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  • Problems with with A* algorithm

    - by V_Programmer
    I'm trying to implement the A* algorithm in Java. I followed this tutorial,in particular, this pseudocode: http://theory.stanford.edu/~amitp/GameProgramming/ImplementationNotes.html The problem is my code doesn't work. It goes into an infinite loop. I really don't know why this happens... I suspect that the problem are in F = G + H function implemented in Graph constructors. I suspect I am not calculate the neighbor F correclty. Here's my code: List<Graph> open; List<Graph> close; private void createRouteAStar(Unit u) { open = new ArrayList<Graph>(); close = new ArrayList<Graph>(); u.ai_route_endX = 11; u.ai_route_endY = 5; List<Graph> neigh; int index; int i; boolean finish = false; Graph current; int cost; Graph start = new Graph(u.xMap, u.yMap, 0, ManhattanDistance(u.xMap, u.yMap, u.ai_route_endX, u.ai_route_endY)); open.add(start); current = start; while(!finish) { index = findLowerF(); current = new Graph(open, index); System.out.println(current.x); System.out.println(current.y); if (current.x == u.ai_route_endX && current.y == u.ai_route_endY) { finish = true; } else { close.add(current); neigh = current.getNeighbors(); for (i = 0; i < neigh.size(); i++) { cost = current.g + ManhattanDistance(current.x, current.y, neigh.get(i).x, neigh.get(i).y); if (open.contains(neigh.get(i)) && cost < neigh.get(i).g) { open.remove(open.indexOf(neigh)); } else if (close.contains(neigh.get(i)) && cost < neigh.get(i).g) { close.remove(close.indexOf(neigh)); } else if (!open.contains(neigh.get(i)) && !close.contains(neigh.get(i))) { neigh.get(i).g = cost; neigh.get(i).f = cost + ManhattanDistance(neigh.get(i).x, neigh.get(i).y, u.ai_route_endX, u.ai_route_endY); neigh.get(i).setParent(current); open.add(neigh.get(i)); } } } } System.out.println("step"); for (i=0; i < close.size(); i++) { if (close.get(i).parent != null) { System.out.println(i); System.out.println(close.get(i).parent.x); System.out.println(close.get(i).parent.y); } } } private int findLowerF() { int i; int min = 10000; int minIndex = -1; for (i=0; i < open.size(); i++) { if (open.get(i).f < min) { min = open.get(i).f; minIndex = i; System.out.println("min"); System.out.println(min); } } return minIndex; } private int ManhattanDistance(int ax, int ay, int bx, int by) { return Math.abs(ax-bx) + Math.abs(ay-by); } And, as I've said. I suspect that the Graph class has the main problem. However I've not been able to detect and fix it. public class Graph { int x, y; int f,g,h; Graph parent; public Graph(int x, int y, int g, int h) { this.x = x; this.y = y; this.g = g; this.h = h; this.f = g + h; } public Graph(List<Graph> list, int index) { this.x = list.get(index).x; this.y = list.get(index).y; this.g = list.get(index).g; this.h = list.get(index).h; this.f = list.get(index).f; this.parent = list.get(index).parent; } public Graph(Graph gp) { this.x = gp.x; this.y = gp.y; this.g = gp.g; this.h = gp.h; this.f = gp.f; } public Graph(Graph gp, Graph parent) { this.x = gp.x; this.y = gp.y; this.g = gp.g; this.h = gp.h; this.f = g + h; this.parent = parent; } public List<Graph> getNeighbors() { List<Graph> aux = new ArrayList<Graph>(); aux.add(new Graph(x+1, y, g,h)); aux.add(new Graph(x-1, y, g,h)); aux.add(new Graph(x, y+1, g,h)); aux.add(new Graph(x, y-1, g,h)); return aux; } public void setParent(Graph g) { parent = g; } } Little Edit: Using the System.out and the Debugger I discovered that the program ALWAYS is check the same "current" graph, (15,8) which is the (u.xMap, u.yMap) position. Looks like it keeps forever in the first step.

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  • Passing ActionListeners in Java, pack()

    - by Crystal
    Two questions. First question is I'm trying to create a simple form that when you press a button, it adds a Person object to the ArrayList. However, since I am not used to GUIs, I tried creating one and am first just trying to get the user input from the JTextField, create an ActionListener object of the appropriate type, so once that works, then I can pass in all the JTextField inputs to create my Person object. Unfortunately, I am not getting any data when I type in something to the firstName JTextField and was wondering if someone could look at my code below. import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.List; import java.util.ArrayList; public class AddressBook { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { AddressBookFrame frame = new AddressBookFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JMenuBar menuBar = new JMenuBar(); frame.setJMenuBar(menuBar); JMenu fileMenu = new JMenu("File"); JMenuItem openItem = new JMenuItem("Open"); JMenuItem saveItem = new JMenuItem("Save"); JMenuItem saveAsItem = new JMenuItem("Save As"); JMenuItem printItem = new JMenuItem("Print"); JMenuItem exitItem = new JMenuItem("Exit"); fileMenu.add(openItem); fileMenu.add(saveItem); fileMenu.add(saveAsItem); fileMenu.add(printItem); fileMenu.add(exitItem); menuBar.add(fileMenu); JMenu editMenu = new JMenu("Edit"); JMenuItem newItem = new JMenuItem("New"); JMenuItem editItem = new JMenuItem("Edit"); JMenuItem deleteItem = new JMenuItem("Delete"); JMenuItem findItem = new JMenuItem("Find"); JMenuItem firstItem = new JMenuItem("First"); JMenuItem previousItem = new JMenuItem("Previous"); JMenuItem nextItem = new JMenuItem("Next"); JMenuItem lastItem = new JMenuItem("Last"); editMenu.add(newItem); editMenu.add(editItem); editMenu.add(deleteItem); editMenu.add(findItem); editMenu.add(firstItem); editMenu.add(previousItem); editMenu.add(nextItem); editMenu.add(lastItem); menuBar.add(editMenu); JMenu helpMenu = new JMenu("Help"); JMenuItem documentationItem = new JMenuItem("Documentation"); JMenuItem aboutItem = new JMenuItem("About"); helpMenu.add(documentationItem); helpMenu.add(aboutItem); menuBar.add(helpMenu); frame.setVisible(true); } }); } } class AddressBookFrame extends JFrame { public AddressBookFrame() { setLayout(new BorderLayout()); setTitle("Address Book"); setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); AddressBookToolBar toolBar = new AddressBookToolBar(); add(toolBar, BorderLayout.NORTH); AddressBookStatusBar aStatusBar = new AddressBookStatusBar("5"); add(aStatusBar, BorderLayout.SOUTH); AddressBookForm form = new AddressBookForm(); add(form, BorderLayout.CENTER); } public static final int DEFAULT_WIDTH = 500; public static final int DEFAULT_HEIGHT = 500; } /* Create toolbar buttons and add buttons to toolbar */ class AddressBookToolBar extends JPanel { public AddressBookToolBar() { setLayout(new FlowLayout(FlowLayout.LEFT)); JToolBar bar = new JToolBar(); JButton newButton = new JButton("New"); JButton editButton = new JButton("Edit"); JButton deleteButton = new JButton("Delete"); JButton findButton = new JButton("Find"); JButton firstButton = new JButton("First"); JButton previousButton = new JButton("Previous"); JButton nextButton = new JButton("Next"); JButton lastButton = new JButton("Last"); bar.add(newButton); bar.add(editButton); bar.add(deleteButton); bar.add(findButton); bar.add(firstButton); bar.add(previousButton); bar.add(nextButton); bar.add(lastButton); add(bar); } } /* Creates the status bar string */ class AddressBookStatusBar extends JPanel { public AddressBookStatusBar(String statusBarString) { setLayout(new FlowLayout(FlowLayout.LEFT)); this.statusBarString = new JLabel("Total number of people: " + statusBarString); add(this.statusBarString); } private JLabel statusBarString; private int totalContacts; } class AddressBookForm extends JPanel { public AddressBookForm() { this.setLayout(new GridLayout(2, 1)); JPanel formPanel = new JPanel(); formPanel.setLayout(new GridLayout(4, 2)); JTextField firstName = new JTextField(20); JTextField lastName = new JTextField(20); JTextField telephone = new JTextField(20); JTextField email = new JTextField(20); JLabel firstNameLabel = new JLabel("First Name: ", JLabel.LEFT); formPanel.add(firstNameLabel); formPanel.add(firstName); JLabel lastNameLabel = new JLabel("Last Name: ", JLabel.LEFT); formPanel.add(lastNameLabel); formPanel.add(lastName); JLabel telephoneLabel = new JLabel("Telephone: ", JLabel.LEFT); formPanel.add(telephoneLabel); formPanel.add(telephone); JLabel emailLabel = new JLabel("Email: ", JLabel.LEFT); formPanel.add(emailLabel); formPanel.add(email); add(formPanel); JPanel buttonPanel = new JPanel(); JButton insertButton = new JButton("Insert"); JButton displayButton = new JButton("Display"); // create button actions AddressBookManager insertAction = new AddressBookManager(firstName.getText()); insertButton.addActionListener(insertAction); buttonPanel.add(insertButton); buttonPanel.add(displayButton); add(buttonPanel); } private List<Person> addressList = new ArrayList<Person>(); private class AddressBookManager implements ActionListener { public AddressBookManager(String text) { // addressList.add( setName(text); System.out.println("Test" + text); } public void actionPerformed(ActionEvent e) { System.out.println("Hello" + name); } public void setName(String name) { this.name = name; } private String name; } } Second question is, how do I make my form not take up the whole center space. I don't like the stretch look and was hoping the JTextFields could be just one line long, not a big box. Same thing with the buttons. Any thoughts? Thanks.

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  • Getting huge lags when downloading files via Service

    - by Copa
    I have a Service which receives URLs to download. The Service than downloads these URLs and save them to a file on the SD Card. When I put more than 2 items in the download queue my device is unusable. It nearly freezes. Huge lags and so on. Any idea? Sourcecode: private static boolean downloading = false; private static ArrayList<DownloadItem> downloads = new ArrayList<DownloadItem>(); /** * called once when the service started */ public static void start() { Thread thread = new Thread(new Runnable() { @Override public void run() { while (true) { if (downloads.size() > 0 && !downloading) { downloading = true; DownloadItem item = downloads.get(0); downloadSingleFile(item.getUrl(), item.getFile()); } } } }); thread.start(); } public static void addDownload(DownloadItem item) { downloads.add(item); } private static void downloadSuccessfullFinished() { if (downloads.size() > 0) downloads.get(0).setDownloaded(true); downloadFinished(); } private static void downloadFinished() { // remove the first entry; it has been downloaded if (downloads.size() > 0) downloads.remove(0); downloading = false; } private static void downloadSingleFile(String url, File output) { final int maxBufferSize = 4096; HttpResponse response = null; try { response = new DefaultHttpClient().execute(new HttpGet(url)); if (response != null && response.getStatusLine().getStatusCode() == 200) { // request is ok InputStream is = response.getEntity().getContent(); BufferedInputStream bis = new BufferedInputStream(is); RandomAccessFile raf = new RandomAccessFile(output, "rw"); ByteArrayBuffer baf = new ByteArrayBuffer(maxBufferSize); long current = 0; long i = 0; // read and write 4096 bytes each time while ((current = bis.read()) != -1) { baf.append((byte) current); if (++i == maxBufferSize) { raf.write(baf.toByteArray()); baf = new ByteArrayBuffer(maxBufferSize); i = 0; } } if (i > 0) // write the last bytes to the file raf.write(baf.toByteArray()); baf.clear(); raf.close(); bis.close(); is.close(); // download finished get start next download downloadSuccessfullFinished(); return; } } catch (Exception e) { // not successfully downloaded downloadFinished(); return; } // not successfully downloaded downloadFinished(); return; }

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  • what is the best method of concatenating a series of binary files into one file?

    - by Andrew
    hello everyone i have a series of PDF byte arrays in a arraylist files that i wish to concatenate into one file, currently when the PDF application trys to open the file is it corrupted: foreach (byte[] array in files) { using (Stream s = new MemoryStream(downloadbytes)) { s.Write(array, 0, array.Length); } } downloadbytes is the resultant concatenated array of bytes below is another implementation which also failed foreach (byte[] array in files) { System.Buffer.BlockCopy(array, 0, downloadbytes, offset, array.Length); offset += array.Length; } any pointers?

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  • how to selectively filter items in a collection

    - by Samuel
    I use the following snippet to filter the list of selected users, where isSelected is a boolean variable. Is there a simpler way (helper function) to populate the selectedUsers collection instead of writing the following lines of code. List<User> selectedUsers = new ArrayList<User>(0); for (User user : this.getUsers()) { if (user.isSelected()) { selectedUsers.add(user.getId()); } }

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  • XMLEncoder in java for serialization

    - by tom
    Im just wondering how i use xmlencoder to serialize ArrayList where foo is my own made class. Do i have to do anything in particular, ie define my own xml structure first and then call toString on each value in my list and write it out? Can anyone point me to a good tutorial? http://java.sun.com/products/jfc/tsc/articles/persistence4/ Thats what i have been looking at but it doesnt seem to mention what to do with non library classes. Thanks

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  • how to find which button has been clicked in app widgets in android?

    - by chrish
    I want to design simple app widget which has two textview and two button for previous/next. I am getting difficult to handle button click in app widget. Actually my desire is,if user click on previous button i want to show previous value and if user click on Next button i want to show next value from database. How to know which button is clicked? here i register button click listener like this public static class UpdateWidgetService extends IntentService { public UpdateWidgetService() { super("UpdateWidgetService"); } @Override protected void onHandleIntent(Intent intent) { AppWidgetManager appWidgetManager = AppWidgetManager .getInstance(this); int incomingAppWidgetId = intent.getIntExtra(EXTRA_APPWIDGET_ID, INVALID_APPWIDGET_ID); if (incomingAppWidgetId != INVALID_APPWIDGET_ID) { updateOneAppWidget(appWidgetManager, incomingAppWidgetId); } } private void updateOneAppWidget(AppWidgetManager appWidgetManager, int appWidgetId) { DatabaseManager dbManager = new DatabaseManager(this); dbManager.open(); String contactNumber, date, status, message; ArrayList<QueuedMessage> listOfQuedMessage = (ArrayList<QueuedMessage>) dbManager .fetchContactNumber(); if (listOfQuedMessage.size() == 0) Log.i("Db", "null"); else{ date = dbManager.fetchDate(); message = dbManager.fetchMessage(); status = dbManager.fetchStatus(); dbManager.closeDatabase(); RemoteViews views = new RemoteViews(this.getPackageName(), R.layout.schdulesms_appwidget_layout); views.setTextViewText(R.id.to_appwidget_saved_data, listOfQuedMessage.get(count).contacNumber); views.setTextViewText(R.id.date_appwidget_saved_data, date); views.setTextViewText(R.id.status_appwidget_saved, status); views.setTextViewText(R.id.message_appwidgset_saved_data, message); **//here i want do** if(button1){ btnNxtClick(views, appWidgetId,listOfQuedMessage.size()); }else{ btPrevClick(views, appWidgetId, listOfQuedMessage.size()); } appWidgetManager.updateAppWidget(appWidgetId, views); } } private void btnNxtClick(RemoteViews views, int appWidgetId,int sizeOfList) { Intent btnNextIntent = new Intent(this, this.getClass()); btnNextIntent.putExtra(EXTRA_APPWIDGET_ID, appWidgetId); PendingIntent btnNextPendingIntent = PendingIntent.getService(this, 0, btnNextIntent, PendingIntent.FLAG_UPDATE_CURRENT); views.setOnClickPendingIntent(R.id.btnNext, btnNextPendingIntent); } private void btPrevClick(RemoteViews views, int appWidgetId,int sizeOfList) { Intent btnNextIntent = new Intent(this, this.getClass()); btnNextIntent.putExtra(EXTRA_APPWIDGET_ID, appWidgetId); PendingIntent btnNextPendingIntent = PendingIntent.getService(this, 0, btnNextIntent, PendingIntent.FLAG_UPDATE_CURRENT); views.setOnClickPendingIntent(R.id.btnPrev, btnNextPendingIntent); } } can anyone help me out from this problem?? thanks

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  • Adding multiple views to a listview.

    - by hwrdprkns
    Hey guys, I tried to add these views to list view using this kind of factory but everytime I try and add the view to a ListActivity, it comes up with nothing. What am I doing wrong? I set my list views like so: List<View> views = new ArrayList<View>(); for(int x =0;x<tagg_views.size();x++) { lv.addHeaderView(views.get(x)); }

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  • Is HashMap in Java collision safe

    - by changed
    Hi I am developing a parser that needs to put key value pairs in hashmap. But a key can have multiple values which i can do in this way HashMap<String,ArrayList<String>> . But what happens if number of keys are very large and it start matching with other key's hashcode. Will that rewrite previous key's value ? thanks -devSunday

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  • Graph Tour with Uniform Cost Search in Java

    - by user324817
    Hi. I'm new to this site, so hopefully you guys don't mind helping a nub. Anyway, I've been asked to write code to find the shortest cost of a graph tour on a particular graph, whose details are read in from file. The graph is shown below: http://img339.imageshack.us/img339/8907/graphr.jpg This is for an Artificial Intelligence class, so I'm expected to use a decent enough search method (brute force has been allowed, but not for full marks). I've been reading, and I think that what I'm looking for is an A* search with constant heuristic value, which I believe is a uniform cost search. I'm having trouble wrapping my head around how to apply this in Java. Basically, here's what I have: Vertex class - ArrayList<Edge> adjacencies; String name; int costToThis; Edge class - final Vertex target; public final int weight; Now at the moment, I'm struggling to work out how to apply the uniform cost notion to my desired goal path. Basically I have to start on a particular node, visit all other nodes, and end on that same node, with the lowest cost. As I understand it, I could use a PriorityQueue to store all of my travelled paths, but I can't wrap my head around how I show the goal state as the starting node with all other nodes visited. Here's what I have so far, which is pretty far off the mark: public static void visitNode(Vertex vertex) { ArrayList<Edge> firstEdges = vertex.getAdjacencies(); for(Edge e : firstEdges) { e.target.costToThis = e.weight + vertex.costToThis; queue.add(e.target); } Vertex next = queue.remove(); visitNode(next); } Initially this takes the starting node, then recursively visits the first node in the PriorityQueue (the path with the next lowest cost). My problem is basically, how do I stop my program from following a path specified in the queue if that path is at the goal state? The queue currently stores Vertex objects, but in my mind this isn't going to work as I can't store whether other vertices have been visited inside a Vertex object. Help is much appreciated! Josh

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  • DataGridView cells not editable when using an outside thread call

    - by joslinm
    Hi, I'm not able to edit my datagridview cells when a number of identical calls takes place on another thread. Here's the situation: Dataset table is created in the main window The program receives in files and processes them on a background thread in class TorrentBuilder : BackgroundWorker creating an array objects of another class Torrent My program receives those objects from the BW result and adds them into the dataset The above happens either on my main window thread or in another thread: I have a separate thread watching a folder for files to come in, and when they do come in, they proceed to call TorrentBuilder.RunWorkerAsynch() from that thread, receive the result, and call an outside class that adds the Torrent objects into the table. When the files are received by the latter thread, the datagridview isn't editable. All of the values come up properly into the datagridview, but when I click on a cell to edit it: I can write letters and everything, but when I click out of it, it immediately reverts back to its original value. If I restart the program, I can edit the same cells just fine. If the values are freshly added from the main window thread, I can edit the cells just fine. The outside thread is called from my main window thread, and sits there in the background. I don't believe it to be ReadOnly because I would have gotten an exception. Here's some code: From my main window class: private void dataGridView_DragDrop(object sender, DragEventArgs e) { ArrayList al = new ArrayList(); string[] files = (string[])e.Data.GetData(DataFormats.FileDrop); foreach (string file in files) { string extension = Path.GetExtension(file); if (Path.GetExtension(file).Equals(".zip") || Path.GetExtension(file).Equals(".rar")) { foreach (string unzipped in dh.UnzipFile(file)) al.Add(unzipped); } else if (Path.GetExtension(file).Equals(".torrent")) { al.Add(file); } } dataGridViewProgressBar.Visible = true; tb.RunWorkerCompleted += new RunWorkerCompletedEventHandler(tb_DragDropCompleted); tb.ProgressChanged += new ProgressChangedEventHandler(tb_DragDropProgress); tb.RunWorkerAsync() } void tb_DragDropCompleted(object sender, RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(data); dataGridViewProgressBar.Visible = false; } From my outside Thread while (autocheck) { if (torrentFiles != null) { builder.RunWorkerAsync(torrentFiles); while (builder.IsBusy) Thread.Sleep(500); } } void builder_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(xml); data.Save(); //Save just does an `AcceptChanges()` and saves to a XML file }

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  • Convert Java.Util.HashMap to System.Collections.IDictionary

    - by Paul
    In Xamarin I've got a .jar I've imported using a Java Binding Library. One of the callbacks has a Java.Lang.Object parameter which gives me Java.Util.HashMap and Java.Util.ArrayList at runtime. I'm abstracting this SDK behind a cross-platform interface, so I need to convert this to a .NET type. It there anything like the ArrayAdapter except in reverse that can convert the Java types to their .NET equivalents?

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  • Fill a array with List data

    - by marionmaiden
    How can I fill a array with the data provided by one List? For example, I have a List with Strings: List l = new ArrayList<String>(); l.add("a"); l.add("b"); l.add("c"); then I want to copy this data into a String array: String[] array = ?

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  • How to pop items from a collection in Java?

    - by Tom Brito
    Is there a method in JDK or apache commons to "pop" a list of elements from a java.util.List? I mean, remove the list of elements and return it, like this method: public Collection pop(Collection elementsToPop, Collection elements) { Collection popped = new ArrayList(); for (Object object : elementsToPop) { if (elements.contains(object)) { elements.remove(object); popped.add(object); } } return popped; }

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  • Why does this compile?

    - by akf
    I was taken aback earlier today when debugging some code to find that something like the following does not throw a compile-time exception: public Test () { HashMap map = (HashMap) getList(); } private List getList(){ return new ArrayList(); } As you can imagine, a ClassCastException is thrown at runtime, but can someone explain why the casting of a List to a HashMap is considered legal at compile time?

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  • Difference between a Deprecated and Legacy API?

    - by Vaibhav Bajpai
    I was studying the legacy API's in the Java's Collection Framework and I learnt that classes such as Vector and HashTable have been superseded by ArrayList and HashMap. However still they are NOT deprecated, and deemed as legacy when essentially, deprecation is applied to software features that are superseded and should be avoided, so, I am not sure when is a API deemed legacy and when it is deprecated.

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  • Randomised objects are assigning themselves to more than one array location

    - by Thaddeus Aid
    this.size = 9; this.populationSize = 10; Random rand = new Random(); Integer[][] easy1 = new Integer[size][size]; easy1 = this.initializeEasy1(easy1); this.sudokuArray = new Sudoku[this.populationSize]; for (int i = 0; i < this.sudokuArray.length; i++){ long seed = rand.nextLong(); System.out.println("" + seed); this.sudokuArray[i] = new Sudoku(easy1, this.size, seed); } I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up? /edit here is the constructor of the class public Sudoku(Integer[][] givensGrid, int s, long seed){ this.size = s; this.givens = givensGrid; this.grid = this.givens.clone(); Random rand = new Random(seed); System.out.println("Random " + rand.nextInt()); // step though each row of the grid for (int i = 0; i < size; i++){ ArrayList<Integer> numbers = new ArrayList<Integer>(); numbers = this.makeNumbers(numbers); // step through each column to find the givens and remove from numbers for (int j = 0; j < size; j++){ if (this.grid[i][j] != 0){ numbers.remove(this.grid[i][j]); } } // go back through the row and assign the numbers randomly for (int j = 0; j < size; j++){ if (this.grid[i][j] == 0){ int r = rand.nextInt(numbers.size()); this.grid[i][j] = numbers.get(r); numbers.remove(r); } } } System.out.println("============="); System.out.println(this.toString()); }

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  • Does the for foreach construct in java create a hard or soft copy?

    - by Doug
    Say I have the following piece of java code ArrayList<Double> myList = new Double[100]; for (Double x : myList) x = randomDouble(); Does this actually modify myList or just the dummy variable? I realize I should just try this code segment out, but I think this is the sort of thing I should be able to google or search for on this site, and several queries so far have turned up nothing useful.

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  • Get random enum from a select group

    - by Coward
    Given a group of about 20 enums that I cannot modify. Im looking for an elegant solution to generate a random enum from a specific sample (ie, 2, 7, 18) I could put these into an arraylist, but thought I would ask if there is something else I could try.

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  • recursion resulting in extra unwanted data

    - by spacerace
    I'm writing a module to handle dice rolling. Given x die of y sides, I'm trying to come up with a list of all potential roll combinations. This code assumes 3 die, each with 3 sides labeled 1, 2, and 3. (I realize I'm using "magic numbers" but this is just an attempt to simplify and get the base code working.) int[] set = { 1, 1, 1 }; list = diceroll.recurse(0,0, list, set); ... public ArrayList<Integer> recurse(int index, int i, ArrayList<Integer> list, int[] set){ if(index < 3){ // System.out.print("\n(looping on "+index+")\n"); for(int k=1;k<=3;k++){ // System.out.print("setting i"+index+" to "+k+" "); set[index] = k; dump(set); recurse(index+1, i, list, set); } } return list; } (dump() is a simple method to just display the contents of list[]. The variable i is not used at the moment.) What I'm attempting to do is increment a list[index] by one, stepping through the entire length of the list and incrementing as I go. This is my "best attempt" code. Here is the output: Bold output is what I'm looking for. I can't figure out how to get rid of the rest. (This is assuming three dice, each with 3 sides. Using recursion so I can scale it up to any x dice with y sides.) [1][1][1] [1][1][1] [1][1][1] [1][1][2] [1][1][3] [1][2][3] [1][2][1] [1][2][2] [1][2][3] [1][3][3] [1][3][1] [1][3][2] [1][3][3] [2][3][3] [2][1][3] [2][1][1] [2][1][2] [2][1][3] [2][2][3] [2][2][1] [2][2][2] [2][2][3] [2][3][3] [2][3][1] [2][3][2] [2][3][3] [3][3][3] [3][1][3] [3][1][1] [3][1][2] [3][1][3] [3][2][3] [3][2][1] [3][2][2] [3][2][3] [3][3][3] [3][3][1] [3][3][2] [3][3][3] I apologize for the formatting, best I could come up with. Any help would be greatly appreciated. (This method was actually stemmed to use the data for something quite trivial, but has turned into a personal challenge. :) edit: If there is another approach to solving this problem I'd be all ears, but I'd also like to solve my current problem and successfully use recursion for something useful.

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  • How do I search the MediaStore for a specific directory instead of entire external storage?

    - by Nick Lopez
    In my app I have an option that allows users to browse for audio files on their phone to add to the app. I am having trouble however with creating a faster way of processing the query code. Currently it searches the entire external storage and causes the phone to prompt a force close/wait warning. I would like to take the code I have posted below and make it more efficient by either searching in a specific folder on the phone or by streamlining the process to make the file search quicker. I am not sure how to do this however. Thanks! public class BrowseActivity extends DashboardActivity implements OnClickListener, OnItemClickListener { private List<Sound> soundsInDevice = new ArrayList<Sound>(); private List<Sound> checkedList; private ListView browsedList; private BrowserSoundAdapter adapter; private long categoryId; private Category category; private String currentCategoryName; private String description; // private Category newCategory ; private Button doneButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.activity_browse); checkedList = new ArrayList<Sound>(); browsedList = (ListView) findViewById(android.R.id.list); doneButton = (Button) findViewById(R.id.doneButton); soundsInDevice = getMediaSounds(); if (soundsInDevice.size() > 0) { adapter = new BrowserSoundAdapter(this, R.id.browseSoundName, soundsInDevice); } else { Toast.makeText(getApplicationContext(), getString(R.string.no_sounds_available), Toast.LENGTH_SHORT) .show(); } browsedList.setAdapter(adapter); browsedList.setOnItemClickListener(this); doneButton.setOnClickListener(this); } private List<Sound> getMediaSounds() { List<Sound> mediaSoundList = new ArrayList<Sound>(); ContentResolver cr = getContentResolver(); String[] projection = {MediaStore.Audio.Media._ID, MediaStore.Audio.Media.DISPLAY_NAME, MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.DATA, MediaStore.Audio.Media.DURATION}; final Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI; Log.v("MediaStore.Audio.Media.EXTERNAL_CONTENT_URI", "" + uri); final Cursor cursor = cr.query(uri, projection, null, null, null); int n = cursor.getCount(); Log.v("count", "" + n); if (cursor.moveToFirst()) { do { String soundName = cursor .getString(cursor .getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME)); Log.v("soundName", "" + soundName); String title = cursor .getString(cursor .getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE)); Log.v("title", "" + title); String path = cursor.getString(cursor .getColumnIndexOrThrow(MediaStore.Audio.Media.DATA)); Log.v("path", "" + path); Sound browsedSound = new Sound(title, path, false, false, false, false, 0); Log.v("browsedSound", "" + browsedSound); mediaSoundList.add(browsedSound); Log.v("mediaSoundList", "" + mediaSoundList.toString()); } while (cursor.moveToNext()); } return mediaSoundList; } public class BrowserSoundAdapter extends ArrayAdapter<Sound> { public BrowserSoundAdapter(Context context, int textViewResourceId, List<Sound> objects) { super(context, textViewResourceId, objects); } @Override public View getView(final int position, View convertView, ViewGroup parent) { ViewHolder viewHolder; View view = convertView; LayoutInflater inflater = getLayoutInflater(); if (view == null) { view = inflater.inflate(R.layout.list_item_browse, null); viewHolder = new ViewHolder(); viewHolder.soundNameTextView = (TextView) view .findViewById(R.id.browseSoundName); viewHolder.pathTextView = (TextView) view .findViewById(R.id.browseSoundPath); viewHolder.checkToAddSound = (CheckBox) view .findViewById(R.id.browse_checkbox); view.setTag(viewHolder); } else { viewHolder = (ViewHolder) view.getTag(); } final Sound sound = soundsInDevice.get(position); if (sound.isCheckedState()) { viewHolder.checkToAddSound.setChecked(true); } else { viewHolder.checkToAddSound.setChecked(false); } viewHolder.soundNameTextView.setText(sound.getName()); viewHolder.pathTextView.setText(sound.getUri()); viewHolder.checkToAddSound .setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { CheckBox cb = (CheckBox) v .findViewById(R.id.browse_checkbox); boolean checked = cb.isChecked(); boolean newValue = checked; updateView(position, newValue); doneButtonStatus(checkedList.size()); } }); return view; } } // Adapter view holder class private class ViewHolder { private TextView soundNameTextView; private TextView pathTextView; private CheckBox checkToAddSound; } // done button On Click @Override public void onClick(View view) { boolean status = getIntent().getBooleanExtra("FromAddCat", false); Log.v("for add category","enters in if"); if(status){ Log.v("for add category","enters in if1"); currentCategoryName = getIntent().getStringExtra("categoryName"); description = getIntent().getStringExtra("description"); boolean existCategory = SQLiteHelper.getCategoryStatus(currentCategoryName); if (!existCategory) { category = new Category(currentCategoryName, description, false); category.insert(); category.update(); Log.v("for add category","enters in if2"); } }else{ categoryId = getIntent().getLongExtra("categoryId",-1); category = SQLiteHelper.getCategory(categoryId); } for (Sound checkedsound : checkedList) { checkedsound.setCheckedState(false); checkedsound.insert(); category.getSounds().add(checkedsound); final Intent intent = new Intent(this, CategoriesActivity.class); finish(); startActivity(intent); } } @Override public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) { boolean checked = true; boolean newValue = false; CheckBox cb = (CheckBox) view.findViewById(R.id.browse_checkbox); if (cb.isChecked()) { cb.setChecked(!checked); newValue = !checked; } else { cb.setChecked(checked); newValue = checked; } updateView(position, newValue); doneButtonStatus(checkedList.size()); } private void doneButtonStatus(int size) { if (size > 0) { doneButton.setEnabled(true); doneButton.setBackgroundResource(R.drawable.done_button_drawable); } else { doneButton.setEnabled(false); doneButton.setBackgroundResource(R.drawable.done_btn_disabled); } } private void updateView(int index, boolean newValue) { System.out.println(newValue); Sound sound = soundsInDevice.get(index); if (newValue == true) { checkedList.add(sound); sound.setCheckedState(newValue); } else { checkedList.remove(sound); sound.setCheckedState(newValue); } } }

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  • Sort a list whit element still in first position

    - by Mercer
    Hello, i have a String list List<String> listString = new ArrayList<String>(); listString.add("faq"); listString.add("general"); listString.add("contact"); I do some processing on the list and i want to sort this list but I want general is still in first position Thx ;)

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