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  • Eclipse gives me a weird error when compiling...

    - by Legend
    I have this function which returns a datatype InetAddress[] public InetAddress [] lookupAllHostAddr(String host) throws UnknownHostException { Name name = null; try { name = new Name(host); } catch (TextParseException e) { throw new UnknownHostException(host); } Record [] records = null; if (preferV6) records = new Lookup(name, Type.AAAA).run(); if (records == null) records = new Lookup(name, Type.A).run(); if (records == null && !preferV6) records = new Lookup(name, Type.AAAA).run(); if (records == null) throw new UnknownHostException(host); InetAddress[] array = new InetAddress[records.length]; for (int i = 0; i < records.length; i++) { Record record = records[i]; if (records[i] instanceof ARecord) { ARecord a = (ARecord) records[i]; array[i] = a.getAddress(); } else { AAAARecord aaaa = (AAAARecord) records[i]; array[i] = aaaa.getAddress(); } } return array; } Eclipse complains that the return type should be byte[][] but when I change the return type to byte[][], it complains that the function is returning the wrong data type. I'm stuck in a loop. Does anyone know what is happening here?

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  • Efficient synchronization of querying an array of resources

    - by Erel Segal Halevi
    There is a list of N resources, each of them can be queried by at most a single thread at a time. There are serveral threads that need to do the same thing at approximately the same time: query each of the resources (each thread has a different query), in arbitrary order, and collect the responses. If each thread loops over the resources in the same order, from 0 to N-1, then they will probably have to wait for each other, which is not efficient. I thought of letting the threads loop over the resources in a random permutation, but this seems too complex and also not so efficient, for example, for 2 resources and 2 threads, in half the cases they will choose the same order and wait for each other. Is there a simple and more efficient way to solve this?

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  • Duplicate Prefix Error in Jsp page with Struts

    - by Cricandcric.com
    Hi, i am creating and Configuring the Struts for the first time, when I place the following Code in my jsp page <%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> <%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%> <%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%> <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles"%> I am getting the error when i move the mouse over the 1st Line "Duplicate Prefix "html" When I move the mouse over the 2nd Line, I am getting as "Duplicate Prefix "html" Similarly for 3rd and 4th Line, Can any one tell me why is this error all about Thanks in advance

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  • Concurrent Programming:Should I write a sequential program first, then add thread safety?

    - by evthim
    I'm working on a project where we have to create a number of threads(actual number will be inputted in by testers (TA's)). I'm having trouble not only with the programming but also with the design, I can't wrap my head around all of the threads that will be invoked and where I might cause errors. The project is due soon so I don't want to waste time on this if it'll actually set me back, but I was wondering if I should write the program like only one thread will be running and everything should be sequential and then later go back and try to add the thread safety parts of the code? Would that take twice the original amount of time? Project Description: Note:I'm going to be as vague as possible so I don't violate any honor codes, sorry :( your program should accept n number of objectA threads, m number of objectB threads, and r number of objectC objectB threads interact with code in objectA. objectA threads interact with code in objectB and objectC objectB and objectC don't directly interact, but do so indirectly through objectA -ex: objectB needs something from objectA. objectA gets the result for that something by calling objectC my confusion stems mostly from the fact that all of this interactions will be done by m+n threads and there are various restrictions throughout the descriptions, like objectB can request something from objectA, and objectA has to wait for objectC to finish that something before returning it to objectB. Also each objectA thread can only work on one instruction from objectB at a time, etc. etc. I just want to know if I write the code so that there is only 1 objectA, 1 objectB and 1 object C, can I go back and easily modify it so that those 1's can be changed to m, n and r? Sorry again, if my description is a little bit confusing.

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  • log4j relative file path

    - by Bob
    Hi, I'd like my web app to log into files with this path: webapp/logs/ I can set the absolute path in the log4j.properties file, but the production environment's directory structure will be different. Is there any way I could do it? Here is how I do: log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=log.out log4j.appender.f.MaxFileSize=100KB This is printing logs into a file named log.log in my eclipse directory (c://eclipse). I'm using Tomcat 6.

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  • Can you return an array from a JAX-WS @WebMethod?

    - by LES2
    I'm pretty sure you can, but in addition to answering the question in the title, could you also explain the pros, cons, caveats, if any, to doing so? I know that you can't return a List, Set, Collection, Map, or any interface, from a WebMethod (which is stupid, IMO, but I don't know what the design reasons were should I should probably withhold judgment). Thanks for any advice. -- LES

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  • Best way to style GWT widgets in a library

    - by helios
    I'm developing some widgets into a library for internal use at the company I work for. I don't know what's the recommended way to style the widgets. There are at least these ways: use Widget.setPrimaryStyleName and let the user provide an external css. We use maven archetypes to build applications so we can provide default styles. Anyway I don't like it very much. use the GWT 2.0 CssResourceBundle. So we can compile the CSS into the module and it will be optimized (and it can be browser-dependant too). provide a module with the styling. Something like the default GWT themes. But I don't know how exactly this works. I want to: make the components as cohesive as I can (don't depend on externally included css's) leave open the door to modify styles (if I want to change the way some widget looks in a concrete application). What's your experience in this subject?

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  • Is it against best practice to throw Exception on most JUnit tests?

    - by Chris Knight
    Almost all of my JUnit tests are written with the following signature: public void testSomething() throws Exception My reasoning is that I can focus on what I'm testing rather than exception handling which JUnit appears to give me for free. But am I missing anything by doing this? Is it against best practice? Would I gain anything by explicitly catching specific exceptions in my test and then fail()'ing on them?

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  • When to use LinkedList<> over ArrayList<>?

    - by sdellysse
    I've always been one to simply use List<String> names = new ArrayList<String>(); I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code. When should LinkedList should be used over ArrayList and vice-versa?

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  • Stuck at being unable to print a substring no more than 4679 characters

    - by Newcoder
    I have a program that does string manipulation on very large strings (around 100K). The first step in my program is to cleanup the input string so that it only contains certain characters. Here is my method for this cleanup: public static String analyzeString (String input) { String output = null; output = input.replaceAll("[-+.^:,]",""); output = output.replaceAll("(\\r|\\n)", ""); output = output.toUpperCase(); output = output.replaceAll("[^XYZ]", ""); return output; } When i print my 'input' string of length 97498, it prints successfully. My output string after cleanup is of length 94788. I can print the size using output.length() but when I try to print this in Eclipse, output is empty and i can see in eclipse output console header. Since this is not my final program, so I ignored this and proceeded to next method that does pattern matching on this 'cleaned-up' string. Here is code for pattern matching: public static List<Integer> getIntervals(String input, String regex) { List<Integer> output = new ArrayList<Integer> (); // Do pattern matching Pattern p1 = Pattern.compile(regex); Matcher m1 = p1.matcher(input); // If match found while (m1.find()) { output.add(m1.start()); output.add(m1.end()); } return output; } Based on this program, i identify the start and end intervals of my pattern match as 12351 and 87314. I tried to print this match as output.substring(12351, 87314) and only get blank output. Numerous hit and trial runs resulted in the conclusion that biggest substring that i can print is of length 4679. If i try 4680, i again get blank input. My confusion is that if i was able to print original string (97498) length, why i couldnt print the cleaned-up string (length 94788) or the substring (length 4679). Is it due to regular expression implementation which may be causing some memory issues and my system is not able to handle that? I have 4GB installed memory.

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  • How significant are JPA lazy loading performance benefits?

    - by Robert
    I understand that this is highly specific to the concrete application, but I'm just wondering what's the general opinion, or at least some personal experiences on the issue. I have an aversion towards the 'open session in view' pattern, so to avoid it, I'm thinking about simply fetching everything small eagerly, and using queries in the service layer to fetch larger stuff. Has anyone used this and regretted it? And is there maybe some elegant solution to lazy loading in the view layer that I'm not aware of?

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  • Revalidate JPanel's parent frame

    - by Tom Brito
    I need show/hide some fields of my panel, and I want the panel to fit the frame. How could I notify to the parent frame to revalidate? I think in pass the frame to my panel's constructor, but I think may have a way this is already done. I remember that there was a protected attribute in JPanel, but there isn't.. maybe i remembering the wrong component.

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  • Hibernate session method to update object

    - by EugeneP
    I need this roadmap of a Hibernate managed object instance. First, I create an instance with initial properties and persist this object in a db. Then session associated with this object is closed. But still, I serialize my object and on the next step deserialize it, invoke some setters, and again, I need to update what changed in a database. What methods of Hibernate session should I use? persist() or save() on the first step and saveOrUpdate() on the second? In fact I see that saveOrUpdate() can be used on each step. What would you recommend?

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  • Weird output of Throwable getMessage()

    - by Ravi Gupta
    Hi I have below pseudo code with throws an exception like this throw new MyException("Bad thing happened","com.stuff.errorCode"); where MyException extends Exception class. So the problem is when I try to get the message from MyException class by calling myEx.getMessage() it returns ???en_US.Bad thing happened??? instead of my original message i.e. Bad thing happened I have checked that MyException class doesn't overrides Throwable class's getMessage() behavior. Below is the how the call passes from MyException.getMessage() to Throwable.getMessage() public MyException(String msg, String sErrorCode){ super(msg); this.sErrorCode = sErrorCode; this.iSeverity = 0; } which then calls public Exception(String message) { super(message); } and finally public Throwable(String message) { fillInStackTrace(); detailMessage = message; } when I do a getMessage on myexception it calls Throwable's getMessage as below public String getMessage() { return detailMessage; } So ideally it should return the original message as I set when throwing the exception. What's the ???en_US thing ?

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  • Collision of dot and line in 2D space

    - by Anderiel
    So i'm trying to make my first game on android. The thing is i have a small moving ball and i want it to bounce from a line that i drew. For that i need to find if the x,y of the ball are also coordinates of one dot from the line. I tried to implement these equations about lines x=a1 + t*u1 y=a2 + t*u2 = (x-a1)/u1=(y-a2)/u2 (t=t which has to be if the point is on the line) where x and y are the coordinates im testing, dot[a1,a2] is a dot that is on the line and u(u1,u2) is the vector of the line. heres the code: public boolean Collided() { float u1 =Math.abs(Math.round(begin_X)-Math.round(end_X)); float u2 =Math.abs(Math.round(begin_Y)-Math.round(end_Y)); float t_x =Math.round((elect_X - begin_X)/u1); float t_y =Math.round((elect_Y - begin_Y)/u2); if(t_x==t_y) { return true; } else { return false; } } points [begin_X,end_X] and [begin_Y,end_Y] are the two points from the line and [elect_X,elect_Y] are the coordinates of the ball theoreticaly it should work, but in the reality the ball most of the time just goes straigth through the line or bounces somewhere else where it shouldnt

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  • garbage collector Issue

    - by Eslam
    this question is like my previous one Given: 3. interface Animal { void makeNoise(); } 4. class Horse implements Animal { 5. Long weight = 1200L; 6. public void makeNoise() { System.out.println("whinny"); } 7. } 8. public class Icelandic extends Horse { 9. public void makeNoise() { System.out.println("vinny"); } 10. public static void main(String[] args) { 11. Icelandic i1 = new Icelandic(); 12. Icelandic i2 = new Icelandic(); 13. Icelandic i3 = new Icelandic(); 14. i3 = i1; i1 = i2; i2 = null; i3 = i1; 15. } 16. } When line 14 is reached, how many objects are eligible for the garbage collector? A. 0 B. 1 C. 2 D. 3 E. 4 F. 6 i choosed A but the right answer is E, but i don't know Why?

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  • real time scenario between interface/abstract class ?

    - by JavaUser
    Hi , Please give me a real time simple example for the below questions : Where to use interface rather abstract class Where to use abstract class rather interface I need code snippet for both . Which takes low memory and which performs well . Do I need to consider the design aspect also? What is the conceptual difference not the syntactical difference .

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  • how to Solve the "Digg" problem in MongoDB

    - by user193116
    A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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  • Calcualting Optimal Site to Site Routing using pre-computed times between sites

    - by Idistic
    Assume that I have a number of sites (locations) and the time it takes to travel from each site to each site is pre-computed Example Data - Site to Site Pre-Calculated Times in minutes From Start Site To A 20 To B 15 To C 15 From Site A To B 10 To C 15 Site B To A 10 To C 20 Site C To A 15 To B 20 4 Sites is fairly simple, but what if the site set was say 1000 sites? Given a large site set What would the best approach be to quickly find the optimal routes from the start site while visiting every other site just once? Route Solutions from Start Site for 3 sites from a start site 1 A(20) B(10) C(20) = 50 2 A(20) C(15) B(20) = 55 3 B(15) A(10) C(15) = 40 4 B(15) C(20) A(15) = 50 5 C(15) A(15) B(10) = 40 6 C(15) B(20) A(10) = 45

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  • Rounding up milliseconds when printing with Joda Time

    - by RoToRa
    I'm implementing a count-down using Joda Time. I only need a display accuracy of seconds. However when printing the time, the seconds are displayed as full seconds, so when the count down reaches, for example, 900ms, then "0" seconds is printed, but as a count-down it would make more sense to display "1" second, until the time actually reaches 0ms. Example: void printDuration(Duration d) { System.out.println( d.toPeriod(PeriodType.time()).toString( new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter() ) ); } printDuration(new Duration(5000)); // Prints "5" => OK printDuration(new Duration(4900)); // Prints "4" => need "5" printDuration(new Duration(1000)); // Prints "1" => OK printDuration(new Duration(900)); // Prints "0" => need "1" printDuration(new Duration(0)); // Prints "0" => OK Basically I need to the seconds to be display rounded up from milliseconds and not rounded down. Is there a way to achieve this with Joda without needing to write my own formatter?

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  • MacPorts 1.8.2 fails to build db46 on Mac OS X 1.6.3

    - by themoch
    I'm trying to put a development environment on my Mac, and to do so I need to install several packages which require db46. When running sudo port install db46 I get the following error: ---> Computing dependencies for db46 ---> Fetching db46 ---> Attempting to fetch patch.4.6.21.1 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.2 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.3 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.4 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch db-4.6.21.tar.gz from http://distfiles.macports.org/db4/4.6.21_6 ---> Verifying checksum(s) for db46 ---> Extracting db46 ---> Applying patches to db46 ---> Configuring db46 ---> Building db46 Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_databases_db46/work/db-4.6.21/build_unix" && /usr/bin/make -j2 all " returned error 2 Command output: ../dist/../libdb_java/db_java_wrap.c:9464: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9487: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9509: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9532: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9563: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9588: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9613: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9638: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9666: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9691: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9716: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9739: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9771: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9796: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9819: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9842: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9867: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jobject' ../dist/../libdb_java/db_java_wrap.c:9899: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9920: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9943: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9966: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jstring' ../dist/../libdb_java/db_java_wrap.c:9991: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:10010: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10046: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10071: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' make: *** [db_java_wrap.lo] Error 1 make: *** Waiting for unfinished jobs.... Note: Some input files use unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. cd ./classes && jar cf ../db.jar ./com/sleepycat Error: Status 1 encountered during processing. I have removed my /usr/local folder completely and it does not seem to help.

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