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  • About local Final varibles in java

    - by Sathish
    In java Program, parameters which is defined as String in method declaration.But in method definition it is accessed as final String variable. Whether it'll lead to some issues (like security, memory problem)? For Example: Method Declaration join(String a,String b); Method definition public void join(final String a,final String b) { Authenticator au = new Authenticator(){ public PasswordAuthentication getPasswordAuthentication(){ return new PasswordAuthentication(a,b)} }; } Please help for me and clarify my doubts. Thanks in advance P.S. I;m accessing a and b as final variable because i've to use it in the inner class.

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  • Java multiline string

    - by skiphoppy
    Coming from Perl, I sure am missing the "here-document" means of creating a multi-line string in source code: $string = <<"EOF" # create a three line string text text text EOF In Java I have to have cumbersome quotes and plus signs on every line as I concatenate my multiline string from scratch. What are some better alternatives? Define my string in a properties file? Edit: Two answers say StringBuilder.append() is preferable to the plus notation. Could anyone elaborate as to why they think so? It doesn't look more preferable to me at all. I'm looking for away around the fact that multiline strings are not a first-class language construct, which means I definitely don't want to replace a first-class language construct (string concatenation with plus) with method calls. Edit: To clarify my question further, I'm not concerned about performance at all. I'm concerned about maintainability and design issues.

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  • Jython java call throws exception asking for 2 args when only one arg is coded

    - by clutch
    I have an Java method I want to call within my Jython servlet running on tomcat5. It looks like this: @SuppressWarnings("unchecked") public School loadByName(String name) { List<School> school; school = getHibernateTemplate().find("from " + getPersistentClass().getName() + " where name = ?", name); return uniqueResult(school); } I call it in Jython using: foobar = SchoolDAOHibernate.loadByName('Univeristy') It throws an error that says loadByName() expects 2 args; got 1. What other argument could it be looking for?

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  • Websphere Java application startup

    - by Tom Barnett
    I have two Java applications running on a Websphere application server. The first application is COTS software (Plateau) I will call App1 and includes an API which can be used in custom applications to interact with App1. This app takes a couple minutes to start in Websphere. The second application is custom software I will call App2 and is deployed as a web service which utilizes the App1 API to interact with App1; so it is dependent on App1. This app takes just seconds to start in Websphere. I run into a problem in certain App1 functionality when we bounce Websphere and the App2 web service is called by a client before the App1 application has fully started. Is there a way I can delay App2 from starting until App1 is fully started in Websphere? Is there a way to design App2 to programmatically check that App1 is available before it attempts to use the API?

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  • Workaround for abstract attributes in Java

    - by deamon
    In Scala I would write an abstract class with an abstract attribute path: abstract class Base { val path: String } class Sub extends Base { override val path = "/demo/" } Java doesn't know abstract attributes and I wonder what would be the best way to work around this limitation. My ideas: a) constructor parameter abstract class Base { protected String path; protected Base(String path) { this.path = path; } } class Sub extends Base { public Sub() { super("/demo/"); } } b) abstract method abstract class Base { // could be an interface too abstract String getPath(); } class Sub extends Base { public String getPath() { return "/demo/"; } } Which one do you like better? Other ideas? I tend to use the constructor since the path value should not be computed at runtime.

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  • Replicating Java's DecimalFormat in C#

    - by Frank Krueger
    I am trying to replicate a subset of Java's DecimalFormat class. Below is what I've come up with. Does this look right to everyone? public class DecimalFormat : NumberFormat { int _maximumFractionDigits; int _minimumFractionDigits; string _format; void RebuildFormat () { _format = "{0:0."; _format += new string ('0', _minimumFractionDigits); if (_maximumFractionDigits > _minimumFractionDigits) { _format += new string ('#', _maximumFractionDigits - _minimumFractionDigits); } _format += "}"; } public override string format (object value) { return string.Format (_format, value); } public override void setMaximumFractionDigits (int n) { _maximumFractionDigits = n; RebuildFormat (); } public override void setMinimumFractionDigits (int n) { _minimumFractionDigits = n; RebuildFormat (); } public override void setGroupingUsed (bool g) { } public static NumberFormat getInstance () { return new DecimalFormat (); } }

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  • java System.nanoTime is really slow. Is it possible to implement a high performance java profiler?

    - by willpowerforever
    I did a test and found the overhead of a function call to System.nanoTime() is at least 500 ns on my machine. Seemed that it is very hard to have a high performance java profiler. For enterprise software, suppose a function takes about 350 seconds and has 12,500,000,000 times of method calls. Therefore, the number of calls to System.nanoTime() is: 12,500,000,000 * 2 = 25,000,000,000 (one for start timestamp, one for end timestamp) And the overhead of System.nanoTime in total is: 500 ns * 25,000,000,000 = 500 * 25000 s = 12500000s. Note: all data from real case. Any better way to acquire the timestamp?

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  • A textbox class only accept integers in Java

    - by alex
    I just want to do a textbox class onl accepts integers.. I have done something, but i think it's not enough. Can anyone help me, please? Thanks... import java.awt.TextField public class textbox extends TextField{ private int value; public textbox(){ super(); } public textbox(int value){ setDeger(value); } public int getValue() { return value; } public void setValue(int value) { this.value = value; } }

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  • java or php tip for small problem

    - by agazerboy
    Hi All, I am having a weird mind gogling problem. Sorry in advance, If I confuse you. I have following data 1 3 5 5 1 2 2 4 8 3 2 9 3 8 4 first column = source 1 second column = source 2 third column = result column First and second column will can create 3rd column and that 3rd column can be used in 1st or 2nd column to make a new 3rd column value. You can see in first row 5 was 3rd column and in 2nd row it was input to make 2 (3rd column) I am looking for a solutin that if it pass 3 it return me (1,4,5) rows and same for other digits. Solution tip can be either in java or php because I just want to get data from a old project to make it work ! Thanks !

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  • Java vs Flash for webcam access

    - by Alfredo Palhares
    I will make a video chat website, but coming from PHP and Python for the web i have no experience with video steaming. What do you recommend? Java or Flash? What's more flexible ? I am thinking of even making a C++ server application for stream controlling with a PHP fronted. Since is going to be a high traffic website and performance is a must. Can you point to some direction? Any documentation? Framework?

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  • Finding Errant Output to System.out in Large Java Program

    - by SvrGuy
    Hi, We have a large java code base [~1 M Lines]. Buried (somewhere) in the code base is some old debug output to System.out that we want to remove (its cluttering things up). The problem is: out code base is so large that we can't easily find where the output is coming from. What we want is a way to see where System.out.println is getting called from (like a stack trace from an exception or some such). Its not suitable to debugging -- the errant output is coming from some errant thread somewhere etc. Any ideas on how to track the source of this errant output down? PS: 99.99% of calls to System.out are legit, and we have thousands of them, so simply searching the code base for System.out calls is not a solution!

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  • Java Socket Disconnect Reporting vs. C# Disconnection

    - by ikurtz
    in C# when a sockets connection is terminated the other node is informed of this before terminating the link thus the remaning node can update the connection status. in Java when i terminate a communication link the other node keeps reporting the connection as valid. do i need to implement a read cycle (makes sense) that reports the connection as lost when it recieves a -1 during read (in C# this is 0 i think)? thank you for your insight. EDIT: thanks to you both. as i suspected and mentioned in my post that an additional check is required to confirm the connected state of a connection.

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  • Comparing two java objects on fly (data type not known)

    - by Narendra
    Hi All, I need to compare different data objects. Can any one tell me how can i do this. I don't know what are the data types i will get priorly. If i need to use any util from apache commons then please give reference to it. At present I am using .equals() for comparing equality of objects .It is working fine when I am comparing quality for two strings. If i am comparing java.sql.date data type then it is showing unequal even though both contains same values. Can any one suggest me on this regard. Thanks, Narendra

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  • How to generate a random alpha-numeric string in Java

    - by Todd
    I've been looking for a simple java algorithm to generate a pseudo-random alpha-numeric string. In my situation it would be used as a unique session/key identifier that would "likely" be unique over 500K+ generation (my needs don't really require anything much more sophisticated) . Ideally I would be able to specify a length depending on my uniqueness needs. For example, a generated string of length 12 might look something like "AEYGF7K0DM1X". Answers: I like @Apocalisp and @erickson's answers equally well. The only downside to @Apocalisp's answer is it requires an apache class. Thanks to both for the help!

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  • Java: is Exception class thread-safe?

    - by Vilius Normantas
    As I understand, Java's Exception class is certainly not immutable (methods like initCause and setStackTrace give some clues about that). So is it at least thread-safe? Suppose one of my classes has a field like this: private final Exception myException; Can I safely expose this field to multiple threads? I'm not willing to discuss concrete cases where and why this situation could occur. My question is more about the principle: can I tell that a class which exposes field of Exception type is thread-safe? Another example: class CustomException extends Exception { ... } Is this class thread-safe?

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  • How to reduce java concurrent mode failure and excessive gc

    - by jimx
    In Java, the concurrent mode failure means that the concurrent collector failed to free up enough memory space form tenured and permanent gen and has to give up and let the full stop-the-world gc kicks in. The end result could be very expensive. I understand this concept but never had a good comprehensive understanding of A) what could cause a concurrent mode failure and B) what's the solution?. This sort of unclearness leads me to write/debug code without much of hints in mind and often has to shop around those performance flags from Foo to Bar without particular reasons, just have to try. I'd like to learn from developers here how your experience is. If you had previous encountered such performance issue, what was the cause and how you addressed it? If you have coding recommendations, please don't be too general. Thanks!

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  • Separation of static and dynamic content in Java EE applications

    - by Dan
    We work with IBM products and we typically use IBM Http Servers (read Apache) as a reverse proxy for our application servers. For performance reasons we serve static content (.gif, .jpg, .css, .html etc.) from our http servers, to ease the burden a bit from the application server. So far, we have to distribute files to http server and configure it manually (writing custom scripts at best.) The problem is the effort needed to keep everything in synch, especially when you need to update the app. Does any Java EE product support this “out of the box”? Is there a way to have application server do this automatically, like in cluster configuration for example, where master node is in charge of distributing the application to other nodes and for keeping everything in synch.

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  • Understanding the concept of inheritance in Java

    - by Nirmal
    Hello All.... I am just refreshing the oops features of the java. So, I have a little confusion regarding inheritance concept. For that I have a following sample code : class Super{ int index = 5; public void printVal(){ System.out.println("Super"); } } class Sub extends Super{ int index = 2; public void printVal(){ System.out.println("Sub"); } } public class Runner { public static void main(String args[]){ Super sup = new Sub(); System.out.println(sup.index+","); sup.printVal(); } } Now above code is giving me output as : 5,Sub. Here, we are overriding printVal() method, so that is understandable that it is accessing child class method only. But I could not understand why it's accessing the value of x from Super class... Thanks in advance....

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  • Java Caching on distributed environment

    - by Naren
    Hi, I am supposed to create a simple replicated cache using java for internal purpose which will be used in a distributed environment. I have seen oracle has implemented Replicated Cache Service. http://wiki.tangosol.com/display/COH32UG/Replicated+Cache+Service The problem I am facing is while doing an update or remove, I acquire lock on other cache's to the point the cache get's updated and notifies others of the change. This is eventually going into a dead lock situation, while removing. Is there any strategy I should follow while updating or removing from cache's. Can I implement a replicated cache without having a primary cache?? Thanks, Naren

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  • Java: JPA classes, refactoring from Date to DateTime

    - by bguiz
    With a table created using this SQL Create Table X ( ID varchar(4) Not Null, XDATE date ); and an entity class defined like so @Entity @Table(name = "X") public class X implements Serializable { @Id @Basic(optional = false) @Column(name = "ID", nullable = false, length = 4) private String id; @Column(name = "XDATE") @Temporal(TemporalType.DATE) private Date xDate; //java.util.Date ... } With the above, I can use JPA to achieve object relational mapping. However, the xDate attribute can only store dates, e.g. dd/MM/yyyy. How do I refactor the above to store a full date object using just one field, i.e. dd/MM/yyyy HH24:mm?

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  • Implementing a 'Send Feedback' feature in a Java desktop application

    - by William
    I would like to implement a 'Send Feedback' option in a Java desktop application. One which will pop up a box for the user to enter a comment, then send it to us along with a screenshot of the application window. How would be the best way to communicate the data to us? Two obvious solutions spring to mind: Email - I'm thinking that the application would connect to an SMTP server set-up by us, with the username/password somehow hidden in the code. SMTP over SSL for security (not of the data being sent, but of the SMTP username/password). Web service - pretty self explanatory. Which of these would be best, or is there a better alternative?

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  • Creating managed file transfer software in java

    - by Shekhar
    Hello, I have been asked to do some POC on how we can provide a software solution which will be able to manage files. Manage files means it will be able to move files from source to destination servers. The client gave us 4 page document detailing what sort of software they are looking for. They dont want to use existing commercial softwares. They want to build their own customizable software. Has anybody worked on this type of project? Please provide your inputs on how should i approach this project. The software should be platform independent and should be built in java.

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  • Java/JAXB: Unmarshall Xml to specific subclass based on an attribute

    - by Frothy
    Is it possible to use JAXB to unmarshall xml to a specific Java class based on an attribute of the xml? <shapes> <shape type="square" points="4" square-specific-attribute="foo" /> <shape type="triangle" points="3" triangle-specific-attribute="bar" /> </shapes> I would like to have a List of Shape objects containing a triangle and a square, each with their own shape-specific attribute. IE: abstract class Shape { int points; //...etc } class Square extends Shape { String square-specific-attribute; //...etc } class Triangle extends Shape { String triangle-specific-attribute; //...etc } I'm currently just putting all attributes in one big "Shape" class and it's less than ideal. I could get this to work if the shapes were properly named xml elements, but unfortunately I don't have control of the xml I'm retrieving. Thanks!

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  • Java Scheduling Calendar

    - by cedric
    Hi. I have a j2ee web application which supports scheduling of execution of jobs. I am looking for a free calendar component written in java which allows scheduling functionalities as well as capable of changing view mode of tasks either by viewing taks for whole year, month view, week view, day view. Do you have any suggestion. Im sorry something came up with the implementation. I dnt have to use this calendar for triggering or calling jobs. I just need to retrieve schedules from database and display it in diff view modes. SO it's just some kind of GUI functionality

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  • Count How many lines in a Java String

    - by Simon Guo
    Need some compact code for counting how many lines in a string. It should be Java Code. And the string is separated by \r or \n will be considered as a separate line. For example, "Hello\nWorld\nThis\nIs\t" should return 4. The prototype is private static int countLines(String str) {...} Can someone provide a compact code? I have solution at here but it is too long, I think. Thank you.

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