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  • Confusion with a while statement evaluating if a number is triangular

    - by Darkkurama
    I've been having troubles trying to figure out how to solve a function. I've been assigned the development of a little programme which tells if a number is "triangular" (a number is triangular when the addition of certain consecutive numbers in the [1,n] interval is n. Following the definition, the number 10 is triangular, because in the [1,10] interval, 1+2+3+4=10). I've coded this so far: class TriangularNumber{ boolean numTriangular(int n) { boolean triangular = false; int i = n; while(n>=0 && triangular){ //UE06 is a class which contains the function "f0", which makes the addition of all the numbers in a determined interval UE06 p = new UE06(); if ((p.f0(1, i))==n) triangular = true; else i=i-1; } return triangular; } boolean testTriangular = numTriangular(10) == true && numTriangular(7) == false && numTriangular(6) == true; public static void main(String[] args){ TriangularNumber p = new TriangularNumber(); System.out.println("testTriangular = " + p.testTriangular); } } According to those boolean tests I made, the function is wrong. As I see the function, it goes like this: I state that the input number in the initial state isn't triangular (triangular=false) and i=n (determining the interval [1,i] where the function is going to be evaluated While n is greater or equals 0 and the number isn't triangular, the loop starts The loop goes like this: if the addition of all the numbers in the [1,i] interval is n, the number is triangular, causing the loop to end. If that statement is false, i goes from i to (i-1), starting the loop again with that particular interval, and so on till the addition is n. I can't spot the error in my "algorithm", any advice? Thanks!

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  • Limiting Row Selection in JTable

    - by Pat
    Is there an easy way to limit the total selection of rows in a JTable? I mean I'd like to allow the user to use shift and ctrl to select a maximum of X rows. If he clicks again on a row it would cancel out all the selections. Sort of how it currently behaves, but while limiting the total amount of selected rows. Here's my current implementation, I'm kind of clueless on how to limit the selection graphically. public class RoomsListView extends AbstractViewPanel { public RoomsListView(DefaultController controller) { this.controller = controller; initUI(); } private void initUI() { tableT = new JTable(RoomsModel.getInstance()); sorter = new TableRowSorter<RoomsModel>(RoomsModel.getInstance()); tableT.setRowSorter(sorter); tableT.setPreferredScrollableViewportSize(new Dimension(CUSTOM_TABLE_WIDTH, CUSTOM_TABLE_HEIGHT)); tableT.addMouseListener(new MouseAdapter() { public void mouseClicked(MouseEvent e) { rowClickedPerformed(e); } }); } private void rowClickedPerformed(MouseEvent e) { } public void modelPropertyChange(PropertyChangeEvent evt) { } public JTable getTable() { return tableT; } private final int CUSTOM_TABLE_WIDTH = -1; private final int CUSTOM_TABLE_HEIGHT = 150; private JTable tableT; private DefaultController controller; private TableRowSorter<RoomsModel> sorter; }

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  • servlet connection to DB

    - by underW
    Initially, after reading books on the subject, I firmly believed that the algorithm for working with a database from a servlet is as follows: create a connection - connect to the database - form a request - send the request to the database - get the query results - process them - close connection - OK. Now, with a better understanding of the practical side, I realized that nobody does it that way, and everything happens through a connection pool according to the following algorithm: initialize the servlet - create a connection pool - a request comes from a user - take a free connection from the pool - form a request - send the request to the database - get the query results - process them - return the connection back to the pool - ok. Now I have this problem: We have 100 users, they are divided into 10 groups, each group has it's own username and password to connect to the database. Moreover, each group may have different rights to the database. How am I supposed to use a connection pool in this situation? If I understand correctly, a pool is nothing more than just a group of similar connections with a single login and password. And here I have 10 pairs of username / password. It looks like I cannot use the pool in this situation. What should I do?

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  • How to write native SQL queries in Hibernate without hardcoding table names and fields?

    - by serg555
    Sometimes you have to write some of your queries in native SQL rather than hibernate HQL. Is there a nice way to avoid hardcoding table names and fields and get this data from existing mapping? For example instead of: String sql = "select user_name from tbl_user where user_id = :id"; something like: String sql = "select " + Hibernate.getFieldName("user.name") + " from " + Hibernate.getTableName(User.class) + " where " + Hibernate.getFieldName("user.id") + " = :id";

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  • Servlet File Upload Memory Consumption

    - by Scott
    Hi, I'm using a servlet to do a multi fileupload (using apache commons fileupload to help). A portion of my code is posted below. My problem is that if I upload several files at once, the memory consumption of the app server jumps rather drastically. This is probably OK if it were only until the file upload is finished, but the app server seems to hang on to the memory and never return it to the OS. I'm worried that when I put this into production I'll end up getting an out of memory exception on the server. Any ideas on why this is happening? I'm thinking the server may have started a session and will give the memory back after it expires, but I'm not 100% positive. if(ServletFileUpload.isMultipartContent(request)) { ServletFileUpload upload = new ServletFileUpload(); FileItemIterator iter = upload.getItemIterator(request); while(iter.hasNext()) { FileItemStream license = iter.next(); if(license.getFieldName().equals("upload_button") || license.getName().equals("")) continue; //DataInputStream stream = new DataInputStream(license.openStream()); InputStream stream = license.openStream(); ArrayList<Integer> byteArray = new ArrayList<Integer>(); int tempByte; do { tempByte = stream.read(); byteArray.add(tempByte); }while(tempByte != -1); stream.close(); byteArray.remove(byteArray.size()-1); byte[] bytes = new byte[byteArray.size()]; int i = 0; for(Integer tByte : byteArray) { bytes[i++] = tByte.byteValue(); } Thanks in advanced!!

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  • How to close IOs?

    - by blackdog
    when i managed IO, i found a problem. i used to close it like this: try { // my code } catch (Exception e) { // my code } finally{ if (is != null) { is.close(); } } but the close method also would throw exception. if i have more than one IO, i have to close all of them. so the code maybe like this: try { // my code } catch (Exception e) { // my code } finally{ if (is1 != null) { is1.close(); } if(is2 != null{ is2.close(); } // many IOs } if is1.close() throws an exception, is2, is3 would not close itself. So i have to type many try-catch-finally to control them. is there other way to solve the problem?

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  • Hibernate - One design problem

    - by Yatendra Goel
    I am learning Hibernate from the tutorial on JBoss website. I have a confusion in a code example located here. There is a Cat class code at 4.1. A simple POJO example. This Cat class has a reference to his mother as private Cat mother; Q1. If the class has an identifier property as id, then wouldn't it be better to store the cat's mother's id instead of cat's mother object. means instead of private Cat mother; wouldn't it be better to have private long motherId; `

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  • Generating the permutations from a number of Characters

    - by adam08
    I'm working on a predictive text solution and have all the words being retrieved from a Trie based on input for a certain string of characters, i.e. "at" will give all words formed with "at" as a prefix. The problem that I have now, is that we are also supposed to return all other possibilities from pressing these 2 buttons, Button 2 and button 8 on the mobile phone, which would also give words formed with, "au, av, bt, bu, bv, ct, cu, cv" (most of which won't have any actual words. Can anyone suggest a solution and how I would go about doing this for calculating the different permutations? (at the moment, I'm prompting the user to enter the prefix (not using a GUI right now)

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  • Is it possible to establish default values for inherited fields in subclasses?

    - by Christian Mann
    I'm trying to establish a default value for inherited fields from superclasses. So, my class hierarchy is thus: Character - Enemy - Boss                 \                   - Hero Each Character has a public static char avatar to represent him on an ASCII playing field. How do I set a default value for the avatar of each class inherited from Character? Thank you!

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  • how to run TimerTask off main UI thread?

    - by huskyd97
    I am having trouble with a TimerTask Interfering with In App Purchasing (Async Tasks). I am weak with Threads, so I believe it is running on the main UI thread, eating up resources. How can I run this outside the UI thread? I have searched, and tried some suggestions using handlers. but seems like I get the same result, app gets really laggy. when I don't run this task (refreshes every 500mS), the activity runs smoothly, and there are no hangs during In app purchases. Your help is appreciated, code snippet below: public class DummyButtonClickerActivity extends Activity { protected Timer timeTicker = new Timer("Ticker"); private Handler timerHandler = new Handler(); protected int timeTickDown = 20; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.mainhd); // start money earned timer handler TimerTask tick = new TimerTask() { public void run() { myTickTask(); } }; timeTicker.scheduleAtFixedRate(tick, 0, 500); // 500 ms each } // End OnCreate protected void myTickTask() { if (timeTickDown == 0) { /// run my code here //total = total + _Rate; timerHandler.post(doUpdateTimeout); } else if(timeTickDown < 0) { // do nothing } timeTickDown--; } private Runnable doUpdateTimeout = new Runnable() { public void run() { updateTimeout(); } }; private void updateTimeout() { // reset tick timeTickDown = 2; // 2* 500ms == once a second } }

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  • hibernate restrictions.in with and, how to use?

    - by cometta
    I have table like below id, employee_no, survey_no, name 1 test 1 test_name 2 test2 1 test_name2 3 test3 1 test_name3 4 test4 2 test_name4 how to query with Restriction.in by combining below AND into one IN statement? IN[ (if(survey_no==1) && employee_no== 'test') , (if(survey_no==1) && employee_no== 'test2') , ... ]

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  • Expose jar resources over web

    - by Heavy Bytes
    I have a web-service (with Spring-WS). I have a jar with several schemas (schema1.xsd, schema2.xsd and schema3.xsd) which I include in my web service. Is there a way to expose the schemas from the jar through a servlet somehow in my web-service wep app? My Spring MessageDispatcherServlet is mapped to /ws/ I would like my schemas to be exposed to /schemas/schema1.xsd /schemas/schema2.xsd and so on. I have an idea how to do it with a servlet, but it's too verbose and there has to be a nicer way. The way I am thinking is have a servlet filter and everything that hits /schemas/ check if it is in my list of allowed resources and display it. This has to be a server agnostic solution. (For instance http://tuckey.org/urlrewrite/ will not work). Thanks.

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  • Find messages from certain key till certain key while being able to remove stale keys.

    - by Alfred
    My problem Let's say I add messages to some sort of datastructure: 1. "dude" 2. "where" 3. "is" 4. "my" 5. "car" Asking for messages from index[4,5] should return: "my","car". Next let's assume that after a while I would like to purge old messages because they aren't useful anymore and I want to save memory. Let's say at time x messages[1-3] became stale. I assume that it would be most efficient to just do the deletion once every x seconds. Next my datastructure should contain: 4. "my" 5. "car" My solution? I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the old messages from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement(efficiently/thread-safe) this or maybe use a library?

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  • Android getSelectedItem, how to use?

    - by user1881184
    Im trying use the spinner control result in order to point it to another screen that would be on the app. For example in the spinner control if the user chose chevy it would then take you to another screen which is coded in chevy.xml and Chevy.class. This is what i have thus far and need some help, as our book only used getSelectedItem and the example was only for an output statement. Please help. import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.widget.AdapterView; import android.widget.AdapterView.OnItemSelectedListener; import android.widget.Spinner; public class Mainpage extends Activity implements OnItemSelectedListener { String carChoice, chevy, ford, dodge, toyota; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); /* carChoice = group.getSelectedItem().toString(); } if (carChoice.compareTo(chevy)==0) { startActivity(new Intent(Mainpage.this, Chevy.class)); */ } public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) { final Spinner group = (Spinner) findViewById(R.id.carGroup); group.setOnItemSelectedListener(this); // TODO Auto-generated method stub String selected = group.getItemAtPosition(1).toString(); } public void onNothingSelected(AdapterView<?> arg0) { // TODO Auto-generated method stub } }

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  • Contact picker in a dialog

    - by tiex
    I have a custom dialog in my android application. I want to have in this dialog a field for choosing a phone number from contacts. This example describes such snippet. However for this example contact picker is created inside an activity and I do not know how to do this if I do not have activity (in case of dialog)

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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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  • How to set Camera View as background with views over it?

    - by Android Student
    So, I'm trying to make the background to one of my apps look "futuristic." I thought of an idea to make the screen look almost transparent yet have views over it. So, it would look something like this: I'm thinking that I can use the camera to capture the background of the phone (without taking a picture, just having the real time view in the background) and then, if possible, place a semi-transparent slightly blurred ImageView over that. Finally, on top of that I can place the other views including the ImageButtons. So, my question is how would I go about doing this? I have searched but haven't found anything relevant. It must be possible; its just how to do it? I don't expect you to give me all the code as an answer, just if you have any ideas that can help or links or code that can point me in the right direction, it would be greatly appreciated! Thanks!

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