I want to implement a kind of "container" in which to store objects (instances) of different types. Then with an iterator I'd call common methods. This is what I have in mind:
Where translate(x, y, z) is a method common for objects in Positionables which objects are of different types (Sphere, Box etc.).
Now I was thinking Positionables could be a List<Positionable> and Positionable is an abstract class and Sphere and Box extends from it. But I don't know how to propagate the call of translate() to the subclasses.
What are the best approaches for this matter? It would be perfect if I could make it so I could somehow use the "with" construction like in the example above.
I have configured form based JAAS in my app. Basically, in web.xml I have declared security constraints on certain jsp page, declared specific roles, login and error pages. So, my login form is:
abstract class A class B extends A class C extends B class D extends C implements SomeInterface
I'm trying to implement a method "doSomething" declared in SomeInterface in class D. While trying to call doSomething in main I get the error message ”The method doSomething is undefined for the type B”
This is my code i main:
B container = new D("1,2,3,4,5,6,7,8"); System.out.println(container.doSomething());
I need container to be an object of type B, because it goes later into a list of type B. According to what I've been told, the only file I need to edit to make this work is class D.
I am trying to implement product method below which returns the set representing the Cartesian product of the current set and a given set (the Cartesian product contains all ordered pairs (a, b) where a belongs to the current set, and b belongs to the given set). The product should be a ListSet <Tuple<E>> object where each ordered pair is a Tuple element. (I have a Tuple class which implements an ordered tuple)
What am I trying to do in the product method : Make 2 for loop and inside the for loop make an array of <E> then set the 2 elements of the tuple then again set tuple and add it to arrayList. how to set 2 elements of the tuple and set tuple ??
public class ListSet<E> implements Iterable<E>{ SinglyLinkedList<E> sl; public ListSet(){ sl = new SinglyLinkedList<E>();
I am trying to make a ChessBoard class composed of an array of JLabels inside a JPanel with a grid layout. I am also trying to override the getPreferredSize method so that the board will change size when I resize the main window (in another class in which I will instancize this class as part of a larger GUI). I got this kind of layout working before, but now I am trying to get it to work with multiple classes. However, after copying in the part of the previous code corresponding to the panel's layout, I am encountering some errors that I don't know how to solve. Specifically, when I try to override the getPreferredSize method, the compiler tells me "method does not override or implement a method from a super type, " and that it can't find the method "getPreferredSize"
Here's my code:
public class ChessBoard extends JPanel//the panel that this class extends is the boardHousing { //mental chess board piece array Piece mentalBoard[][] = new Piece[8][8]; //actual GUI chessboard JLabel Array static JLabel chessBoard[][] = new JLabel[8][8];
[Code] ....
I would just think that I was overriding the method incorrectly, but the weird thing is that I got that specific section of code to work before -- the only thing different now is that there are multiple classes, so my ChessBoard class itself is extending JPanel.
I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{ private int x, y; Point (int x, int y) { this.x =x; this.y = y;
Okay, I am supposed to implement the functionalities of the Set class using a private data member of type ListReferencedBased<E>,how the ListReferenceBased works with what I am trying to accomplish.I am trying to complete Set.java, and I have barely started and much of the code doesn't work. ListReferenceBased was given to me completed.
import java.util.Iterator; pubic class ListReferenceBased<E> implements ListInterface<E>, Iterable<E>{ /** reference to the first element of the list */ private Node<E> head; /** number of items in list */ private int numItems;
I have a JPanel with vertical BoxLayout. It contains four components. I set the JPanel to LEFT_ALIGNMENT, which has no effect on its components. I set the first component to LEFT_ALIGNMENT, which has no effect. Only after I have set all four components to LEFT_ALIGNMENT do any of them align properly.
This suggests that it is impossible to have varying alignments in a container. They must all be the same alignment.
I accept that this is just the way things are: "Java works in mysterious ways." And I'm sure that it is possible to work around this limitation by stacking boxes that themselves have different internal alignments.
But I still wonder what in the world was going on in the minds of the Java developers. Is there a rational reason for this oddity?
This raises my most serious criticism of Swing: the hidden gotcha. Swing is a tangled mess of cross-connecting requirements that are impossible to divine by simple inspection of the documentation. If you want to use, say, a JRadioButton, it's not enough to study the documentation on JRadioButtons; you must also consult lots of documents for which there is no obvious connection to JRadioButton other than it being part of Swing.
I am looking for a way to have a Servlet (my container is Tomcat) calling a JSP file and processing it in order to retrieve the generated HTML. The compete scenario:
I have virtual shop and whenever a purchase is being carried out, the customer is redirected to a Servlet that post-processes the purchase (list of the items, etc.)
Among all these, the Servlet is also supposed to send me an email about the new purchase. I would like to have nice designed HTML mail and not just a simple plain text notification. I thought of having a designated JSP as a view, and it will only be available from the Servlet container, for this purpose. One way is having the Servlet create an HTTPClient (or any other method of network communication) to my own host and ask for the JSP.
I wonder if there is a simpler way to ask my own container to process a JSP, since I am not really making a request to an outside web application. Something like getServletContext.processAndReturnJsp("mail.jsp")
BTW, if you think my approach is too cumbersome to fill an email with HTML code, it would be great to know of a simpler way.
the focus traversal policy (hereafter "tab order") in forms and panels doesn't follow the order in which controls were inserted into the container, but is derived from the position of the components on the form or panel. This is very neat (and probably allows sloppy coders and GUI builders to exist without actually ever thinking about the tab order), except when it isn't. As when you actually want to specify a different component order, for example.
In the following example, I've created a form with two columns of buttons. I want the tab order to go through the first column of buttons, followed by second column of buttons (ie. a column-by-column schema). The default tab order is row-by-row, however, and can be obtained for reference by commenting out the setupFocus() call in the constructor.
I had hoped that the ContainerOrderFocusTraversalPolicy would do the job, but there is a couple of problems (which I've addressed in the setupFocus() method). Firstly, the container itself is part of the focus chain. This at least is easily remediable by calling setFocusable(false), but I don't have to do that with the initial focus traversal policy, so I wonder why I have to do it with this one. The other problem is more pressing, though - the ContainerOrderFocusTraversalPolicy lets me (un)hapilly tab through JLabels. Again, I've fixed this, but the initial policy knows all by itself that it's not a good idea to focus a JLabel. Moreover, I'm afraid there might be other components that do not receive focus with the original policy, but ContainerOrderFocusTraversalPolicy might plod though them.
isn't there some focus traversal policy implementation that I could just set and it would tab through exactly the same components as the original policy, except it would order them according to their order in the container?
I read JEE6 doc and confused with : Does container managed entity manager (injected by PersistenceContext annotation) is thread-safe in stateless session bean in multiple-thread env?
See code below, if there are 2 requests to stateless sesion bean in 2 concurrent threads , is it using same Entity Manager Instance or not?
@Stateless(name = "HRFacade", mappedName = "HR_FACES_EJB_JPA-HRFacade-HRFacade") public class HRFacadeBean implements HRFacade, HRFacadeLocal { @Resource SessionContext sessionContext;
If you have final int i = 1; short s = 1; switch(s) { case i: System.out.println(i); }
it runs fine. Note that the switch expression is of type short (2 bytes) and the case constant is of type int (4 bytes).My question is: Is the type irrelevant as long as the value is within the boundaries of the type of the switch expression?I have the feeling that this is true since:
byte b = 127; final int i = 127; switch(b) { case i: System.out.println(i); }
This runs fine again, but if I change the literal assigned to i to 128, which is out of range for type byte, then the compiler complains.Is it true that in the first example the short variable and in the second example the byte variable (the switch expressions) are first implicitly converted to an int and then compared with the case constants?
Got a problem with generics, which I'm still pretty new at. Here's a program that compiles fine:
import java.util.ArrayList; import javax.swing.JComponent; public class Experiments { public static void main(String[] args) { ListHolder holder = new ListHolder();
[Code] ....
It's useless, but it compiles. If I change Line 14, however, to add a generic type parameter to the ListHolder class, Line 10 no longer compiles:
import java.util.ArrayList; import javax.swing.JComponent; public class Experiments { public static void main(String[] args) { ListHolder holder = new ListHolder();
[Code] ....
I get this error:
Uncompilable source code - incompatible types: java.lang.Object cannot be converted to javax.swing.JComponent at experiments.Experiments.main(Experiments.java:10)
Apparently, the introduction of the type parameter leaves the compiler thinking that aList is of type Object. I can cast it, like this:
JComponent c = ((ArrayList<JComponent>)holder.aList).iterator().next();
That makes the compiler happy, but why is it necessary? How does adding the (unused) type parameter to the ListHolder class end up making the compiler think the aList member of an instance of ListHolder is of type Object?
I'm trying to parse and compare the content of a zip file. However I'm stuck at what SHOULD be a very simple problem, however I can't seem to find a solution. I have done the following:
ZipInputStream zin1 = new ZipInputStream(fin); ZipEntry ze1 = null; fin2 = new FileInputStream(fileName2); ZipInputStream zin2 = new ZipInputStream(fin2); ZipEntry ze2 = null; //fin.close(); ze1 = zin1.getNextEntry(); ze2 = zin2.getNextEntry();
Which gives me the first entry of each zipfile as a ZipEntry type object. I have tried getting the path of the file (inside the zip file) and using this to create a File type object. This does not seem to work though I get:
Exception in thread "main" java.io.FileNotFoundException: My DocumentsmetadatacoreProperties.xml (The system cannot find the file specified) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(Unknown Source) at java.io.FileReader.<init>(Unknown Source)
And this is because I get a null return from trying to create the File file1 = new File(correctLocation);
I guess I cannot access the file inside a zip file this way. So my question is how can I make a ZipEntry type object into a File type object?
The objective of the code is to add new records based on existing records with a partial change to the key. I'm getting "type of the expression must be an array type but it resolved to DstidArray" on dsTidRecTbl[i]
String stMajor = request.getParameter("stMajorVersion"); String stMinor = request.getParameter("stMinorVersion"); String stPatch = request.getParameter("stPatchVersion"); StringBuffer stKeySB = new StringBuffer(stMajor+stMinor+stPatch); String stKey = new String(stKeySB.toString()); DstidArray dsTidRecTbl = new DstidArray(stKey); request.setAttribute("dsTidRecTbl", dsTidRecTbl);
I need to design 'notepad' application as my assignment.
Requirement: Only text is allowed, all the characters are having same size and font. It should have feature like new, open, save , save as , exit , UNDO , find , replace and font.
For this i use JTextArea and menu bar .
I am able to develop features like new, open, save , save as , exit. Need to implement now UNDO , find , replace and font but struck at 'UNDO'.
UNDO feature should be enable only when user writing in the writing area but not when it opens any file. What i thought is to have a flag on whenever user save whatever he wrote and if he use select UNDO then it check for the flag. If flag is ON then it will not do UNDO and if flag is not set then it cleared everything from the Text Area.
