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• creative way for implementing Data object with it's corespanding buisness logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity reasons lets call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I loose my hierarchy freedom, does any of you have any creative solution for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• Performance intensive string splitting and manipulation in java

  - by juhanic

  What is the most efficient way to split a string by a very simple separator? Some background: I am porting a function I wrote in C with a bunch of pointer arithmetic to java and it is incredibly slow(After some optimisation still 5* slower). Having profiled it, it turns out a lot of that overhead is in String.split The function in question takes a host name or ip address and makes it generic: 123.123.123.123-*.123.123.123 a.b.c.example.com-*.example.com This can be run over several million items on a regular basis, so performance is an issue.

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• Can you dynamically resize a java.util.concurrent.ThreadPoolExecutor while it still has tasks waitin

  - by Edward Shtern

  I'm working with a java.util.concurrent.ThreadPoolExecutor to process a number of items in parallel. Although the threading itself works fine, at times we've run into other resource constraints due to actions happening in the threads, which made us want to dial down the number of Threads in the pool. I'd like to know if there's a way to dial down the number of the threads while the threads area actually working. I know that you can call setMaximumPoolSize() and/or setCorePoolSize(), but these only resize the pool once threads become idle, but they don't become idle until there are no tasks waiting in the queue.

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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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• Com port don't work in java

  - by ?????? ?????

  Does't work with java... don't sent message to my microchip. please help public static void main(String[] args) { SerialPort serialPort = new SerialPort("COM1"); try { serialPort.openPort(); serialPort.setParams(9600, 8, 1, 0); serialPort.setParams(SerialPort.BAUDRATE_9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE); serialPort.writeBytes("Test"); readBytes(), ???? ?? ??????? ?????? byte[] buffer = serialPort.readBytes(10); //????????? ???? serialPort.closePort(); } catch (SerialPortException ex) { System.out.println(ex); } } } byte[] Write "[@B********" Star is a random number.

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• Java Spring 3.0 MVC Annotation vs COC. Whats the preferred method in the Java community?

  - by Athens

  I am using Spring's MVC framework for an application I'm hosting on Google's App Engine. So far, my controllers are registered via the @Controller annotation; however, prior to getting into Spring, I evaluated ASP.net MVC 2 which requires no configuration and is based on convention. Is convention over configuration (COC) the current and preferred method in the Java community to implement MVC with Spring. Also, this may be a result of my limited knowledge so far but i noticed that i could only instantiate my Controllers the required constuctor injection if i use the COC method via the ControllerClassNameHandlerMapping. For instance the following controller bean config will fail if i use the defaultannotationhandlermapping. <bean id="c" class="com.domain.TestController"> <constructor-arg ref="service" /> </bean> <bean id="service" class="com.domain.Service" /> My com.domain.TestController controller works fine if i use ControllerClassNameHandlerMapping/COC but it results in an error when i use defaultannotationhandlermapping/Annotations.

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• Connecting Java se Client to Glassfish

  - by Henrik Bierbum Bacher

  We are having some difficulties connecting our Java SE standalone client with the EJB module deployed on a remote GlassFish server. Pointers to how we are supposed to connect our client would be appreciated. The client code we currently has to get the initial context: props.setProperty("org.omg.CORBA.ORBInitialHost", "*remotehost*"); props.setProperty("org.omg.CORBA.ORBInitialPort", "portNumber"); javax.naming.InitialContext ic = new javax.naming.InitialContext(props); *We have tried several different port numbers; 3700, 7676, 8080.. The closest we are getting, got us the error: "Error in GIOP magic". I read that jms are using port 7676 as a broker port for a bunch of dynamically generated ports, but can't figure out how to specify those ports in order to create proper port-forwards.

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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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• 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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• 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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• 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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• 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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• Java: IDE working well with Maven War overlays

  - by Thorbjørn Ravn Andersen

  We have a Java EE 6 web application which is fully mavenized, and we use the Maven "war overlay" facility to add customer specific files, and which currently runs in Glassfish 3.1. We have traditionally used Eclipse for development, but I have found that the combination of Maven processing and War deployments may not be optimal in terms of deployment times, and that the mavenization allows us to use any IDE with good Maven support. Therefore is Eclipse the best bet for our particular scenario (maven war overlays - glassfish, and debugging it) or is e.g. Netbeans or IntelliJ better? Please, back opinions with actual experiences, thanks.

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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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• 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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• 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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• 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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• 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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• 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: 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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• 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 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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• 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: 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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• 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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