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  • Java/Android get array from xml

    - by Ashley
    I have a list of longitude and longitude points in an xml file that is used throughout my application. I find my self repeating this code to get points often and think there must be a better way? String[] mTempArray = getResources().getStringArray(R.array.stations); int len = mTempArray.length; mStationArray = new ArrayList<Station>(); for(int i = 0; i < len; i++){ Station s = new Station(); String[] fields = mTempArray[i].split("[\t ]"); s.setValuesFromArray(fields); Log.i("ADD STATION", ""+s); mStationArray.add(s); } XML is in the format of: <?xml version="1.0" encoding="utf-8"?> <resources> <array name="stations"> <item> <name>Station name</name> <longitude>1111111</longitude> <latitude>11111</latitude> <code>1</code> </item> And another (possible) problem is that to get just one station I have to get all of them and pull the one I want from the array. Is this going to be considerably slower? Can I make this array consistent throughout the app? (But keeping the separate Intent methodology)

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  • How to end a thread in java?

    - by beagleguy
    hi all, I have 2 pools of threads ioThreads = (ThreadPoolExecutor)Executors.newCachedThreadPool(); cpuThreads = (ThreadPoolExecutor)Executors.newFixedThreadPool(numCpus); I have a simple web crawler that I want to create an iothread, pass it a url, it will then fetch the url and pass the contents over to a cpuThread to be processed and the ioThread will then fetch another url, etc... At some point the IO thread will not have any new pages to crawl and I want to update my database that this session is complete. How can I best tell when the threads are all done processing and the program can be ended?

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  • Java Matrix Transpose strangeness going on

    - by user1459976
    ok so im making my own Matrix class. and i have a transpose method that transposes a matrix. this is the block in the main method Matrix m1 = new Matrix(4,2); m1.fillMatrix(1,2,3,4,5,6,7,8); System.out.println("before " + m1.toString()); m1.transpose(); System.out.println("after " + m1.toString()); this is where it gets messed up, at m1.transpose(); in the transpose() method public Matrix transpose() { if(isMatrix2) { Matrix tempMatrix = new Matrix(row, col); // matrix2 contents are emptied once this line is executed for(int i=0; i < row; i++) { for(int j=0; j < col; j++) tempMatrix.matrix2[i][j] = matrix2[i][j]; } so for some reason, the tempMatrix.matrix2 has the same id as this.matrix2. so when the codes executes Matrix tempMatrix = new Matrix(row,col); then the contents of this.matrix2 is emptied. anyone know what might be going on here?

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  • java: assigning object reference IDs for custom serialization

    - by Jason S
    For various reasons I have a custom serialization where I am dumping some fairly simple objects to a data file. There are maybe 5-10 classes, and the object graphs that result are acyclic and pretty simple (each serialized object has 1 or 2 references to another that are serialized). For example: class Foo { final private long id; public Foo(long id, /* other stuff */) { ... } } class Bar { final private long id; final private Foo foo; public Bar(long id, Foo foo, /* other stuff */) { ... } } class Baz { final private long id; final private List<Bar> barList; public Baz(long id, List<Bar> barList, /* other stuff */) { ... } } The id field is just for the serialization, so that when I am serializing to a file, I can write objects by keeping a record of which IDs have been serialized so far, then for each object checking whether its child objects have been serialized and writing the ones that haven't, finally writing the object itself by writing its data fields and the IDs corresponding to its child objects. What's puzzling me is how to assign id's. I thought about it, and it seems like there are three cases for assigning an ID: dynamically-created objects -- id is assigned from a counter that increments reading objects from disk -- id is assigned from the number stored in the disk file singleton objects -- object is created prior to any dynamically-created object, to represent a singleton object that is always present. How can I handle these properly? I feel like I'm reinventing the wheel and there must be a well-established technique for handling all the cases.

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  • How are ambigous methods resolved in java ?

    - by Jijoy
    Hi, I have a question. package org.study.algos; public class Study { public static void main(String[] args) { A a = new A(); a.m1(null); } } class A { public void m1(String s) { System.out.println("String"); System.out.println(s); } public void m1(Object obj) { System.out.println("Object"); System.out.println(obj); } } Here, the output is String null Why does the JVM resolve the method to one with a String argument? Thanks in advance J

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  • implementing keepalives with Java

    - by Bilal
    Hi All, I am biulding a client-server application where I have to implement a keepalive mechanism in order to detect that the client has crashed or not. I have separate threads on both client and server side. the client thread sends a "ping" then sleeps for 3 seconds, while the server reads the BufferedInput Stream and checks whether ping is received, if so it makes the ping counter eqauls zero, else it increments the counter by +1, the server thread then sleeps for 3 seconds, if the ping counter reaches 3, it daclares the client as dead. The problem is that when the server reads the input stream, its a blocking call, and it blocks untill the next ping is received, irrespective of how delayed it is, so the server never detects a missed ping. any suggestions, so that I can read the current value of the stream and it doesn't block if there is nothing on the incoming stream. Thanks,

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  • What is an Enterprise Java Bean really?

    - by HDave
    On the Tomcat FAQ it says: "Tomcat is not an EJB server. Tomcat is not a full J2EE server." But if I: use Spring to supply an application context annotate my entities with JPA annotations (and use Hibernate as a JPA provider) configure C3P0 as a connection pooling data source annotate my service methods with @Transactional (and use Atomikos as JTA provider) Use JAXB for marshalling and unmarshalling and possibly add my own JNDI capability then don't I effectively have a JEE application server? And then aren't my beans EJBs? Or is there some other defining characteristic? What is it that a JEE compliant app server gives you that you can't easily/readily get from Tomcat with some 3rd party subsystems?

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  • How does file creation work in Java

    - by Ankur
    I am trying to create a file using File newFile = new File("myFile"); However no file called "myFile" is created. This is within a Web application Project i.e. proper form to be pakaged as a WAR but I am calling it as part of a main method (just to see how this works). How can I make it so that a new file is created at a location relative to the current one i.e not have to put in an absolute path.

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  • Java: refactoring static constants

    - by akf
    We are in the process of refactoring some code. There is a feature that we have developed in one project that we would like to now use in other projects. We are extracting the foundation of this feature and making it a full-fledged project which can then be imported by its current project and others. This effort has been relatively straight-forward but we have one headache. When the framework in question was originally developed, we chose to keep a variety of constant values defined as static fields in a single class. Over time this list of static members grew. The class is used in very many places in our code. In our current refactoring, we will be elevating some of the members of this class to our new framework, but leaving others in place. Our headache is in extracting the foundation members of this class to be used in our new project, and more specifically, how we should address those extracted members in our existing code. We know that we can have our existing Constants class subclass this new project's Constants class and it would inherit all of the parent's static members. This would allow us to effect the change without touching the code that uses these members to change the class name on the static reference. However, the tight coupling inherent in this choice doesn't feel right. before: public class ConstantsA { public static final String CONSTANT1 = "constant.1"; public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } after: public class ConstantsA extends ConstantsB { public static final String CONSTANT1 = "constant.1"; } public class ConstantsB { public static final String CONSTANT2 = "constant.2"; public static final String CONSTANT3 = "constant.3"; } In our existing code branch, all of the above would be accessible in this manner: ConstantsA.CONSTANT2 I would like to solicit arguments about whether this is 'acceptable' and/or what the best practices are.

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  • When can Java produce a NaN (with specific code question)

    - by Brent
    I'm a bit perplexed by some code I'm currently writing. I am trying to preform a specific gradient descent (main loop included below) and depending on the initial conditions I will alternatively get good looking results (perhaps 20% of the time) or everything becomes NaN (the other 80% of the time). However it seems to me that none of the operations in my code could produce NaN's when given honest numbers! My main loop is: // calculate errors delta = m1 + m2 - M; eta = f1 + f2 - F; for (int i = 0; i < numChildren; i++) { epsilon[i] = p[i]*m1+(1-p[i])*m2+q[i]*f1+(1-q[i])*f2-C[i]; } // use errors in gradient descent // set aside differences for the p's and q's float mDiff = m1 - m2; float fDiff = f1 - f2; // first update m's and f's m1 -= rate*delta; m2 -= rate*delta; f1 -= rate*eta; f2 -= rate*eta; for (int i = 0; i < numChildren; i++) { m1 -= rate*epsilon[i]*p[i]; m2 -= rate*epsilon[i]*(1-p[i]); f1 -= rate*epsilon[i]*q[i]; f2 -= rate*epsilon[i]*(1-q[i]); } // now update the p's and q's for (int i = 0; i < numChildren; i++) { p[i] -= rate*epsilon[i]*mDiff; q[i] -= rate*epsilon[i]*fDiff; } This behavior can be seen when we have rate = 0.01; M = 30; F = 30; C = {15, 25, 35, 45}; with the p[i] and q[i] chosen randomly uniformly between 0 and 1, m1 and m2 chosen randomly uniformly to add to M, and f1 and f2 chosen randomly uniformly to add up to F. Does anyone see anything that could create these NaN's?

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  • What are the alternatives for Java authentication?

    - by Crusader
    Preferably something that integrates well with a Flex front end. Yes the Spring Security guys say this is possible, but all examples seem to use legacy jsp tag libraries making them half useless as examples. I don't want to spend a month setting up and learning how to use a security tool. I would like a tool which supports using annotations (@RolesAllowed etc), MINIMAL XML, and 'remember-me' features (not cookie based). Apache Shiro seems to support Flex/Silverlight/Swing as well but I'd like to know if there are any other alternatives that are NOT container specific.

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  • Why is Java String indexOf failing?

    - by Binaryrespawn
    Hi all, this must be quite simple but I am having great difficulty. You see I am trying to find a string within another string as follows. e = input.indexOf("-->"); s = input.indexOf("<!--"); input = input.replace(input.substring(s, e + 3), " "); The integers e and s are returning -1 in that it was not found and this is causing the replace method to fail. The test string I am using is "Chartered Certified<!--lol--> Accountants (ACCA)". I tried to creat a new string object and pass in the string as an argument as follows e=input.indexOf(new String("<!--")); This yielded the same result. Any ideas ?

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  • Java String object creation

    - by Ajay
    Hi, 1) What is difference in thers two statements: String s1 = "abc"; and String s1 = new String("abc") 2) as i am not using new in first statement, how string object will be created Thanks

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  • Java - JPA - @Version annotation

    - by Yatendra Goel
    I am new to JPA. I am cofused about the @Version annotation. How it works? I have googled it and found various answers whose extract is as follows: JPA uses a version field in your entities to detect concurrent modifications to the same datastore record. When the JPA runtime detects an attempt to concurrently modify the same record, it throws an exception to the transaction attempting to commit last. But still I am not sure how it works? ================================================================================== Also as from the following lines: You should consider version fields immutable. Changing the field value has undefined results. Does it mean that we should declare our version field as final

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  • StringBufferInputStream Question in Java

    - by JJG
    I want to read an input string and return it as a UTF8 encoded string. SO I found an example on the Oracle/Sun website that used FileInputStream. I didn't want to read a file, but a string, so I changed it to StringBufferInputStream and used the code below. The method parameter jtext, is some Japanese text. Actually this method works great. The question is about the deprecated code. I had to put @SuppressWarnings because StringBufferInputStream is deprecated. I want to know is there a better way to get a string input stream? Is it ok just to leave it as is? I've spent so long trying to fix this problem that I don't want to change anything now I seem to have cracked it. @SuppressWarnings("deprecation") private String readInput(String jtext) { StringBuffer buffer = new StringBuffer(); try { StringBufferInputStream sbis = new StringBufferInputStream (jtext); InputStreamReader isr = new InputStreamReader(sbis, "UTF8"); Reader in = new BufferedReader(isr); int ch; while ((ch = in.read()) > -1) { buffer.append((char)ch); } in.close(); return buffer.toString(); } catch (IOException e) { e.printStackTrace(); return null; } }

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  • permute data for a HashMap in Java

    - by tuxou
    hi i have a linkedhashmap and i need to permute (change the key of the values) between 2 random values example : key 1 value 123 key 2 value 456 key 3 value 789 after random permutation of 2 values key 1 value 123 key 2 value 789 key 3 value 456 so here I permuted values between key 2 and key 3 thank you; sample of the code of my map : Map map = new LinkedHashMap(); map =myMap.getLinkedHashMap(); Set key = map.keySet(); for(Iterator it = cles.iterator(); it.hasNext();) { Integer cle = it.next(); ArrayList values = (ArrayList)map.get(cle);//an arrayList of integers int i = 0; while(i < values.size()) { //i donno what to do here i++; } }

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  • java overloaded method

    - by Sean Nguyen
    Hi, I have an abstract template method: class abstract MyTemplate { public void something(Object obj) { doSomething(obj) } protected void doSomething(Object obj); } class MyImpl extends MyTemplate { protected void doSomething(Object obj) { System.out.println("i am dealing with generic object"); } protected void doSomething(String str) { System.out.println("I am dealing with string"); } } public static void main(String[] args) { MyImpl impl = new MyImpl(); impl.something("abc"); // --> this return "i am dealing with generic object" } How can I print "I am dealing with string" w/o using instanceof in doSomething(Object obj)? Thanks,

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  • Relating text fields to check boxes in Java

    - by Finzz
    This program requires the user to login and request a database to access. The program then gets a connection object, searches through the database storing the column names into a vector for later use. The problem comes with implementing text fields to allow the user to search for specific values within the database. I can get the check boxes and text fields to appear using a gridlayout and add them to a panel. How do I relate the text fields to their appropriate check box? I've tried adding them to a vector, but then they can't also be added to the panel as well. I've searched for a way to name the text fields as the loop cycles through the column names, but it seems impossible to do without having them declared ahead of time. This can't be done either, as it's impossible to determine the attributes that the user will request. I just need to be able to know the names of the text fields so I can test to see if the user entered information and perform the necessary logic. Let me know if you have to see the rest of the code to give an answer, but hopefully you get the general idea of what I'm trying to accomplish. Picture of UI: try { ResultSet r2 = con.getMetaData().getColumns("", "", rb.getText(), ""); colNames1 = new Vector<String>(); columns1 = new Vector<JCheckBox>(); while (r2.next()) { colNames1.add(r2.getString(4)); JCheckBox cb = new JCheckBox(r2.getString(4)); JTextField tf = new JTextField(10); columns1.add(cb); p3.add(cb); p3.add(tf); } }

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  • Creating a New Reverse Java Array

    - by mandir08
    Given an array of ints length 3, return a new array with the elements in reverse order, so {1, 2, 3} becomes {3, 2, 1}. public int[] reverse3(int[] nums) { int[] values = new int[3]; for(int i=0; i<=nums.length-1; i++) { for(int j=nums.length-1; j>=0; j--) { values[i]=nums[j]; } } return values; } I cant get this to work properly, usually the last int in the array, becomes every single int in the new array

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