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  • What was your "aha moment" in understanding delegates?

    - by CM90
    Considering the use of delegates in C#, does anyone know if there is a performance advantage or if it is a convenience to the programmer? If we are creating an object that holds a method, it sounds as if that object would be a constant in memory to be called on, instead of loading the method every time it is called. For example, if we look at the following Unity3D-based code: public delegate H MixedTypeDelegate<G, H>(G g) public class MainParent : MonoBehaviour // Most Unity classes inherit from M.B. { public static Vector3 getPosition(GameObject g) { /* GameObject is a Unity class, and Vector3 is a struct from M.B. The "position" component of a GameObject is a Vector3. This method takes the GameObject I pass to it & returns its position. */ return g.transform.position; } public static MixedTypeDelegate<GameObject, Vector3> PositionOf; void Awake( ) // Awake is the first method called in Unity, always. { PositionOf = MixedTypeDelegate<GameObject, Vector3>(getPosition); } } public class GameScript : MainParent { GameObject g = new GameObject( ); Vector3 whereAmI; void Update( ) { // Now I can say: whereAmI = PositionOf(g); // Instead of: whereAmI = getPosition(g); } } . . . But that seems like an extra step - unless there's that extra little thing that it helps. I suppose the most succinct way to ask a second question would be to say: When you had your aha moment in understanding delegates, what was the context/scenario/source? Thank you!

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  • How to implement iterator as an attribute of a class in Java

    - by de3
    Hi, let's say I have this simple MyArray class, with two simple methods: add, delete and an iterator. In the main method we can see how it is supposed to be used: public class MyArray { int start; int end; int[] arr; myIterator it; public MyArray(){ this.start=0; this.end=0; this.arr=new int[500]; it=new myIterator(); } public void add(int el){ this.arr[this.end]=el; this.end++; } public void delete(){ this.arr[this.start]=0; this.start++; } public static void main(String[] args){ MyArray m=new MyArray(); m.add(3); m.add(299); m.add(19); m.add(27); while(m.it.hasNext()){ System.out.println(m.it.next()); } } And then MyIterator should be implemented somehow: import java.util.Iterator; public class myIterator implements Iterator{ @Override public boolean hasNext() { // TODO Auto-generated method stub return false; } @Override public Object next() { // TODO Auto-generated method stub return null; } @Override public void remove() { // TODO Auto-generated method stub } } MyIterator should iterate arr from MyArray class, from start to end values; both are also attributes of MyArray. So, as MyIterator should use MyArray attributes, how should MyIterator be implemented? Perhaps I can send the current object in the initialization: it=new myIterator(this); But I guess it's not the best soultion. Or maybe MyArray itself should implement Iterator interface? How is this solved?

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  • Works on emulator but not on device

    - by Klaus
    Hello Community, I have an inner handler class that calls the method sendMessage. sendMessige is outside the handler class, but inside the conatining Android java class. On the emulator (AVD 2.2) it works fine, but on my Android 2.2 device the method sendMessage is not called at all. Inner handler class: private Handler handler2 = new Handler() { public void handleMessage(Message msg) { if (GeoSetting.equals("s") && (inNumber.equals(definedNumber))) **SendService.this.sendMessage(definedNumber, DisplayLoc)**; if (GeoSetting.equals("a")) **SendService.this.sendMessage(inNumber, DisplayLoc)**; stopService(new Intent(getApplicationContext(), GeoService.class)); }; The method that should be called: private void sendMessage(String sendNumber, String sendText){ Toast.makeText(getApplicationContext(), "done!!!", Toast.LENGTH_LONG).show(); SmsManager sms = SmsManager.getDefault(); try { sms.sendTextMessage(sendNumber, null, sendText, null, null); if (Message == true) {Toast.makeText(getApplicationContext(), "Sending SMS to "+sendNumber+": "+sendText, Toast.LENGTH_LONG).show();} } catch (Exception exeption){ Toast.makeText(getApplicationContext(), "Something is wrong, could not send SMS!", Toast.LENGTH_LONG).show(); } Toast.makeText(getApplicationContext(), "method called!", Toast.LENGTH_LONG).show(); } Does anybody have an idea why sendMessage is not called on the real device? Thank you for the help!

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  • Programming logic best practice - redundant checks

    - by eldblz
    I'm creating a large PHP project and I've a trivial doubt about how to proceed. Assume we got a class books, in this class I've the method ReturnInfo: function ReturnInfo($id) { if( is_numeric($id) ) { $query = "SELECT * FROM books WHERE id='" . $id . "' LIMIT 1;"; if( $row = $this->DBDrive->ExecuteQuery($query, $FetchResults=TRUE) ) { return $row; } else { return FALSE; } } else { throw new Exception('Books - ReturnInfo - id not valid.'); } } Then i have another method PrintInfo function PrintInfo($id) { print_r( $this->ReturnInfo($id) ); } Obviously the code sample are just for example and not actual production code. In the second method should I check (again) if id is numeric ? Or can I skip it because is already taken care in the first method and if it's not an exception will be thrown? Till now I always wrote code with redundant checks (no matter if already checked elsewhere i'll check it also here) Is there a best practice? Is just common sense? Thank you in advance for your kind replies.

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  • is there a Java GUI for dummies ?

    - by MHero
    Hello, first I want to apologize about my english, it may be not clear enough. Well, I'm new to Java programming, and I search over this web about use of Swing, AWT, 2D, etc. but I didn't get the answer I was looking for. I want to know about a book or method to learn Java GUI programming (not even sure this is a propper term). Previous answers guide me to Filthy Rich Clients by Romain Guy and also to The Swing Tutorial in Sun Web Page. and No offense, but...the first one seems too complex and the second one a bit disorganize. so I ask about a more "for dummies" method. Thanks EDIT: Thanks everyboy, you're very kind and serious. I want to clear some things that I didn't state for being my first question. I dont' want to use autogenerated code(Don't want to say why only focus on my question for consistency) Also I've read Deitel & Deitel and it's a good beginners book but it seems to me that doesn't cover layout(and other details) Finally, I tried to read netbeans generated code but it's a mess find method by method and function by function the way that the IDE does it I hope this edition helps to solve my question

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  • Does Spring MVC form submit data bind children objects automagically?

    - by predhme
    I have a data model that is something like this: public class Report { // report owner private User user; ... typical getter setter ... } public class User { ... omitted for clarity } What happens is when a report is created, the current user is set to the report user object. When the report is edited, the spring controller handling the POST request is receiving a report where the user object is null. Here is what my controller looks like: @Controller @RequestMapping("/report") public class ReportController { @RequestMapping(value = "/edit/{id}", method = RequestMethod.GET) public String editReport(@PathVariable Long id, Model model) { Report r = backend.getReport(id); // fully loads object model.addAttribute("report", report); return "report/edit"; } @RequestMapping(value = "/edit/{id}", method = RequestMethod.POST) public String process(@ModelAttribute("report") Report r) { backend.save(r); return "redirect:/report/show" + r.getId(); } } I ran things throw the debugger and it looks like in the editReport method the model object is storing the fully loaded report object (I can see the user inside the report). On the form jsp I can do the following: ${report.user.username} and the correct result is rendered. However, when I look at the debugger in the process method, the passed in Report r has a null user. I don't need to do any special data binding to ensure that information is retained do I?

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  • Working with Java using methods and arrays [closed]

    - by jordan
    Hi i'm a newb at java and for one of my labs I have to create a instant messenger client with these requirements: add buddyList instance variable add IMClient constructor to create ArrayList addBuddy method removeBuddy method findBuddy method printBuddyList method what's the best way to go about this? so far I have this: public class IMClient { private String userId; // User id private String password; // Password private int status; // Status code for user: 1 - Online, 2 - Off-line, 3 - Away public IMClient(String userId, String password, int status) { super(); this.userId = userId; this.password = password; this.status = status; } // Returns true if password as a parameter matches password instance variable. public boolean checkPassword(String password) { return this.password.equals(password); } public String toString() { StringBuffer buf = new StringBuffer(100); buf.append(" User id: "); buf.append(userId); buf.append(" Password: "); buf.append(password); buf.append(" Status: "); buf.append(status); return buf.toString(); } public String getUserId() { return userId; } public void setUserId(String userId) { this.userId = userId; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getStatus() { return status; } public void setStatus(int status) { this.status = status; } public static void main(String[] args) { } }

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  • What is a good use case for static import of methods?

    - by Miserable Variable
    Just got a review comment that my static import of the method was not a good idea. The static import was of a method from a DA class, which has mostly static methods. So in middle of the business logic I had a da activity that apparently seemed to belong to the current class: import static some.package.DA.*; class BusinessObject { void someMethod() { .... save(this); } } The reviewer was not keen that I change the code and I didn't but I do kind of agree with him. One reason given for not static-importing was it was confusing where the method was defined, it wasn't in the current class and not in any superclass so it too some time to identify its definition (the web based review system does not have clickable links like IDE :-) I don't really think this matters, static-imports are still quite new and soon we will all get used to locating them. But the other reason, the one I agree with, is that an unqualified method call seems to belong to current object and should not jump contexts. But if it really did belong, it would make sense to extend that super class. So, when does it make sense to static import methods? When have you done it? Did/do you like the way the unqualified calls look? EDIT: The popular opinion seems to be that static-import methods if nobody is going to confuse them as methods of the current class. For example methods from java.lang.Math and java.awt.Color. But if abs and getAlpha are not ambiguous I don't see why readEmployee is. As in lot of programming choices, I think this too is a personal preference thing. Thanks for your response guys, I am closing the question.

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  • Could someone help me debug my app (not very big)?

    - by Alex
    Not sure if this kind of help is accepted to ask for here, tell me if it isn't. It has to get done before tomorrow, it's not entirerly finished but it should work somewhat ok by now. I'm trying to use the Eclipse debugger (not very used to it). I have my top-level or main class, which is Game, in which I have a constructor and a main method. In the main method I create a new "Game", initiating the constructor. public static void main(String[] args){ Game chess = new Game(); } public Game(){ Board board = new Board(); That's the first thing the debugger reacts to: Thread [main] (Suspended) ClassNotFoundException(Object).<init>() line: 20 [local variables unavailable] ClassNotFoundException(Throwable).<init>(String, Throwable) line: 217 ClassNotFoundException(Exception).<init>(String, Throwable) line: not available ClassNotFoundException.<init>(String) line: not available URLClassLoader$1.run() line: not available AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$ExtClassLoader(URLClassLoader).findClass(String) line: not available Launcher$ExtClassLoader.findClass(String) line: not available Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader.loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available Game.<init>() line: 15 Game.main(String[]) line: 11 Line 11 is the one line in my main method, line 15 is the instantiation of "board".

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  • How to acheieve this kind of behaviour in asp.net mvc

    - by kumar
    Hello Friends,, I have this two Action result methods. public ActionResult GetStudentInfo(StudentBE s) { return PartialView("editStudent", s); } public ActionResult GenericList() { StudentBE codes = new StudentBE(); codes.lookcodes= GetStudentCodes(new string[] { "A", "B", "C, "D", "E" }); return PartialView(codes); } // Lookcodes display dropdownlist boxes in the GeneridList view.. In genericList view I hvae beginForm.. <% using (Html.BeginForm("Updatestudent", "expense", FormMethod.Post, new { @id = "id" })) { %> <% } %> so My updatestudent method is [HttpPost] public JsonResult Updatestudent(StudentBE e) { var status = common.Update(e.student); } } return Json(status.ToString()); } Here is my problem.. the GetStudentInfo Actionresult is having each student information.. in UpdateStudent method Update Method calls the DB calls for stored procedure to update each user information now to update each user I need to call GetstudentInfo each time to get student information to update..? how to call GetStudentInfo method here to get studentinformation? student informatin may be multiple that is more than one student informaton... can anybody help me out.. thanks

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  • How to implement the "System.out.println(ClassName::MethodName <then my message>)" of Eclipse in Netbeans?

    - by Sen
    I would like to know if there is the same feature as in eclipse to automatically generate and print the System.out.println(ClassName::MethodName <then my message>) functionality (which will print the class name and method name for debugging in the console) in Netbeans also. For example, in Eclipse Editor, Typing syst + Ctrl+ Space will auto generate a System.out.println(ClassName::MethodName ) type output in the console. Is such a method available in Netbeans? As of now, I have only two methods here in Netbeans: sout + Tab (System.out.println()) and soutv + Tab (System.out.println(prints the variable used just above the line)) automatically. Let me rephrase, instead of myMethod1, I want to get the enclosing method name. Eg. : public class X { public void myMethod1(int a) { System.out.println(X::myMethod1()); // This should be produced when I type the Code-Template abbreviation (example: syst) and press tab (or corresponding key). } } public class Y { public void myMethod2(int b) { System.out.println(Y::myMethod2()); // This should be produced when I type the Code-Template abbreviation (example: syst) and press tab (or corresponding key). } } Update: With the following code template: syst = System.out.println("${classVar editable="false" currClassName default="getClass()"}"); I am able to print the classname, but still no clue for the Method name.

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  • Is there a way in VS2008 (c#) to see all the possible exception types that can originate from a meth

    - by Matt
    Is there a way in VS2008 IDE for c# to see all the possible exception types that can possibly originate from a method call or even for an entire try-catch block? I know that intellisense or the object browser tells me this method can throw these types of exceptions but is there another way than using the object browser everytime? Something more accessible when coding? Furthermore, I don't think intellisense or the object browser do anything more than read the XML code comments. Shouldn't it be possible to scan a class's source and find all the exception types that can be thrown. (Forget path-ing based on method input, just scan the code for exception types) Am I wrong? Extending this idea, you should be able to hover over the 'try' or 'catch' keywords and present a tooltip with all the types of exceptions that can be thrown. My question boils down to, does a VS2008 add on like this exist? Does VS2010 do this perhaps? If not, could you implement it the way I've described, by scanning the class code for thrown exception types and would people find it useful. Exceptions bubble up so you have to scan every bit of code every method call, which I guess could be impractical, though I suppose you could build an index the first time and increase your speed that way. (It might be a cool little project....)

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  • remove 2 subviews in one go.

    - by Pavan
    hi, I am trying to remove two viewcontrollers (that have been added on top of each other) with one method. I have made the views in interfacebuilder. they all have their own .h and .m files to go with it. Scenario I am in: I have a main menu which has the view2 header file imported. In a method I add the second view on top of the superview like so view2ViewController * view2 = [[view2ViewController alloc] initWithNibName:@"view2ViewController" bundle:nil]; [self.view addSubview:view2.view]; then in view 2 I have added the view 3 header file so i can add view 3 as a subview ontop of view2. i have another method which is connected again to interface builder to a UIButton so upon button press a method gets called in view2 which adds view 3 on top in exactly the same way like so: view3ViewController * view3 = [[view3ViewController alloc] initWithNibName:@"view3ViewController" bundle:nil]; [self.view addSubview:view3.view]; What im trying to solve: I have a button in view 3 which should remove view 3.... and then it should also remove view 2 aswell so the main screen is visible. How can this be achieved? What I have so far: [self.view removeFromSuperview]; This however only removes View 3... but leaves view 2 in place. What needs to be modified so that i can remove view 2 as well?? Any help is appreciated.

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  • XNA, C# - Check if a Vector2 path crosses another Vector2 path.

    - by Nick
    Hello all, I have an XNA question for those with more experience in these matters than myself (maths). Background: I have a game that implements a boundary class, this simply hosts 2 Vector2 objects, a start and an end point. The current implementation crudely handles collision detection by assuming boundaries are always vertical or horizontal, i.e. if start.x and end.x are the same check I am not trying to pass x etc. Ideally what I would like to implement is a method that accepts two Vector2 parameters. The first being a current location, the second being a requested location (where I would like to move it to assuming no objections). The method would also accept a boundary object. What the method should then do is tell me if I am going to cross the boundry in this move. this could be a bool or ideally something representing how far I can actually move. This empty method might explain better than I can in words. /// <summary> /// Checks the move. /// </summary> /// <param name="current">The current.</param> /// <param name="requested">The requested.</param> /// <param name="boundry">The boundry.</param> /// <returns></returns> public bool CheckMove(Vector2 current, Vector2 requested, Boundry boundry) { //return a bool that indicated if the suggested move will cross the boundry. return true; }

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  • c# - sqllite dosnt save data i inserted

    - by samy
    I'm messing around with SQL lite and learning it. I got a table called People, I got some method that connect to the database and do some stuff, like show all the info. Now I'm trying to insert some data and here it get wierd for me. I have this method: private void ExecuteQuery(string txtQuery) { SetConnection(); sql_con.Open(); sql_cmd = sql_con.CreateCommand(); sql_cmd.CommandText = txtQuery; sql_cmd.ExecuteNonQuery(); sql_con.Close(); } and to see all the data I've got this method: private void LoadData() { SetConnection(); sql_con.Open(); sql_cmd = sql_con.CreateCommand(); string CommandText = "SELECT * FROM People"; DB = new SQLiteDataAdapter(CommandText, sql_con); DS.Reset(); DB.Fill(DS); DT = DS.Tables[0]; dataGridView1.DataSource = DT; sql_con.Close(); } When I inset some data and right afther it I call the LoadData(), I can see all the changes I made. After I close the program, and then open it agian and call LoadData(), I don't see the new info that I inserted before. I got some data that I used SQL lite GUI app to insert, and I can see that data every time I call the LoadData() method, but not mine. Do I need to do somthing else to make sure SQL lite saves all the data?

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  • C# Passing objects and list of objects by reference

    - by David Liddle
    I have a delegate that modifies an object. I pass an object to the delegate from a calling method, however the calling method does not pickup these changes. The same code works if I pass a List as the object. I thought all objects were passed by reference so any modifications would be reflected in the calling method? I can modify my code to pass a ref object to the delegate but am wondering why this is necessary? public class Binder { protected delegate int MyBinder<T>(object reader, T myObject); public void BindIt<T>(object reader, T myObject) { //m_binders is a hashtable of binder objects MyBinder<T> binder = m_binders["test"] as MyBinder<T>; int i = binder(reader, myObject); } } public class MyObjectBinder { public MyObjectBinder() { m_delegates["test"] = new MyBinder<MyObject>(BindMyObject); } private int BindMyObject(object reader, MyObject obj) { //make changes to obj in here } } ///calling method in some other class public void CallingMethod() { MyObject obj = new MyObject(); MyBinder binder = new MyBinder(); binder.BindIt(myReader, obj); //don't worry about myReader //obj should show reflected changes }

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  • An Array returned by a model association is not an Array?

    - by Warren
    We have a model association that looks something like this: class Example < ActiveRecord::Base has_many :others, :order => 'others.rank' end The rank column is an integer type. The details of these particular models are not really important though as we have found the same problem with other has_many associations between other models. We have also added to the Enumerable module: module Enumerable def method_missing(name) super unless name.to_s[0..7] == 'collect_' method = name.to_s[8..-1] collect{|element| element.send(method)} end end This adds a collect_id method that we can use to get an array of record ids from an array of ActiveRecord objects. So if we use a normal ActiveRecord find :all, we get a nice array which we can then use collect_id on but if we use Example.others.collect_id, we get NoMethodError: undefined method `collect_id' for #<Class:0x2aaaac0060a0> Example.others.class returns "Array" so is it lying or confused? Our solution thus far has been to use it this way: Example.others.to_a.collect_id This works but this seems a bit strange. Why would you have to do that? We are on Ruby 1.8.7 and Rails 2.3.4

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  • Moq basic questions

    - by devoured elysium
    I made the following test for my class: var mock = new Mock<IRandomNumberGenerator>(); mock.Setup(framework => framework.Generate(0, 50)) .Returns(7.0); var rnac = new RandomNumberAverageCounter(mock.Object, 1, 100); rnac.Run(); double result = rnac.GetAverage(); Assert.AreEqual(result, 7.0, 0.1); The problem here was that I changed my mind about what range of values Generate(int min, int max) would use. So in Mock.Setup() I defined the range as from 0 to 50 while later I actually called the Generate() method with a range from 1 to 100. I ran the test and it failed. I know that that is what it's supposed to happen but I was left wondering if isn't there a way to launch an exception or throw in a message when trying to run the method with wrong params. Also, if I want to run this Generate() method 10 times with different values (let's say, from 1 to 10), will I have to make 10 mock setups or something, or is there a special method for it? The best I could think of is this (which isn't bad, I'm just asking if there is other better way): for (int i = 1; i < 10; ++i) { mock.Setup(framework => framework.Generate(1, 100)) .Returns((double)i); }

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  • Java: GatheringByteChannel advantages?

    - by Jason S
    I'm wondering when the GatheringByteChannel's write methods (taking in an array of ByteBuffers) have advantages over the "regular" WritableByteChannel write methods. I tried a test where I could use the regular vs. the gathering write method on a FileChannel, with approx 400KB/sec total in ByteBuffers of between 23-27 bytes in length in both cases. Gathering writes used an array of 64. The regular method used up approx 12% of my CPU, and the gathering method used up approx 16% of my CPU (worse than the regular method!) This tells me it's NOT useful to use gathering writes on a FileChannel around this range of operating parameters. Why would this be the case, and when would you ever use GatheringByteChannel? (on network I/O?) Relevant differences here: public void log(Queue<Packet> packets) throws IOException { if (this.gather) { int Nbuf = 64; ByteBuffer[] bbufs = new ByteBuffer[Nbuf]; int i = 0; Packet p; while ((p = packets.poll()) != null) { bbufs[i++] = p.getBuffer(); if (i == Nbuf) { this.fc.write(bbufs); i = 0; } } if (i > 0) { this.fc.write(bbufs, 0, i); } } else { Packet p; while ((p = packets.poll()) != null) { this.fc.write(p.getBuffer()); } } }

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  • multiplying all elements in an array by an outside number?

    - by prodo
    I need to multiple all the values in an array by 3000 which in turn would create a new array that I will use to subtract from another array. I've tried to create a separate method that would do that for me but all I got back in the multiplied array was a bunch of numbers and symbols strangely? here is the code that I wrote public static void main(String[] args) { int numberOfTaxpayers = Integer.parseInt(JOptionPane.showInputDialog("Enter how many users you would like to calculate taxes for: "); int[] usernumChild = new int[numberOfTaxPayers]; for (int i = 0; i < usernumChild.length; i++) { usernumChild[i] = Integer.parseInt(JOptionPane.showInputDialog("Enter number of children for user "+ (i+1) +": ")); }//this for loop finds out the number of children per user so we can later multiply each input by 3000 to create an array that determine dependency exemption for each user int[] depndExemp = multiply(usernumChild, 3000);//this was the calling of the multiply method... somewhere here is the error!! }//end main method public static int[] multiply(int[] children, int number) { int array[] = new int[children.length]; for( int i = 0; i < children.length; i++) { children[i] = children[i] * number; }//end for return array; }//this is the method that I was shown in a previous post on how to create return an array in this the dependency exemption array but when I tested this by printing out the dependency array all I received were a jumble of wrong numbers.

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  • How to delay program for a certain number of milliseconds, or until a key is pressed?

    - by Jack
    I need to delay my program's execution for a specified number of milliseconds, but also want the user to be able to escape the wait when a key is pressed. If no key is pressed the program should wait for the specified number of milliseconds. I have been using Thread.Sleep to halt the program (which in the context of my program I think is ok as the UI is set to minimise during the execution of the main method). I have thought about doing something like this: while(GetAsyncKeyState(System.Windows.Forms.Keys.Escape) == 0 || waitTime > totalWait) { Thread.Sleep(100); waitTime += 100; } As Thread.Sleep will wait until at least the time specified before waking the thread up, there will obviously be a large unwanted extra delay as it is scaled up in the while loop. Is there some sort of method that will sleep for a specified amount of time but only while a condition holds true? Or is the above example above the "correct" way to do it but to use a more accurate Sleep method? If so what method can I use? Thanks in advance for your help.

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  • Patterns to deal with with functions that can have different kinds of results.

    - by KaptajnKold
    Suppose you have an method on an object that given the some input alters the objects state if the input validates according to some complex logic. Now suppose that when the input doesn't validate, it can be due to several different things, each of which we would like to be able to deal with in different ways. I'm sure many of you are thinking: That's what exceptions are for! I've thought of this also. But my reservation against using exceptions is that in some cases there is nothing exceptional about the input not validating and I really would like to avoid using exceptions to control what is really just in the expected flow of the program. If there were only one interpretation possible, I could simply choose to return a boolean value indicating whether or not the operation resulted in a state change or not and the respond appropriately when it did not. There is of course also the option to return a status code which the client can then choose to interpret or not. I don't like this much either because there is nothing semantic about status codes. The solution I have so far is to always check for each possible situation which I am able to handle before I call the method which then returns a boolean to inform the client if the object changed state. This leaves me the flexibility to handle as few or as many as the possible situations as I wish depending on the context I am in. It also has the benefit of making the method I am calling simpler to write. The drawback is that there is quite a lot of duplication in the client code wherever I call the method. Which of these solutions do you prefer and why? What other patterns do people use for providing meaningful feedback from functions? I know that some languages support multiple return values, and I if I had that option I would surely prefer it.

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  • retrieving and restoring textview information from sharedpreferences

    - by user1742524
    I have an activity that allows user to enter notes and store them in dynamically created textviews. However, when the use leaves the activity and returns, all the created textviews disappear. How can i store store or retrieve all of these created textviews, whenever i return to the activity? Also, i think that my sharedpreferences will be overwriting each time a new textview is added. Any suggestions? public class DocNoteActivity extends Activity { private LinearLayout nLayout; private EditText etDocNote; private Button btnAdd1; public static final String PREFS_NAME = "MyPrefsFile"; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.adddocnote); etDocNote = (EditText) findViewById(R.id.editDocNote); btnAdd1 = (Button) findViewById(R.id.btnAdd1); nLayout = (LinearLayout) findViewById(R.id.linearLayout); TextView tvNote = new TextView(this); tvNote.setText(""); btnAdd1.setOnClickListener(onClick()); } private OnClickListener onClick() { // TODO Auto-generated method stub return new OnClickListener(){ public void onClick(View v) { // TODO Auto-generated method stub String newDocNote = etDocNote.getText().toString(); nLayout.addView(createNewTextView(newDocNote)); getSharedPreferences("myprefs", 0).edit().putString("etDocNote", newDocNote).commit(); } }; } private TextView createNewTextView(String newText) { // TODO Auto-generated method stub LayoutParams lparams = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); TextView tvNote = new TextView(this); tvNote.setLayoutParams(lparams); tvNote.setText(newText); return tvNote; } }

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  • Having an issue with the "this" modifier...

    - by user344246
    I have this method in City class. It should create a new city based on the object which the method is applied to: public City newCity(string newCityName, int dX, int dY) { City c=new City(this); //based on a constructor : City(City c){} c.CityName=newCityName; c.NoOfNeighborhoods=1; c.NumOfResidents=0; c.CityCenter.Move(dX,dY); return c; } CityCenter is of type "Point" which has two fields - x,y. the Move method in Point class is ment to change the CityCenter location. It looks like this: public void Move(int dX, int dY) { this.X = x + dX; this.Y = y + dY; } What happens is that the new object,c and the existing City object are both changed. I think that "this" modifier works on the existing object too... How can I take advantage of the Move method without causing this behavior? Note: this is a closed API, so I can only add private methods to the project.

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  • public String shorthand(String in)

    - by luvthug
    Hi All, I am stuck on this code. The code should use the class StringBuilder to build an output string by appending non-vowel characters from its argument in to the result it returns. It needs to identify vowels to be removed using the helper metod i created which is public boolean isVowel(char c). public String shorthand(String in) this is the method I need help with. I have created the stringbuilder but the if condition does not accept isVowel method. import java.io.*; import java.util.*; public class Shorthand { public boolean isVowel(char c) { if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' || c == 'A'|| c == 'E'||c == 'I'|| c == 'O'|| c == 'U') { return true; } else { return false; } } //TODO Complete the shorthand method public String shorthand(String in) //this is the code I need help with { StringBuilder vowel = new StringBuilder(); if (isVowel() == false)strong text { vowel.append(in); } return vowel.toString(); } //TODO Complete the run method public void run() throws IOException { String yourLine; Scanner sc = new Scanner(System.in); yourLine = sc.nextLine(); while(!yourLine.equals("*")); { System.out.println("Enter your line of text"); } yourLine = sc.nextLine(); } }

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