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  • Execute external program from Java

    - by Saurabh Lalwani
    Hi, I am trying to execute a program from the Java code. Here is my code: public static void main(String argv[]) { try { String line; Process p = Runtime.getRuntime().exec( "/bin/bash -c ls > OutputFileNames.txt"); BufferedReader input = new BufferedReader( new InputStreamReader(p.getInputStream())); while ((line = input.readLine()) != null) { System.out.println(line); } input.close(); } catch (Exception err) { err.printStackTrace(); } } My OS is Mac OS X 10.6. If I remove the "> OutputFileNames.txt" from the getRuntime().exec() method, all the file names are printed on the console just fine. But I need it to be printed to a file. Also, if I change the command to: Process p = Runtime.getRuntime().exec( "cmd \c dir > OutputFileNames.txt"); and run it on Windows, it runs and prints the results in the file perfectly fine too. I have read the other posts for executing another application from Java but none seemed to relate to my problem. I would really appreciate any help I can get. Thanks,

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  • Read text file in java

    - by user326091
    Hi, I have a text file. I would like to retrieve the content from one line to another line. For example, the file may be 200K lines. I want to read the content from line 78 to line 2735. Since the file may be very large, I do not want to read the whole content into the memory. thanks Frank

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  • using arrays to get best memory alignment and cache use, is it necessary?

    - by Alberto Toglia
    I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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  • Under Windows CE, how can I check which RAM based DLLs are loaded in virtual memory space?

    - by Michal Drozdowicz
    I have a problem with loading a DLL under Windows Mobile 5.0. I'm pretty confident that this is caused by running out of the application virtual memory (the 32 MB slot of the process, as explained in Windows CE .NET Advanced Memory Management). I'm looking for a way to actually make sure that this is the issue and investigate whether my efforts bring expected results. Do you know of a way to check the contents of the virtual memory application slot? Any applications that can help me with this task?

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  • Java JRE vs GCJ

    - by Martijn Courteaux
    Hi, I have this results from a speed test I wrote in Java: Java real 0m20.626s user 0m20.257s sys 0m0.244s GCJ real 3m10.567s user 3m5.168s sys 0m0.676s So, what is the but of GCJ then? With this results I'm sure I'm not going to compile it with GCJ! I tested this on Linux, are the results in Windows maybe better than that? This was the code from the application: public static void main(String[] args) { String str = ""; System.out.println("Start!!!"); for (long i = 0; i < 5000000L; i++) { Math.sqrt((double) i); Math.pow((double) i, 2.56); long j = i * 745L; String string = new String(String.valueOf(i)); string = string.concat(" kaka pipi"); // "Kaka pipi" is a kind of childly call in Dutch. string = new String(string.toUpperCase()); if (i % 300 == 0) { str = ""; } else { str += Long.toHexString(i); } } System.out.println("Stop!!!"); }

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  • Why and How to avoid Event Handler memory leaks ?

    - by gillyb
    Hey There, I just came to realize, by reading some questions and answers on StackOverflow, that adding event handlers using += in C# (or i guess, other .net languages) can cause common memory leaks... I have used event handlers like this in the past many times, and never realized that they can cause, or have caused, memory leaks in my applications. How does this work (meaning, why does this actually cause a memory leak) ? How can I fix this problem ? Is using -= to the same event handler enough ? Are there common design patterns or best practices for handling situations like this ? Example : How am I supposed to handle an application that has many different threads, using many different event handlers to raise several events on the UI ? Are there any good and simple ways to monitor this efficiently in an already built big application ? Thanks in advance!

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  • is there a Java GUI for dummies ?

    - by MHero
    Hello, first I want to apologize about my english, it may be not clear enough. Well, I'm new to Java programming, and I search over this web about use of Swing, AWT, 2D, etc. but I didn't get the answer I was looking for. I want to know about a book or method to learn Java GUI programming (not even sure this is a propper term). Previous answers guide me to Filthy Rich Clients by Romain Guy and also to The Swing Tutorial in Sun Web Page. and No offense, but...the first one seems too complex and the second one a bit disorganize. so I ask about a more "for dummies" method. Thanks EDIT: Thanks everyboy, you're very kind and serious. I want to clear some things that I didn't state for being my first question. I dont' want to use autogenerated code(Don't want to say why only focus on my question for consistency) Also I've read Deitel & Deitel and it's a good beginners book but it seems to me that doesn't cover layout(and other details) Finally, I tried to read netbeans generated code but it's a mess find method by method and function by function the way that the IDE does it I hope this edition helps to solve my question

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  • Read large amount of data from file in Java

    - by Crozin
    Hello I've got text file that contains 1 000 002 numbers in following formation: 123 456 1 2 3 4 5 6 .... 999999 100000 Now I need to read that data and allocate it to int variables (the very first two numbers) and all the rest (1 000 000 numbers) to an array int[]. It's not a hard task, but - it's horrible slow. My first attempt was java.util.Scanner: Scanner stdin = new Scanner(new File("./path")); int n = stdin.nextInt(); int t = stdin.nextInt(); int array[] = new array[n]; for (int i = 0; i < n; i++) { array[i] = stdin.nextInt(); } It works as excepted but it takes about 7500 ms to execute. I need to fetch that data in up to several hundred of milliseconds. Then I tried java.io.BufferedReader: Using BufferedReader.readLine() and String.split() I got the same results in about 1700 ms, but it's still too many. How can I read that amount of data in less that 1 second? The final result should be equal to: int n = 123; int t = 456; int array[] = { 1, 2, 3, 4, ..., 999999, 100000 };

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  • Java if/else behaving strangely

    - by Alex
    I'm a real newbie to java, so please excuse me if this is a hopelessly straightforward problem. I have the following from my java game server: // Get input from the client DataInputStream in = new DataInputStream (server.getInputStream()); PrintStream out = new PrintStream(server.getOutputStream()); disconnect=false; while((line = in.readLine().trim()) != null && !line.equals(".") && !line.equals("") && !disconnect) { System.out.println("Received "+line); if(line.equals("h")){ out.println("h"+EOF); // Client handshake System.out.println("Matched 1"); }else if (line.equals("<policy-file-request/>")) { out.println("..."+EOF); // Policy file System.out.println(server.getInetAddress()+": Policy Request"); disconnect=true; System.out.println("Matched 2"); }else if(line.substring(0,3).equals("GET")||line.substring(0,4).equals("POST")){ out.println("HTTP/1.0 200 OK\nServer: VirtuaRoom v0.9\nContent-Type: text/html\n\n..."); // HTML status page disconnect=true; System.out.println("Matched 3"); } else { System.out.println(server.getInetAddress()+": Unknown command, client disconnected."); disconnect=true; System.out.println("Matched else"); } } server.close(); First of all, the client sends an "h" packet, and expects the same back (handshake). However, I want it to disconnect the client when an unrecognised packet is received. For some reason, it responds fine to the handshake and HTML status request, but the else clause is never executed when there's an unknown packet. Thanks

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  • Java Swing - Adding a row # column to a JTable

    - by llm
    I have data from a database loaded into a JTable through a custom table model. I want to have a column (should be the first column) which simply shows the display row number (i.e. it is not tied to any data (or sorting) but is simply the row number on the screen starting at 1). These "column headers" should be grayed out like the row headers. Any idea how to do this? Thanks

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  • Why aren't Java's generics implicitly polymorphic?

    - by froadie
    I'm a bit confused about how Java generics handle inheritance / polymorphism. Assume the following hierarchy - Animal (Parent) Dog - Cat (Children) So suppose I have a method doSomething(List<Animal> animals). By all the rules of inheritance and polymorphism, I would assume that a List<Dog> is a List<Animal> and a List<Cat> is a List<Animal> - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of any subset of Animal by saying doSomething(List<? extends Animal> animals). I understand that this is Java's behavior. My question is why? Why is polymorphism generally implicit, but when it comes to generics it must be specified?

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  • need help with some basic java.

    - by Racket
    Hi, I'm doing the first chapter exercises on my Java book and I have been stuck for a problem for a while now. I'll print the question, prompt/read a double value representing a monetary amount. Then determine the fewest number of each bill and coin needed to represent that amount, starting with the highest (assume that a ten dollar bill is the maximum size needed). For example, if the value entered is 47,63 (forty-seven dollars and sixty-three cents), and the program should print the equivalent amount as: 4 ten dollar bills 1 five dollar bills 2 one dollar bills 2 quarters 1 dimes 0 nickels 3 pennies" etc. I'm doing an example exactly as they said in order to get an idea, as you will see in the code. Nevertheless, I managed to print 4 dollars, and I can't figure out how to get "1 five dollar", only 7 dollars (see code). Please, don't do the whole code for me. I just need some advice in regards to what I said. Thank you. import java.util.Scanner; public class PP29 { public static void main (String[] args) { Scanner sc = new Scanner (System.in); int amount; double value; double test1; double quarter; System.out.println("Enter \"double\" value: "); value = sc.nextDouble(); amount = (int) value / 10; // 47,63 / 10 = 4. int amount2 = (int) value % 10; // 47 - 40 = 7 quarter = value * 100; // 47,63 * 100 = 4736 int sum = (int) quarter % 100; // 4763 / 100 => 4763-4700 = 63. System.out.println(amount); System.out.println(amount2); } }

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  • Why Is Java Missing Access Specifiers?

    - by Tom Tresansky
    Does anyone understand why Java is missing: An access specifier which allows access by the class and all subclasses, but NOT by other classes in the same package? (Protected-minus) An access specifier which allows access by the class, all classes in the same package, AND all classes in any sub-package? (Default-plus) An access specifier which adds classes in sub-packages to the entities currently allowed access by protected? (Protected-plus) I wish I had more choices than protected and default. In particular, I'm interested in the Protected-plus option. Say I want to use a Builder/Factory patterned class to produce an object with many links to other objects. The constructors on the objects are all default, because I want to force you to use the factory class to produce instances, in order to make sure the linking is done correctly. I want to group the factories in a sub-package to keep them all together and distinct from the objects they are instantiating---this just seems like a cleaner package structure to me. No can do, currently. I have to put the builders in the same package as the objects they are constructing, in order to gain the access to defaults. But separating project.area.objects from project.area.objects.builders would be so nice. So why is Java lacking these options? And, is there anyway to fake it?

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  • Java Socket Closes After Connection?

    - by Matthew
    Why does this port/socket close once a connection has been made by a client? package app; import java.io.*; import java.net.*; public class socketServer { public static void main(String[] args) { int port = 3333; boolean socketBindedToPort = false; try { ServerSocket ServerSocketPort = new ServerSocket(port); System.out.println("SocketServer Set Up on Port: " + port); socketBindedToPort = true; if(socketBindedToPort == true) { Socket clientSocket = null; try { clientSocket = ServerSocketPort.accept();//This method blocks until a socket connection has been made to this port. System.out.println("Waiting for client connection on port:" + port); /** THE CLIENT HAS MADE A CONNECTION **/ System.out.println("CLIENT IS CONENCTED"); } catch (IOException e) { System.out.println("Accept failed: " + port); System.exit(-1); } } else { System.out.println("Socket did not bind to the port:" + port); } } catch(IOException e) { System.out.println("Could not listen on port: " + port); System.exit(-1); } } }

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  • Java execution details in System.out

    - by John
    As I remember there is a magic command line option in Java that turn on writing of operations that are currently executed to console. The output was looked like byte code. I do not mean -verbose, because it prints only class loading, while this option outputs information like memory allocation etc.

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  • how to do sorting using java

    - by karthikacyr
    hi friends, I have text file with list of alphabets and numbers. I want to do sorting w.r.t this number using java. My text file looks like this: a---12347 g---65784 r---675 I read the text file and i split it now. But i dont know how to perform sorting . I am new to java. Please give me a idea. My output want to be g---65784 a---12347 r---675 Plese help me. Thanks in advance. My coding is String str = ""; BufferedReader br = new BufferedReader(new FileReader("counts.txt")); while ((str = br.readLine()) != null) { String[] get = str.split("----"); When i search the internet all suggest in the type of arrays. I tried. But no use.How to inlude the get[1] into array. int arr[]=new int[50] arr[i]=get[1]; for(int i=0;i<50000;i++){ for(int j=i+1;j<60000;j++){ if(arr[i]arr[j]){ System.out.println(arr[i]); } }

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  • Shared memory of same DLL in different 32 bit processes is sometimes different in a terminal session

    - by KBrusing
    We have an 32 bit application consisting of some processes. They communicate with shared memory of a DLL used by every process. Shared memory is build with global variables in C++ by "#pragma data_seg ("Shared")". When running this application sometime during starting a new process in addition to an existing (first) process we observe that the shared memory of both processes is not the same. All new started processes cannot communicate with the first process. After stopping all of our processes and restarting the application (with some processes) everything works fine. But sometime or other after successfully starting and finishing new processes the problem occurs again. Running on all other Windows versions or terminal sessions on Windows server 2003 our application never got this problem. Is there any new "feature" on Windows server 2008 that might disturb the hamony of our application?

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  • How to manage memory for ios with large csv files?

    - by Pell000
    I'm new to ios development, and I'm running into issues relating to memory management and my approaches to dealing with large datasets. Right now, I am loading the csv files and storing the relevant data as objects in memory at app initialization. Some of the csv files are larger than 1MB, and in total, my app uses about 180MB of memory. This is obviously way too high of a number (unless the info I found is wrong and this is an acceptable number, then please let me know). I feel as though there is a fundamental flaw in my approach: is there a way I can avoid storing the csv files in the project itself? Or, is there a kind of "lazy" loading I can do so that I can simply look up info in the csv file, as opposed to loading all of the data from it at once? Any help would do. I think that I need a new perspective in how to manage this more efficiently.

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  • Avoiding instanceof in Java

    - by Mark Lutton
    Having a chain of "instanceof" operations is considered a "code smell". The standard answer is "use polymorphism". How would I do it in this case? There are a number of subclasses of a base class; none of them are under my control. An analogous situation would be with the Java classes Integer, Double, BigDecimal etc. if (obj instanceof Integer) {NumberStuff.handle((Integer)obj);} else if (obj instanceof BigDecimal) {BigDecimalStuff.handle((BigDecimal)obj);} else if (obj instanceof Double) {DoubleStuff.handle((Double)obj);} I do have control over NumberStuff and so on. I don't want to use many lines of code where a few lines would do. (Sometimes I make a HashMap mapping Integer.class to an instance of IntegerStuff, BigDecimal.class to an instance of BigDecimalStuff etc. But today I want something simpler.) I'd like something as simple as this: public static handle(Integer num) { ... } public static handle(BigDecimal num) { ... } But Java just doesn't work that way. I'd like to use static methods when formatting. The things I'm formatting are composite, where a Thing1 can contain an array Thing2s and a Thing2 can contain an array of Thing1s. I had a problem when I implemented my formatters like this: class Thing1Formatter { private static Thing2Formatter thing2Formatter = new Thing2Formatter(); public format(Thing thing) { thing2Formatter.format(thing.innerThing2); } } class Thing2Formatter { private static Thing1Formatter thing1Formatter = new Thing1Formatter(); public format(Thing2 thing) { thing1Formatter.format(thing.innerThing1); } } Yes, I know the HashMap and a bit more code can fix that too. But the "instanceof" seems so readable and maintainable by comparison. Is there anything simple but not smelly?

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  • Java Multi threading - Avoid duplicate request processing

    - by seawaves
    I have following multi threaded environment scenario - Requests are coming to a method and I want to avoid the duplicate processing of concurrent requests coming. As multiple similar requests might be waiting for being processed in blocked state. I used hashtable to keep track of processed request, but it will create memory leaks, so how should keep track of processed request and avoid the same requests to be processed which may be in blocking state.

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  • Dont understand the concept of extends in URL.openConnection() in JAVA

    - by user1722361
    Hi I am trying to learn JAVA deeply and so I am digging into the JDK source code in the following lines: URL url = new URL("http://www.google.com"); URLConnection tmpConn = url.openConnection(); I attached the source code and set the breakpoint at the second line and stepped into the code. I can see the code flow is: URL.openConnection() - sun.net.www.protocol.http.Handler.openConnection() I have two questions about this First In URL.openConnection() the code is: public URLConnection openConnection() throws java.io.IOException { return handler.openConnection(this); } handler is an object of URLStreamHandler, define as blow transient URLStreamHandler handler; But URLStreamHandler is a abstract class and method openConnection() is not implement in it so when handler calls this method, it should go to find a subclass who implement this method, right? But there are a lot classes who implement this methods in sun.net.www.protocol (like http.Hanlder, ftp.Handler ) How should the code know which "openConnection" method it should call? In this example, this handler.openConnection() will go into http.Handler and it is correct. (if I set the url as ftp://www.google.com, it will go into ftp.Handler) I cannot understand the mechanism. second. I have attached the source code so I can step into the JDK and see the variables but for many classes like sun.net.www.protocol.http.Handler, there are not source code in src.zip. I googled this class and there is source code online I can get but why they did not put it (and many other classes) in the src.zip? Where can I find a comprehensive version of source code? Thanks!

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  • Java Daemon Threading with JNI

    - by gwin003
    I have a Java applet that creates a new non-daemon thread like so: Thread childThread = new Thread(new MyRunnable(_this)); childThread.setDaemon(false); childThread.start(); Then my MyRunnable object calls a native method that is implemented in C++: @Override public void run() { while (true) { if (!ran) { System.out.println("isDaemon: " + Thread.currentThread().isDaemon()); _applet.invokePrintManager(_applet.fFormType, _applet.fFormName, _applet.fPrintImmediately, _applet.fDataSet); ran = true; } } } This C++ method calls into a C# DLL that shows a form. My problem is, whenever the user navigates away from the page with a Java applet on it, JVM (and my C# form) is killed. I need the form and JVM to remain open until it is closed by the user. I tried setting my thread to be a non-daemon thread, which is working because System.out.println("isDaemon: " + Thread.currentThread().isDaemon() prints isDaemon: false. Is there something related to the way that the C# form is created (is there another thread I'm not accounting for) or something I am overlooking?? My thread is not a daemon thread, but the JVM is being killed anyways.

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