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  • Accessing variablss through a different class within the constructor of latter classes of an object

    - by Haxed
    In the code below, I've added two lines that print output. The first line prints junk as usual, but surprisingly the second one gives me a compilation error. Why? class Student { private String name; public Student(String name){ this.name = name; } public String getName(){ return name; } } class StudentServer { public StudentServer(){ Student[] s = new Student[30]; s[0] = new Student("Nick"); // LINE 01: This compiles, although prints junk System.out.println(s[0]); // LINE 02: I get a error called cannot find symbol System.out.println(s[0].getName()); } public static void main(){ new StudentServer(); } } Many Thanks

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  • avoid NullPointerException at the first cycle

    - by user1508419
    I have this piece of code: EventSnapshot snapshotEvent = new EventSnapshot(); EventSnapshot currentEvent = new EventSnapshot(); do { ... currentEvent.setContent(in_stats); ... if(!snapshotEvent.equals(currentEvent)) snapshotEvent.setContent(in_stats); } while(true); At the first cycle I get a NullPointerException because obviously the object snapshotEvent is empty. At the second cycle this doesn't happen.how can avoid this problem?

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  • Help for creating a random String

    - by Max
    I need to create a random string which should be between the length of 6 to 10 but it sometimes generates only about the length of 3 to 5. Here's my code. Can anyone would be able to find out the problem? :( int lengthOfName = (int)(Math.random() * 4) + 6; String name = ""; /* randomly choosing a name*/ for (int j = 0; j <= lengthOfName; j++) { int freq = (int)(Math.random() * 100) + 1; if(freq <= 6){ name += "a"; }if(freq == 7 && freq == 8){ name += "b"; }if(freq >= 9 && freq <= 11){ name += "c"; }if(freq >= 12 && freq <= 15){ name += "d"; }if(freq >= 16 && freq <= 25){ name += "e"; }if(freq == 26 && freq == 27){ name += "f"; }if(freq == 28 && freq == 29){ name += "g"; }if(freq >= 30 && freq <= 33){ name += "h"; }if(freq >= 34 && freq <= 48){ name += "i"; }if(freq == 49 && freq == 50){ name += "j"; }if(freq >= 51 && freq <= 55){ name += "k"; }if(freq >= 56 && freq <= 60){ name += "l"; }if(freq == 61 && freq == 62){ name += "m"; }if(freq >= 63 && freq <= 70){ name += "n"; }if(freq >= 71 && freq <= 75){ name += "o"; }if(freq == 76 && freq == 77){ name += "p"; }if(freq == 78){ name += "q"; }if(freq >= 79 && freq <= 84){ name += "r"; }if(freq == 85 && freq == 86){ name += "s"; }if(freq == 87 && freq == 88){ name += "t"; }if(freq >= 89 && freq <= 93){ name += "u"; }if(freq == 94){ name += "v"; }if(freq == 95 && freq == 96){ name += "w"; }if(freq == 97){ name += "x"; }if(freq == 98 && freq == 99){ name += "y"; }if(freq == 100){ name += "z"; } }

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  • How can i attach data to a JTA transaction? (or uniquely identify it)

    - by kwyjibo
    I have a getStockQuote() function that will get a current stock quote for a symbol from the stock market. My goal is that within a JTA transaction, the first call to getStockQuote() will fetch a stock quote, but all subsequent calls within the same transaction will reuse the same stock quote (e.g.: it will not try to fetch a new quote). If a different transaction starts, or another transaction runs concurrently, i would expect the other transaction to fetch its own stock quote on its first call. This would be similar to how you can configure JPA providers to only fetch a database row from the database once, and use the cached value for subsequent access to the same database row within the transaction. Does anyone have tips on how this can be achieved?

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  • "Overriding" instance variables in subtype: Possible risks?

    - by sebastiangeiger
    Say I had a class SuperClass and two subclasses SubClassA and SubClassB that inherit from SuperClass. abstract class SuperClass{ ... List someList; ... } class SubClassA extends SuperClass{ ... List<String> someList; ... } class SubClassB extends SuperClass{ ... List<Integer> someList; ... } That way it is convenient because I can get someList.size() in Superclass and have Typesafety in the Subclasses. The problem is that it does not "feel" right, can you think of potential hazards this apporach has that I am not aware of?

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  • Does a servlet knows the encoding of the sent form that specified using http-equiv?

    - by Daziplqa
    Does a servlet knows the encoding of the sent form that specified using http-equiv? When I specify an encoding of a POSTed form using http-equiv like that: <HTML> <head> <meta http-equiv='Content-Type' content='text/html; charset=gb2312'/> </head> <BODY > <form name="form" method="post" > <input type="text" name="v_rcvname" value="????"> </form> </BODY> </HTML> And then at the servlet I use the method, request.getCharacterEncoding() I got null ! So, Is there a way that I can tell the server that I am encoding the data in some char encoding??

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  • Update rich:dataTable binding on Ajax selectionchange

    - by MilkJug
    I want to find the current selection of the data table whenever a selection changes. I can update other items using: <a4j:ajax render=":tmp,:tmp2" event="selectionchange"> But I cannot find the current selection - I think the major issue is that the UIExtendedDataTable backing does not get updated on the Ajax request. Is there a way to update the current selection on a selectionchange (Using RichFaces 4)?

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  • pass Value from class to JFrame

    - by MYE
    Hello everybody! i have problem between pass value from Class to another JFrame my code write follow MVC Model. Therefore i have 1 class is controller , one jframe is view and 1 class is model. i have some handle process on controller to get value on it and i want this value to jframe but not pass by constructor . How can i pass value from class to jframe and when value be pass jframe will use it to handle. Ex: public class A{ private String str; public A(){ } public void handle(){ ViewFrame v = new ViewFrame(); v.setVisible(true); v.pack(). v.setSize(330,600); str = "Hello World"; //init value here v.getString(str);// pass value to jframe here. } } ======================= public class ViewFrame extends JFrame{ private String str; public ViewFrame (){ System.out.println(str); } public String getString(String str){ return this.str = str; } } but it return null??

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  • How to see full compile path in Eclipse?

    - by alleywayjack
    I have looked for an answer for this nearly every where that I can think of, but there doesn't seem to be any way to actually SEE what Eclipse "runs" to compile the projects (as it does need the JDK installed and visible to actually build). I ask because I imported a few jars into my project, and even though I've looked through all the javac documentation, I can't seem to figure out how to mimic it quite like Eclipse does. I really, really need to be able to compile on the command line in this case - Eclipse or any other IDE just isn't what is needed. I started to look through the Eclipse source, and although this sounds lazy, I just became overwhelmed and figured I would ask here first, hoping someone else had the same question at one point.

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  • Print unique ascii characters in eclipse console

    - by Shaded
    Hey guys, Kind of a strange question but... here it goes. Recently my application threw an IOException that the text only had a clubs symbol in it (like the suit in cards) I know this is probably because there was a number in there that was cast to a char and printed to the screen, and I've found where that might have happened. The only problem is, I can't recreate it in eclipse because the eclipse console doesn't want to print those characters for me. All I get are boxes. I figure this is an encoding issue or something but I need eclipse to print out those characters just like the windows console would. Is there a setting I can change to do this?

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  • Validation - Data Integrity

    - by Thomas
    A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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  • How do you search through a map?

    - by Jack Null
    I have a map: Map<String, String> ht = new HashMap(); and I would like to know how to search through it and find anything matching a particular string. And if it is a match store it into an arraylist. The map contains strings like this: 1,2,3,4,5,5,5 and the matching string would be 5. So for I have this: String match = "5"; ArrayList<String> result = new ArrayList<String>(); Enumeration num= ht.keys(); while (num.hasMoreElements()) { String number = (String) num.nextElement(); if(number.equals(match)) { result.add(number); } }

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  • How can find out the system default currency symbol on BlackBerry?

    - by ageektrapped
    I have a need to display a currency value in my application. There doesn't seem to be an easy way to do this with the RIM API, so I'm reduced to creating my own solution (a common refrain for BlackBerry development, unfortunately) Currently I'm using the Formatter class, from javax.microedition.locale like so protected String formatResult(double result) { try { Locale l = Locale.getDefaultForSystem(); Formatter formatter = new Formatter(l.toString()); return formatter.formatCurrency(result); } catch (UnsupportedLocaleException e) { return "This fails for the default locale because BlackBerry sucks"; } } I always hit the catch block in the simulator. Since this doesn't work by default on the simulator, I'm hesitant to put it in the application. So I have two questions: Can anyone tell me if the above solution is the way to go? And how to fix it, of course. Is there a way I can retrieve the currency symbol for the current locale programmatically so I can format myself?

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  • Strange performance behaviour

    - by plastilino
    I'm puzzled with this. In my machine Direct calculation: 375 ms Method calculation: 3594 ms, about TEN times SLOWER If I place the method calulation BEFORE the direct calculation, both times are SIMILAR. Woud you check it in your machine? class Test { static long COUNT = 50000 * 10000; private static long BEFORE; /*--------METHOD---------*/ public static final double hypotenuse(double a, double b) { return Math.sqrt(a * a + b * b); } /*--------TIMER---------*/ public static void getTime(String text) { if (BEFORE == 0) { BEFORE = System.currentTimeMillis(); return; } long now = System.currentTimeMillis(); long elapsed = (now - BEFORE); BEFORE = System.currentTimeMillis(); if (text.equals("")) { return; } String message = "\r\n" + text + "\r\n" + "Elapsed time: " + elapsed + " ms"; System.out.println(message); } public static void main(String[] args) { double a = 0.2223221101; double b = 122333.167; getTime(""); /*--------DIRECT CALCULATION---------*/ for (int i = 1; i < COUNT; i++) { Math.sqrt(a * a + b * b); } getTime("Direct: "); /*--------METHOD---------*/ for (int k = 1; k < COUNT; k++) { hypotenuse(a, b); } getTime("Method: "); } }

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  • Quartz: triggering multiple jobs

    - by Phanindra
    In Quarts, can I use a single trigger to schedule multiple jobs, so that all the jobs gets executed in parallel. What is the best way to do this. Example, every hour execute Jobs j1, j2, ..., jn in parallel. Assuming that there is no dependency between the jobs.

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  • Best way to reuse a Runnable

    - by Gandalf
    I have a class that implements Runnable and am currently using an Executor as my thread pool to run tasks (indexing documents into Lucene). executor.execute(new LuceneDocIndexer(doc, writer)); My issue is that my Runnable class creates many Lucene Field objects and I would rather reuse them then create new ones every call. What's the best way to reuse these objects (Field objects are not thread safe so I cannot simple make them static) - should I create my own ThreadFactory? I notice that after a while the program starts to degrade drastically and the only thing I can think of is it's GC overhead. I am currently trying to profile the project to be sure this is even an issue - but for now lets just assume it is.

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