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  • SwingWorker in Java (beginner question)

    - by Malachi
    I am relatively new to multi-threading and want to execute a background task using a Swingworker thread - the method that is called does not actually return anything but I would like to be notified when it has completed. The code I have so far doesn't appear to be working: private void crawl(ActionEvent evt) { try { SwingWorker<Void, Void> crawler = new SwingWorker<Void, Void>() { @Override protected Void doInBackground() throws Exception { Discoverer discover = new Discoverer(); discover.crawl(); return null; } @Override protected void done() { JOptionPane.showMessageDialog(jfThis, "Finished Crawling", "Success", JOptionPane.INFORMATION_MESSAGE); } }; crawler.execute(); } catch (Exception ex) { JOptionPane.showMessageDialog(this, ex.getMessage(), "Exception", JOptionPane.ERROR_MESSAGE); } } Any feedback/advice would be greatly appreciated as multi-threading is a big area of programming that I am weak in.

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  • substitute in a nested list (prolog)

    - by linda
    /* substitute(X,Y,Xs,Ys) is true if the list Ys is the result of substituting Y for all occurrences of X in the list Xs. This is what I have so far: subs(_,_,[],[]). subs(X,Y,[X|L1],[Y|L2]):- subs(X,Y,L1,L2). subs(X,Y,[H|L1],[H|L2]):- X\=H, not(H=[_|_]), subs(X,Y,L1,L2). subs(X,Y,[H|_],[L2]):- X\=H, H=[_|_], subs(X,Y,H,L2). My code works except it omits the elements following the nested list. For example: ?- subs(a,b,[a,[a,c],a],Z). Z = [b, [b, c]] . What should I add to this program?

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  • Intel IA-32 Assembly

    - by Kay
    I'm having a bit of difficulty converting the following java code into Intel IA-32 Assembly: class Person() { char name [8]; int age; void printName() {...} static void printAdults(Person [] list) { for(int k = 0; k < 100; k++){ if (list[k].age >= 18) { list[k].printName(); } } } } My attempt is: Person: push ebp; save callers ebp mov ebp, esp; setup new ebp push esi; esi will hold name push ebx; ebx will hold list push ecx; ecx will hold k init: mov esi, [ebp + 8]; mov ebx, [ebp + 12]; mov ecx, 0; k=0 forloop: cmp ecx, 100; jge end; if k>= 100 then break forloop cmp [ebx + 4 * ecx], 18 ; jl auxloop; if list[k].age < 18 then go to auxloop jmp printName; printName: auxloop: inc ecx; jmp forloop; end: pop ecx; pop ebx; pop esi; pop ebp; Is my code correct? NOTE: I'm not allowed to use global variables.

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  • A[i] * A[j] = k in O(nlog(n))

    - by gleb-pendler
    A is an Array of n positive int numbers k given int Algorithm should find if there is a pair of numbers which product gives the result a. A[i] * A[j] = k b. A[i] = A[j] + k if there is such a couple the algorithm should return thier index. thanks in advance.

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  • Context Free Language Question (Pumping Lemma)

    - by Maixy
    I know this isn't directly related to programming, but I was wondering if anyone know how to apply the pumping lemma to the following proof: Show that L={(a^n)(b^n)(c^m) : n!=m} is not a context free language I'm pretty confident with applying pumping lemmas, but this one is really irking me. What do you think?

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  • JOptionPane opening another JFrame

    - by mike_hornbeck
    So I'm continuing my fight with this : http://stackoverflow.com/questions/2923545/creating-java-dialogs/2926126 task. Now my JOptionPane opens new window with envelope overfiew, but I can't change size of this window. Also I wanted to have sender's data in upper left corner, and receiver's data in bottom right. How can I achieve that ? There is also issue with OptionPane itself. After I click 'OK' it opens small window in the upper left corner of the screen. What is this and why it's appearing ? My code: import java.awt.*; import java.awt.Font; import javax.swing.*; public class Main extends JFrame { private static JTextField nameField = new JTextField(20); private static JTextField surnameField = new JTextField(); private static JTextField addr1Field = new JTextField(); private static JTextField addr2Field = new JTextField(); private static JComboBox sizes = new JComboBox(new String[] { "small", "medium", "large", "extra-large" }); public Main(){ JPanel mainPanel = new JPanel(); mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS)); getContentPane().add(mainPanel); JPanel addrPanel = new JPanel(new GridLayout(0, 1)); addrPanel.setBorder(BorderFactory.createTitledBorder("Receiver")); addrPanel.add(new JLabel("Name")); addrPanel.add(nameField); addrPanel.add(new JLabel("Surname")); addrPanel.add(surnameField); addrPanel.add(new JLabel("Address 1")); addrPanel.add(addr1Field); addrPanel.add(new JLabel("Address 2")); addrPanel.add(addr2Field); mainPanel.add(addrPanel); mainPanel.add(new JLabel(" ")); mainPanel.add(sizes); String[] buttons = { "OK", "Cancel"}; int c = JOptionPane.showOptionDialog( null, mainPanel, "My Panel", JOptionPane.DEFAULT_OPTION, JOptionPane.PLAIN_MESSAGE, null, buttons, buttons[0] ); if(c ==0){ new Envelope(nameField.getText(), surnameField.getText(), addr1Field.getText() , addr2Field.getText(), sizes.getSelectedIndex()); } setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); pack(); setVisible(true); } public static void main(String[] args) { new Main(); } } class Envelope extends JFrame { private final int SMALL=0; private final int MEDIUM=1; private final int LARGE=2; private final int XLARGE=3; public Envelope(String n, String s, String a1, String a2, int i){ Container content = getContentPane(); JPanel mainPanel = new JPanel(); mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS)); mainPanel.add(new JLabel("John Doe")); mainPanel.add(new JLabel("FooBar str 14")); mainPanel.add(new JLabel("Newark, 45-99")); JPanel dataPanel = new JPanel(); dataPanel.setFont(new Font("sansserif", Font.PLAIN, 32)); //set size from i mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS)); mainPanel.setBackground(Color.ORANGE); mainPanel.add(new JLabel("Mr "+n+" "+s)); mainPanel.add(new JLabel(a1)); mainPanel.add(new JLabel(a2)); content.setSize(450, 600); content.setBackground(Color.ORANGE); content.add(mainPanel, BorderLayout.NORTH); content.add(dataPanel, BorderLayout.SOUTH); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); pack(); setVisible(true); } }

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  • class header+ implementation

    - by igor
    what am I doing wrong here? I keep on getting a compilation error when I try to run this in codelab (turings craft) Instructions: Write the implementation (.cpp file) of the GasTank class of the previous exercise. The full specification of the class is: A data member named amount of type double. A constructor that no parameters. The constructor initializes the data member amount to 0. A function named addGas that accepts a parameter of type double . The value of the amount instance variable is increased by the value of the parameter. A function named useGas that accepts a parameter of type double . The value of the amount data member is decreased by the value of the parameter. A function named getGasLevel that accepts no parameters. getGasLevel returns the value of the amount data member. class GasTank{ double amount; GasTank(); void addGas(double); void useGas(double); double getGasLevel();}; GasTank::GasTank(){ amount=0;} double GasTank::addGas(double a){ amount+=a;} double GasTank::useGas(double a){ amount+=a;} double GasTank::getGasLevel(){ return amount;}

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  • Finding the heaviest length-constrained path in a weighted Binary Tree

    - by Hristo
    UPDATE I worked out an algorithm that I think runs in O(n*k) running time. Below is the pseudo-code: routine heaviestKPath( T, k ) // create 2D matrix with n rows and k columns with each element = -8 // we make it size k+1 because the 0th column must be all 0s for a later // function to work properly and simplicity in our algorithm matrix = new array[ T.getVertexCount() ][ k + 1 ] (-8); // set all elements in the first column of this matrix = 0 matrix[ n ][ 0 ] = 0; // fill our matrix by traversing the tree traverseToFillMatrix( T.root, k ); // consider a path that would arc over a node globalMaxWeight = -8; findArcs( T.root, k ); return globalMaxWeight end routine // node = the current node; k = the path length; node.lc = node’s left child; // node.rc = node’s right child; node.idx = node’s index (row) in the matrix; // node.lc.wt/node.rc.wt = weight of the edge to left/right child; routine traverseToFillMatrix( node, k ) if (node == null) return; traverseToFillMatrix(node.lc, k ); // recurse left traverseToFillMatrix(node.rc, k ); // recurse right // in the case that a left/right child doesn’t exist, or both, // let’s assume the code is smart enough to handle these cases matrix[ node.idx ][ 1 ] = max( node.lc.wt, node.rc.wt ); for i = 2 to k { // max returns the heavier of the 2 paths matrix[node.idx][i] = max( matrix[node.lc.idx][i-1] + node.lc.wt, matrix[node.rc.idx][i-1] + node.rc.wt); } end routine // node = the current node, k = the path length routine findArcs( node, k ) if (node == null) return; nodeMax = matrix[node.idx][k]; longPath = path[node.idx][k]; i = 1; j = k-1; while ( i+j == k AND i < k ) { left = node.lc.wt + matrix[node.lc.idx][i-1]; right = node.rc.wt + matrix[node.rc.idx][j-1]; if ( left + right > nodeMax ) { nodeMax = left + right; } i++; j--; } // if this node’s max weight is larger than the global max weight, update if ( globalMaxWeight < nodeMax ) { globalMaxWeight = nodeMax; } findArcs( node.lc, k ); // recurse left findArcs( node.rc, k ); // recurse right end routine Let me know what you think. Feedback is welcome. I think have come up with two naive algorithms that find the heaviest length-constrained path in a weighted Binary Tree. Firstly, the description of the algorithm is as follows: given an n-vertex Binary Tree with weighted edges and some value k, find the heaviest path of length k. For both algorithms, I'll need a reference to all vertices so I'll just do a simple traversal of the Tree to have a reference to all vertices, with each vertex having a reference to its left, right, and parent nodes in the tree. Algorithm 1 For this algorithm, I'm basically planning on running DFS from each node in the Tree, with consideration to the fixed path length. In addition, since the path I'm looking for has the potential of going from left subtree to root to right subtree, I will have to consider 3 choices at each node. But this will result in a O(n*3^k) algorithm and I don't like that. Algorithm 2 I'm essentially thinking about using a modified version of Dijkstra's Algorithm in order to consider a fixed path length. Since I'm looking for heaviest and Dijkstra's Algorithm finds the lightest, I'm planning on negating all edge weights before starting the traversal. Actually... this doesn't make sense since I'd have to run Dijkstra's on each node and that doesn't seem very efficient much better than the above algorithm. So I guess my main questions are several. Firstly, do the algorithms I've described above solve the problem at hand? I'm not totally certain the Dijkstra's version will work as Dijkstra's is meant for positive edge values. Now, I am sure there exist more clever/efficient algorithms for this... what is a better algorithm? I've read about "Using spine decompositions to efficiently solve the length-constrained heaviest path problem for trees" but that is really complicated and I don't understand it at all. Are there other algorithms that tackle this problem, maybe not as efficiently as spine decomposition but easier to understand? Thanks.

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  • Constructing a Binary Tree from its traversals

    - by user991710
    I'm trying to construct a binary tree (unbalanced), given its traversals. I'm currently doing preorder + inorder but when I figure this out postorder will be no issue at all. I realize there are some question on the topic already but none of them seemed to answer my question. I've got a recursive method that takes the Preorder and the Inorder of a binary tree to reconstruct it, but is for some reason failing to link the root node with the subsequent children. Note: I don't want a solution. I've been trying to figure this out for a few hours now and even jotted down the recursion on paper and everything seems fine... so I must be missing something subtle. Here's the code: public static <T> BinaryNode<T> prePlusIn( T[] pre, T[] in) { if(pre.length != in.length) throw new IllegalArgumentException(); BinaryNode<T> base = new BinaryNode(); base.element = pre[0]; // * Get root from the preorder traversal. int indexOfRoot = 0; if(pre.length == 0 && in.length == 0) return null; if(pre.length == 1 && in.length == 1 && pre[0].equals(in[0])) return base; // * If both arrays are of size 1, element is a leaf. for(int i = 0; i < in.length -1; i++){ if(in[i].equals(base.element)){ // * Get the index of the root indexOfRoot = i; // in the inorder traversal. break; } // * If we cannot, the tree cannot be constructed as the traversals differ. else throw new IllegalArgumentException(); } // * Now, we recursively set the left and right subtrees of // the above "base" root node to whatever the new preorder // and inorder traversals end up constructing. T[] preleft = Arrays.copyOfRange(pre, 1, indexOfRoot + 1); T[] preright = Arrays.copyOfRange(pre, indexOfRoot + 1, pre.length); T[] inleft = Arrays.copyOfRange(in, 0, indexOfRoot); T[] inright = Arrays.copyOfRange(in, indexOfRoot + 1, in.length); base.left = prePlusIn( preleft, inleft); // * Construct left subtree. base.right = prePlusIn( preright, inright); // * Construc right subtree. return base; // * Return fully constructed tree } Basically, I construct additional arrays that house the pre- and inorder traversals of the left and right subtree (this seems terribly inefficient but I could not think of a better way with no helpers methods). Any ideas would be quite appreciated. Side note: While debugging it seems that the root note never receives the connections to the additional nodes (they remain null). From what I can see though, that should not happen... EDIT: To clarify, the method is throwing the IllegalArgumentException @ line 21 (else branch of the for loop, which should only be thrown if the traversals contain different elements.

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  • Multiple actions upon a case statement in Haskell

    - by Schroedinger
    One last question for the evening, I'm building the main input function of my Haskell program and I have to check for the args that are brought in so I use args <- getArgs case length args of 0 -> putStrLn "No Arguments, exiting" otherwise -> { other methods here} Is there an intelligent way of setting up other methods, or is it in my best interest to write a function that the other case is thrown to within the main? Or is there an even better solution to the issue of cases. I've just got to take in one name.

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  • Dynamic programming: Largest diamond(rhombus) block

    - by Darksody
    I have a small program to do in Java. I have a 2D array filled with 0 and 1, and I must find the largest rhombus (as in square rotated by 90 degrees) and their numbers. Example: 0 1 0 0 0 1 1 0 1 1 1 0 1 0 1 1 1 1 0 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 Result: 1 1 1 1 1 1 1 1 1 1 1 1 1 The problem is similar to this SO question. If you have any idea, post it here.

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  • Limit Connections with semaphores

    - by Robert
    I'm trying to limit the number of connections my server will accept using semaphores, but when running, my code doesn't seem to make this restriction - am I using the semaphore correctly? eg. I have hardcoded the number of permit as 2, but I can connect an unlimited number of clients... public class EServer implements Runnable { private ServerSocket serverSocket; private int numberofConnections = 0; private Semaphore sem = new Semaphore(2); private volatile boolean keepProcessing = true; public EServer(int port) throws IOException { serverSocket = new ServerSocket(port); } @Override public void run() { while (keepProcessing) { try { sem.acquire(); Socket socket = serverSocket.accept(); process(socket, getNextConnectionNumber()); } catch (Exception e) { } finally { sem.release(); } } closeIgnoringException(serverSocket); } private synchronized int getNextConnectionNumber() { return ++numberofConnections; } // processing related methods }

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  • Which web Tier Framework for a public commercial website with heavy load ?

    - by Maxime ARNSTAMM
    Hello everyone, As a part of an enterprise architecture exercise, i need to find a java-based framework filling these constraints : heavy (i think) load : 5000 concurrent connections widely known : can't be too exotic, the contractors would be too high priced. relatively easy to use : developpement time must be reasonnable must be as compliant as possible with the css/html layout produced by a designer Must look like "web 2.0" from the marketing point of view. What i learned from my limited experience is : jsf : 1, don't know. 2, 3 ok. 4 not ok (at least not without huge effort) wicket : 1, not really. 2, 3 and 4 ok. gwt : 1, don't know. 2, 3 ok. 4 not ok (but more ok than jsf) others : not really "web 2.0" or not really known I'm really junior, so my ideas about those frameworks are probably wrong, that's why i come to you, stackoverflowees. Thanks for helping :)

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  • javascript robot

    - by sarah
    hey guys! I need help making this robot game in javascript (notepad++) please HELP! I'm really confused by the functions <html> <head><title>Robot Invasion 2199</title></head> <body style="text-align:center" onload="newGame();"> <h2>Robot Invasion 2199</h2> <div style="text-align:center; background:white; margin-right: auto; margin-left:auto;"> <div style=""> <div style="width: auto; border:solid thin red; text-align:center; margin:10px auto 10px auto; padding:1ex 0ex;font-family: monospace" id="scene"></pre> </div> <div><span id="status"></span></div> <form style="text-align:center"> PUT THE CONTROL PANEL HERE!!! </form> </div> <script type="text/javascript"> // GENERAL SUGGESTIONS ABOUT WRITING THIS PROGRAM: // You should test your program before you've finished writing all of the // functions. The newGame, startLevel, and update functions should be your // first priority since they're all involved in displaying the initial state // of the game board. // // Next, work on putting together the control panel for the game so that you // can begin to interact with it. Your next goal should be to get the move // function working so that everything else can be testable. Note that all nine // of the movement buttons (including the pass button) should call the move // function when they are clicked, just with different parameters. // // All the remaining functions can be completed in pretty much any order, and // you'll see the game gradually improve as you write the functions. // // Just remember to keep your cool when writing this program. There are a // bunch of functions to write, but as long as you stay focused on the function // you're writing, each individual part is not that hard. // These variables specify the number of rows and columns in the game board. // Use these variables instead of hard coding the number of rows and columns // in your loops, etc. // i.e. Write: // for(i = 0; i < NUM_ROWS; i++) ... // not: // for(i = 0; i < 15; i++) ... var NUM_ROWS = 15; var NUM_COLS = 25; // Scene is arguably the most important variable in this whole program. It // should be set up as a two-dimensional array (with NUM_ROWS rows and // NUM_COLS columns). This represents the game board, with the scene[i][j] // representing what's in row i, column j. In particular, the entries should // be: // // "." for empty space // "R" for a robot // "S" for a scrap pile // "H" for the hero var scene; // These variables represent the row and column of the hero's location, // respectively. These are more of a conveniece so you don't have to search // for the "H" in the scene array when you need to know where the hero is. var heroRow; var heroCol; // These variables keep track of various aspects of the gameplay. // score is just the number of robots destroyed. // screwdrivers is the number of sonic screwdriver charges left. // fastTeleports is the number of fast teleports remaining. // level is the current level number. // Be sure to reset all of these when a new game starts, and update them at the // appropriate times. var score; var screwdrivers; var fastTeleports; var level; // This function should use a sonic screwdriver if there are still charges // left. The sonic screwdriver turns any robot that is in one of the eight // squares immediately adjacent to the hero into scrap. If there are no charges // left, then this function should instead pop up a dialog box with the message // "Out of sonic screwdrivers!". As with any function that alters the game's // state, this function should call the update function when it has finished. // // Your "Sonic Screwdriver" button should call this function directly. function screwdriver() { // WRITE THIS FUNCTION } // This function should move the hero to a randomly selected location if there // are still fast teleports left. This function MUST NOT move the hero on to // a square that is already occupied by a robot or a scrap pile, although it // can move the hero next to a robot. The number of fast teleports should also // be decreased by one. If there are no fast teleports left, this function // should just pop up a message box saying so. As with any function that alters // the game's state, this function should call the update function when it has // finished. // // HINT: Have a loop that keeps trying random spots until a valid one is found. // HINT: Use the validPosition function to tell if a spot is valid // // Your "Fast Teleport" button s

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  • How do I make software that preserves database integrity and correctness?

    - by user287745
    I have made an application project in Visual Studio 2008 C#, SQL Server from Visual Studio 2008. The database has like 20 tables and many fields in each. I have made an interface for adding deleting editing and retrieving data according to predefined needs of the users. Now I have to Make to project into software which I can deliver to my professor. That is, he can just double click the icon and the software simply starts. No Visual Studio 2008 needed to start the debugging. The database will be on one powerful computer (dual core latest everything Windows XP) and the user will access it from another computer connected using LAN. I am able to change the connection string to the shared database using Visual Studio 2008/ debugger whenever the server changes but how am I supposed to do that when it's software? There will by many clients. Am I supposed to give the same software to every one, so they all can connect to the database? How will the integrity and correctness of the database be maintained? I mean the db.mdf file will be in a folder which will be shared with read and write access. So it's not necessary that only one user will write at a time. So is there any coding for this or?

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  • How to write a function to output unconstant loop

    - by tunpishuang
    Here is the function description test($argv) $argv is an array, for example $argv=array($from1,$to1,$from2,$to2.....); array items must be even. $argv=array(1,2,4,5) : this will output values like below: 1_4 1_5 2_4 2_5 The number of array $argv's is not constant. Maybe 3 or 4 levels of loop will be outputed. I know this will used RECURSIVE , but i don't know exactly how to code.

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