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  • Using mail servers in java

    - by sword101
    greeting all i want to use a mail server where the users send emails to it and then i parse this emails then do some action please suggest me what mail server to be used and where to start some links,tutorials,guide is very appreciated .

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  • Java - Circular Garbage Collection

    - by aloh
    A <- B <- C <- D <- A... // A is firstNode, D is lastNode if ( length == 1 ) { firstNode = null; lastNode = null; firstNode.next = null; firstNode.prev = null; } else { Node secondNode = firstNode.next; Node secondToLast = lastNode.prev; firstNode.next = null; firstNode.prev = null; lastNode.next = null; lastNode.prev = null; secondNode.prev = null; secondToLast.next = null; firstNode = null; lastNode = null; } That should send everything in between as candidates for garbage collection, I hope?

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  • Are there any other Java schedulers besides Quartz(FOSS) and Flux(Commercial)

    - by mP
    I am interested in finding out about other job scheduling packages besides Quartz and Flux. Given the plethora of web frameworks i find it perculiar that there is really only one scheduler. Are there others that perhaps are very much unknown/unpopular ? Spring Batch Not really a scheduling solution but rather a batch job coordinator etc. http://static.springsource.org/spring-batch/faq.html#schedulers How does Spring Batch differ from Quartz? Is there a place for them both in a solution? Spring Batch and Quartz have different goals. Spring Batch provides functionality for processing large volumes of data and Quartz provides functionality for scheduling tasks. So Quartz could complement Spring Batch, but are not excluding technologies. A common combination would be to use Quartz as a trigger for a Spring Batch job using a Cron expression and the Spring Core convenience SchedulerFactoryBean .

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  • How to solve following issue in java?

    - by lakshmi
    Im getting following error while running the query. org.hibernate.hql.ast.QuerySyntaxException: expecting CLOSE, found 'LIMIT' near line 1, column 194 [from com.claystone.db.Gpsdata where id.mobileunitid = '2090818044' and gpsdate in (select id.gpsdate from com.claystone.db.Gpsdata where id.mobileunitid = '2090818044' ORDER BY id.gpsdate DESC LIMIT 1 ) and gpsstatus='true'] This is my Query.Please give the suggession what is the mistake in this query? data=session.createQuery[from com.claystone.db.Gpsdata where id.mobileunitid = '2090818044' and gpsdate in (select id.gpsdate from com.claystone.db.Gpsdata where id.mobileunitid = '2090818044' ORDER BY id.gpsdate DESC LIMIT 1 ) and gpsstatus='true']

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  • Java NullPointerException when traversing a non-null recordset

    - by Tim
    Hello again - I am running a query on Sybase ASE that produces a ResultSet that I then traverse and write the contents out to a file. Sometimes, this will throw a NullPointerException, stating that the ResultSet is null. However, it will do this after printing out one or two records. Other times, with the same exact input, I will receive no errors. I have been unable to consistently produce this error. The error message is pointing to a line: output.print(rs.getString(1)); It appears to happen when the query takes a little longer to run, for some reason. The recordset returns thus far have been very small (4 to 7 records). Sometimes I'll have to run the app 3 or 4 times, then the errors will just stop, as though the query was getting "warmed up". I've run the query manually and there doesn't appear to be any performance problems. Thanks again!

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  • Java Runtime.freeMemory() returning bizarre results when adding more objects

    - by Sotirios Delimanolis
    For whatever reason, I wanted to see how many objects I could create and populate a LinkedList with. I used Runtime.getRuntime().freeMemory() to get the approximation of free memory in my JVM. I wrote this: public static void main(String[] arg) { Scanner kb = new Scanner(System.in); List<Long> mem = new LinkedList<Long>(); while (true) { System.out.println("Max memory: " + Runtime.getRuntime().maxMemory() + ". Available memory: " + Runtime.getRuntime().freeMemory() + " bytes. Press enter to use more."); String s = kb.nextLine(); if (s.equals("m")) for (int i = 0; i < 1000000; i++) { mem.add(new Long((new Random()).nextLong())); } } } If I write in m, the app adds a million Long objects to the list. You would think the more objects (to which we have references, so can't be gc'ed), the less free memory. Running the code: Max memory: 1897725952. Available memory: 127257696 bytes. m Max memory: 1897725952. Available memory: 108426520 bytes. m Max memory: 1897725952. Available memory: 139873296 bytes. m Max memory: 1897725952. Available memory: 210632232 bytes. m Max memory: 1897725952. Available memory: 137268792 bytes. m Max memory: 1897725952. Available memory: 239504784 bytes. m Max memory: 1897725952. Available memory: 169507792 bytes. m Max memory: 1897725952. Available memory: 259686128 bytes. m Max memory: 1897725952. Available memory: 189293488 bytes. m Max memory: 1897725952. Available memory: 387686544 bytes. The available memory fluctuates. How does this happen? Is the GC cleaning up other things (what other things are there on the heap to really clean up?), is the freeMemory() method returning an approximation that's way off? Am I missing something or am I crazy?

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  • system out output for double numbers in a java program

    - by Nikunj Chauhan
    I have a program where I am generating two double numbers by adding several input prices from a file based on a condition. String str; double one = 0.00; double two = 0.00; BufferedReader in = new BufferedReader(new FileReader(myFile)); while((str = in.readLine()) != null){ if(str.charAt(21) == '1'){ one += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } else{ two += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } } in.close(); System.out.println("One: " + one); System.out.println("Two: " + two); The output is like: One: 2773554.02 Two: 6.302505836000001E7 Question: None of the input have more then two decimals in them. The way one and two are getting calculated exactly same. Then why the output format is like this. What I am expecting is: One: 2773554.02 Two: 63025058.36 Why the printing is in two different formats ? I want to write the outputs again to a file and thus there must be only two digits after decimal.

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  • Best approach to create a security environment in Java

    - by Tom Brito
    I need to create a desktop application that will run third party code, and I need to avoid the third party code from export by any way (web, clipboard, file io) informations from the application. Somethig like: public class MyClass { private String protectedData; public void doThirdPartyTask() { String unprotedtedData = unprotect(protectedData); ThirdPartyClass.doTask(unprotectedData); } private String unprotect(String data) { // ... } } class ThirdPartyClass { public static void doTask(String unprotectedData) { // Do task using unprotected data. // Malicious code may try to externalize the data. } } I'm reading about SecurityManager and AccessControler, but I'm still not sure what's the best approach to handle this. What should I read about to do this implementation?

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  • Dynamic Clock in java

    - by jt153
    I want to implement a clock within my program to diusplay the date and time while the program is running. I have looked into the getCurrentTime() method and timers but none of them seem to do what I would like. The problem is I can get the current time when the program loads but it never updates. Any suggestions on something to look into would be greatly appreciated!

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  • How a thread should close itself in Java?

    - by Roman
    This is a short question. At some point my thread understand that it should suicide. What is the best way to do it: Thread.currentThread().interrupt(); return; By the way, why in the first case we need to use currentThread? Is Thread does not refer to the current thread?

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  • Memory allocation in java

    - by Girish
    class Someobject { int i=10; } public class OtherObject { public static void main(String args[]) { Someobject obj=new Someobject(); System.out.println(obj.i); } } Please tell me in which section of the memory: This entire code will load. Where will someobject will be stored. Where will obj will be stored Where will i be stored. Thanks every one in advance.

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  • java - unwanted object overwriting

    - by gosling
    Hello everyone! I'm trying to make a program that solves the logic wheels puzzle. I construct the root node and I try to produce the different child-nodes that are produced by making different moves of the wheels. The problem is that while I try to produce the children, the root node is overwrited,and everything is messed-up and I really don't know why. Here you can find the puzzle logic wheels. I represent the wheels as 3x3 arrays. Here is the code that implements the moves: public Node turn_right(Node aNode, int which_wheel) { Node newNode = new Node(aNode.getYellow_wheel(),aNode.getBlue_wheel(),aNode.getGreen_wheel()); int[][] yellow = new int[3][3]; int[][] blue = new int[3][3]; int[][] green = new int[3][3]; if(which_wheel==0) //turn yellow wheel of this node to right { yellow[1][0] = newNode.getYellow_wheel()[0][0]; yellow[2][0] = newNode.getYellow_wheel()[1][0]; yellow[2][1] = newNode.getYellow_wheel()[2][0]; yellow[2][2] = newNode.getYellow_wheel()[2][1]; yellow[1][2] = newNode.getYellow_wheel()[2][2]; yellow[0][2] = newNode.getYellow_wheel()[1][2]; yellow[0][1] = newNode.getYellow_wheel()[0][2]; yellow[0][0] = newNode.getYellow_wheel()[0][1]; blue = newNode.getBlue_wheel(); blue[1][0] = newNode.getYellow_wheel()[1][2]; blue[2][0] = newNode.getYellow_wheel()[2][2]; green = newNode.getGreen_wheel(); } else if(which_wheel == 1)// turn blue wheel of this node to right { blue[1][0] = newNode.getBlue_wheel()[0][0]; blue[2][0] = newNode.getBlue_wheel()[1][0]; blue[2][1] = newNode.getBlue_wheel()[2][0]; blue[2][2] = newNode.getBlue_wheel()[2][1]; blue[1][2] = newNode.getBlue_wheel()[2][2]; blue[0][2] = newNode.getBlue_wheel()[1][2]; blue[0][1] = newNode.getBlue_wheel()[0][2]; blue[0][0] = newNode.getBlue_wheel()[0][1]; yellow = newNode.getYellow_wheel(); yellow[0][2] = newNode.getBlue_wheel()[0][0]; yellow[1][2] = newNode.getBlue_wheel()[1][0]; green = newNode.getGreen_wheel(); green[1][0] = newNode.getBlue_wheel()[1][2]; green[2][0] = newNode.getBlue_wheel()[2][2]; } else if (which_wheel == 2)//turn green wheel of this node to right { green[0][0] = newNode.getGreen_wheel()[0][1]; green[0][1] = newNode.getGreen_wheel()[0][2]; green[0][2] = newNode.getGreen_wheel()[1][2]; green[1][2] = newNode.getGreen_wheel()[2][2]; green[2][2] = newNode.getGreen_wheel()[2][1]; green[2][1] = newNode.getGreen_wheel()[2][0]; green[2][0] = newNode.getGreen_wheel()[1][0]; green[1][0] = newNode.getGreen_wheel()[0][0]; yellow = newNode.getYellow_wheel(); blue = newNode.getBlue_wheel(); blue[0][2] = newNode.getGreen_wheel()[0][0]; blue[1][2] = newNode.getGreen_wheel()[1][0]; } newNode= new Node(yellow,blue,green); return newNode; } There is another function, like this one that does the oposite:it turns the wheels to left. My problem is that I do not want object's aNode tables to be overwritten. Thank you very much.

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  • Java generics: Illegal forward reference

    - by Arian
    Given a generic interface interface Foo<A, B> { } I want to write an implementation that requires A to be a subclass of B. So I want to do class Bar<A, B super A> implements Foo<A, B> { } // --> Syntax error or class Bar<A extends B, B> implements Foo<A, B> { } // --> illegal forward reference But the only solution that seems to work is this: class Bar<B, A extends B> implements Foo<A, B> { } which is kind of ugly, because it reverses the order of the generic parameters. Are there any solutions or workarounds to this problem?

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  • Should I catch exceptions thrown when closing java.sql.Connection

    - by jb
    Connection.close() may throw SqlException, but I have always assumed that it is safe to ignore any such exceptions (and I have never seen code that does not ignore them). Normally I would write: try{ connection.close(); }catch(Exception e) {} Or try{ connection.close(); }catch(Exception e) { logger.log(e.getMessage(), e); } The question is: Is it bad practice (and has anyone had problems when ignoring such exeptions). When Connection.close() does throw any exception. If it is bad how should I handle the exception. Comment: I know that discarding exceptions is evil, but I'm reffering only to exceptions thrown when closing a connection (and as I've seen this is fairly common in this case). Does anyone know when Connection.close() may throw anything?

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  • Java program has errors, 80 lines of code

    - by user2961687
    I have a problem with a program. It contains a lot of errors in Eclipse. Sorry for my english and thank you in advance. Here is the task: I. Declare a class that contains private fields Jam: String taste, double weight Create constructors containing variables as parameters: (String taste, double weight), (double weight), (String taste). Parameters constructors should initialize class fields. In case the constructor does not provide the necessary parameter, it must be assumed that the field taste must have the value "No Name" and weight - 100.0. Introduce the use of all constructors creating objects that represent three kinds of jams. Note: it must be assumed that the only constructor with two parameters can be assigned to fields of the class. Declare a class Jar that contains the field Jam jam, a dedicated constructor initiating all declared fields and methods: open close isItOpen Next, create an object of class Jar and fill it with the selected type of jam, operations repeat for all the kinds of jams. This is my code this far: public class App { public static void main(String[] args) { Jam strawberry = new Jam("strawberry", 20.45); Jam raspberry = new Jam(40.50); Jam peach = new Jam("peach"); Jar jar_1 = new Jar(); Jar jar_2 = new Jar(); Jar jar_3 = new Jar(); jar_1.open(); jar_1.fillIn(strawberry); jar_2.fillIn(peach); jar_3.fillIn(raspberry); } } class Jam { String taste; double weight; public Jam(String taste, double weight) { this.taste = taste; this.weight = weight; } public Jam(double weight) { this.taste = "No name"; this.weight = weight; } public Jam(String taste) { this.taste = taste; this.weight = 100.0; } } class Jar { public Jam Jam = new Jam(); private String state_jar; public Jar() { Jam.weight = 0; Jam.taste = ""; state_jar = "closed"; } public static String open() { state_jar = open; return state_jar; } public static String close() { state_jar = "closed"; return state_jar; } public static boolean isItOpen() { return state_jar; } public void fillIn(Jam jam) { if (isItOpen == false) open(); this.Jam.weight = jam.weight; this.Jam.taste = jam.taste; this.Jam.close(); } }

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  • Size of Objects in Java Heap w/ Regards to Methods

    - by Eric
    I know about primitives and objects living on the heap, but how does the number of methods effect heap size of the object? For example: public class A { int x; public getX() { return x; } } public class B { int x; public getX() { return x; } public getXString() { return String.valueOf(x); } public doMoreInterestingStuff() { return x * 42; } //etc } When instantiated, both objects live on the heap, both have memory allocated to their primitive x, but is B allocated more heap space due to having more method signatures? Or are those ONLY on the classLoader? In this example its trivial, but when there are 100,000+ of these objects in memory at any given time I imagine it could add up.

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  • customising serialisation of java collections using xstream

    - by Will Goring
    I have an object that needs to be serialised as XML, which contains the following field: List<String> tags = new List<String>(); XStream serialises it just fine (after some aliases) like this: <tags> <string>tagOne</string> <string>tagTwo</string> <string>tagThree</string> <string>tagFour</string> </tags> That's OK as far as it goes, but I'd like to be able to rename the <string> elements to, say, <tag>. I can't see an obvious way to do that from the alias documentation on the XStream site. Am I missing something obvious?

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