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  • directory traversal in Java using different regular and enhanced for loops

    - by user3245621
    I have this code to print out all directories and files. I tried to use recursive method call in for loop. With enhanced for loop, the code prints out all the directories and files correctly. But with regular for loop, the code does not work. I am puzzled by the difference between regular and enhanced for loops. public class FileCopy { private File[] childFiles = null; public static void main(String[] args) { FileCopy fileCopy = new FileCopy(); File srcFile = new File("c:\\temp"); fileCopy.copyTree(srcFile); } public void copyTree(File file){ if(file.isDirectory()){ System.out.println(file + " is a directory. "); childFiles = file.listFiles(); /*for(int j=0; j<childFiles.length; j++){ copyTree(childFiles[j]); } This part is not working*/ for(File a: childFiles){ copyTree(a); } return; } else{ System.out.println(file + " is a file. "); return; } } }

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  • Java generics conversion

    - by LittleGreenMan
    I have build a generic datacontainer and now I want to manipulate data depending on their type. However, I get an incompatable types warning. What am I doing wrong? Type _Value; public void set(Type t) throws Exception { if (_Value instanceof Integer && t instanceof Integer) { _Value = (((Integer) t - _MinValue + getRange()) % getRange()) + _MinValue; } else if (_Value instanceof Boolean && t instanceof Boolean) { _Value = t; } else throw new Exception("Invalid type"); }

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  • Java > SimpleDateFormat > Month + 1 Why ?

    - by Natim
    Hello, I am using SimpleDateFormat to display a Calendar like this : public String getDate() { String DATE_FORMAT = "EEEE, dd/MM/yyyy HH:mm:ss"; SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT); System.err.println(date.getTime().getMonth()); return sdf.format(date.getTime()); } The shell returns 6 and the display : mardi, 06/07/2010 12:44:52 It can't be possible ? Why ? Thanks

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  • Negative look ahead java

    - by venu
    I need an expression to capture a string like this "A"[A string that is NOT atleast 5 and atmost 6 digits]"B", In other words capture anything that is NOT the following A[0-9][0-9][0-9][0-9][0-9]B A[0-9][0-9][0-9][0-9][0-9][0-9]B I have tried the negative look ahead regex = "a((?![0-9]{5,6}).)*d" ; But it fails to capture all scenarios. Please help venu

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  • Trimming byte array when converting byte array to string in Java/Scala

    - by prosseek
    Using ByteBuffer, I can convert a string into byte array: val x = ByteBuffer.allocate(10).put("Hello".getBytes()).array() > Array[Byte] = Array(104, 101, 108, 108, 111, 0, 0, 0, 0, 0) When converting the byte array into string, I can use new String(x). However, the string becomes hello?????, and I need to trim down the byte array before converting it into string. How can I do that? I use this code to trim down the zeros, but I wonder if there is simpler way. def byteArrayToString(x: Array[Byte]) = { val loc = x.indexOf(0) if (-1 == loc) new String(x) else if (0 == loc) "" else new String(x.slice(0,loc)) }

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  • java.lang.classcastExcption

    - by Tara Singh
    Hi, I have an array list of objects in my application. private static ArrayList<Player> userList=new ArrayList<Player>(); In my application, I am converting this list to byte array and then sending it to other clients. At client When I am trying to cast it back to the ArrayList, its giving me casting error. I am doing this in client side after receiving this list as byte array: ArrayList<Player> pl = (ArrayList<Player>) toObject(receivedByteArray); where toObject is my function to convert the byte array to object; Any Suggestions please !!! Thanks.

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  • Regular expression one or more times JAVA

    - by user1381564
    Hi i am trying to match a string against a pattern this is the possible string signal CS, NS, dl: stateType := writeOrRead0; signal CS, pS : stateType := writeOrRead0; signal dS : stateType := writeOrRead0; i am only concerned with the pattern as far as the first colon. but the number of signals define can be more than one it could be three or four even this is the regular expression i have ^signal\\s*(\\w+),*\\s*(\\w+)\\s*: it will pick up the second two signal but and for the second one it picks up CS and pS and but the d and S in the next signal when i use matcher.group() come up seperately Can anyone give me an expression that will pick up all signal names whether there is one two three or more?

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  • Java: Protected classes?

    - by incrediman
    I'd like to be able to have two protected classes in my package. That is, I do not want files outside of my package to see them as visible - they will be for internal use within the package only. How can I do this?

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  • synchronizing reads to a java collection

    - by jeff
    so i want to have an arraylist that stores a series of stock quotes. but i keep track of bid price, ask price and last price for each. of course at any time, the bid ask or last of a given stock can change. i have one thread that updates the prices and one that reads them. i want to make sure that when reading no other thread is updating a price. so i looked at synchronized collection. but that seems to only prevent reading while another thread is adding or deleting an entry to the arraylist. so now i'm onto the wrapper approach: public class Qte_List { private final ArrayList<Qte> the_list; public void UpdateBid(String p_sym, double p_bid){ synchronized (the_list){ Qte q = Qte.FindBySym(the_list, p_sym); q.bid=p_bid;} } public double ReadBid(String p_sym){ synchronized (the_list){ Qte q = Qte.FindBySym(the_list, p_sym); return q.bid;} } so what i want to accomplish with this is only one thread can be doing anything - reading or updating an the_list's contents - at one time. am i approach this right? thanks.

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  • Java Web Server with Jetty - TCP Connections Taking Long

    - by daysleeper
    I have an application with fairly high traffic (20K req/min) running on the JVM with a Jetty servlet container on Ubuntu. Below is my Jetty configuration: 10 20 2000 2 When I analyze the network traffic, I realize that sometimes it is taking long to establish TCP connections on the port that Jetty is running. The long connections are varying between 3.0s and 9.0s. The port is configured to accept MAX number of TCP connections. Do you know what might be causing the delay in accepting connections? Thanks

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  • Help making a button open another app with Java/Android

    - by user569503
    I am trying to learn to make a simple app that opens a couple of other apps to eliminate the need for another apps. I just can't figure it out. From reading here and other places it seems this should work. Button batteryhistory = (Button)findViewById(R.string.BatteryHistoryButtonDialog); batteryhistory.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Intent i = new Intent(); ComponentName n = new ComponentName("com.android.settings", "com.android.settings.BatteryHistory"); i.setComponent(n); startActivity(i); Thanks so much for the help :D

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  • can this keyword be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • Java: Converting UTF 8 to String

    - by kujawk
    When I run the following program: public static void main(String args[]) throws Exception { byte str[] = {(byte)0xEC, (byte)0x96, (byte)0xB4}; String s = new String(str, "UTF-8"); } on Linux and inspect the value of s in jdb, I correctly get: s = "ì–´" on Windows, I incorrectly get: s = "?" My byte sequence is a valid UTF-8 character in Korean, why would it be producing two very different results?

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  • Java Thread Message Passing

    - by pkulak
    I'm writing an Android app. I have a main method, which creates and runs a new Thread using an anonymous inner Runnable class. The run() method, when it's done, calls a method on it's parent class (in the main thread) that calls notifyDataSetChanged() so that the main thread can redraw the new data. This is causing all kinds of trouble (ViewRoot$CalledFromWrongThreadException). The thing is, this method being called from the worker thread is on the class that's created in the UI thread. Shouldn't that be running on the UI thread? Or am I missing something? Here's some code about what I'm talking about: public class Mealfire extends Activity { @Override public void onCreate(Bundle icicle) { (new Thread() { public void run() { // Do a bunch of slow network stuff. update(); } }).start(); } private void update() { myAdapter.notifyDatasetChanged(); } }

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  • What is Java Message Service (JMS) for?

    - by Daniel
    I am currently evaluating JMS and I don't get what I could use it for. Currently, I believe this would be a Usecase: I want to create a SalesInvoice PDF and print it when an SalesOrder leaves the Warehouse, so during the Delivery transaction I could send a transactional print request which just begins when the SalesOrder transaction completes successfully. Now I found out most JMS products are standalone server. Why would a need a Standalone Server for Message Processing, vs. e.g. some simple inproc processing with Quartz scheduler? How does it interact with my application? Isn't it much too slow? What are Usecases you already implemented successfully?

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Reverse a given sentence in java

    - by giri
    This was the question asked me in amazon interview. I could not solve the problem properly, Write a program to reverse a given sentence like "This is interview question" the output must be "question interview is this".Can any tell me how to get this done? Thanks in advance

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  • Big-Oh running time of code in Java (are my answers accurate

    - by Terry Frederick
    the Method hasTwoTrueValues returns true if at least two values in an array of booleans are true. Provide the Big-Oh running time for all three implementations proposed. // Version 1 public boolean has TwoTrueValues( boolean [ ] arr ) { int count = 0; for( int i = 0; i < arr. length; i++ ) if( arr[ i ] ) count++; return count >= 2; } // Version 2 public boolean hasTwoTrueValues( boolean [ ] arr ) { for( int i = 0; i < arr.length; i++ ) for( int j = i + 1; j < arr.length; j++ ) if( arr[ i ] && arr[ j ] ) return true; } // Version 3 public boolean hasTwoTrueValues( boolean [ ] arr ) { for( int i = 0; i < arr.length; i++ if( arr[ i ] ) for( int j = i + 1; j < arr.length; j++ ) if( arr[ j ] ) return true; return false; } For Version 1 I say the running time is O(n) Version 2 I say O(n^2) Version 3 I say O(n^2) I am really new to this Big Oh Notation so if my answers are incorrect could you please explain and help.

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  • Localized text in Java

    - by Eager Learner
    My requirement is to display localized text messages in a J2EE web application. I know J2EE provides very good support for this. My question is what is the practice followed to have the localized messages stored to be used by the application. If I want to display Japanese / Chinese kind of messages which are not like English like char sets how do we get that messages/text into the properties files or Database tables.

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  • Creating a 2d matrix from an array (java)

    - by anna
    I'm supposed to write a method that creates a 2d matrix from an array, for instance: ({1, 2, 3, 4}, 3) should return the matrix {{1, 2, 3}, {4}} public class Matrix { public static int[][]toM(int[] array, int a) { int[][]matrix = new int [(array.length + a- 1)/ a][a]; for (int i = 0; i < array.length; i++){ int value = array[i]; value = value++; for (int row = 0; row < (array.length + a- 1)/a; row++) { for (int col = 0; col < a; col++) { matrix[row][col]= value++; } } } return matrix; } } I'm getting [[4, 5, 6], [7, 8, 9]]?

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  • Help using recursion in Java

    - by Mercer
    I have a class Group. In the class I have two fields, idGroup IdGroupGroup. Groups may be part of other groups. My class Group is defined in a HashMap<Integer,Integer>; the key is IdGroupGroup and value is idGroup. I want to search the map for a particular idGroup; can I use recursion to do this?

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