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  • How to call implemented method of generic enum in Java?

    - by Justin Wiseman
    I am trying pass an enum into a method, iterate over that enums values, and call the method that that enum implements on all of those values. I am getting compiler errors on the part "value.getAlias()". It says "The method getAlias() is undefined for the type E" I have attempted to indicate that E implements the HasAlias interface, but it does not seem to work. Is this possible, and if so, how do I fix the code below to do what I want? The code below is only meant to show my process, it is not my intention to just print the names of the values in an enum, but to demonstate my problem. public interface HasAlias{ String getAlias(); }; public enum Letters implements HasAlias { A("The letter A"), B("The letter B"); private final String alias; public String getAlias(){return alias;} public Letters(String alias) { this.alias = alias; } } public enum Numbers implements HasAlias { ONE("The number one"), TWO("The number two"); private final String alias; public String getAlias(){return alias;} public Letters(String alias) { this.alias = alias; } } public class Identifier { public <E extends Enum<? extends HasAlias>> void identify(Class<E> enumClass) { for(E value : enumClass.getEnumConstants()) { System.out.println(value.getAlias()); } } }

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  • Does MultiThreading in Java takes much time for task completion?

    - by Geeta
    I have to search for a string in 10 large size files (in zip format 70 MB) and have to print the lines with the search string to corresponding 10 output files.(i.e. file 1 output should be in output_file1...file2--- output_file2). The same program takes 15 mins for a single file. But if use 10 threads to read 10 files and to write in 10 different files it should complete in 15 mins but its taking 40 mins. How can I solve this. Or multithreading will take this much time only?

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  • How do I keep JTextFields in a Java Swing BoxLayout from expanding?

    - by Matthew
    I have a JPanel that looks something like this: JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); ... panel.add (jTextField1); panel.add (Box.createVerticalStrut(10)); panel.add (jButton1); panel.add (Box.createVerticalStrut(30)); panel.add (jTextField2); panel.add (Box.createVerticalStrut(10)); panel.add (jButton2); ... //etc. My problem is that the JTextFields become huge vertically. I want them to only be high enough for a single line, since that is all that the user can type in them. The buttons are fine (they don't expand vertically). Is there any way to keep the JTextFields from expanding? I'm pretty new to Swing, so let me know if I'm doing everything horribly wrong.

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  • Is an ArrayList automatically declared static in Java, if it is an instance variable?

    - by Alex
    I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (st1 ,st2 ,st3) and I want to make new objects of aClass: { aClass obj1,obj2,obj3; obj1=new aClass(st1); obj2=new aClass(st2); obj3=new aClass(st3); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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  • How does a Java Arraylist contains() method evaluate objects?

    - by mvid
    Say i create one object and add it to my ArrayList. If I then create another object with exactly the same constructor input, will the contain() method evaluate the two objects to be the same? Assume the constructor doesn't do anything funny with the input, and the variables stored in both objects are identical. ArrayList<Thing> basket = new ArrayList<Thing>(); Thing thing = new Thing(100); basket.add(thing); Thing another = new Thing(100); basket.contains(another); // true or false?

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  • Is there a Java 1.5 varargs API for slf4j yet?

    - by Josh
    I want to get rid of this lot... public void info(String msg); public void info(String format, Object arg); public void info(String format, Object arg1, Object arg2); public void info(String format, Object[] argArray); ...and replace it with this one... public void info(String format, Object ... args); ...so that my logging syntax doesn't have to change depending on the number of arguments I want to log. There seems to be lots of discussion and work around it, but where is it? Or should I wrap the wrapper that is slf4j?

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  • Where to store global variables like file paths in java ?

    - by Jules Olléon
    In my application I use some icons. Where should I store the path of the directory containing those icons ? The icons are used in different classes so it doesn't really make sense to store them in one of those classes in particular. I read that global variables are evil, but is it acceptable to use a class (eg Commons) containing only public static final fields to store this king of data ? What solution is used in professional applications ?

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  • In Java, how do you parse through a single word string?

    - by Fraz
    I'm trying to parse though a string made up of a single word. How would you go about assigning the last letter of the word to a variable? I was thinking of using the Scanner class to parse the word and make each letter an element in an array but it seems Scanner.next() only goes through whole words and not the individual letters. Any help?

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  • Java- Copy file to either new file or existing file.

    - by jared
    Hi- I would like to write a function copy(File f1, File f2) f1 is always a file. f2 is either a file or a directory. If f2 is a directory I would like to copy f1 to this directory (the file name should stay the same). If f2 is a file I would like to copy the contents of f1 to the end of the file f2. So for example if F2 has the contents: 2222222222222 And F1 has the contents 1111111111111 And I do copy(f1,f2) then f2 should become 2222222222222 1111111111111 Thanks!

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  • Java long task - Did it stop writing to file?

    - by rockit
    I am writing a lot of data to a file, and while keeping my eye on the file it eventually stopped growing in size. Essentially my task is getting information from a database, and printing out all non-unique values in column A. Since there are many rows to the database table, and the database table is across my network, this is taking days to complete. Thus I'm concerned that since the file isn't growing, that it isn't actually writing to the file anymore. Which is odd, I have no "catch"'s in my code, so if there was a problem writing to file, wouldn't it have thrown an error?! Should I let the task complete (estimate 2-3 days from today), or is there something else that I don't know going on here making my application not write to the file?! my algorithm goes something like this Declare file Create new file Open file for writing get database connection get resultset from database for each row in the resultset - write column "A" to file - if row# % 100000 then write to screen "completed " + row# + " rows" when no more rows exist close file write to screen - "completed"

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  • How to map oracle timestamp to appropriate java type in hibernate?

    - by jschoen
    I am new to hibernate and I am stumped. In my database I have tables that have a columns of TIMESTAMP(6). I am using Netbeans 6.5.1 and when I generate the hibernate.reveng.xml, hbm.xml files, and pojo files it sets the columns to be of type Serializable. This is not what I expected, nor what I want them to be. I found this post on the hibernate forums saying to place: in the hibernate.reveng.xml file. In Netbeans you are not able to generate the mappings from this file (it creates a new one every time) and it does not seem to have the ability to re-generate them from the file either (at least according to this it is slated to be available in version 7). So I am trying to figure out what to do. I am more inclined to believe I am doing something wrong since I am new to this, and it seems like it would be a common problem for others. So what am I doing wrong? If I am not doing anything wrong, how do I work around this? I am using Netbeans 6.5, Oracle 10G, and I believe Hibernate 3 (it came with my netbeans). Edit: Meant to say I found this stackoverflow question, but it is really a different problem.

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  • How to get rid of library references problem? Java

    - by Nitesh Panchal
    Hello, I created a web application and it used several libraries once upon a time. So i added them but later on i found alternative and actually better ways to do the same things. So i removed references from my project for those jars and libraries. Everything works fine but when i move the same project to my friend's laptop Netbeans 6.8 simply doesn't let me deploy the project and gives the whole bundle of errors of libraries that i used previously but i don't now. I removed all references from build.impl file and then when i deploy it, it works fine. But when i do a clean and build and try to deploy it, build.impl automatically again adds those lines of xml which contain references to libraries an again gives me a whole long list of errors. How do i get rid of this? I am really tired of these silly errors. Thanks in advance :)

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  • How to set JComboBox not to select an element when created? (Java)

    - by Alex Cheng
    Hi all. Problem: I am using JComboBox, and tried using setSelectionIndex(-1) in my code (this code is placed in caretInvoke()) suggestionComboBox.removeAllItems(); for (int i = 0; i < suggestions.length; i++) { suggestionComboBox.addItem(suggestions[i]); } suggestionComboBox.setSelectedIndex(-1); suggestionComboBox.setEnabled(true); This is the initial setting when it was added to a pane: suggestionComboBox = new JComboBox(); suggestionComboBox.setEditable(false); suggestionComboBox.setPreferredSize(new Dimension(25, 25)); suggestionComboBox.addActionListener(new SuggestionComboBoxListener()); When the caretInvoke triggers the ComboBox initialisation, even before the user selects an element, the actionPerformed is already triggered (I tried a JOptionPane here): First popup (notice that "flow byte_jump" is selected): Second popup (I think the setSelectionIndex is executed) Then in the end: The problem is: My program autoinserts the selected text when the user selects an element from the ComboBox. So without the user selecting anything, it is automatically inserted already. How can I overcome the problem in this situation? Thanks.

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  • How to test whether a char is NOT in a string? (java, junit)

    - by JB
    As title says, im having trouble with my junit tests passing for checking if a character is not in a string and how to check if an empty string doesnt have a character. here is the method i have: public static boolean isThere(String s, char value){ for(int x = 0; x <= s.length(); x++){ if(s.charAt(x) == value){ return true; } else if(s.length() == 0){ return false; } } return false; And here is the junit test: public void testIsThere() { { String sVal = "Jeff George"; boolean hasA = StringMethods.isThere(sVal,'e'); assertTrue(hasA); boolean hasE = StringMethods.isThere(sVal, 'o'); assertTrue(hasE); boolean notIn = StringMethods.isThere(sVal,'b'); assertTrue(notIn); } { String sVal = ""; boolean nothingIn = StringMethods.isThere(sVal,'a'); assertFalse(nothingIn); boolean notIn = StringMethods.isThere(sVal,'b'); assertFalse(notIn); } } Thank you very much, appreciated

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