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  • In java can i have more than one class/object in a file?

    - by David
    So the way i've been told to do things is you have your file and the file name is Classname.java and then the code is something like this: class ClassName { SOME METHODS main {} } and then thats all. I'd like to have two objects defined and used within the same .java file. (i don't want to have to put the other class in a difernt file just because i'd like to send this to someone and i want to avoid hasstle of atatching multiple files to an email [the lazy do make good programers though if you think about it]) is it possible to do this? do i have to do anything special and if so what? what are some mistakes i'm likely to make or that you have made in the past when doing this?

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  • How to make my Java Swing application a Client-Server application?

    - by Jonas
    I have made a Java Swing application. Now I would like to make it a Client-Server application. All clients should be notified when data on the server is changed, so I'm not looking for a Web Service. The Client-Server application will be run on a single LAN, it's a business application. The Server will contain a database, JavaDB. What technology and library is easiest to start with? Should I implement it from scratch using Sockets, or should I use Java RMI, or maybe JMS? Or are there other alternatives that are easier to start with? And is there any server library that I should use? Is Jetty an alternative?

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  • Is there a Java unit-test framework that auto-tests getters and setters?

    - by Michael Easter
    There is a well-known debate in Java (and other communities, I'm sure) whether or not trivial getter/setter methods should be tested. Usually, this is with respect to code coverage. Let's agree that this is an open debate, and not try to answer it here. There have been several blog posts on using Java reflection to auto-test such methods. Does any framework (e.g. jUnit) provide such a feature? e.g. An annotation that says "this test T should auto-test all the getters/setters on class C, because I assert that they are standard". It seems to me that it would add value, and if it were configurable, the 'debate' would be left as an option to the user.

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  • Is It possible to use the second part of this code for repository patterns and generics

    - by newToCSharp
    Is there any issues in using version 2,to get the same results as version 1. Or is this just bad coding. Any Ideas public class Customer { public int CustomerID { get; set; } public string EmailAddress { get; set; } int Age { get; set; } } public interface ICustomer { void AddNewCustomer(Customer Customer); void AddNewCustomer(string EmailAddress, int Age); void RemoveCustomer(Customer Customer); } public class BALCustomer { private readonly ICustomer dalCustomer; public BALCustomer(ICustomer dalCustomer) { this.dalCustomer = dalCustomer; } public void Add_A_New_Customer(Customer Customer) { dalCustomer.AddNewCustomer(Customer); } public void Remove_A_Existing_Customer(Customer Customer) { dalCustomer.RemoveCustomer(Customer); } } public class CustomerDataAccess : ICustomer { public void AddNewCustomer(Customer Customer) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } public void AddNewCustomer(string EmailAddress, int Age) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } public void RemoveCustomer(Customer Customer) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } } // VERSION 2 public class Customer_New : DataRespository<CustomerDataAccess> { public int CustomerID { get; set; } public string EmailAddress { get; set; } public int Age { get; set; } } public class DataRespository<T> where T:class,new() { private T item = new T(); public T Execute { get { return item; } set { item = value; } } public void Update() { //TO BE CODED } public void Save() { //TO BE CODED } public void Remove() { //TO BE CODED } } class Program { static void Main(string[] args) { Customer_New cus = new Customer_New() { Age = 10, EmailAddress = "[email protected]" }; cus.Save(); cus.Execute.RemoveCustomer(new Customer()); // Repository Version Customer customer = new Customer() { EmailAddress = "[email protected]", CustomerID = 10 }; BALCustomer bal = new BALCustomer(new CustomerDataAccess()); bal.Add_A_New_Customer(customer); } } }

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  • How to use menu bars with different patterns?

    - by vahini
    I'm using Visual studio 2005, ASP.NET and C#. I want to use menu bars which have an active look to them when their respective target page is the one currently showing. Imagine a user clicks a menu item, navigation to the target page occurs and the menu item they selected is now differing, in say, color to that of the other items in the menu as a means to indicate this is the currently active location. How might one achieve this?

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  • Best approach to creating a database driven Java website?

    - by Craig Whitley
    I'm fairly new to programming and new to java, but I'd like to jump in the deep end with a little database driven website project. I've read quite a lot about requirements in the 'real world' requesting experience with Spring and Hibernate, so I have those installed on netbeans and a project created (if I hit run I get the default spring page). Now I just need a little guidance as to where to start designing my app (please tell me if I'm getting in a bit too over my head for a beginner!). Should I start off with my classes? - create all my classes as they map to my database tables and decide which attributes and methods each will require? Can anyone suggest any good books for maybe.. making a java based website from scratch (i.e. from design right through to deployment) that might be useful for a beginner? Any help appreciated thanks.

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  • Why do Java and C# not have implicit conversions to boolean?

    - by Shaun
    Since I started Java it's been very aggravating for me that it doesn't support implicit conversions from numeric types to booleans, so you can't do things like: if (flags & 0x80) { ... } instead you have to go through this lunacy: if ((flags & 0x80) != 0) { ... } It's the same with null and objects. Every other C-like language I know including JavaScript allows it, so I thought Java was just moronic, but I've just discovered that C# is the same (at least for numbers, don't know about null/objects): http://msdn.microsoft.com/en-us/library/c8f5xwh7(VS.71).aspx Microsoft changed it on purpose from C++, so why? Clearly I'm missing something. Why change (what I thought was) the most natural thing in the world to make it longer to type? What on Earth is wrong with it?

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  • Database design question

    - by Lijo
    Hi Team, I have an interesting database design problem that I formulated while travelling by a bus, coming back from my home. Design a normalized database for a bus ticketing system (not reservation system). In each trip, the conductor of the bus will give tickets to its passengers after collecting fare from them. Passengers travel from a various source places to various destination places. The system must be able to give a report of the places for which the number of passengers was more than 2. Suppose the stops for the bus are L1,L2, L3 and L4 Suppose passenger P1 travels from L1 to L4. P2 travels from L2 to L4. P3 travels from L3 to L4. The report should list only (L3-L4) for which it has more than 2 travelers. Can you please help me to solve the following problems 1) Design a normalized database 2) Write a query for the report 3) Is there any site that gives these kinds of interesting database design questions and answers? Thanks Lijo

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  • Which Java library lets me initialize an object's properties from a properties file?

    - by Kjetil Ødegaard
    Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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  • Usage patterns/use cases for DI or when to start using it

    - by Fabian
    I'm not sure for which use cases one should to use DI in the application. I know that injecting services like PlaceService or CalculationService etc fits very well but should I also create my domain objects with DI like a User? What is if the User has only one constructor which requires a first and lastname. Is this solveable with DI? Should I use DI to create the instances for Set/List interfaces or is this pure overkill? I use guice primarily.

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  • Java: Is there a way to efficiently insert or remove many elements from the middle of a LinkedList?

    - by allyourcode
    I was expecting to find this in Java's LinkedList, since the point of linked lists is to be able to efficiently insert (and remove) anywhere (assuming you have some kind of pointer to the location where you want to insert or remove). I'm not finding anything in the API though. Am I overlooking something? The closest thing I can find to this are the add and remove method in ListIterator. This has some limitations though. In particular, other iterators become invalid as soon as the underlying LinkedList is modified via remove, according to the API. This is born out in my tests as well; the following program results in a IllegalStateException: import java.util.*; public class RemoveFromLinkedList { public static void main(String[] args) { LinkedList<Integer> myList= new LinkedList<Integer>(); for (int i = 0; i < 10; ++i) { myList.add(i); } ListIterator<Integer> i1 = myList.listIterator(); ListIterator<Integer> i2 = myList.listIterator(); for (int i = 0; i < 3; ++i) { i1.next(); i2.next(); } System.out.println("i1.next() should be 3: " + i1.next()); i1.remove(); i1.remove(); // Exception! System.out.println("i2.next() should be 5: " + i2.next()); } } Ideally, what I'm expecting is something like this: // In my imagination only. This is the way Java actually works, afaict. // Construct two insertion/deletion points in LinkedList myLinkedList. myIterator = myLinkedList.iterator(); for (...) { myIterator.next(); } start = myIterator.clone(); for (...) { myIterator.next(); } // Later... after = myLinkedList.spliceAfter(myIterator, someOtherLinkedList); // start, myIterator, and after are still all valid; thus, I can do this: // Removes everything I just spliced in, as well as some other stuff before that. myLinkedList.remove(start, after); // Now, myIterator is invalid, but not start, nor after. C++ has something like this for its list class (template). Only iterators pointing to moved elements become invalidated, not ALL iterators.

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  • Convert a string representation of a hex dump to a byte array using Java?

    - by ravigad
    I am looking for a way to convert a long string (from a dump), that represents hex values into a byte array. I couldn't have phrased it better than the person that posted the same question here: http://www.experts-exchange.com/Programming/Programming_Languages/Java/Q_21062554.html But to keep it original, I'll phrase it my own way: suppose I have a string "00A0BF" that I would like interpreted as the byte[] {0x00,0xA0,0xBf} what should I do? I am a Java novice and ended up using BigInteger and watching out for leading hex zeros. But I think it is ugly and I am sure I am missing something simple...

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  • What is the most efficient algorithm for reversing a String in Java?

    - by Hultner
    I am wondering which way to reverse a string in Java that is most efficient. Should I use some sort of xor method? The easy way would be to put all the chars in a stack and put them back into a string again but I doubt that's a very efficient way to do it. And please do not tell me to use some built in function in Java. I am interested in learning how to do it not to use an efficient function but not knowing why it's efficient or how it's built up.

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  • What's the best way to replace the first letter of a string in Java?

    - by froadie
    I'm trying to convert the first letter of a string to lowercase. I know there's a capitalize method, but I want to accomplish the opposite. This is the code I used: value.substring(0,1).toLowerCase() + value.substring(1) Effective, but feels a bit manual. Are there any other ways to do it? Any better ways? Any Java string functions that do it for you? I was thinking of using something like a replace function, but Java's replace doesn't accept an index as a parameter. You have to pass the actual character/substring. Another way I can think of doing it is something like: value.replaceFirst(value.charAt(0), value.charAt(0).toLowerCase()) Except that replaceFirst expects 2 strings, so the value.charAt(0)s would probably need to be replaced with value.substring(0,1)s. Is this any better? Does it matter? Is there any standard way to do this?

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  • Why learn Perl, Python, Ruby if the company is using C++, C# or Java as the application language?

    - by szabgab
    I wonder why would a C++, C#, Java developer want to learn a dynamic language? Assuming the company won't switch its main development language from C++/C#/Java to a dynamic one what use is there for a dynamic language? What helper tasks can be done by the dynamic languages faster or better after only a few days of learning than with the static language that you have been using for several years? Update After seeing the first few responses it is clear that there two issues. My main interest would be something that is justifiable to the employer as an expense. That is, I am looking for justifications for the employer to finance the learning of a dynamic language. Aside from the obvious that the employee will have broader view, the employers are usually looking for some "real" benefit.

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  • Java program runs smoothly in Netbeans but slowly in Eclipse and as an executed jar. WTF?

    - by comp sci balla
    A java program that does frequent swing/awt painting animation (but nothing more advanced than g.fillOval(...)) runs at a consistent 60fps in Netbeans, and at about 6fps when ran in Eclipse or executed as a jar file from a unix terminal. The program was developed in Netbeans and is run-of-the-mill desktop application (not webstart or japplet or ...). This is occurring in Ubuntu 10 with java 1.6. How is this possible? The universe no longer makes sense to me.

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  • Patterns for avoiding jQuery silent fails

    - by Matias
    Is there any good practice to avoid your jQuery code silently fail? For example: $('.this #is:my(complexSelector)').doSomething(); I know that every time this line get executed, the selector is intended to match at least one element, or certain amount of elements. Is there any standard or good way to validate that? I thought about something like this: var $matchedElements = $('.this #is:my(complexSelector)'); if ($matchedElements.length < 0) throw 'No matched elements'; $matchedElements.doSomething(); Also I think unit testing would be a valid option instead of messing the code. My question may be silly, but I wonder whether there is a better option than the things that I'm currently doing or not. Also, maybe I'm in the wrong way checking if any element match my selector. However, as the page continues growing, the selectors could stop matching some elements and pieces of functionality could stop working inadvertently.

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