimal changes to the Client, and creating a new concrete class for the implementations. I'm still learning, so there might be a lot of things wrong here. Please tell me how I can encapsulate all the concrete classes, and if there is anything wrong with my approach. Many Thanks! PS: I'm very excited to get into software architecture, but still am a beginner, so take it easy on me. :)

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• Help with java threads or executors: Executing several MySQL selects, inserts and updates simmultane

  - by Martin

  Hi. I'm writing an application to analyse a MySQL database, and I need to execute several DMLs simmultaneously; for example: // In ResultSet rsA: Select * from A; rsA.beforeFirst(); while (rsA.next()) { id = rsA.getInt("id"); // Retrieve data from table B: Select * from B where B.Id=" + id; // Crunch some numbers using the data from B // Close resultset B } I'm declaring an array of data objects, each with its own Connection to the database, which in turn calls several methods for the data analysis. The problem is all threads use the same connection, thus all tasks throw exceptios: "Lock wait timeout exceeded; try restarting transaction" I believe there is a way to write the code in such a way that any given object has its own connection and executes the required tasks independent from any other object. For example: DataObject dataObject[0] = new DataObject(id[0]); DataObject dataObject[1] = new DataObject(id[1]); DataObject dataObject[2] = new DataObject(id[2]); ... DataObject dataObject[N] = new DataObject(id[N]); // The 'DataObject' class has its own connection to the database, // so each instance of the object should use its own connection. // It also has a "run" method, which contains all the tasks required. Executor ex = Executors.newFixedThreadPool(10); for(i=0;i<=N;i++) { ex.execute(dataObject[i]); } // Here where the problem is: Each instance creates a new connection, // but every DML from any of the objects is cluttered in just one connection // (in MySQL command line, "SHOW PROCESSLIST;" throws every connection, and all but // one are idle). Can you point me in the right direction? Thanks

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• asp.net mvc postback

  - by user266909

  I have a controller with the following two Edit methods. The edit form displays correctly with all additional dropdown lists from the FormViewModel. However, when I changed some field values and submitted the form. None of the changed fields were saved. The fields in the postbask collection have default or null values. I have another edit form which update another table. On submit, the changed values are saved. Does anyone know why? // GET: /Transfers/Edit/5 public ActionResult Edit(int id) { Transfer transfer = myRepository.GetTransfer(id); if (transfer == null) return View("NotFound"); return View(new TransferFormViewModel(transfer)); } // // POST: /Transfers/Edit/5 [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(int id, Transfer collection) { Transfer transfer = vetsRepository.GetTransfer(id); if (transfer == null) return View("NotFound"); else { try { UpdateModel(transfer); vetsRepository.Save(); return RedirectToAction("Details", new { id = transfer.TransfersID }); } catch { ModelState.AddModelErrors(transfer.GetRuleViolations()); return View(new TransferFormViewModel(transfer)); } } }

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• Overload the behavior of count() when called on certain objects

  - by Tom

  In PHP 5, you can use magic methods, overload some classes, etc. In C++, you can implement functions that exist is STL as long as the argument types are different. Is there a way to do this in PHP? An example of what I'd like to do is this: class a { function a() { $this->list = array("1", "2"); } } $blah = new a(); count($blah); I would like blah to return 2. IE count the values of a specific array in the class. So in C++, the way I would do this might look like this: int count(a varName) { return count(varName->list); } Basically, I am trying to simplify data calls for a large application so I can call do this: count($object); rather than count($object->list); The list is going to be potentially a list of objects so depending on how it's used, it could be really nasty statement if someone has to do it the current way: count($object->list[0]->list[0]->list); So, can I make something similar to this: function count(a $object) { count($object->list); } I know PHP's count accepts a mixed var, so I don't know if I can override an individual type.

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• Watching variables in SSIS during debug

  - by Tom H.

  I have a project in SSIS and I've added an Execute SQL Task which sends its result out to a variable. I wanted to confirm the value because I was worried that it would try to write it out as a resultset object rather than an actual integer (in this case I'm returning a COUNT). My first thought was just to run it in debug mode and add the global variable to my Watch window. Unfortunately, when I right-click on the Watch window, the option to "Add Variable" is greyed out. What am I missing here? I've gotten around confirming that my variable is set correctly, so I'm not interested in methods like putting a script in to do a MsgBox with the value or anything like that. For future reference I'd like to be able to watch variables in debug mode. If there are some kind of constraints on that then I'd like to know the what and why of it all if anyone knows. The help is woefully inadequate on this one and every "tutorial" that I can find just says, "Add the variable to the Watch window and debug" as though there should never be a problem doing that. Thanks for any insight!

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• Obj-c method override/polymorphism problem

  - by Rod

  Ok, so I'm using Objective-C. Now, say I have: TopClass : NSObject - (int) getVal {return 1;} MidClass : TopClass - (int) getVal {return 2;} BotClass : MidClass - (int) getVal {return 3;} I then put objects of each type into an NSMutableArray and take one out. What I want to do is run the getVal func on the appropriate object type, but when I put id a = [allObjects objectAtIndex:0]; if ([a isKindOfClass:[TopClass class]]) { int i; i = [a getVal]; } I get firstly a warning about multiple methods called getVal (presumably because the compiler can't determine the actual object type until runtime). But more seriously I also get an error "void value not ignored as it should be" and it won't compile. If I don't try and use the return from [a getVal] then it compiles fine e.g. [a getval]; //obviously no good if I want to use the return value It will also work if I use isMemberOfClass statements to cast the object to a class before running the function e.g. if ([a isMemberOfClass:[BotClass]) i = [(BotClass*) a getVal]; But surely I shouldn't have to do this to get the functionality I require? Otherwise I'll have to put in a statement for every single subclass, and worse have to add a new line if I add a new sub class, which rather defeats the point of method overriding doesn't it? Surely there is a better way?

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• Hibernate 1:M relationship ,row order, constant values table and concurrency

  - by EugeneP

  table A and B need to have 1:M relationship a and b are added during application runtime, so A created, then say 4 B's created. Each B instance has to come in order, so that I could later extract them in the same order as I added them. The app will be a web-app running on Tomcat, so 10 instances may work simultaneously. So my question are: 1) How to preserve inserting order, so that I could extract B instances that A references in the same order as I persisted them. That's tricky, because we add to a Collection and then it gets saved (am I right?). So, it depends on how Hibernate saves it, what if it changes the order in what we added instances? I've seen something like LIST instead of SET when describing relationships, is that what I need? 2) How to add a 3-rd column to B so that I could differentiate the instances, something like SEX(M,F,U) in B table. Do I need a special table, or there's and easy way to describe constants in Hibernate. What do you recommend? 3) Talking about concurrency, what methods do you recommend to use? There should be no collisions in the db and as you see, there might easily be some if rows are not inserted (PK added) right where it is invoked without delays ?

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• Just a small help about switch's use

  - by Laurent Fournier

  If an answer on this already exist, my apologies i've not found on this question... is this statement correct if i want presice actions on integers from -2 to 0, and for those between 1 and 6 apply the same methods with only my integer who'll change ? Like this: public void setCaseGUI(Point pt, int i, boolean b){ plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setSelected(b); plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setIcon(null); switch(i) { case -2: plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setText("F"); plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setForeground(Color.red); break; case -1: plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setText("B"); plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setForeground(Color.red); break; case 0: plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setText(""); plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setForeground(null); break; case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8: plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setText(String.valueOf(i)); plateau.cellule[(int)pt.getAbs()][(int)pt.getOrd()].setForeground(null); break; default: System.out.println("Erreur de changement d'état/case !"); } } Please don't be too harsh on me i've started to learn dev only a few month ago

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• Dynamic WebService implementation

  - by chardex

  I have a set of different interfaces and I need to give them access via web services. I have implemented this task in .NET as follows: dynamically generated interface implementation on the IL, marked methods with WebMethod annotation, and in *.asmx handler called generated stub. More needs to be able to change the method signatures (eg change the type of certain argument or add new arguments), ie not always explicitly implement an interface, and use it as a decorator pattern. Example: interface ISomeService { void simpleMetod (String arg1); void customMetod (CusomType arg1, Integer arg2); } // Need to dynamically generate such class @WebService class SomeWebService { private ISomeService someService = new SomeServiceImpl (); @WebMethod public void simpleMethod (String arg1) { someService.simpleMethod (arg1); } @WebMethod public void customMethod (String arg1, Integer arg2) { someService.customMethod (CusomType.fromString (arg1), arg2); } } Interfaces such as ISomeService quite a lot. And manually write code like this I don't want. I work with Java recently, what technology/libraries should be used to solve such task. Thanks.

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• I can't find the homepage for my ASP.NET MVC site :(

  - by Pure.Krome

  Hi folks, really simple question here. when I remove the default route, I returns an empty page to the browser :- routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } ); Now before everyone starts shouting "that's because that's the default route to access all action methods, etc.." .. i know that. My question is - what code / routes does the default framework try and call .. which makes that Default Route get used/kick in? Why? I don't wish to make that my default route regex (don't ask why - this is some R&D) but I still need the main home page .. ie. Home/Index . If i try and just add that route, it doesn't get called and an empty page is returned. So -- what does the framework try and call when a user doesn't provide any urls? It's like there's some secret default document stuff set up? Cheers :)

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• Dont understand the concept of extends in URL.openConnection() in JAVA

  - by user1722361

  Hi I am trying to learn JAVA deeply and so I am digging into the JDK source code in the following lines: URL url = new URL("http://www.google.com"); URLConnection tmpConn = url.openConnection(); I attached the source code and set the breakpoint at the second line and stepped into the code. I can see the code flow is: URL.openConnection() - sun.net.www.protocol.http.Handler.openConnection() I have two questions about this First In URL.openConnection() the code is: public URLConnection openConnection() throws java.io.IOException { return handler.openConnection(this); } handler is an object of URLStreamHandler, define as blow transient URLStreamHandler handler; But URLStreamHandler is a abstract class and method openConnection() is not implement in it so when handler calls this method, it should go to find a subclass who implement this method, right? But there are a lot classes who implement this methods in sun.net.www.protocol (like http.Hanlder, ftp.Handler ) How should the code know which "openConnection" method it should call? In this example, this handler.openConnection() will go into http.Handler and it is correct. (if I set the url as ftp://www.google.com, it will go into ftp.Handler) I cannot understand the mechanism. second. I have attached the source code so I can step into the JDK and see the variables but for many classes like sun.net.www.protocol.http.Handler, there are not source code in src.zip. I googled this class and there is source code online I can get but why they did not put it (and many other classes) in the src.zip? Where can I find a comprehensive version of source code? Thanks!

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• How to determine if a C++ usertype has been registered with tolua

  - by czuger

  We use tolua++ to generate Lua bindings for C++ classes. Assume I have a C++ class: class Foo { //Some methods in Foo, irrelevant to question. }; and a tolua .pkg file with the following contents class Foo { }; Consider the following function: void call_some_lua_function(lua_State* luaState) { Foo* myFoo = new Foo(); tolua_pushusertype(luaState, (void*)myFoo, "Foo"); //More code to actually call Lua, irrelevant to question. } Now, the actual question: tolua_pushusertype causes a segfault in Lua if the 3rd parameter does not correspond to a valid fully qualified string of a C++ class that was registered with a call to tolua_cclass. So, if parameter 3 where "Bar", we get a segfault. What I would like to do is the following: void call_some_lua_function(lua_State* luaState) { //determine if tolua is aware of my type, how to do this? //Something like: //if(!tolua_iscpptype_registered("Foo")) //{ // abort gracefully //} Foo* myFoo = new Foo(); tolua_pushusertype(luaState, (void*)myFoo, "Foo"); //More code to actually call Lua, irrelevant to question. } Is there a way to do this using tolua?

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• Help with string equality in Java

  - by annayena

  The following function accepts 2 strings, the 2nd (not 1st) possibly containing *'s (asterisks). An * is a replacement for a string (empty, 1 char or more), it can appear appear (only in s2) once, twice, more or not at all, it cannot be adjacent to another * (ab**c), no need to check that. public static boolean samePattern(String s1, String s2) It returns true if strings are of the same pattern. It must be recursive, not use any loops, static or global variables. Also it's prohibited to use the method equals in the String class. Can use local variables and method overloading. Can use only these methods: charAt(i), substring(i), substring(i, j), length(). Examples: 1: TheExamIsEasy; 2: "The*xamIs*y" ---> true 1: TheExamIsEasy; 2: "Th*mIsEasy*" ---> true 1: TheExamIsEasy; 2: "*" ---> true 1: TheExamIsEasy; 2: "TheExamIsEasy" ---> true 1: TheExamIsEasy; 2: "The*IsHard" ---> FALSE I am stucked on this question for many hours now! I need the solution in Java please kindly help me.

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• Are Interfaces "Object"?

  - by PrashantGupta

  package inheritance; class A{ public String display(){ return "This is A!"; } } interface Workable{ public String work(); } class B extends A implements Workable{ public String work(){ return "B is working!"; } } public class TestInterfaceObject{ public static void main(String... args){ B obj=new B(); Workable w=obj; //System.out.println(w.work()); //invoking work method on Workable type reference System.out.println(w.display()); //invoking display method on Workable type reference //System.out.println(w.hashCode()); // invoking Object's hashCode method on Workable type reference } } As we know that methods which can be invoked depend upon the type of the reference variable on which we are going to invoke. Here, in the code, work() method was invoked on "w" reference (which is Workable type) so method invoking will compile successfully. Then, display() method is invoked on "w" which yields a compilation error which says display method was not found, quite obvious as Workable doesn't know about it. Then we try to invoke the Object class's method i.e. hashCode() which yields a successful compilation and execution. How is it possible? Any logical explanation?

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• Is the below thread pool implementation correct(C#3.0)

  - by Newbie

  Hi Experts, For the first time ever I have implemented thread pooling and I found it to be working. But I am not very sure about the way I have done is the appropriate way it is supposed to be. Would you people mind in spending some valuable time to check and let me know if my approach is correct or not? If you people find that the approach is incorrect , could you please help me out in writing the correct version. I have basicaly read How to use thread pool and based on what ever I have understood I have developed the below program as per my need public class Calculation { #region Private variable declaration ManualResetEvent[] factorManualResetEvent = null; #endregion public void Compute() { factorManualResetEvent = new ManualResetEvent[2]; for (int i = 0; i < 2; i++){ factorManualResetEvent[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(ThreadPoolCallback, i);} //Wait for all the threads to complete WaitHandle.WaitAll(factorManualResetEvent); //Proceed with the next task(s) NEXT_TASK_TO_BE_EXECUTED(); } #region Private Methods // Wrapper method for use with thread pool. public void ThreadPoolCallback(Object threadContext) { int threadIndex = (int)threadContext; Method1(); Method2(); factorManualResetEvent[threadIndex].Set(); } private void Method1 () { //Code of method 1} private void Method2 () { //Code of method 2 } #endregion }

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• What does the `new` keyword do

  - by Mike

  I'm following a Java tutorial online, trying to learn the language, and it's bouncing between two semantics for using arrays. long results[] = new long[3]; results[0] = 1; results[1] = 2; results[2] = 3; and: long results[] = {1, 2, 3}; The tutorial never really mentioned why it switched back and forth between the two so I searched a little on the topic. My current understanding is that the new operator is creating an object of "array of longs" type. What I do not understand is why do I want that, and what are the ramifications of that? Are there certain "array" specific methods that won't work on an array unless it's an "array object"? Is there anything that I can't do with an "array object" that I can do with a normal array? Does the Java VM have to do clean up on objects initialized with the new operator that it wouldn't normally have to do? I'm coming from C, so my Java terminology, may not be correct here, so please ask for clarification if something's not understandable.

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• What is Rails way to DRY up the controller pattern of verifying :id is for a valid object (else redirect to error page)

  - by jpwynn

  One of my controllers has close to 100 methods (eg routes) and nearly every one starts out the same code to redirect to an error page if the id param is invalid, followed by a similar check if the user that id doesn't belong in the user's account: def something @foo = Foo.find_by_guid(params[:id]) unless @foo @msg ||= { :title => 'No such page!', :desc => "There is no such page!" } render :action => "error" and return end unless @foo.owner_id == current_user.id @msg ||= { :title => 'Really?', :desc => "There is no such page." } render :action => "error" and return end What is the best way to DRY up that sort of page id and owner id validation, given the code is doing a render ... and return? What I don't want to do at this point is offload it to a blackbox roles and permissions library like CanCan... my goal is simply to have the in-app code to handle this be as clean as possible.

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• how to pass instance variables between handlers (routes) in sinatra (without flash, sessions, class variable or db)?

  - by jj_

  Say you have: get '/' do haml :index end get '/form' do haml :form end post '/form' do @message = params[:message] redirect to ('/') --- how to pass @message here? end I'd like the @message instance variable to be available (passed to) in "/" action as well, so I can show it in haml view. How can I do that without using session, flash, a @@class_variable, or db persistence ? I'd simply like to pass values as if I was working with passing values between methods. I don't want to use session cookies because user could have them turned off, I don't like it being a class variable which is exposed to all code, and I don't need to overhead of a db. Thanks edit: This is another question explaining a very easy way to deal with this in rails Passing parameters in rails redirect_to This is some more info i gathered around from forums. The following works for rails, i've tried it in Sinatra but no luck, but please try it, maybe I did something wrong, I don't know, and if this code help someone come up with a new idea, please share it If you are redirecting to action2 at the end of action1, just append the value to the end of the redirect: my_var = <some logic> redirect_to :action => 'action2', :my_var => my_var on the same thread another user proposes the folowing: def action1 redirect_to :action => 'action2', :value => params[:current_varaible] end def action2 puts params[:value].inspect end source: http://www.ruby-forum.com/topic/134953 Can something like this work in Sinatra? Thanks

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• Why are my thread being terminated ?

  - by Sephy

  Hi, I'm trying to repeat calls to methods through 3 differents threads. But after I start my threads, during the next iteration of my loop, they are all terminated so nothing is executed... The code is as follows : public static void main(String[] args) { main = new Main(); pollingThread.start(); } static Thread pollingThread = new Thread() { @Override public void run() { while (isRunning) { main.poll(); // test the state of the threads try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }; }; public void poll() { if (clientThread == null) { clientThread = new Thread(new Runnable() { @Override public void run() { //create some objects } }); clientThread.start(); } else if (clientThread.isAlive()) { // do some treatment } if (gestionnaireThread == null) { gestionnaireThread = new Thread(new Runnable() { @Override public void run() { //create some objects }; }); gestionnaireThread.start(); } else if (gestionnaireThread.isAlive()) { // do some treatment } if (marchandThread == null) { marchandThread = new Thread(new Runnable() { @Override public void run() { // create some objects }; }); marchandThread.start(); } else if (marchandThread.isAlive()) { // do some treatment } } And for some reason, when I test the state of my different threads, they appear as runnable and then a the 2nd iteration, they are all terminated... What am I doing wrong? I actually have no error, but the threads are terminated and so my loop keeps looping and telling me the threads are terminated.... Thanks for any help.

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• Main purpose of this task is to calculate volumes and surface areas of three dimensional geometric shapes like, cylinders, cones.

  - by Csc_Girl_Geek

  In Java Language Design your classes as below introducing: an Interface named “GeometricShapes” an abstract class named “ThreeDShapes” two child classes of ThreeDShapes: Cylinders and Cones. One test class names “TestShapes” Get the output for volumes and surface areas of cylinders and cones along with respective values of their appropriate input variables. Try to use toString() method and array. Your classes should be designed with methods that are required for Object-Oriented programming. So Far I Have: package Assignment2; public interface GeometricShapes { public void render(); public int[] getPosition(); public void setPosition(int x, int y); } package Assignment2; public abstract class ThreeDShapes implements GeometricShapes { public int[] position; public int[] size; public ThreeDShapes() { } public int[] getPosition() { return position; } public void setPosition(int x, int y) { position[0] = x; position[1] = y; } } package Assignment2; public class Cylinders extends ThreeDShapes { public Cylinder() { } public void render() { } } I don't think this is right and I do not know how to fix it. :( Please help.

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• Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

  - by theFunkyEngineer

  I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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• Associate two sets of values

  - by PJW

  I have the following code - public static int GetViewLevel(string viewLevelDesc) { try { switch (viewLevelDesc) { case "All": return 0; case "Office": return 10; case "Manager": return 50; default: throw new Exception("Invalid View Level Description"); } } catch (Exception eX) { throw new Exception("Action: GetViewLevel()" + Environment.NewLine + eX.Message); } } public static string GetViewLevelDescription(int viewLevel) { try { switch (viewLevel) { case 0: return "All"; case 10: return "Office"; case 50: return "Manager"; default: throw new Exception("Invalid View Level Description"); } } catch (Exception eX) { throw new Exception("Action: GetViewLevelDescription()" + Environment.NewLine + eX.Message); } } The two static Methods enable me to either get an int ViewLevel from a string ViewLevelDesc or vice versa. I'm sure the way I have done this is far more cumbersome than it needs to be, and I'm looking for some advice how to achieve the same objective but more concisely. The list of int / string pairs will increase significantly. The ones in the above code are just the first three I intend to use.

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