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  • How to identify/handle text file newlines in Java?

    - by rafrafUk
    Hi Everyone! I get files in different formats coming from different systems that I need to import into our database. Part of the import process it to check the line length to make sure the format is correct. We seem to be having issues with files coming from UNIX systems where one character is added. I suspect this is due to the return carriage being encoded differently on UNIX and windows platform. Is there a way to detect on which file system a file was created, other than checking the last character on the line? Or maybe a way of reading the files as text and not binary which I suspect is the issue? Thanks Guys !

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  • How do I make this Java code operate properly? [Multi-threaded, race condition]

    - by Fixee
    I got this code from a student, and it does not work properly because of a race condition involving x++ and x--. He added synchronized to the run() method trying to get rid of this bug, but obviously this only excludes threads from entering run() on the same object (which was never a problem in the first place) but doesn't prevent independent objects from updating the same static variable x at the same time. public class DataRace implements Runnable { static volatile int x; public synchronized void run() { for (int i = 0; i < 10000; i++) { x++; x--; } } public static void main(String[] args) throws Exception { Thread [] threads = new Thread[100]; for (int i = 0; i < threads.length; i++) threads[i] = new Thread(new DataRace()); for (int i = 0; i < threads.length; i++) threads[i].start(); for (int i = 0; i < threads.length; i++) threads[i].join(); System.out.println(x); // x not always 0! } } Since we cannot synchronize on x (because it is primitive), the best solution I can think of is to create a new static object like static String lock = ""; and enclose the x++ and x-- within a synchronized block, locking on lock. But this seems really awkward. Is there a better way?

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  • Java generic function for performing calculations on integer, on double?

    - by Daniel
    Is this possible? Surely if you passed in a double, any sort of function implementation code which casts an object to an Integer would not be able to work unless the cast 'Integer' was specifically used? I have a function like: public static void increment(Object o){ Integer one = (Integer)o; system.out.println(one++); } I cant see how this could be made generic for a double? I tried public static <E> void increment(E obj){ E one = (E)o; system.out.println(one++); } but it didn't like it?

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  • How can Java assignment be made to point to an object instead of making a copy?

    - by Matthew Piziak
    In a class, I have: private Foo bar; public Constructor(Foo bar) { this.bar = bar; } Instead of creating a copy of bar from the object provided in the parameter, is it possible to include a pointer to bar in the constructor such that changing the original bar changes the field in this object? Another way of putting it: int x = 7; int y = x; x = 9; System.out.print(y); //Prints 7. It is possible to set it up so that printing y prints 9 instead of 7?

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  • What is my error in a map in java?

    - by amveg
    Hello everyone I am trying to solve this problem: http://www.cstutoringcenter.com/problems/problems.php?id=4, but I cant figure out why my code doesnt solve this, I mean in the "for" how can I can multiply the letters? what is my error?, It just tell always 7, but I want to multiple all the letters, I hope you can help me enter code here public class ejercicio3 { public static void main(String args[]) { Map<Character, Integer> telefono = new HashMap<Character, Integer>(); telefono.put('A', 2); telefono.put('B', 2); telefono.put('C', 2); telefono.put('D', 3); telefono.put('E', 3); telefono.put('F', 3); telefono.put('G', 4); telefono.put('H', 4); telefono.put('I', 4); telefono.put('J', 5); telefono.put('K', 5); telefono.put('L', 5); telefono.put('M', 6); telefono.put('N', 6); telefono.put('O', 6); telefono.put('P', 7); telefono.put('R', 7); telefono.put('S', 7); telefono.put('T', 8); telefono.put('U', 8); telefono.put('V', 8); telefono.put('W', 9); telefono.put('X', 9); telefono.put('Y', 9); String mensaje = "Practice"; int producto = 1; for (char c : mensaje.toCharArray()) { if (telefono.containsKey(c)) { producto = telefono.get(c) * producto; System.out.println(producto); } } } }

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  • Trying to use a list iterator to print out entire linked list in Java. Infinite loop for some reaso

    - by Matt
    I created my list: private static List list = new LinkedList(); and my iterator: ListIterator itr = list.listIterator(); and use this code to try to print out the list... Only problem is, it never comes out of the loop. When it reaches the tail, shouldn't it come out of the loop, because there is no next? Or is it going back to the head like a circular linked list? It is printing so quickly and my computer locks up shortly after, so I can't really tell what is going on. while (itr.hasNext()) System.out.println(itr.next());

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  • How to plot the graph(line) from a file in java?

    - by kiran
    I have a directory containing list of files. Those files have some list of values as x and y ordered as line by line. And my question is just I would like to read those files one by one and to plot line graphs based on those values. Could you please help me for that?

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  • Java/Swing: JTable.rowAtPoint doesn't work correctly for points outside the table?

    - by Jason S
    I have this code to get a row from a JTable that is generated by a DragEvent for a DropTarget in some component C which may or may not be the JTable: public int getRowFromDragEvent(DropTargetDragEvent event) { Point p = event.getLocation(); if (event.getSource() != this.table) { SwingUtilities.convertPointToScreen(p, event.getDropTargetContext().getComponent()); SwingUtilities.convertPointFromScreen(p, this.table); if (!this.table.contains(p)) { System.out.println("outside table, would be row "+this.table.rowAtPoint(p)); } } return this.table.rowAtPoint(p); } The System.out.println is just a hack right now. What I'm wondering, is why the System.out.println doesn't always print "row -1". When the table is empty it does, but if I drag something onto the table's header row, I get the println with "row 0". This seems like a bug... or am I not understanding how rowAtPoint() works?

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  • Java: How to display a multi-line ToolTip with AWT?

    - by Martijn Courteaux
    Hi, I wrote an application and now I'm making a tray-icon. Now I want to set a multi-line tooltiptext to the tray-icon. But I don't know how. I know how to do this with Swing: component.setToolTipText("<html>Line 1<br>Line2</html>"); But this doesn't work with AWT. Also serarating lines by \n doesn't work. Any help would be very appreciated. Thanks

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  • Java: Best approach to have a long list of variables needed all the time without consuming memory?

    - by evilReiko
    I wrote an abstract class to contain all rules of the application because I need them almost everywhere in my application. So most of what it contains is static final variables, something like this: public abstract class appRules { public static final boolean IS_DEV = true; public static final String CLOCK_SHORT_TIME_FORMAT = "something"; public static final String CLOCK_SHORT_DATE_FORMAT = "something else"; public static final String CLOCK_FULL_FORMAT = "other thing"; public static final int USERNAME_MIN = 5; public static final int USERNAME_MAX = 16; // etc. } The class is big and contains LOTS of such variables. My Question: Isn't setting static variables means these variables are floating in memory all the time? Do you suggest insteading of having an abstract class, I have a instantiable class with non-static variables (just public final), so I instantiate the class and use the variables only when I need them. Or is what am I doing is completely wrong approach and you suggest something else?

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  • What is the purpose of Process class in Java?

    - by Nitesh Panchal
    Runtime objRuntime = Runtime.getRuntime(); String strBackupString = "mysqldump -u " + userName + " -p" + password + " " + dbName; Process objProcess = objRuntime.exec(strBackupString); This is used for backup of database. But what exactly happens? Can anybody make me explain, what is the purpose of Runtime and Process class? Is this class used to act as if we are typing command from command prompt? Then what should i pass to objRuntime.exec() if i want to open notepad? And is the command executed as soon as we call exec method? If yes, then what purpose does Process serve here? I really can't understand these two classes. Please make me understand. Thanks in advance :)

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  • I'm maintaining a java class that's 40K lines long.. problem?

    - by Billworth Vandory
    This may be a subjective question leading to deletion but I would really like some feedback. Recently, I moved to another very large enterprise project where I work as a C++ developer. I was aghast to find most classes in the project are anywhere from 8K to 50K lines long with methods that are 1K to 8K lines long. It's mostly business logic dealing with DB tables and data management, full of conditional statements to handle the use cases. Are classes this large common in large enterprise systems? I realize without looking at the code it's hard to make a determination, but have you ever worked on a system with classes this large?

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  • JAVA : How to get the positions of all matches in a String?

    - by user692704
    I have a text document and a query (the query could be more than one word). I want to find the position of all occurrences of the query in the document. I thought of the documentText.indexOf(query) and using regular expression but I could not make it work. I end up with the following method: First, I have create a dataType called QueryOccurrence public class QueryOccurrence implements Serializable{ public QueryOccurrence(){} private int start; private int end; public QueryOccurrence(int nameStart,int nameEnd,String nameText){ start=nameStart; end=nameEnd; } public int getStart(){ return start; } public int getEnd(){ return end; } public void SetStart(int i){ start=i; } public void SetEnd(int i){ end=i; } } Then, I have used this datatype in the following method: public static List<QueryOccurrence>FindQueryPositions(String documentText, String query){ // Normalize do the following: lower case, trim, and remove punctuation String normalizedQuery = Normalize.Normalize(query); String normalizedDocument = Normalize.Normalize(documentText); String[] documentWords = normalizedDocument.split(" ");; String[] queryArray = normalizedQuery.split(" "); List<QueryOccurrence> foundQueries = new ArrayList(); QueryOccurrence foundQuery = new QueryOccurrence(); int index = 0; for (String word : documentWords) { if (word.equals(queryArray[0])){ foundQuery.SetStart(index); } if (word.equals(queryArray[queryArray.length-1])){ foundQuery.SetEnd(index); if((foundQuery.End()-foundQuery.Start())+1==queryArray.length){ //add the found query to the list foundQueries.add(foundQuery); //flush the foundQuery variable to use it again foundQuery= new QueryOccurrence(); } } index++; } return foundQueries; } This method return a list of all occurrence of the query in the document each one with its position. Could you suggest any easer and faster way to accomplish this task. Thanks

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