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• transmit a java.lang.reflect.Proxy over a network

  - by panzi

  Is there a convenient way to transmit an object including its code (the class) over a network (not just the instance data)? Don't ask me why I want to do this. It's in an assignment. I asked several times if that is really what they meant and the didn't rephrase their answer so I guess they really want us to transmit code (not just the field data) over a network. To be honest I have no clue why we need a Proxy in this assignment anyway, just writing a simple class would do IMO. The assignment says that we should instantiate the proxy on the server and transmit it to the client (and yes, they talk about a java.lang.reflect.Proxy, they name this class). Because there is no class file for a proxy I can't deploy that. I guess I would have to somehow read out the bytecode of the generated Proxy, transmit it to the client and then load it. Which makes absolutely no sense at all, but this seems what they want us to do. I don't get why.

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• Is it possible to have an enum field in a class persisted with OrmLite?

  - by htf

  Hello. I'm trying to persist the following class with OrmLite: public class Field { @DatabaseField(id = true) public String name; @DatabaseField(canBeNull = false) public FieldType type; public Field() { } } The FieldType is a public enum. The field, corresponding to the type is string in SQLite (is doesn't support enums). When I try to use it, I get the following exception: INFO [main] (SingleConnectionDataSource.java:244) - Established shared JDBC Connection: org.sqlite.Conn@5224ee Exception in thread "main" org.springframework.beans.factory.BeanInitializationException: Initialization of DAO failed; nested exception is java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:51) at orm.FieldDAO.getInstance(FieldDAO.java:17) at orm.Field.fromString(Field.java:23) at orm.Field.main(Field.java:38) Caused by: java.lang.IllegalArgumentException: Unknown field class class enums.FieldType for field FieldType:name=type,class=class orm.Field at com.j256.ormlite.field.FieldType.<init>(FieldType.java:54) at com.j256.ormlite.field.FieldType.createFieldType(FieldType.java:381) at com.j256.ormlite.table.DatabaseTableConfig.fromClass(DatabaseTableConfig.java:82) at com.j256.ormlite.dao.BaseJdbcDao.initDao(BaseJdbcDao.java:116) at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:48) ... 3 more So how do I tell OrmLite, values on the Java side are from an enum?

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• Create cross platform Java SWT Application

  - by mchr

  I have written a Java GUI using SWT. I package the application using an ANT script (fragment below). <jar destfile="./build/jars/swtgui.jar" filesetmanifest="mergewithoutmain"> <manifest> <attribute name="Main-Class" value="org.swtgui.MainGui" /> <attribute name="Class-Path" value="." /> </manifest> <fileset dir="./build/classes" includes="**/*.class" /> <zipfileset excludes="META-INF/*.SF" src="lib/org.eclipse.swt.win32.win32.x86_3.5.2.v3557f.jar" /> </jar> This produces a single jar which on Windows I can just double click to run my GUI. The downside is that I have had to explicitly package the windows SWT package into my jar. I would like to be able to run my application on other platforms (primarily Linux and OS X). The simplest way to do it would be to create platform specific jars which packaged the appropriate SWT files into separate JARs. Is there a better way to do this? Is it possible to create a single JAR which would run on multiple platforms?

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• Java, Massive message processing with queue manager (trading)

  - by Ronny

  Hello, I would like to design a simple application (without j2ee and jms) that can process massive amount of messages (like in trading systems) I have created a service that can receive messages and place them in a queue to so that the system won't stuck when overloaded. Then I created a service (QueueService) that wraps the queue and has a pop method that pops out a message from the queue and if there is no messages returns null, this method is marked as "synchronized" for the next step. I have created a class that knows how process the message (MessageHandler) and another class that can "listen" for messages in a new thread (MessageListener). The thread has a "while(true)" and all the time tries to pop a message. If a message was returned, the thread calls the MessageHandler class and when it's done, he will ask for another message. Now, I have configured the application to open 10 MessageListener to allow multi message processing. I have now 10 threads that all time are in a loop. Is that a good design?? Can anyone reference me to some books or sites how to handle such scenario?? Thanks, Ronny

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• Java NullPointerException In the constructor's class

  - by AndreaF

  I have made a Java class where I have defined a constructor and some methods but I get a NullPointer Exception, and I don't know how I could fix It. public class Job { String idJob; int time; int timeRun; Job j1; List<Job> startBeforeStart; List<Job> restricted; Job(String idJob, int time){ this.idJob=idJob; this.time=time; } public boolean isRestricted() { return restricted.size() != 0; } public void startsBeforeStartOf(Job job){ startBeforeStart.add(job); job.restricted.add(this); } public void startsAfterStartOf(Job job){ job.startsBeforeStartOf(this); } public void checkRestrictions(){ if (!isRestricted()){ System.out.println("+\n"); } else{ Iterator<Job> itR = restricted.iterator(); while(itR.hasNext()){ Job j1 = itR.next(); if(time>timeRun){ System.out.println("-\n"); time--; } else { restricted.remove(j1); } } } } @Override public boolean equals(Object obj) { return obj instanceof Job && ((Job) obj).idJob.equals(idJob); } public void run() { timeRun++; } } PS Looking in a forum a user says that to fix the error I should make an ArrayList inside the constructor (without modify the received parameters that should remain String id and int time), but I haven't understand what He mean.

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• this is my first time asking here, I wanted to create a linked list while sorting it thanks

  - by user2738718

  package practise; public class Node { // node contains data and next public int data; public Node next; //constructor public Node (int data, Node next){ this.data = data; this.next = next; } //list insert method public void insert(Node list, int s){ //case 1 if only one element in the list if(list.next == null && list.data > s) { Node T = new Node(s,list); } else if(list.next == null && list.data < s) { Node T = new Node(s,null); list.next = T; } //case 2 if more than 1 element in the list // 3 elements present I set prev to null and curr to list then performed while loop if(list.next.next != null) { Node curr = list; Node prev = null; while(curr != null) { prev = curr; curr = curr.next; if(curr.data > s && prev.data < s){ Node T = new Node(s,curr); prev.next = T; } } // case 3 at the end checks for the data if(prev.data < s){ Node T = new Node(s,null); prev.next = T; } } } } // this is a hw problem, i created the insert method so i can check and place it in the correct order so my list is sorted This is how far I got, please correct me if I am wrong, I keep inserting node in the main method, Node root = new Node(); and root.insert() to add.

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• Project Euler, Problem 10 java solution now working

  - by Dennis S

  Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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• add database Tablenames to the JList in java

  - by Litecia

  // Declare JList private JList jlstTab, jlstCol; . . . DefaultListModel dlmTables = new DefaultListModel(); DefaultListModel dlmCol = new DefaultListModel(); // Instantiate dlmTables.addElement("kl"); jlstTab= new JList(dlmTables); jlstTab.setSelectedIndex(0); jlstTab.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); . . . . Connect to the database public static void main(String args[]) { DBToolSwing cs = new DBToolSwing("DB Tool Swing"); try DBAccessObject dbAccess1 = new DBAccessObject("jdbc:odbc:JavaClassDSN"); DBAccessObject dbAccess2 = new DBAccessObject(); ResultSet rsTables = dbAccess1.getDatabaseTableNames(); while (rsTables.next()) System.out.println(rsTables.getString("TABLE_NAME")); I need to get the table names from the database, the output shouldn't be printed on the screen, instead I need the output added to the JlstTab so dlmTables.addElement("TABLE_NAME"); Please if someone can help I would appreciate it. Thanks in advance.

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• Sorting arrays in java

  - by user360706

  Write a static method in Java : public static void sortByFour (int[] arr) That receives as a paramater an array full of non-negative numbers (zero or positive) and sorts the array in the following way : In the beginning of the array all the numbers that devide by four without a remainder will appear. After them all the numbers in the array that devide by 4 with a remainder of 1 will appear. After them all the numbers in the array that devide by 4 with a remainder of 2 will appear. In the end of the array all the rest numbers (those who divide by 4 with the remainder 3) will appear. (The order of the numbers in each group doesn't matter) The method must be the most efficient it can. This is what I wrote but unfortunately it doesn't work well... :( public static void swap( int[] arr, int left, int right ) { int temp = arr[left]; arr[left] = arr[right]; arr[right] = temp; } public static void sortByFour( int[] arr ) { int left = 0; int right = ( arr.length - 1 ); int mid = ( arr.length / 2 ); while ( left < right ) { if ( ( arr[left] % 4 ) > ( arr[right] % 4 ) ) { swap( arr, left, right ); right--; } if ( ( arr[left] % 4 ) == ( arr[right] % 4 ) ) left++; else left++; } } Can someone please help me by fixing my code so that it will work well or rewriting it?

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• Most awkward/misleading method in Java Base API ?

  - by JG

  I was recently trying to convert a string literal into a boolean, when the method "boolean Boolean.getBoolean(String name)" popped out of the auto-complete window. There was also another method ("boolean Boolean.parseBoolean(String s)") appearing right after, which lead me to search to find out what were the differences between these two, as they both seemed to do the same. It turns out that what Boolean.getBoolean(String name) really does is to check if there exists a System property (!) of the given name and if its value is true. I think this is very misleading, as I'm definitely not expecting that a method of Boolean is actually making a call to System.getProperty, and just by looking at the method signature, it sure looks (at least to me) like it should be used to parse a String as a boolean. Sure, the javadoc states it clearly, but I still think the method has a misleading name and is not in the right place. Other primitive type wrappers, such as Integer also have a similar method. Also, it doesn't seem to be a very useful method to belong in the base API, as I think it's not very common to have something like -Darg=true. Maybe it's a good question for a Java position interview: "What is the output of Boolean.getBoolean("true")?". I believe a more appropriate place for those methods would be in the System class, e.g., getPropertyAsBoolean; but again, I still think it's unnecessary to have these methods in the base API. It'd make sense to have these in something like the Properties class, where it's very common to do this kind of type conversions. What do you think of all this ? Also, if there's another "awkward" method that you're aware of, please post it. N.B. I know I can use Boolean.valueOf or Boolean.parseBoolean to convert a string literal into a boolean, but I'm just looking to discuss the API design.

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• Java Enumeration of Musical Notes

  - by Crupler

  How would you create an enumeration of the musical notes in Java, with each notes having an octave and then a keyed variable? This is what I have so far... public enum Notes { c, cS, d, dS, e, f, fS, g, gS, a, aS, b; int octave; boolean isPlaying; } So when I access the enums in my code I write something like this... Notes.c.octave = 4; Notes.c.isPlaying = true; Now here is my question: How can I have an isPlaying boolean for each note in each octave? Like so: Notes.c.octave.isPlaying = true; Or would I have to go like: public enum Notes { c1, cS1, d1, dS1, e1, f1, fS1, g1, gS1, a1, aS1, b1 c2, cS2, d2, dS2, e2, f2, fS2, g2, gS2, a2, aS2, b2; etc... boolean isPlaying; } Thank you in advance for taking your time to answer this question!

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• Java/JAXB: Accessing property of object in a list

  - by Mark Lewis

  Hello Using JAXB I've created a series of classes which represent my XML schema. Validating against the schema an XML file has thus become a 'tree' of java objects representing the XML. Now I'd like to access, delete and add an object of one the created types in my tree. If I've got classes' methods arranged like this: RootType class has: public List<FQType> getFq() { // and setter return fq; } FQType class has: public RemapType getRemap() { // and setter return remap; } RemapType class has: public String getSource() { // and setter return source; } What's the most concise way to code reading and writing of the 'source' member of a RemapType instance in an FQType instance with, say, fqtypeID=1, in an array of type RootType (in which RootType instances also each have rootID)? Currently I'm using a for loop Iterator in which is an if rootID = mySelectedRootID. In the if I nest a second for loop Iterator over the contained FQType instances and in that a second if fqTypeID = mySelectedFQTypeID. IE for loop iterator/if statement pairs to recognise the object of desire. With all the bells and whistles this way is nearly 15 lines of code to access a data type - can I do this in one line? Thanks

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• Combining Java hashcodes into a "master" hashcode

  - by Nick Wiggill

  I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java library, I know that it works just fine. Then I have a Boundary class, which holds 2 vectors, "start" and "end" (representing the endpoints of a line). The values of these 2 vectors are what characterize the boundary. /*class Boundary*/ ... public int hashCode() { return 1013 * (start.hashCode()) ^ 1009 * (end.hashCode()); } Here I have attempted to create a good hashCode() for the unique 2-tuple of vectors (start & end) constituting this boundary. My question: Is this hashCode() implementation going to work? (Note that I have used 2 different prime numbers in the latter hashCode() implementation; I don't know if this is necessary but better to be safe than sorry when trying to avoid common factors, I guess -- since I presume this is why primes are popular for hashing functions.)

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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• File mkdirs() method not working in android/java

  - by Leif Andersen

  I've been pulling out my hair on this for a while now. The following method is supposed to download a file, and save it to the location specified on the hard drive. private static void saveImage(Context context, boolean backgroundUpdate, URL url, File file) { if (!Tools.checkNetworkState(context, backgroundUpdate)) return; // Get the image try { // Make the file file.getParentFile().mkdirs(); // Set up the connection URLConnection uCon = url.openConnection(); InputStream is = uCon.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); // Download the data ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } // Write the bits to the file OutputStream os = new FileOutputStream(file); os.write(baf.toByteArray()); os.close(); } catch (Exception e) { // Any exception is probably a newtork faiilure, bail return; } } Also, if the file doesn't exist, it is supposed to make the directory for the file. (And if there is another file already in that spot, it should just not do anything). However, for some reason, the mkdirs() method never makes the directory. I've tried everything from explicit parentheses, to explicitly making the parent file class, and nothing seems to work. I'm fairly certain that the drive is writable, as it's only called after that has already been determined, also that is true after running through it while debugging. So the method fails because the parent directories aren't made. Can anyone tell me if there is anything wrong with the way I'm calling it? Also, if it helps, here is the source for the file I'm calling it in: https://github.com/LeifAndersen/NetCatch/blob/master/src/net/leifandersen/mobile/android/netcatch/services/RSSService.java Thank you

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• Override java methods without affecting parent behaviour

  - by Timmmm

  suppose I have this classes (sorry it's kind of hard to think of a simple example here; I don't want any "why would you want to do that?" answers!): class Squarer { public void setValue(int v) { mV = v; } public int getValue() { return mV; } private int mV; public void square() { setValue(getValue() * getValue()); } } class OnlyOddInputsSquarer extends Squarer { @Override public void setValue(int v) { if (v % 2 == 0) { print("Sorry, this class only lets you square odd numbers!") return; } super.setValue(v); } } auto s = new OnlyOddInputsSquarer(); s.setValue(3); s.square(); This won't work. When Squarer.square() calls setValue(), it will go to OnlyOddInputsSquarer.setValue() which will reject all its values (since all squares are even). Is there any way I can override setValue() so that all the functions in Squarer still use the method defined there? PS: Sorry, java doesn't have an auto keyword you haven't heard about! Wishful thinking on my part.

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• Java Applet 411 Content Length

  - by user1903006

  I am new to Java. I wrote an applet with a gui that sends results (int w and int p) to a server, and I get the "411 Length Required" error. What am I doing wrong? How do you set a Content-Length? This is the method that communicates with the server: public void sendPoints1(int w, int p){ try { String url = "http://somename.com:309/api/Results"; String charset = "UTF-8"; String query = String.format("?key=%s&value=%s", URLEncoder.encode(String.valueOf(w), charset), URLEncoder.encode(String.valueOf(p), charset)); String length = String.valueOf((url + query).getBytes("UTF-8").length); HttpURLConnection connection = (HttpURLConnection) new URL(url + query).openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Content-Length", length); connection.connect(); System.out.println("Responce Code: " + connection.getResponseCode()); System.out.println("Responce Message: " + connection.getResponseMessage()); } catch (Exception e) { System.err.println(e.getMessage()); } }

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• A question on webpage representation in Java

  - by Gemma

  Hello there. I've followed a tutorial and came up with the following method to read the webpage content into a CharSequence public static CharSequence getURLContent(URL url) throws IOException { URLConnection conn = url.openConnection(); String encoding = conn.getContentEncoding(); if (encoding == null) { encoding = "ISO-8859-1"; } BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(),encoding)); StringBuilder sb = new StringBuilder(16384); try { String line; while ((line = br.readLine()) != null) { sb.append(line); sb.append('\n'); } } finally { br.close(); } return sb; } It will return a representation of the webpage specified by the url. However,this representation is hugely different from what I use "view page source" in my Firefox,and since I need to scrape data from the original webpage(some data segement in the original "view page source" file),it will always fail to find required text on this Java representation. Did I go wrong somewhere?I need your advice guys,thanks a lot for helping!

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• Java SOAP - Need help on Body and ChildElement manipulation

  - by techventure

  Hi guys I'm trying to write some code in java to learn more about coding with WSDL and SOAP. I've been able to build up a BodyElement for a given namespace. But when i come to adding the childElements I'm runnig intp problems. For example given :'<'to:checkAccount xmlns:to="http://foo" '<'to:id test' <'/to:id '<'to:password test '<'/to:password '<'to:checkAccount " I'm able to set the bodyElement(to:checkAccount), but when i try to add the childElements (to:id, to:password) , the childElement needs to have the "to" prefix otherwise it won't work. ie. sf = SOAPFactory.newInstance(); Name childName = sf.createName("id"); SOAPElement symbol = bodyElement.addChildElement(childName); this doesn't work since it doesn't have the "to" prefix to id and password. I cannot do Name childName = sf.createName("id","to",null); as it gives me an error saying wrong namespace... can someone tell me how i can add to:id and to:password to to:checkAccount ?

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• Getting a "for each" loop in Java to run in different order everytime

  - by R Stokes

  Hi, Basically my problem is that I'm trying to write a method that finds a random path in a graph of strings, which takes as it's parameters a start string, an integer length and a Vector of strings that will store the path. I'm attempting to do this by first adding the starting string to our blank vector, recursing through its neighbors until the vector's length (not including the start node) is the same as the integer length specified in the parameters. I've provided my code so far here: public Vector<String> findRandomPathFrom(String n, int len, Vector<String> randomPath){ randomPath.add(n); if (randomPath.size() == len + 1) return randomPath; for (String m : this.neighbours(n)){ if (!randomPath.contains(m) && findRandomPathFrom(m, len, randomPath) != null) return randomPath; } path.setSize(path.size() - 1); return null; } It seems to be working fine, returning a path with exactly the number of strings specified after the given start string. However, for any given starting string it generates the EXACT same path everytime, which kind of defeats the purpose of it being a random path generator. I'm guessing this problem is related to my "for each" loop, which loops through all the neighbouring strings of your current string. It seems to just be going with the first string in the neighbours vector every single time. Can anyone help me fix this problem so that it will choose a random neighbour instead of going in order? tl;dr - Any way of getting a "for each" loop in java to process a collection in a random order as oppoosed to start-to-finsih? Thanks in advance

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• Reading lines of data from text files using java

  - by razshan

  I have a text file with x amount of lines. each line holds a integer number. When the user clicks a button, an action is performed via actionlistener where it should list all the values as displayed on the text file. However, right now I have linenum set to 10 implying I already told the code that just work with 10 lines of the text file. So, if my text file has only 3 rows/lines of data...it will list those lines and for rest of the other 7 lines, it will spit out "null". I recall there is a way to use ellipsis to let the program know that you don't know the exact value but at the end it calculates it based on the given information. Where my given information will the number of lines with numbers(data). Below is part of the code. private class thehandler implements ActionListener{ public void actionPerformed(ActionEvent event){ BufferedReader inputFile=null; try { FileReader freader =new FileReader("Data.txt"); inputFile = new BufferedReader(freader); String MAP = ""; int linenum=10; while(linenum > 0) { linenum=linenum-1; MAP = inputFile.readLine();//read the next line until the specfic line is found System.out.println(MAP); } } catch( Exception y ) { y.printStackTrace(); } }}

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• java array pass by reference does not work?

  - by stdnoit

  guys i thought almost all language including java pass array into function as reference (modifiable) but somehow it does not work here. and the testArray is still 1,2,3 with size of 3 strange enough, when if i change result[i] = 2 to a[1] =2; it work . it did pass by reference what is wrong with this code? at the end, i had a = result; (which update the a). did result get removed from stack. that is why a still get to the original a ? i am confused. thanks class Test { public static void main(String[] args) { int[] testArray = {1,2,3}; equalize(testArray, 6); System.out.println("test Array size :" + testArray.length); for(int i = 0; i < testArray.length; i++) System.out.println(testArray[i]); } public static void equalize(int[] a, int biggerSize) { if(a.length > biggerSize) throw new Error("Array size bigger than biggerSize"); int[] result = new int[biggerSize]; // System.arraycopy(a, 0, result, 0, a.length); // int array default value should be 0 for(int i = 0; i < biggerSize; i++) result[i] = 2; a = result; } }

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• Java Recursion Triangle Standing on Tip

  - by user1629075

  I was wondering how to create triangle out of asterisks on its tip rather than on its base. I have the code for making it stand on its base: public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = printTriangle(count - 1); p = p + "*"; System.out.print(p); System.out.print("\n"); return p; } But then I'm stuck on how to have the greatest number of stars on the top, and then the next least, and so on. I was thinking something along the terms of having (count - p) to have the input of rows be subtracted from the amount of decrease, but then i was confused by this idea because p is string. EDIT: I tried changing the position of printTriangle(count - 1) using my original method without iterations and got 1 star per each line; how can I fix this? public class triangles { public static void main(String[] args) { printTriangle(5); } public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = ""; p = p + "*"; System.out.print(p); System.out.print("\n"); p = printTriangle(count - 1); return p; } }

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• java setting resolution and print size for an Image

  - by Ingrid

  I wrote a program that generates a BufferedImage to be displayed on the screen and then printed. Part of the image includes grid lines that are 1 pixel wide. That is, the line is 1 pixel, with about 10 pixels between lines. Because of screen resolution, the image is displayed much bigger than that, with several pixels for each line. I'd like to draw it smaller, but when I scale the image (either by using Image.getScaledInstance or Graphics2D.scale), I lose significant amounts of detail. I'd like to print the image as well, and am dealing with the same problem. In that case, I am using this code to set the resolution: HashPrintRequestAttributeSet set = new HashPrintRequestAttributeSet(); PrinterResolution pr = new PrinterResolution(250, 250, ResolutionSyntax.DPI); set.add(pr); job.print(set); which works to make the image smaller without losing detail. But the problem is that the image is cut off at the same boundary as if I hadn't set the resolution. I'm also confused because I expected a larger number of DPI to make a smaller image, but it's working the other way. I'm using java 1.6 on Windows 7 with eclipse.

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• Java RSA Encrypt using .NET XML Key File - need help

  - by badMonkey

  In .net I have generated the following public key file: <RSAKeyValue> <Modulus>xTSiS4+I/x9awUXcF66Ffw7tracsQfGCn6g6k/hGkLquHYMFTCYk4mOB5NwLwqczwvl8HkQfDShGcvrm47XHKUzA8iadWdA5n4toBECzRxiCWCHm1KEg59LUD3fxTG5ogGiNxDj9wSguCIzFdUxBYq5ot2J4iLgGu0qShml5vwk=</Modulus> <Exponent>AQAB</Exponent> .NET is happy to encrypt using it's normal methods. I am trying to use this key to encode a string in Java and am running into an Arithmetic problem (exception) when I attempt to encrypt the string. The following is the code I am using to encrypt: byte[] modulusBytes = Base64.decode(this.getString(R.string.public_key_modulus)); byte[] exponentBytes = Base64.decode(this.getString(R.string.public_key_exponent)); BigInteger modulus = new BigInteger( modulusBytes ); BigInteger exponent = new BigInteger( exponentBytes); RSAPublicKeySpec rsaPubKey = new RSAPublicKeySpec(modulus, exponent); KeyFactory fact = KeyFactory.getInstance("RSA"); PublicKey pubKey = fact.generatePublic(rsaPubKey); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal( new String("big kitty dancing").getBytes() ); It is the final line in the code block that fails. I have looked at numerous examples and this is the best I could come up with. If it is not obvious, the R.string.public_key_modulus is a copy/paste of the text in the Modulus element, same applies for exponent.

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