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  • java servlet:response.sendRedirect() not giving illegal state exception if called after commit of re

    - by sahil garg
    after commit of response as here redirect statement should give exception but it is not doing so if this redirect statemnet is in if block.but it does give exception in case it is out of if block.i have shown same statement(with marked stars ) at two places below.can u please tell me reason for it. protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub synchronized (noOfRequests) { noOfRequests++; } PrintWriter pw=null; response.setContentType("text/html"); response.setHeader("foo","bar"); //response is commited because of above statement pw=response.getWriter(); pw.print("hello : "+noOfRequests); //if i remove below statement this same statement is present in if block.so statement in if block should also give exception as this one do, but its not doing so.why? ***response.sendRedirect("http://localhost:8625/ServletPrc/login% 20page.html"); if(true) { //same statement as above ***response.sendRedirect("http://localhost:8625/ServletPrc/login%20page.html"); } else{ request.setAttribute("noOfReq", noOfRequests); request.setAttribute("name", new Name().getName()); request.setAttribute("GmailId",this.getServletConfig().getInitParameter("GmailId") ); request.setAttribute("YahooId",this.getServletConfig().getInitParameter("YahooId") ); RequestDispatcher view1=request.getRequestDispatcher("HomePage.jsp"); view1.forward(request, response); } }

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  • create a sparse BufferedImage in java

    - by elgcom
    I have to create an image with very large resolution, but the image is relatively "sparse", only some areas in the image need to draw. For example with following code /* this take 5GB memory */ final BufferedImage img = new BufferedImage( 36000, 36000, BufferedImage.TYPE_INT_ARGB); /* draw something */ Graphics g = img.getGraphics(); g.drawImage(....); /* output as PNG */ final File out = new File("out.png"); ImageIO.write(img, "png", out); The PNG image on the end I created is ONLY about 200~300 MB. The question is how can I avoid creating a 5GB BufferedImage at the beginning? I do need an image with large dimension, but with very sparse color information. Is there any Stream for BufferedImage so that it will not take so much memory?

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  • NullPointerException Java help

    - by KP65
    Hello guys. I've been tearing my hair out the past few hours trying to solve this problem. Every time I click on a JButton which should open a JFrame(And it does), i get a stacktrace saying I have a null point exception at these bits of code: In class A i have: aButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { B instanceofB = new B(userSession.getBalance()); }); and Class B super.getSomeBtn().setVisible(false); This is where the stacktrace says the errors are in the two above sections. I have a line exactly the same as the one above in Class B and it works fine? Really stuck here!

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  • Most Elegant Way to write isPrime in java

    - by Anantha Kumaran
    public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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  • JAVA Inheritance Generics and Casting.

    - by James Moore
    Hello, I have two classes which both extends Example. public class ClassA extends Example { public ClassA() { super("a", "class"); } .... } public class ClassB extends Example { public ClassB() { super("b", "class"); } .... } public class Example () { public String get(String x, String y) { return "Hello"; } } So thats all very well. So suppose we have another class called ExampleManager. With example manager I want to use a generic type and consequently return that generic type. e.g. public class ExampleManager<T extends Example> { public T getExample() { return new T("example","example"); // So what exactly goes here? } } So where I am returning my generic type how do i get this to actually work correctly and cast Example as either classA or classB? Many Thanks

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  • How do I display java.lang.* object allocations in Eclipse profiler?

    - by Martin Wickman
    I am profiling an application using the Eclipse profiler. I am particularly interested in number of allocated object instances of classes from java.lang (for instance java.lang.String or java.util.HashMap). I also want to know stuff like number of calls to String.equals() etc. I use the "Object Allocations" tab and I shows all classes in my application and a count. It also shows all int[], byte[], long[] etc, but there is no mention of any standard java classes. For instance, this silly code: public static void main(String[] args) { Object obj[] = new Object[1000]; for (int i = 0; i < 1000; i++) { obj[i] = new StringBuffer("foo" + i); } System.out.println (obj[30]); } Shows up in the Object Allocations tab as 7 byte[]s, 4 char[]s and 2 int[]s. It doesn't matter if I use 1000 or 1 iterations. It seems the profiler simply ignores everything that is in any of the java.* packages. The same applies to Execution Statistics as well. Any idea how to display instances of java.* in the Eclipse Profiler?

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  • Android/Java Append String + int

    - by xger86x
    Hi, i have a question, what is the best way to append ints and Strings to build a new String? In the allocation debug tool i see too much allocations if i use the operator +. But i have tried also with StringBuffer and there are still too much allocations. Anyone can help me? Thanks

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  • Call a method of subclass in Java

    - by eyecreate
    If I have a base class Base thing = null; of which there is a subclass class Subclass extends Base and I instigate it as thing = new Subclass how would I call a method that is specifically in Subclass, but not in Base? ex. Base has only method() Subclass has method() and specialMethod() the method specialMethod() is the one I want to call.

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  • Selenium Webdriver Java - looking for alternatives for Actions and Robot when performing drag-and-drop

    - by Ja-ke Alconcel
    I first tried Actions class and the drag-and-drop does work on different elements, however it was unable to locate the a specific draggable element on it's exact screen/webpage position. Here's the code I've used: Point loc = driver.findElement(By.id("thiselement")).getLocation(); System.out.println(loc); WebElement drag = driver.findElement(By.id("thiselement")); Actions test = new Actions(driver); test.dragAndDropBy(drag, 0, 60).build().perform(); I checked the element with it's pixel location and it prints (837, -52), which was somewhere on top of the webpage and was pixels away from the actual element. Then I tried using the Robot class and works perfectly fine on my script, but can only provide constant successful runs on a single test machine, running it with a different machine with different screen resolution and screen size will render the script to fail due to the dependency of Robot on the pixel location of the element. The sample code of the Robot script I'm using: Robot dragAndDrop = new Robot(); dragAndDrop.mouseMove(945, 166); //actual pixel location of the draggable element dragAndDrop.mousePress(InputEvent.BUTTON1_MASK); sleep(3000); dragAndDrop.mouseMove(945, 226); dragAndDrop.mouseRelease(InputEvent.BUTTON1_MASK); sleep(3000); Is there any alternative for Actions and Robot to automate drag-and-drop? Or maybe a help on working the script to work on Actions as I really can't use Robot. Thanks in advance.

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  • Java io ugly try-finally block

    - by Tom Brito
    Is there a not so ugly way of treat the close() exception to close both streams then: InputStream in = new FileInputStream(inputFileName); OutputStream out = new FileOutputStream(outputFileName); try { copy(in, out); } finally { try { in.close(); } catch (Exception e) { try { // event if in.close fails, need to close the out out.close(); } catch (Exception e2) {} throw e; // and throw the 'in' exception } out.close(); }

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  • `return value' from Constructor Exception in Java?

    - by Lajos Nagy
    Take a look that the following code snippet: A a = null try { a = new A(); } finally { a.foo(); // What happens at this point? } Suppose A's constructor throws a runtime exception. At the marked line, am I always guaranteed to get a NullPointerException, or foo() will get invoked on a half constructed instance?

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  • Issue with Java join() method.

    - by gmunk
    First of all here are some code snippets: http://pastebin.com/9ZCwekXs http://pastebin.com/TtLLXPYP I'm trying to animate some images. The thing is that I want the main thread to wait for the animation thread to finish and then to continue. I searched around, read a little bit and decided to use the join() method. It perfectly waits for the thread to finish but I doesn't animate correctly. The repaint() method gets called 2 times instead of nine. I think maybe the problem is because I used singletons. Here is the singleton implementation. http://pastebin.com/bA3qLZJE

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  • PreparedStatement question in Java against Oracle.

    - by fardon57
    Hi everyone, I'm working on the modification of some code to use preparedStatement instead of normal Statement, for security and performance reason. Our application is currently storing information into an embedded derby database, but we are going to move soon to Oracle. I've found two things that I need your help guys about Oracle and Prepared Statement : 1- I've found this document saying that Oracle doesn't handle bind parameters into IN clauses, so we cannot supply a query like : Select pokemon from pokemonTable where capacity in (?,?,?,?) Is that true ? Is there any workaround ? ... Why ? 2- We have some fields which are of type TIMESTAMP. So with our actual Statement, the query looks like this : Select raichu from pokemonTable where evolution = TO_TIMESTAMP('2500-12-31 00:00:00.000', 'YYYY-MM-DD HH24:MI:SS.FF') What should be done for a prepared Statement ? Should I put into the array of parameters : 2500-12-31 or TO_TIMESTAMP('2500-12-31 00:00:00.000', 'YYYY-MM-DD HH24:MI:SS.FF') ? Thanks for your help, I hope my questions are clear ! Regards,

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  • Java Programming Homework

    - by user1427476
    Write a program to read in a file containing the names of the employ of a company and store them in an array of Strings named Employ []. Read another file containing the Salaries of each employ written in the same order and store them in another array of integers named salary[] (contents of both files are shown below). Finally create a file stating for example. Mr. XYZ receive $75,500.00 per year (Note that salary is stored as integer but displayed here as double with a comma separating thousands. This formatting needs to be done using DecimalFormat Class)

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  • Joining remote paths in Java

    - by Mickael Marrache
    I'm using the FTP library provided by Apache (commons-net). I want to check if a file exists on the FTP server so I use the listFiles method of FTPClient: ftpClient.listFiles(remoteFileDir + "\\" + fileName); The current directory is the FTP server root directory. So, the value of remoteFileDir is a path relative to this root directory. My question concerns the merge between the remote directory path and the file name. What is the right way to do it? For a local file, I would do: File file = new File(remoteFileDir,fileName); but here it doesn't work since when I call file.getAbsolutePath(), I get an absolute path for the file in the local current directory which is not what I want. Also, I guess the merging has been done according to my local environment. PS: I looked at How are paths determined on a remote machines? but it doesn't help me. Thanks

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  • asking the container to notify your application whenever a session is about to timeout in Java

    - by user136101
    Which method(s) can be used to ask the container to notify your application whenever a session is about to timeout?(choose all that apply) A. HttpSessionListener.sessionDestroyed -- correct B. HttpSessionBindingListener.valueBound C. HttpSessionBindingListener.valueUnbound -- correct this is kind of round-about but if you have an attribute class this is a way to be informed of a timeout D. HttpSessionBindingEvent.sessionDestroyed -- no such method E. HttpSessionAttributeListener.attributeRemoved -- removing an attribute isn’t tightly associated with a session timeout F. HttpSessionActivationListener.sessionWillPassivate -- session passivation is different than timeout I agree with option A. 1) But C is doubtful How can value unbound be tightly coupled with session timeout.It is just the callback method when an attribute gets removed. 2) and if C is correct, E should also be correct. HttpSessionAttributeListener is just a class that wants to know when any type of attribute has been added, removed, or replaced in a session. It is implemented by any class. HttpSessionBindingListener exists so that the attribute itself can find out when it has been added to or removed from a session and the attribute class must implement this interface to achieve it. Any ideas…

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  • Strange problem with simple multithreading program in Java

    - by Elizabeth
    Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

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  • Best approach to create a security environment in Java

    - by Tom Brito
    I need to create a desktop application that will run third party code, and I need to avoid the third party code from export by any way (web, clipboard, file io) informations from the application. Somethig like: public class MyClass { private String protectedData; public void doThirdPartyTask() { String unprotedtedData = unprotect(protectedData); ThirdPartyClass.doTask(unprotectedData); } private String unprotect(String data) { // ... } } class ThirdPartyClass { public static void doTask(String unprotectedData) { // Do task using unprotected data. // Malicious code may try to externalize the data. } } I'm reading about SecurityManager and AccessControler, but I'm still not sure what's the best approach to handle this. What should I read about to do this implementation?

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  • export a JOGL applet and embedd into a html page

    - by nkint
    hi guys it is some time that i'm testing opengl with java and JOGL. now i have good result and i wanto to pubblish it on web. but i have some problem. i'm in eclipse, and i'm testing an Applet with JOGL. first of all i have this run time error (but the program works correctly): java.lang.IllegalArgumentException: adding a window to a container at java.awt.Container.checkNotAWindow(Container.java:431) at java.awt.Container.addImpl(Container.java:1039) at java.awt.Container.add(Container.java:365) at AppletHelloWorld.init(AppletHelloWorld.java:30) at sun.applet.AppletPanel.run(AppletPanel.java:424) at java.lang.Thread.run(Thread.java:619) then i found this incredibly clear page and i do what is said, i open html with the browser, the libs are downloaded but it stops at "Starting applet AppletHelloWorld" that is the name i gave to my applet. mayebe i miss something like main function or exporting well the jar? this is my main code: public class AppletHelloWorld extends Applet { public static void main(String[] args) { JFrame fr=new JFrame(); fr.setBounds(0,0,1015,600); fr.add(new AppletHelloWorld()); fr.setVisible(true); } public void init() { setLayout(null); MyJOGLProject canvas = new MyJOGLProject(); //MyJOGLProject extends JFrame canvas.run(); Container c = new Container(); c.add(canvas); add(c); } //....

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