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  • Add elements to Arraylist and it replaces all previous elements in Java

    - by pie154
    I am adding elements to a ArrayList and it adds the first one correctly but then when I add any subsequent elements it wipes replaces the other elements with the value form the most recently added and adds a new element to the ArrayList. I ran test using arraylist and ints and even another created class and it worked perfectly but soemthing about the custon class i am using here causes problems. The code for the array list is public static void main(String args[]){ List<BasicEvent> list = new ArrayList<BasicEvent>(); list.add(new BasicEvent("Basic", "Door", 9, 4444, new Date(12,04,2010), new Time(12,04,21), 1, 0.98, 0)); list.add(new BasicEvent("Composite", "Door", 125, 4444, new Date(12,04,2010), new Time(12,04,20), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Door", 105, 88, new Date(12,04,2010), new Time(12,05,23), 1, 0.98, 0)); list.add(new BasicEvent("Basic", "Door", 125, 12, new Date(12,04,2010), new Time(12,05,28), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Door", 129, 25, new Date(12,04,2010), new Time(12,05,30), 1, 0.98, 0)); list.add(new BasicEvent("Basic", "Door", 125, 63, new Date(12,04,2010), new Time(12,04,20), 1, 0.98, 1)); list.add(new BasicEvent("Basic", "Detect", 127, 9, new Date(12,04,2010), new Time(12,05,29), 1, 0.98, -1)); for(int i=0;i<list.size();i++) {System.out.println("list a poition " + i + " is " + BasicEvent.basicToString(list.get(i)));} And the code for the custom class basicEvent is public class BasicEvent { public static String Level; public static String EType; public static double xPos; public static double yPos; public static Date date; public static Time time; public static double Rlb; public static double Sig; public static int Reserved; public BasicEvent(String L, String E, double X, double Y, Date D, Time T, double R, double S, int Res){ Level = L; EType = E; xPos = X; yPos = Y; date = D; time = T; Rlb = R; Sig = S; Reserved = Res; }; public static String basicToString(BasicEvent bse){ String out = bse.getLevel() + ";" + bse.getEtype() + ";" + bse.getxPos() + ";" + bse.getyPos() + ";" + bse.getDate().dateAsString() + ";" + bse.getTime().timeAsString() + ";" + bse.getRlb() + ";" + bse.getSig() + ";" + bse.getReserved(); return out; }

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  • java casting confusion

    - by Stardust
    Could anyone please tell me why the following casting is resulting in compile time error: Long l = (Long)Math.pow(5,2); But why not the following: long l = (long)Math.pow(5,2);

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  • How to simulate an unhandled exception in Java

    - by Martin Wiboe
    Hi, I am creating some multi-threaded code, and I have created a JobDispatcher class that creates threads. I want this object to handle any unhandled exceptions in the worker threads, and so I am using Thread.setUncaughtExceptionHandler(this); Now, I would like to test this functionality - how can I generate an unhandled exception in the run() method of my worker object? Thanks, Martin

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  • java serialization and final fields

    - by mdma
    I have an class defining an immutable value type that I now need to serialize. The immutability comes from the final fields which are set in the constructor. I've tried serializing, and it works (surprisingly?) - but I've no idea how. Here's an example of the class public class MyValueType implements Serializable { private final int value; private transient int derivedValue; public MyValueType(int value) { this.value = value; this.derivedValue = derivedValue(value); } // getters etc... } Given that the class doesn't have a no arg constructor, how can it be instantiated and the final field set? (An aside - I noticed this class particularly because IDEA wasn't generating a "no serialVersionUID" inspection warning for this class, yet successfully generated warnings for other classes that I've just made serializable.)

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  • Java: how to get all subdirs recursively?

    - by HH
    Before debugging the late-hour-out-of-bound-recursive-function: is there a command to get subdirs? giveMeSubDirs(downToPath)? // WARNING: RECURSION out of bound public HashSet<FileObject> getAllDirs(String path) { HashSet<FileObject> checkedDirs = new HashSet<FileObject>(); HashSet<FileObject> allDirs = new HashSet<FileObject>(); String startingPath = path; File fileThing = new File(path); FileObject fileObject = new FileObject(fileThing); for (FileObject dir : getDirsInDir(path)) { // SUBDIR while ( !checkedDirs.contains(dir) && !(getDirsInDir(dir.getFile().getParent()).size() == 0)) { // DO NOT CHECK TOP DIRS if any bottom dir UNCHECKED! while ( uncheckedDirsOnLevel(path, checkedDirs).size() > 0) { while (getDirsInDir(path).size() == 0 || (numberOfCheckedDirsOnLevel(path, checkedDirs)==getDirsInDir(path).size())) { allDirs.add(new FileObject(new File(path))); checkedDirs.add(new FileObject(new File(path))); if(traverseDownOneLevel(path) == startingPath ) return allDirs; //get nearer to the root path = traverseDownOneLevel(path); } path = giveAnUncheckedDir(path, checkedDirs); if ( path == "NoUnchecked.") { checkedDirs.add(new FileObject( (new File(path)).getParentFile() )); break; } } } } return allDirs; }

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  • Cloning java ArrayList and preventing it from modifications

    - by user222164
    I have a data structure like a database Rowset, which has got Rows and Rows have Columns. I need to initialize a Columns with null values, current code is to loop thru each column for a row and initialize values to NULL. Which is very inefficient if you have 100s or rows and 10s of column. So instead I am keeping a initialized ArrayList of columns are RowSet level, and then doing a clone of this Arraylist for individual rows, as I believe clone() is faster than looping thru each element. row.columnsValues = rowsset.NullArrayList.clone() Problem with this is NullArrayList can be accidentally modified after being cloned, thus sacrificing the integrity of ArrayList at RowSet level, to prevent I am doing 3 things 1) Delcaring ArrayList as final 2) Any elements I insert are final or null 3) Methods thurough this arrayList are passed to other arrays are declared a final. Sounds like a plan, do you see any holes ?

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  • Java Collections Sort not accepting comparator constructor with arg

    - by harmzl
    I'm getting a compiler error for this line: Collections.sort(terms, new QuerySorter_TFmaxIDF(myInteger)); My customized Comparator is pretty basic; here's the signature and constructor: public class QuerySorter_TFmaxIDF implements Comparator<Term>{ private int numberOfDocs; QuerySorter_TFmaxIDF(int n){ super(); numberOfDocs = n; } } Is there an error because I'm passing an argument into the Comparator? I need to pass an argument...

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  • Write wave files to memory in Java

    - by Cliff
    I'm trying to figure out why my servlet code creates wave files with improper headers. I use: AudioSystem.write( new AudioInputStream( new ByteArrayInputStream(memoryBytes), new AudioFormat(22000, 16, 1, true,false), memoryBytes.length ), AudioFileFormat.Type.WAVE, servletOutputStream ); taking a byte array from memory containing raw PCM samples and a servlet output stream that gets returned to the client. In the result I get a normal wave file but with zeros in the chunk size fields. Is the API broken? I would think that the size could be filled in using the size passed in the audio input stream. But now, after typing this out I'm thinking its not making this info available to the outer write() method on AudioSystem. It seems like the AudioSystem.write call needs a size parameter unless it is able to pull the size from the stream... which wouldn't work with an arbitrary sized stream. Does anyone know how to make this example work?

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  • Symbol error in java application using netbeans when adding a shared project to library

    - by Malachi
    I have a project which has shared functionality between three other projects and have linked these to existing projects as I normally would using the add project functionality of the libraries folder. This all used to work however when I started up Netbeans yesterday it just wasn't working as in the other projects won't compile even though the projects are linked. It can recognise the packages - just the actual classes themselves were not recognised... and to add to the weirdness some of the classes are getting picked up fine. I have checked the dist folder of the shared project and the Shared.jar file exists. Also I have checked the Jar and the other classes that are not being recognises are there also. Any suggestions?

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  • Adding look and feel into java application

    - by Samurai
    I am working with NetBeans 6.5 IDE and i have downloaded a look and feel jar file. I added that to NetBeans by palette manager but i don't know how to use it to my application using code. Anybody please tell me that how to add look and feel into my application? Thanks..

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  • Implementing Java Priority Queue

    - by Kay
    public class PriorityQueue<T> { private PriorityNode<T> head, tail; private int numItems; public PriorityQueue(){ numItems = 0; head=null; tail=null; } public void add(int priority, T value){ PriorityNode<T> newNode = new PriorityNode<T>(priority,value); if(numItems == 0){ head = newNode; tail = newNode; } else{ head.setNext(newNode); head = newNode; } } } Where PriorityNode is defined as: public class PriorityNode<T> implements Comparable<T> { private T value; private PriorityNode<T> next; private int priority; public PriorityNode(int priority,T newValue){ value = newValue; next = null; priority = 0; } public PriorityNode(T newValue){ value = newValue; next = null; priority = 0; } public void setPriority(int priority){ this.priority = priority; } public int getPriority(){ return this.priority; } public T getValue(){ return value; } public PriorityNode<T> getNext(){ return next; } public void setNext(PriorityNode<T> nextNode){ this.next = nextNode; } public void setValue(T newValue){ value = newValue; } public int compareTo(int pri) { // TODO Auto-generated method stub if(this.priority<pri){ return -1; } else if(this.priority == pri){ return 0; } else{ return 1; } } } I'm having a lot of difficulty using the Comparator here and implementing a priority queue - please point me in the right direction.

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  • Java : HTTP POST Request

    - by SpunkerBaba
    I have to do a http post request to a web-service for authenticating the user with username and password. The Web-service guy gave me following information to construct HTTP Post request. POST /login/dologin HTTP/1.1 Host: webservice.companyname.com Content-Type: application/x-www-form-urlencoded Content-Length: 48 id=username&num=password&remember=on&output=xml The XML Response that i will be getting is <?xml version="1.0" encoding="ISO-8859-1"?> <login> <message><![CDATA[]]></message> <status><![CDATA[true]]></status> <Rlo><![CDATA[Username]]></Rlo> <Rsc><![CDATA[9L99PK1KGKSkfMbcsxvkF0S0UoldJ0SU]]></Rsc> <Rm><![CDATA[b59031b85bb127661105765722cd3531==AO1YjN5QDM5ITM]]></Rm> <Rl><![CDATA[[email protected]]]></Rl> <uid><![CDATA[3539145]]></uid> <Rmu><![CDATA[f8e8917f7964d4cc7c4c4226f060e3ea]]></Rmu> </login> This is what i am doing HttpPost postRequest = new HttpPost(urlString); How do i construct the rest of the parameters?

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  • Java webapp: where/how to automatically set each picture's width/height

    - by NoozNooz42
    For several reasons, a lot of "webmaster guides" (like Google and Yahoo!'s webmaster guides/guidelines) repeats several times that it is better to always put the width and height attribute of the img tag. One of the most obvious reason is that the elements in the page won't seem to be "jumping around" to a new location after every picture is loaded (always setting the correct width/height sure gets rid of this behavior). And there are other reasons to follow these guidelines / best practices. So: if we consider that these are indeed good practices if there are a lot of pictures and they are changing often if pictures aren't changing between two .war re-deploy (that is: there's no user-contributed picture) if we don't want to manually edit all these width/height attributes How do we automatically/programmatically serve HTML pages where every img tag have their width/height attribute correctly set as the best practice recommend?

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  • Java - getConstructor() ?

    - by msr
    Hello, I wrote the question as a comment in the code, I think its easier to understand this way. public class Xpto{ protected AbstractClass x; public void foo(){ // AbstractClass y = new ????? Car or Person ????? /* here I need a new object of this.x's type (which could be Car or Person) I know that with x.getClass() I get the x's Class (which will be Car or Person), however Im wondering how can I get and USE it's contructor */ // ... more operations (which depend on y's type) } } public abstract class AbstractClass { } public class Car extends AbstractClass{ } public class Person extends AbstractClass{ }

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  • Java anonymous class efficiency implications

    - by Po
    Is there any difference in efficiency (e.g. execution time, code size, etc.) between these two ways of doing things? Below are contrived examples that create objects and do nothing, but my actual scenarios may be creating new Threads, Listeners, etc. Assume the following pieces of code happen in a loop so that it might make a difference. Using anonymous objects: void doSomething() { for (/* Assume some loop */) { final Object obj1, obj2; // some free variables IWorker anonymousWorker = new IWorker() { doWork() { // do things that refer to obj1 and obj2 } }; } } Defining a class first: void doSomething() { for (/* Assume some loop */) { Object obj1, obj2; IWorker worker = new Worker(obj1, obj2); } } static class Worker implements IWorker { private Object obj1, obj2; public CustomObject(Object obj1, Object obj2) {/* blah blah */} @Override public void doWork() {} }; Thank you :)

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  • Java RandomAccessFile - dealing with different newline styles?

    - by waitinforatrain
    Hey, I'm trying to seek through a RandomAccessFile, and as part of an algorithm I have to read a line, and then seek backwards from the end of the line E.g String line = raf.readLine(); raf.seek (raf.getFilePointer() - line.length() + m.start() + m.group().length()); //m is a Matcher for regular expressions I've been getting loads of off-by-one errors and couldn't figure out why. I just discovered it's because some files I'm reading from have UNIX-style linefeeds, \r\n, and some have just windows-style \n. Is there an easy to have the RandomAccessFile treat all linefeeds as windows-style linefeeds?

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  • Java: Print and access List <String[]>

    - by battousai622
    Im reading in a file and storing it in t1. How do i access the elements in t1? When i try to print it i get addresses instead of values. Also whats the dif between string and string[]? CSVReader reader = new CSVReader(new FileReader("src/new_acquisitions.csv")); List <String[]> t1 = reader.readAll(); int i = 0 while(i < t1.size()) { System.out.println(t1.get(i)); i++; } output: [Ljava.lang.String;@9304b1 [Ljava.lang.String;@190d11 [Ljava.lang.String;@a90653 [Ljava.lang.String;@de6ced

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  • How to wrap Java String.format()?

    - by BlinK_
    Hey everyone, I would like to wrap the String.format() method with in my own Logger class. I can't figure a way how to pass arguments from my method to String.format(). public class Logger { public static void format(String format, Object... args) { print(String.format(format, args)); // <-- this gives an error obviously. } public static void print(String s) { System.out.println(s); } }

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  • Mixed alignment with Java Swing's GroupLayout

    - by zigdon
    I'm trying to build a GUI window in my application. What I'm trying to do is have a window, with a few buttons at the top, and a large text area. Something like this: +--------------------------------------------------+ | [button1] [button2] [button3] | | +----------------------------------------------+ | | | text area | | | | | | | | | | | | | | | +----------------------------------------------+ | +--------------------------------------------------+ I'm almost there, using GroupLayout: layout.setHorizontalGroup( layout.createParallelGroup() .addGroup(layout.createSequentialGroup() .addComponent(button1) .addComponent(button2)) .addComponent(closeWindow)) .addComponent(textarea1) ); layout.setVerticalGroup( layout.createSequentialGroup() .addGroup(layout.createParallelGroup() .addComponent(button1) .addComponent(button2) .addComponent(button3)) .addComponent(textarea) ); The problem is that this ends up with button3 aligned to the left, with the other two. I can't seem to figure out how I can specify the alignment on just that one button. I can do GroupLayout.Alignment.TRAILING on the entire button bar, but that hits all 3 buttons, which is also not quite right. So what's the correct approach? Since the alignment only applies for Parallel Groups, I don't think having a HorizontalGroup with two Sequential Groups in it will help? What am I missing?

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  • static block instance block java Order

    - by Rollerball
    Having read this question In what order are the different parts of a class initialized when a class is loaded in the JVM? and the related JLS. I would like to know in more detail why for example having class Animal (superclass) and class Dog (subclass) as following: class Animal { static{ System.out.println("This is Animal's static block speaking"): } { System.out.println("This is Animal's instance block speaking"); } class Dog{ static{ System.out.println("This is Dog's static block speaking"); } { System.out.println("This is Dog's instance block speaking"); } public static void main (String [] args) { Dog dog = new Dog(); } } Ok before instantiating a class its direct superclass needs to be initialized (therefore all the statics variables and block need to be executed). So basically the question is: Why after initializing the static variables and static blocks of the super class, control goes down to the subclass for static variables initialization rather then finishing off the initialization of also the instance member? The control goes like: superclass (Animal): static variables and static blocks subclass (Dog): static variables and static blocks superclass (Animal): instance variables and instance blocks sublcass (Dog):instance variables and instance blocks What is the reason why it is in this way rather than : superclass -> static members superclass -> instance members subclass -> static members sublcass-> instance members

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  • What is faster- Java or C# (Or good old C)?

    - by Rexsung
    I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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