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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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  • How to leave out some statements while executing java code?

    - by iamrohitbanga
    In C++ if we do not want some statements to compile into code that ships like assert function calls, we control their compilation through #ifndef preprocessor directives. How do we do this in Java? I have some System.out.println() statements for debugging which I would like to remove for the final code. one way is to make them execute conditionally under the affect of a boolean variable. Is there a better way of doing this? As I have a java swing application I can turn off the System.out.println statements without affecting the output. What is the method of doing this?

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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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  • What is the use of Method Overloading in Java when it is achieved by changing the sequence of parameters in the argument list?

    - by MediumOne
    I was reading a Java training manual and it said that Method Overloading in Java can be achieved by having a different argument list. It also said that the argument list could differ in (i). Number of parameters (ii). Datatype of parameters (iii). Sequence of parameters My concern is about (iii). What is the use of trying to overload a method just by changing the sequence of parameters? I am unable to think of any benefits by this way.

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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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  • 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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  • 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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  • In Java, how do I set a return type if an exception occurs?

    - by beagleguy
    hey all, I'm new to Java and was wondering if I define a method to return a database object like import java.sql.*; public class DbConn { public Connection getConn() { Connection conn; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); if(System.getenv("MY_ENVIRONMENT") == "development") { String hostname = "localhost"; String username = "root"; String password = "root"; } conn = DriverManager.getConnection("jdbc:mysql:///mydb", username, password); return conn; } catch(Exception e) { throw new Exception(e.getMessage()); } } } if the connection fails when I try to create it what should I return? eclipse is telling me I have to return a Connection object but if it fails I'm not sure what to do. thanks!

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Best Design for creating Historic Reports on GAE

    - by charming30
    My App requires Daily reports based on various user activities. My current design does not sum the daily totals in database, which means I must compute them everytime. For example A report that shows Top 100 users based on the number of submissions they have made on a given day. For such a report If I have 50,000 users, what is the best way to create daily report? How to create monthly and yearly report with such data? If this is not a good design, then how to deal with such design decision when the metrics of the report are not clear during db design and by the time it is clear we already have huge data with limited parameters (fields). Please advice.

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