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  • Casting Class into String and Vice Versa in JAVA

    - by topgun_ivard
    I have a program in which I need to store a Class object into memory by casting it into String. Is it possible to convert the String back into the original Class so that I can use that class variables? I am doing this in JAVA. Example: test.java class hello{ public String h1; public String h2; } public class test { public static void main(String[] args) { hello h = new hello(); h.h1 = "hello"; h.h2 = "world"; String s = h.toString(); System.out.println("Print s : "+s); // Now I need to convert String s into type hello so that // I can do this: // (hello)s.h1; // (hello)s.h2; } } NOTE: this is not a homework, this is a personal project and I would be grateful if anyone can help! Thanks! Ivar

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  • Benchmark of Java Try/Catch Block

    - by hectorg87
    I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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  • Call javascript function from Java (Groovy) class

    - by ashkanr
    Hi, I have a javascript function (very big one!) that I need its functionality in a Java (Groovy) class. It is a simple calendar converter. I can rewrite it in groovy but just want to know if it is possible to call javascript function from a java (groovy) method? I guess functional testing libraries like selenium and Canoo should have something like this, am I right? PS: I don't want to wake up a real-world browser in order to use its JS runtime env. Thanks,

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  • How do I cast from int to generic type Integer?

    - by Rob Kent
    I'm relatively new to Java and am used to generics in C# so have struggled a bit with this code. Basically I want a generic method for getting a stored Android preference by key and this code, albeit ugly, works for a Boolean but not an Integer, when it blows up with a ClassCastException. Can anyone tell me why this is wrong and maybe help me improve the whole routine (using wildcards?)? public static <T> T getPreference(Class<T> argType, String prefKey, T defaultValue, SharedPreferences sharedPreferences) { ... try { if (argType == Boolean.class) { Boolean def = (Boolean) defaultValue; return argType.cast(sharedPreferences.getBoolean(prefKey, def)); } else if (argType == Integer.class) { Integer def = (Integer) defaultValue; return argType.cast(sharedPreferences.getInt(prefKey, def)); } else { AppGlobal.logWarning("getPreference: Unknown type '%s' for preference '%s'. Returning default value.", argType.getName(), prefKey); return defaultValue; } } catch (ClassCastException e) { AppGlobal.logError("Cast exception when reading pref %s. Using default value.", prefKey); return defaultValue; } } I've tried various ways - using the native int, casting to an Integer, but nothing works.

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  • New to JEE; architecture suggestions for a service/daemon?

    - by Kate
    I am brand new to the JEE world. As an exercise to try and familiarize myself with JEE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Parameters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a JEE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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  • Java: how to take a screenshot fast

    - by user350789
    I am implementing a simple eye tracker, which requires fast screenshoting of what is happening on the screen simultaneously with capturing the video from webcam. The thing is that the way of doing it with Robot, mentioned here: http://stackoverflow.com/questions/2475303/java-library-for-capturing-active-window-screenshot is extremely slow. By the way, retrieving the video from a webcam works much faster and returns the byte array, which is very fast to be processed. Does anybody know a faster solution? C++ libraries, which can be linked to Java for doing this may help as well. Thank you!

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  • web service client in java

    - by user622222
    I want to generate a client program using the service I am unable to display the results, how can I do so? import java.rmi.RemoteException; public class searchtry { public static void main(String[] args) throws RemoteException { SearchRequest request=new SearchRequest(); SearchRequestType1 type1=new SearchRequestType1(); query.setAppId("*********************************"); //Windows Live gave this id for using that service query.setSources(new SourceType[]{SourceType.Web}); query.setQuery("Java"); aratip.setParameters(request); SearchResponseType0 answer= client.search(type1); System.out.println(answer.toString()); }

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  • Please , Explain these java code ..?

    - by soma
    I want understand these code before java lab exam especially methode import javax.swing.; import java.util.; import java.text.*; public class EnglishCalendar { public static String[] months = { "January" , "February" , "March", "April" , "May" , "June", "July" , "August" , "September", "October" , "November" , "December" }; public static int days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; private void showMonth(int m, int y) { int lead_spaces = 0; if (m < 0 || m > 11) { System.out.println("It should be 1 to 12"); } else { System.out.println(); System.out.println(" " + months[m] + " " + y); System.out.println(); GregorianCalendar cal = new GregorianCalendar(y, m, 0); System.out.println("Su Mo Tu We Th Fr Sa "); lead_spaces = cal.get(Calendar.DAY_OF_WEEK); int day_of_month = days[m]; if (cal.isLeapYear(cal.get(Calendar.YEAR)) && m == 1){ day_of_month++;} for (int i = 0; i < lead_spaces; i++) { System.out.print(" "); } for (int i = 1; i <= day_of_month; i++) { if (i < 10) System.out.print(" "); System.out.print(i); if ((lead_spaces + i) % 7 == 0) { System.out.println(); } else { System.out.print(" "); } } System.out.println(); } } private static void doSimpleDateFormat() { Calendar now = Calendar.getInstance(); SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); System.out.print(" \n It is now : " + formatter.format(now.getTime())); System.out.println(); } public static void main(String[] args) { String mo = JOptionPane.showInputDialog("Month"); String ye = JOptionPane.showInputDialog("Year"); int mon = new Integer(mo).intValue(); int yea = new Integer(ye).intValue(); EnglishCalendar k = new EnglishCalendar(); k.showMonth(mon - 1 , yea); doSimpleDateFormat(); } }

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  • Calling a JAVA method from C++ with JNI, no parameters

    - by PRNDL Development Studios
    Please bear with me, I am an iPhone developer and this whole android this confuses me a bit. I have some c++ methods that are called from a cocos2d-x CCMenuItem. Therefore I cannot send any parameters, according to the docs. I need to open a url with the android browser which will require me to call a JAVA function to start a new intent. I understand that I need to create a VM, however the below code gives me the error: jni/../../Classes/MyClass.cpp:184: error: 'JNI_CreateJavaVM' was not declared in this scope I was looking at this thread: Calling a java method from c++ in Android But he uses parameters, and I can't do that. And I don't see where those are in his code to just make them myself. I don't know what the string should be in the 'Find Class' method. Also, I assume it is pretty terrible to create a new VM instance in every method I need to call. How would I create one as a singleton to use across the board? This is my c++ code called by my menu item: #include <jni.h> ... JavaVM *vm; // Global ... void OptionsScene::website(){ JNIEnv *env; JavaVMInitArgs vm_args; vm_args.version = JNI_VERSION_1_2; vm_args.nOptions = 0; vm_args.ignoreUnrecognized = 1; jint result = JNI_CreateJavaVM(&vm, (void **)&env, &vm_args); // This line still errors jclass clazz = env->FindClass("com/prndl/project/WebExecute"); jmethodID method = env->GetMethodID(clazz, "website", "(Ljava/lang/String;)V"); env->CallVoidMethod(NULL,method); vm->DestroyJavaVM(); And this is the JAVA Method that I need to call: public class WebExecute extends Activity{ public void website(){ Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.com")); startActivity(browserIntent); } } Honestly, I am struggling with this, any help is appreciated. Thanks.

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  • Have an external java application by notified of changes to Entity EJBs in JBoss AS

    - by John
    I'm trying to connect an external application to a JBoss AS container. The external application is a Java application that is currently being notified of changes to database entities through a JMS topic. I've added an EntityLifecycleListener class to all my entities that publishes a serialized (and unwrapped) copy of the entity to the JMS topic. The problem is that this implementation ignores the transaction boundaries of the JBoss container. For example, the @PostUpdate event can be fire, generating the JMS message for that entity, but the transaction could be rolled back causing the external application to be notified of an invalid change and become unsync'd. I need my external application to only be notified of successful commits to the database, but I need to be able to publish the entire java POJO to the external application. Is there an official way of doing this?

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  • Vectors for a 2D/3D World in Java

    - by jax
    I reading about Mathematics in Games and am wondering what is the best way to represent a Vector location in Java. I know there is a Vector class but I don't think this is what I need. There is also a Matrix class which looks like it may be what I want (a 1 dimensional matrix maybe). In particular, if I were to create a location Vector such as: v(x,y,z) where x,y and z are the coordinates in 3D space, what would be the best way to represent this in Java. It would be nice if I could also add, subtract and find the dot-product of Vectors. ideas?

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  • Secure Gmail login on web browser from external Java program

    - by Zach Scrivena
    Is there a secure way of logging into a Gmail account on a web browser, from an external Java program? I know the following works, but is there a safer alternative? Desktop.getDesktop().browse(new URI( "https://www.google.com/accounts/ServiceLoginAuth?continue=http://mail.google.com/gmail" + "&service=mail&Email=LOGIN&Passwd=PASSWORD&null=Sign+in")); Clarification: The external Java program is GmailAssistant, a Gmail notifier that already uses the IMAP capabilities of JavaMail. I just need a way of allowing the user to access the account directly in a web browser.

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  • Java template classes using generator or similar?

    - by Hugh Perkins
    Is there some library or generator that I can use to generate multiple templated java classes from a single template? Obviously Java does have a generics implementation itself, but since it uses type-erasure, there are lots of situations where it is less than adequate. For example, if I want to make a self-growing array like this: class EasyArray { T[] backingarray; } (where T is a primitive type), then this isn't possible. This is true for anything which needs an array, for example high-performance templated matrix and vector classes. It should probably be possible to write a code generator which takes a templated class and generates multiple instantiations, for different types, eg for 'double' and 'float' and 'int' and 'String'. Is there something that already exists that does this? Edit: note that using an array of Object is not what I'm looking for, since it's no longer an array of primitives. An array of primitives is very fast, and uses only as much space a sizeof(primitive) * length-of-array. An array of object is an array of pointers/references, that points to Double objects, or similar, which could be scattered all over the place in memory, require garbage collection, allocation, and imply a double-indirection for access. Edit2: good god, voted down for asking for something that probably doesn't currently exist, but is technically possible and feasible? Does that mean that people looking for ways to improve things have already left the java community? Edit3: Here is code to show the difference in performance between primitive and boxed arrays: int N = 10*1000*1000; double[]primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } Object[] objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } tic(); primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } toc(); tic(); objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } toc(); Results: double[] array: 148 ms Double[] array: 4614 ms Not even close!

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  • Sending Email using Java

    - by Sunny
    Hi Guys, I want my Java application to send out emails to users. But I cant get a good solution. Now, I got some on Google but they use a SMTP server which I dont have. I was wondering if setting up one on my Linux machine would be easy? So, I am using mailx now to send out emails but it sends emails from root which is definately not good. Is there any way to send out emails from a proper email using java? like you can do in php and other languages?

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  • How Can I Implement This In Java?

    - by davit-datuashvili
    first of all i am doing programs in java language this code is merely taken from web site i have not question about divide and conqurer algorithms but about function and it's argument here is code of ternary search def ternarySearch(f, left, right, absolutePrecision): #left and right are the current bounds; the maximum is between them if (right - left) < absolutePrecision: return (left + right)/2 leftThird = (2*left + right)/3 rightThird = (left + 2*right)/3 if f(leftThird) < f(rightThird): return ternarySearch(f, leftThird, right, absolutePrecision) return ternarySearch(f, left, rightThird, absolutePrecision) i am not asking once again how implement it in java i am asking for example how define function?for example let y=x^+3 yes we can determine it as public static int y(int x){ return x*x+3; } but here return ternarySearch(f, leftThird, right, absolutePrecision) function f does not have argument and how do such?please help me

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  • Quick to develop web app in Java

    - by Mike Q
    Hi all, I need to develop a basic web app very quickly (1 week) for a demo. My requirements are Java (I need to make use of existing Java libraries to access the relevant data) 2 screens One for static data view, maybe some search parameters Other for basic form entry No fancy AJAX required Ideally easy for a web designer to come in and tart it up as necessary, without having to rewrite everything My first stop was going to be to checkout Wicket as I've heard good things about it. I don't have the time right now to dive into anything heavy, which probably writes off JSF in my mind (I played with JSF1, steep learning curve which I've now slid back down). I'm happy to treat the result as throwaway so if there's a framework which starts of well but then doesn't scale up to bigger projects, that would be ok. Any suggestions appreciated on frameworks/approach.

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  • Converting a C++ Checksum function to Java

    - by user1897599
    I'm trying to convert this C++ checksum to Java but for the time being I've failed. What am I doing wrong? What is it supposed to do? It is supposed to return a positive checksum for a buffer in OpenGL Here's the C part. DWORD QuickChecksum(DWORD *data, int size){ if(!data) { return 0x0; } DWORD sum; DWORD tmp; sum = *data; for(int i = 1; i < (size/4); i++) { tmp = data[i]; tmp = (DWORD)(sum >> 29) + tmp; tmp = (DWORD)(sum >> 17) + tmp; sum = (DWORD)(sum << 3) ^ tmp; } return sum; } And here is what I have tried in Java. As far As I know DWORD is 32bit so I use int in a long to get a unsigned int which should be done in java with ? I've been looking at this problem so much now that I've grown blind to it. public static long getChecksum(byte[] data, int size) { long sum, tmp; sum = getInt(new byte[]{data[0], data[1], data[2], data[3]},true) & 0xFF; for(int I = 4; I < data.length; I += 4) { tmp = getInt(new byte[]{data[I],data[I+1],data[I+2],data[I+3]},true) & 0xFF; tmp = (sum >>> 29) + tmp; tmp = (sum >>> 17) + tmp; sum = (sum << 3) ^ tmp; } return sum & 0xFF; } private static int getInt(byte[] bytes, boolean big) { ByteBuffer bb = ByteBuffer.wrap(bytes); return bb.getInt(); } Thank you all for your help!

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  • File download using Java, Struts 2 and AJAX

    - by amar4kintu
    Hello Friends, I want to give file download using java,struts2 and ajax. On my html page there is a button called "export" clicking on which ajax call will be made which will execute a query and will create .xls file using code and I want to give that file for download to user without storing it on hard drive. Does any one know how to do that using struts2 and ajax in java? Is there any example available? Let me know if you need more details from me... Thanks. amar4kintu

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  • java nested for() loop throws ArrayIndexOutOfBoundsException

    - by Mike
    I'm working through a JPanel exercise in a Java book. I'm tasked with creating a 5x4 grid using GridLayout. When I loop through the container to add panels and buttons, the first add() throws the OOB exception. What am I doing wrong? package mineField; import java.awt.*; import javax.swing.*; @SuppressWarnings("serial") public class MineField extends JFrame { private final int WIDTH = 250; private final int HEIGHT = 120; private final int MAX_ROWS = 5; private final int MAX_COLUMNS = 4; public MineField() { super("Minefield"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Container mineFieldGrid = getContentPane(); mineFieldGrid.setLayout(new GridLayout(MAX_ROWS, MAX_COLUMNS)); // loop through arrays, add panels, then add buttons to panels. for (int i = 0; i < MAX_ROWS; i++) { JPanel[] rows = new JPanel[i]; mineFieldGrid.add(rows[i], rows[i].getName()); rows[i].setBackground(Color.blue); for (int j = 0; j < MAX_COLUMNS; j++) { JButton[] buttons = new JButton[i]; rows[i].add(buttons[j], buttons[j].getName()); } } mineFieldGrid.setSize(WIDTH, HEIGHT); mineFieldGrid.setVisible(true); } public int setRandomBomb(Container con) { int bombID; bombID = (int) (Math.random() * con.getComponentCount()); return bombID; } /** * @param args */ public static void main(String[] args) { //int randomBomb; //JButton bombLocation; MineField minePanel = new MineField(); //minePanel[randomBomb] = minePanel.setRandomBomb(minePanel); } } I'm sure I'm over-engineering a simple nested for loop. Since I'm new to Java, please be kind. I'm sure I'll return the favor some day.

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