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  • Cookie questions in Java

    - by user220201
    Hi, How do I differentiate between multiple cookies set through my site? I am setting two kinds of cookies one to see if the user has visited the site or not and an other one for authentication. How do I differentiate between these two? I get both of them when someone accesses a page after authentication. Do I add extra information to the Cookie Value or is there some other way? I understand the setName() function will change the name (from jsessionid) for every cookie from then on. Am I correct? Pav

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  • Dijkstra's Algorithm explanation java

    - by alchemey89
    Hi, I have found an implementation for dijkstras algorithm on the internet and was wondering if someone could help me understand how the code works. Many thanks private int nr_points=0; private int[][]Cost; private int []mask; private void dijkstraTSP() { if(nr_points==0)return; //algorithm=new String("Dijkstra"); nod1=new Vector(); nod2=new Vector(); weight=new Vector(); mask=new int[nr_points]; //initialise mask with zeros (mask[x]=1 means the vertex is marked as used) for(int i=0;i<nr_points;i++)mask[i]=0; //Dijkstra: int []dd=new int[nr_points]; int []pre=new int[nr_points]; int []path=new int[nr_points+1]; int init_vert=0,pos_in_path=0,new_vert=0; //initialise the vectors for(int i=0;i<nr_points;i++) { dd[i]=Cost[init_vert][i]; pre[i]=init_vert; path[i]=-1; } pre[init_vert]=0; path[0]=init_vert; pos_in_path++; mask[init_vert]=1; for(int k=0;k<nr_points-1;k++) { //find min. cost in dd for(int j=0;j<nr_points;j++) if(dd[j]!=0 && mask[j]==0){new_vert=j; break;} for(int j=0;j<nr_points;j++) if(dd[j]<dd[new_vert] && mask[j]==0 && dd[j]!=0)new_vert=j; mask[new_vert]=1; path[pos_in_path]=new_vert; pos_in_path++; for(int j=0;j<nr_points;j++) { if(mask[j]==0) { if(dd[j]>dd[new_vert]+Cost[new_vert][j]) { dd[j]=dd[new_vert]+Cost[new_vert][j]; } } } } //Close the cycle path[nr_points]=init_vert; //Save the solution in 3 vectors (for graphical purposes) for(int i=0;i<nr_points;i++) { nod1.addElement(path[i]); nod2.addElement(path[i+1]); weight.addElement(Cost[path[i]][path[i+1]]); } }

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  • Override Java System.currentTimeMillis

    - by Mike Clark
    Is there a way, either in code or with JVM arguments, to override the current time, as presented via System.currentTimeMillis, other than manually changing the system clock on the host machine? A little background: We have a system that runs a number of accounting jobs that revolve much of their logic around the current date (ie 1st of the month, 1st of the year, etc) Unfortunately, a lot of the legacy code calls functions such as new Date() or Calendar.getInstance(), both of which eventually call down to System.currentTimeMillis. For testing purposes, right now, we are stuck with manually updating the system clock to manipulate what time and date the code thinks that the test is being run. So my question is: Is there a way to override what is returned by System.currentTimeMillis? For example, to tell the JVM to automatically add or subtract some offset before returning from that method? Thanks in advance!

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  • Java Concurrency : Volatile vs final in "cascaded" variables?

    - by Tom
    Hello Experts, is final Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); the same as volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); in case the inner Map is accessed by different Threads? or is even something like this required: volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); volatile Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); In case the it is NOT a "cascaded" map, final and volatile have in the end the same effect of making shure that all threads see always the correct contents of the Map... But what happens if the Map iteself contains a map, as in the example... How do I make shure that the inner Map is correctly "Memory barriered"? Tanks! Tom

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  • UTF-8 character encoding in Java

    - by user332523
    Hello, I am having some problems getting some French text to convert to UTF8 so that it can be displayed properly, either in a console, text file or in a GUI element. The original string is HANDICAP+ES which is supposed to be HANDICAPÉES No matter how I tried converting it, it appears the same way. Any ideas on how I can do this conversion? Thanks, Cam

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  • Cast element in Java For Each statement

    - by Carl Summers
    Is it possible (or even advisable) to cast the element retrieved from a for each statement in the statement itself? I do know that each element in list will be of type . I.E.: List<BaseType> list = DAO.getList(); for(<SubType> element : list){ // Cannot convert from element type <BaseType> to <SubType> ... } rather than: List <BaseType> list = DAO.getList(); for(<BaseType> el : list){ <SubType> element = (<SubType>)el; ... }

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  • Data table with legends in JfreeChart/Java

    - by TiNS
    Hi All, I am using JFreeChart to generate images. I am trying to create barchart like below. I am able to create it successfully without data table. I tried to get more information from the jfreechar forums and found this post. According to the post , its not supported by JfreeChart. Is it still not supported by jfreechart API ? If yes, can I use any other charting (open source) tool to generate chart with data table ? Thanks

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  • Quickest way to write to file in java

    - by user1097772
    I'm writing an application which compares directory structure. First I wrote an application which writes gets info about files - one line about each file or directory. My soulution is: calling method toFile Static PrintWriter pw = new PrintWriter(new BufferedWriter( new FileWriter("DirStructure.dlis")), true); String line; // info about file or directory public void toFile(String line) { pw.println(line); } and of course pw.close(), at the end. My question is, can I do it quicker? What is the quickest way? Edit: quickest way = quickest writing in the file

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  • Java - Thread problem

    - by Yatendra Goel
    My question is related to all those methods(including Thread.sleep(...)) which throw InterruptedException. I found a statement on Sun's tutorial saying InterruptedException is an exception that sleep throws when another thread interrupts the current thread while sleep is active. Is that means that the interrupt will be ignored if the sleep is not active at the time of interrupt? Suppose I have two threads: threadOne and threadTwo. threadOne creates and starts threadTwo. threadTwo executes a runnable whose run method is something like: public void run() { : : try { Thread.sleep(10 * 1000); } catch (InterruptedException e) { return; } : : : // In the middle of two sleep invocations : : try { Thread.sleep(10 * 1000); } catch (InterruptedException e) { return; } : : } After thread creation, threadOne interrupts threadTwo. Suppose the threadTwo is in the middle of two sleep invocations at the time of interrupt (when no sleep method was active), then will the second sleep method throw InterrupteException as soon as it is invoked? If not, then will this interrupt will be ignored forever? How to be sure that threadTwo will always know about the interrupt (doesn't matter whether its one of the sleep method is active or not)?

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  • java Database framework comparison

    - by user293655
    Hi, I want to create an application that synchronize a database to multiple databases(various type of databases). I'm looking for a framework that suitable to do this. I was looking for something just get the Object of the data (like a resultset) then copy that object to the destination database. Or comparing between 2 data. Any ideas? Thanks,

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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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  • Java fixed memory map

    - by juber
    Hi, Is there a simple, efficient Map implementation that allows a limit on the memory to be used by the map. My use case is that I want to allocate dynamically most of the memory available at the time of its creation but I don't want OutOFMemoryError at any time in future. Basically, I want to use this map as a cache, but but I wanna avoid heavy cache implementations like EHCache. My need is simple (at most an LRU algorithm)

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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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  • Writing to an already existing file using FileWriter Java

    - by delo
    Is there anyway I can write to an already existing file using Filewriter For example when the user clicks a submit button: FileWriter writer = new FileWriter("myfile.csv"); writer.append("LastName"); writer.append(','); writer.append("FirstName"); writer.append('/n'); writer.append(LastNameTextField.getText()); writer.append(','); writer.append(FirstNameTextField.getText()); I want to be able to write new data into the already existing myfile.csv without having to recreate a brand new one every time

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  • Implement dictionary using java

    - by ahmad
    Task Dictionary ADT The dictionary ADT models a searchable collection of key-element entries Multiple items with the same key are allowed Applications: word-definition pairs Dictionary ADT methods: find(k): if the dictionary has an entry with key k, returns it, else, returns null findAll(k): returns an iterator of all entries with key k insert(k, o): inserts and returns the entry (k, o) remove(e): remove the entry e from the dictionary size(), isEmpty() Operation Output Dictionary insert(5,A) (5,A) (5,A) insert(7,B) (7,B) (5,A),(7,B) insert(2,C) (2,C) (5,A),(7,B),(2,C) insert(8,D) (8,D) (5,A),(7,B),(2,C),(8,D) insert(2,E) (2,E) (5,A),(7,B),(2,C),(8,D),(2,E) find(7) (7,B) (5,A),(7,B),(2,C),(8,D),(2,E) find(4) null (5,A),(7,B),(2,C),(8,D),(2,E) find(2) (2,C) (5,A),(7,B),(2,C),(8,D),(2,E) findAll(2) (2,C),(2,E) (5,A),(7,B),(2,C),(8,D),(2,E) size() 5 (5,A),(7,B),(2,C),(8,D),(2,E) remove(find(5)) (5,A) (7,B),(2,C),(8,D),(2,E) find(5) null (7,B),(2,C),(8,D),(2,E) Detailed explanation: NO Specific requirements: please Get it done i need HELP !!!

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  • java.sql.SQLException: Parameter index out of range (3 > number of parameters, which is 2)

    - by sam
    @WebMethod(operationName = "SearchOR") public SearchOR getSearchOR (@WebParam(name = "comp") String comp, @WebParam(name = "name") String name) { //TODO write your implementation code here: SearchOR ack = null; try{ String simpleProc = "{ call getuser_info_or(?,?)}"; CallableStatement cs = con.prepareCall(simpleProc); cs.setString(1, comp); cs.setString(2, name); ResultSet rs = cs.executeQuery(); System.out.print("2"); /* int i = 0, j = 0; if (rs.last()) { i = rs.getRow(); ack = new SearchOR[i]; rs.beforeFirst(); }*/ while (rs.next()) { // ack[j] = new SearchOR(rs.getString(1), rs.getString(2)); // j++; ve.add(rs.getString(1)); ve.add(rs.getString(2)); }}catch ( Exception e) { e.printStackTrace(); System.out.print(e); } return ack; } I am getting error at portion i have made bold.It is pointing to that location.My Query is here: DELIMITER $$ DROP PROCEDURE IF EXISTS discoverdb.getuser_info_or$$ MySQL returned an empty result set (i.e. zero rows). CREATE PROCEDURE discoverdb.getuser_info_or ( IN comp VARCHAR(100), IN name VARCHAR(100), OUT Login VARCHAR(100), OUT email VARCHAR(100) ) BEGIN SELECT sLogin, sEmail INTO Login, email FROM ad_user WHERE company = comp OR sName=name; END $$ MySQL returned an empty result set (i.e. zero rows). DELIMITER ;

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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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  • 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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