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  • Java generic Comparable where subclasses can't compare to eachother

    - by dege
    public abstract class MyAbs implements Comparable<MyAbs> This would work but then I would be able to compare class A and B with each other if they both extend MyAbs. What I want to accomplish however is the exact opposite. So does anyone know a way to get the generic type to be the own class? Seemed like such a simple thing at first... Edit: To explain it a little further with an example. Say you have an abstract class animals, then you extend it with Dogs and ants. I wouldn't want to compare ants with Dogs but I however would want to compare one dog with another. The dog might have a variable saying what color it is and that is what I want to use in the compareTo method. However when it comes to ants I would rather want to compare ant's size than their color. Hope that clears it up. Could possibly be a design flaw however.

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  • Java BufferedReader readline blocking?

    - by tgguy
    I want to make an HTTP request and then get the response as sketched here: URLConnection c = new URL("http://foo.com").openConnection(); c.setDoOutput(true); /* write an http request here using a new OutputStreamWriter(c.getOutputStream) */ BufferedReader reader = new BufferedReader(new InputStreamReader(c.getInputStream)); reader.readLine(); But my question is, if the request I send takes a long time before a response is received, what happens in the call reader.readLine() above? Will this process stay running/runnable on the CPU or will it get taken off the CPU and be notified to wake up and run again when there is IO to be read? If it stays on the CPU, what can be done to make it get off and be notified later?

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  • Static and overriding in Java

    - by Abhishek Jain
    public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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  • Close resources before exiting JFrame and TCP communication in Java

    - by Oz Molaim
    1. I'm writing a chat based application on TCP communication. I'm using NetBeans and I want to add functionality to the default EXIT_ON_CLOSE when exiting JFrame. The reason of course is because I want to clean resources and end threads safely. How can I call a method that clear resources and only then close the JFrame safely and end the process. 2. I need to implement the server side. The server has List/HashMap/Queue of 'Socket' with their chat nick-names. Is there any simple design pattern to do it correctly because I don't want to re-invent the wheel. thanks.

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  • Java Swing - Problem in disabling JCheckbox

    - by Yatendra Goel
    I am disabling a JCheckbox and then enabling it with the help of setEnabled(...) method. But the problem is if I disable a unselected checkbox, then it becomes selected after I enable it. I want all of them to have the same state after being enabled that they had before being disabled.

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  • Using XPath on String in Android (JAVA)

    - by Rav
    I am looking for some examples of using xpath in Android? Or if anyone can share their experiences. I have been struggeling to make tail or head of this problem :-( I have a string that contains a standard xml file. I believe I need to convert that into an xml document. I have found this code which I think will do the trick: public static Document stringToDom(String xmlSource) throws SAXException, ParserConfigurationException, IOException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); return builder.parse(new InputSource(new StringReader(xmlSource))); } Next steps Assuming the code above is OK, I need to apply xpath to get values from cat: "/animal/mammal/feline/cat" I look at the dev doc here: http://developer.android.com/reference/javax/xml/xpath/XPath.html and also look online, but I am not sure where to start! I have tried to use the following code: XPathFactory xPathFactory = XPathFactory.newInstance(); // To get an instance of the XPathFactory object itself. XPath xPath = xPathFactory.newXPath(); // Create an instance of XPath from the factory class. String expression = "SomeXPathExpression"; XPathExpression xPathExpression = xPath.compile(expression); // Compile the expression to get a XPathExpression object. Object result = xPathExpression.evaluate(xmlDocument); // Evaluate the expression against the XML Document to get the result. But I get "Cannot be resolved". Eclipse doesn't seem to be able to fix this import. I tried manually entering: javax.xml.xpath.XPath But this did not work. Does anyone know any good source code that I can utilise, for Android platform? 1.5

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  • Size of Objects in Java Heap w/ Regards to Methods

    - by Eric
    I know about primitives and objects living on the heap, but how does the number of methods effect heap size of the object? For example: public class A { int x; public getX() { return x; } } public class B { int x; public getX() { return x; } public getXString() { return String.valueOf(x); } public doMoreInterestingStuff() { return x * 42; } //etc } When instantiated, both objects live on the heap, both have memory allocated to their primitive x, but is B allocated more heap space due to having more method signatures? Or are those ONLY on the classLoader? In this example its trivial, but when there are 100,000+ of these objects in memory at any given time I imagine it could add up.

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  • How to resize .jpg images in Java?

    - by Daeyun
    This is what I want to do: Input: ArrayList that contains a bunch of .jpg URLs Download the image (using HttpURLConnection maybe?) Resize Save as xxx.jpg, locally I don't know where to start. I'd appreciate if anyone can tell me what to study to do the steps 1~3.

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  • java - volatile keyword

    - by Tiyoal
    Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not? Thanks a lot.

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  • Java: downloading issue using BufferedInputStream, BufferedOutputStream

    - by nkr1pt
    When downloading a rar file from the internet with the code below, the downloaded file is larger than it actually is. Not sure what causes this? bis = new BufferedInputStream(urlConn.getInputStream()); bos = new BufferedOutputStream(new FileOutputStream(outputFile)); eventBus.fireEvent(this, new DownloadStartedEvent(item)); int read; byte[] buffer = new byte[2048]; while ((read = bis.read(buffer)) != -1) { bos.write(buffer); } eventBus.fireEvent(this, new DownloadCompletedEvent(item));

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  • Is it possible to run Weblogic with 8gb heap size in a 64bit java/linux environment

    - by Per Arneng
    Setup: 64bit Linux 64bit SUN Jvm 1.6.0_20 Weblogic 10.3 Is it possible to run Weblogic 10.3 in this setup with a maximum heap size of 8gb? We have recived answers from oracle support that states that it might not be possible to address more than 4gb with this setup. Please submit any official links that support any statements that it is possible to run this setup with more than 4gb of heap size. We can not find any documentation of any limits of heap size when running with this setup. Thanx

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  • Caesar Cipher in Java (Spanish Characters)

    - by Rodolfo
    I've reading this question, and I was wondering if Is there any way to consider the whole range of characters? For example, "á", "é", "ö", "ñ", and not consider " " (the [Space])? (For example, my String is "Hello World", and the standard result is "Khoor#Zruog"; I want to erase that "#", so the result would be "KhoorZruog") I'm sure my answer is in this piece of code: if (c >= 32 && c <= 127) { // Change base to make life easier, and use an // int explicitly to avoid worrying... cast later int x = c - 32; x = (x + shift) % 96; chars[i] = (char) (x + 32); } But I've tried some things, and it didn't work.

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  • remove duplicates from object array data java

    - by zahir hussain
    hi i want to know how to remove duplicates in object. for example cat c[] = new cat[10]; c[1].data = "ji"; c[2].data = "pi"; c[3].data = "ji"; c[4].data = "lp"; c[5].data = "ji"; c[6].data = "pi"; c[7].data = "jis"; c[8].data = "lp"; c[9].data = "js"; c[10].data = "psi"; i would like to remove the duplicates value from object array. thanks and advance

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  • java Getting a list of words from a Trie

    - by adam08
    I'm looking to use the following code to not check whether there is a word matching in the Trie but to return a list all words beginning with the prefix inputted by the user. Can someone point me in the right direction? I can't get it working at all..... public boolean search(String s) { Node current = root; System.out.println("\nSearching for string: "+s); while(current != null) { for(int i=0;i<s.length();i++) { if(current.child[(int)(s.charAt(i)-'a')] == null) { System.out.println("Cannot find string: "+s); return false; } else { current = current.child[(int)(s.charAt(i)-'a')]; System.out.println("Found character: "+ current.content); } } // If we are here, the string exists. // But to ensure unwanted substrings are not found: if (current.marker == true) { System.out.println("Found string: "+s); return true; } else { System.out.println("Cannot find string: "+s +"(only present as a substring)"); return false; } } return false; } }

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  • Java paint speed relative to color model

    - by Jon
    I have a BufferedImage with an IndexColorModel. I need to paint that image onto the screen, but I've noticed that this is slow when using an IndexColorModel. However, if I run the BufferedImage through an identity affine transform it creates an image with a DirectColorModel and the painting is significantly faster. Here's the code I'm using AffineTransformOp identityOp = new AffineTransformOp(new AffineTransform(), AffineTransformOp.TYPE_BILINEAR); displayImage = identityOp.filter(displayImage, null); I have three questions 1. Why is painting the slower on an IndexColorModel? 2. Is there any way to speed up the painting of an IndexColorModel? 3. If the answer to 2. is no, is this the most efficient way to convert from an IndexColorModel to a DirectColorModel? I've noticed that this conversion is dependent on the size of the image, and I'd like to remove that dependency. Thanks for the help

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  • Multiple consecutive alerts in Java ME

    - by Casebash
    According to the documentation, Display.setCurrent doesn't work if the current displayable is an alert. Does anyone know how to work around this so that we can go from one alert to another? I am using CLDC 1.0 and MIDP 2.0. My attempt The spec does allow us to edit an alert while it is on screen, but some Nokia phones don't handle it well at all. So I am now trying to go from the alert to a canvas, then back to the alert. Of course I don't want the user to interact with the previous canvas, so it seems that I am forced to create a new blank canvas. As a sidenote, this has the slight disadvantage of looking worse on phones which still have the previous screen when an alert is shown. The bigger problem is how to transition from the blank canvas back to an alert once the canvas is loaded. Testing on the Motorola emulator revealed that showNotify is not called after returning from an alert to the previous screen. I guess I could create the next alert in the paint method, but this seems like a ugly hack.

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  • Get the key and value of Map that is used Inside another Map (JAVA)

    - by Umair Iqbal
    I am using a map inside another map, The key of the outer map is Integer and the value is another Map. I get the values as expected but I don't know how to get the key and value of teh inner map. Here is the code Map<Integer, Map<Integer, Integer>> cellsMap = new HashMap<Integer, Map<Integer, Integer>>(); Map<Integer , Integer> bandForCell = cellsMap.get(band_number); if (bandForCell == null) bandForCell = new HashMap<Integer, Integer>(); bandForCell.put(erfcn, cell_found); cellsMap.put(band_number, bandForCell); csv.writeCells((Map<Integer, Map<Integer, Integer>>) cellsMap); public void writeCells (Map<Integer, Map<Integer, Integer>> cellsMap ) throws IOException { for (Map.Entry<Integer, Map<Integer, Integer>> entry : cellsMap.entrySet()) { System.out.println("Key: " + entry.getKey() + ". Value: " + entry.getValue() + "\n"); } } Out put of my Map Key: 20 Value: {6331=0, 6330=1, 6329=1, 6328=0, 6335=1, 6437=0, 6436=1} The value in the above output is another map. How can I get the key and value of the inner map from the value of the outer map? Like Keys of inner map = 6331, 6330, 6329 .... and values of inner map = 0 , 1 , 1 , 0 ... Thanks

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