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  • Validating IPv4 string in Java

    - by Mat Banik
    Bellow method is validating if string is correct IPv4 address it returns true if it is valid. Any improvements in regex and elegance would be very appreciated: public static boolean validIP(String ip) { if (ip == null || ip.isEmpty()) return false; ip = ip.trim(); if ((ip.length() < 8) & (ip.length() > 15)) return false; try { Pattern pattern = Pattern.compile("^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"); Matcher matcher = pattern.matcher(ip); return matcher.matches(); } catch (PatternSyntaxException ex) { return false; } }

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  • Pattern for version-specific implementations of a Java class

    - by Mike Monkiewicz
    So here's my conundrum. I am programming a tool that needs to work on old versions of our application. I have the code to the application, but can not alter any of the classes. To pull information out of our database, I have a DTO of sorts that is populated by Hibernate. It consumes a data object for version 1.0 of our app, cleverly named DataObject. Below is the DTO class. public class MyDTO { private MyWrapperClass wrapper; public MyDTO(DataObject data) { wrapper = new MyWrapperClass(data); } } The DTO is instantiated through a Hibernate query as follows: select new com.foo.bar.MyDTO(t1.data) from mytable t1 Now, a little logic is needed on top of the data object, so I made a wrapper class for it. Note the DTO stores an instance of the wrapper class, not the original data object. public class MyWrapperClass { private DataObject data; public MyWrapperClass(DataObject data) { this.data = data; } public String doSomethingImportant() { ... version-specific logic ... } } This works well until I need to work on version 2.0 of our application. Now DataObject in the two versions are very similar, but not the same. This resulted in different sub classes of MyWrapperClass, which implement their own version-specific doSomethingImportant(). Still doing okay. But how does myDTO instantiate the appropriate version-specific MyWrapperClass? Hibernate is in turn instantiating MyDTO, so it's not like I can @Autowire a dependency in Spring. I would love to reuse MyDTO (and my dozens of other DTOs) for both versions of the tool, without having to duplicate the class. Don't repeat yourself, and all that. I'm sure there's a very simple pattern I'm missing that would help this. Any suggestions?

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  • add database Tablenames to the JList in java

    - by Litecia
    // Declare JList private JList jlstTab, jlstCol; . . . DefaultListModel dlmTables = new DefaultListModel(); DefaultListModel dlmCol = new DefaultListModel(); // Instantiate dlmTables.addElement("kl"); jlstTab= new JList(dlmTables); jlstTab.setSelectedIndex(0); jlstTab.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); . . . . Connect to the database public static void main(String args[]) { DBToolSwing cs = new DBToolSwing("DB Tool Swing"); try DBAccessObject dbAccess1 = new DBAccessObject("jdbc:odbc:JavaClassDSN"); DBAccessObject dbAccess2 = new DBAccessObject(); ResultSet rsTables = dbAccess1.getDatabaseTableNames(); while (rsTables.next()) System.out.println(rsTables.getString("TABLE_NAME")); I need to get the table names from the database, the output shouldn't be printed on the screen, instead I need the output added to the JlstTab so dlmTables.addElement("TABLE_NAME"); Please if someone can help I would appreciate it. Thanks in advance.

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  • Rad upload Java applet and z-index

    - by Belgurinn
    I'm using Rad upload for drag and drop upload. It's working perfectly except I'm having a problem with the z-index. I'm also using jquery UI on the site and the overlay doesn't cover the applet. Any ideas on how to control the z-index. It would be nice if there where a setting like in flash where you control wmode. But I've tried z-index on the div that controls it and no result.

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  • Regex to match pattern with subdomain in java gives issues

    - by Ramesh
    I am trying to match the sub domain of an url using http://([a-z0-9]*.)?example.com/.* which works perfectly for these cases. http://example.com/index.html http://test.example.com/index.html http://test1.example.com/index.html http://www.example.com/122/index.html But the problem is it matches for this URL too. http://www.test.com/?q=http://example.com/index.html if an URL with another domain has the URL in path it matches.Can any one tell me how to match for current domain only. getting the host will work but i need to match full URL.

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  • Java: JButton actionListener explantation

    - by MrDoctorProfessorTyler
    I am extremely confused as to how a JButton works. I have read over the oracle documents of the JButton, but I have failed to see how a JButton can have an actionlistener added to it. I have really always wondered how things like JFrames and all that can have things like .addMouseListener and all that. Can anyone explain how a JButton can have an actionListener added to it like the .addActionListener(...) syntax?

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  • Update music file details - Java.

    - by Desorder
    Hi all, Well, I'm a music fan guy, and now with my 18000 music collection, it's getting very hard to maintain. So, I would like to ask I could of question to help to write an app to maintain it for me. 1- How can I access a music file and read details of it? I mean, I would like to write some code and passing the directory, my app would read all the music files (understand mp3 files) and with that I would like to access details like title, artist, length and so on... 2- Is there a public source that I could access and update my file? A webservice somewhere that I could connect, query some information based on song name, or artist or whatever. I would like to achieve a final result of given a directory, my app would read the file, collect some information and query the source for a complete list of detail and update my file. Thank you guys for any help...

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  • how does serializable work in java?

    - by Karl Trumstedt
    If I have an instance of a class that I store in a session I need to make it serializable. This class has a static variable, will this be serialized in every instance stored? The static variable is a reference to a cache containing a lot of data in the background. Will all of this data be serialized? If so, it seems preferable to make this variable transient and re-fetch the cache instance each time the instance is restored. Maybe not store the cache instance at all in the class. Will the constructor execute when a class is restored from a serialized state? if not is there any other method I can use to re-instate a transient variable?

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  • Covariant return types in Java enums

    - by Kelvin Chung
    As mentioned in another question on this site, something like this is not legal: public enum MyEnum { FOO { public Integer doSomething() { return (Integer) super.doSomething(); } }, BAR { public String doSomething() { return (String) super.doSomething(); } }; public Object doSomething(); } This is due to covariant return types apparently not working on enum constants (again breaking the illusion that enum constants are singleton subclasses of the enum type...) So, how about we add a bit of generics: is this legal? public enum MyEnum2 { FOO { public Class<Integer> doSomething() { return Integer.class; } }, BAR { public Class<String> doSomething() { return String.class; } }; public Class<?> doSomething(); } Here, all three return Class objects, yet the individual constants are "more specific" than the enum type as a whole...

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  • Clone List Elements in Java

    - by Amir Rachum
    Hi all, I have a variable of type List<RelationHeader>. Now I want to copy all the elements in this list to a new list, but I want to actually copy all the members by value (clone them). Is there a quick command to do this, or do I need to iterate over the list and copy them one at a time?

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  • Garbage Collection in Java

    - by simion
    On the slides I am revising from it says the following: Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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  • finding out memory allocation hotspots in java

    - by Zamir
    Our GC is working hard and we have some pauses that we want to decrease. We have some memory allocation issues that we want to solve before or while we are tweaking with the actual JVM GC args. I would like to know which objects are making the GC sweat: is there a way to know which objects are evacuated every time the GC is working? is there a way to know which objects are moved between areas every time the GC is working? Is there a way to know which objects are in Eden area? I am working extensively with Jprofiler and Memory Analyzer. I would like to get this information on a running application in my staging environment.

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  • Strange Java Socket Behavior (Connects, but Doesn't Send)

    - by Donald Campbell
    I have a fairly complex project that boils down to a simple Client / Server communicating through object streams. Everything works flawlessly for two consecutive connections (I connect once, work, disconnect, then connect again, work, and disconnect). The client connects, does its business, and then closes. The server successfully closes both the object output stream and the socket, with no IO errors. When I try to connect a third time, the connection appears to go through (the ServerSocket.accept() method goes through and an ObjectOutputStream is successfully created). No data is passed, however. The inputStream.readUnshared() method simply blocks. I have taken the following memory precautions: When it comes time to close the sockets, all running threads are stopped, and all objects are nulled out. After every writeUnshared() method call, the ObjectOutputBuffer is flushed and reset. Has anyone encountered a similar problem, or does anyone have any suggestions? I'm afraid my project is rather large, and so copying code is problematic. The project boils down to this: SERVER MAIN ServerSocket serverSocket = new ServerSocket(port); while (true) { new WorkThread(serverSocket.accept()).start(); } WORK THREAD (SERVER) public void run() { ObjectInputBuffer inputBuffer = new ObjectInputBuffer(new BufferedInputStream(socket.getInputStream())); while (running) { try { Object myObject = inputBuffer.readUnshared(); // do work is not specified in this sample doWork(myObject); } catch (IOException e) { running = false; } } try { inputBuffer.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } CLIENT public Client() { Object myObject; Socket mySocket = new Socket(address, port); try { ObjectOutputBuffer output = new ObjectOutputBuffer(new BufferedOutputStream(mySocket.getOutputStream())); output.reset(); output.flush(); } catch (Exception e) { System.out.println("Could not get an input."); mySocket.close(); return; } // get object data is not specified in this sample. it simply returns a serializable object myObject = getObjectData(); while (myObject != null) { try { output.writeUnshared(myObject); output.reset(); output.flush(); } catch (Exception e) { e.printStackTrace(); break; } // catch } // while try { output.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } Thank you to everyone who may be able to help!

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  • Why doesn't Java Map extends Collection?

    - by polygenelubricants
    I was surprised by the fact that Map<?,?> is not a Collection<?>. I thought it'd make a LOT of sense if it was declared as such: public interface Map<K,V> extends Collection<Map.Entry<K,V>> After all, a Map<K,V> is a collection of Map.Entry<K,V>, isn't it? So is there a good reason why it's not implemented as such?

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  • java increase xmx dynamically at runtime

    - by Tomer
    Hi, I have a jvm server in my machine, now I want to have 2 apservers of mine sitting in same machine, however I want the standby one to have a really low amount of memory allocated with xmx because its passive, one the main server (active) goes down I want to allocate more memory to my passive server which is already up without restarting it (I have have them both having too much xmx - note they would consume memory at startup and I cant allow possibility of outOfMemory). So I want passive - low xmx once active goes down I want my passive to receive much more xmx. is there a way for me to achieve that. Thanks

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  • A very strange problem -> CSS file not detected .Java web application

    - by Nitesh Panchal
    Hello, If i browse my site using http://localhost:8080/abc/Login/index.jsf, everything works fine. But if browse it using simply http://localhost:8080/abc, the page is shown but all its images and css files are missing. What can be the problem? I have this in my web.xml :- <form-login-config> <form-login-page>/Login/index.jsf</form-login-page> <form-error-page>/Login/index.jsf</form-error-page> </form-login-config> Probably, images are not getting referenced correctly. Can anybody help me? I have referenced css file as follows :- <link href="./Css/MainStyleSheet.css" rel="stylesheet" type="text/css" /> where Css is folder in Login

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  • [Java] Safe way of exposing keySet().

    - by Jake
    This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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  • Java, merging two arrays evenly

    - by user2435044
    What would be the best way to merge two arrays of different lengths together so they are evenly distributed in the new array? Say I have the following arrays String[] array1 = new String[7]; String[] array2 = new String[2]; String[] mergedArray = new String[array1.length + array2.length]; I would want mergedArray to have the following elements array1 array1 array1 array2 array1 array1 array1 array2 array1 but if I were to change the size of the arrays to String[] array1 = new String[5]; String[] array2 = new String[3]; String[] mergedArray = new String[array1.length + array2.length]; then I would want it to be array1 array2 array1 array2 array1 array2 array1 array1 basically if it can be helped each array2 element shouldn't be touching each other; exception if array2 has a size larger than array1.

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  • Java String object creation

    - by Ajay
    Hi, 1) What is difference in thers two statements: String s1 = "abc"; and String s1 = new String("abc") 2) as i am not using new in first statement, how string object will be created Thanks

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