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  • Is an "infinite" iterator bad design?

    - by Adamski
    Is it generally considered bad practice to provide Iterator implementations that are "infinite"; i.e. where calls to hasNext() always(*) return true? Typically I'd say "yes" because the calling code could behave erratically, but in the below implementation hasNext() will return true unless the caller removes all elements from the List that the iterator was initialised with; i.e. there is a termination condition. Do you think this is a legitimate use of Iterator? It doesn't seem to violate the contract although I suppose one could argue it's unintuitive. public class CyclicIterator<T> implements Iterator<T> { private final List<T> l; private Iterator it; public CyclicIterator<T>(List<T> l) { this.l = l; this.it = l.iterator(); } public boolean hasNext() { return !l.isEmpty(); } public T next() { T ret; if (!hasNext()) { throw new NoSuchElementException(); } else if (it.hasNext()) { ret = it.next(); } else { it = l.iterator(); ret = it.next(); } return ret; } public void remove() { it.remove(); } }

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  • Comparable and Comparator contract with regards to null

    - by polygenelubricants
    Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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  • How to enable logs for sitemesh

    - by atomsfat
    Is ther any form to enable logs for sitemesh ? I already put this in the log4j configuration but it doesn't work <!-- Appenders --> <appender name="console" class="org.apache.log4j.ConsoleAppender"> <param name="Target" value="System.out" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%-5p: %c - %m%n" /> </layout> </appender> <logger name="com.opensymphony"> <level value="debug"/> </logger> <logger name="org.springframework.beans"> <level value="warn" /> </logger> <logger name="org.springframework.binding"> <level value="debug" /> </logger> <logger name="org.springframework.jdbc"> <level value="warn" /> </logger> <logger name="org.springframework.transaction"> <level value="warn" /> </logger> <logger name="org.springframework.orm"> <level value="warn" /> </logger> <logger name="org.springframework.web"> <level value="debug" /> </logger> <logger name="org.springframework.webflow"> <level value="debug" /> </logger> <!-- Root Logger --> <root> <priority value="warn" /> <appender-ref ref="console" /> </root>

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  • Accessing selected node of richfaces tree from Javascript

    - by kazanaki
    Hello This should be a very simple question. I have a richfaces tree that is rendered using JSF. When the user clicks on a node I want a javascript function to run. Nothing more nothing less. No redirects, no re-submit, no-rerender, no Ajax. Just plain old Javascript. I have seen the onselected attribute of the tree and it indeed fires a Javascript method. But of course I want to know which node was clicked. Here is what I have so far <head> <script type="text/javascript"> function documentClicked(nodeRef) { alert("Node is "+nodeRef); } </script> </head> <rich:tree switchType="client" value="#{ajaxDocumentTree.rootNode}" var="document" onselected="documentClicked()" > <rich:treeNode iconLeaf="../images/tree/doc.gif" icon="../images/tree/doc.gif"> <h:outputText value="#{doc.friendlyName}" /> </rich:treeNode> But this does not work because nodeRef is undefined. I expected that the first argument of the callback would be the selected node but this is not the case. So the question is this: How do I fire a Javascript function with the selected node from a richfaces tree?

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  • Invert linear linked list

    - by ArtWorkAD
    Hi, a linear linked list is a set of nodes. This is how a node is defined (to keep it easy we do not distinguish between node an list): class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } public String toString(){ if(this.link != null){ return this.data.toString() + this.link.toString(); }else{ return this.data.toString() ; } } public void inc(){ this.data = new Integer((Integer)this.data + 1); } public void lappend(Node list){ Node child = this.link; while(child != null){ child = child.link; } child.link = list; } public Node copy(){ if(this.link != null){ return new Node(new Integer((Integer)this.data), this.link.copy()); }else{ return new Node(new Integer((Integer)this.data), null); } } public Node invert(){ Node child = this.link; while(child != null){ child = child.link; } child.link = this;.... } } I am able to make a deep copy of the list. Now I want to invert the list so that the first node is the last and the last the first. The inverted list has to be a deep copy. I started developing the invert function but I am not sure. Any Ideas? Update: Maybe there is a recursive way since the linear linked list is a recursive data structure. I would take the first element, iterate through the list until I get to a node that has no child and append the first element, I would repeat this for the second, third....

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  • What is the best way to handle validity dates in applications ?

    - by user214626
    Hello, How do we model these objects ? Scenario 1: Price changes in a time period EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-02-01 Null 900$ So, if the price changes to 910$ on 2009-02-15, then the system should automatically update the expiry date on the previous effective price to 2009-02-14, to keep it consistent. Scenario 2: No price specified between 2009-02-01 to 2009-02-28 EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-03-01 Null 900$ So, if new price is specified for 2009-02-15 onwards , then the system should automatically set the expiry date on the record to be inserted to 2009-02-28, because already a record effective from 2009-03-01 exists. Please suggest an effective way to handle these scenarios to model my framework, or are there any frameworks around that can do this . Thanks

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  • Eclipse RCP: Actions VS Commands

    - by Dot
    Hi, What are differences between Actions and Commands in the context of Eclipse RCP? I know that they both contribute to the menu entries, but which one is better? And why? Of all the online resources I read, I could not get a firm understanding of the differences between both. I have not actually tried to use them, but just wanted to understand them to start with from higher level point of view. Thanks

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  • Counter that will remember it's value

    - by owca
    I have a task to operate on complex number. Each number consists of double r = real part, double i = imaginary part and String name. Name must be set within constructor, so I've created int counter, then I'm sending it's value to setNextName function and get name letter back. Unfortunately incrementing this 'counter' value works only within costructor and then it is once again set to 0. How to deal with that?Some constant value? And second problem is that I also need to provide setNextNames(char c) function that will change the counter current value. The code : public class Imaginary { private double re; private double im; private String real; private String imaginary; private String name; private int counter=0; public Imaginary(double r, double u){ re = r; im = u; name = this.setNextName(counter); counter++; } public static String setNextName(int c){ String nameTab[] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N", "O","P","Q","R","S","T","U","W","V","X","Y","Z"}; String setName = nameTab[c]; System.out.println("c: "+c); return setName; } public static String setNextName(char c){ // //don't know how to deal with this part // }

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  • How to integrate Guice 2 into Wicket?

    - by deamon
    I want to use Guice 2 with Wicket 1.4. There is a "wicket-guice" package, which uses Guice 1. Can someone give me an example how to configure Wicket to use Guice 2 for injection (with Maven). As you can see blow, I've found a solution, but I wonder, if it would be better to use Guice Servlets and register the whole Wicket Application as a ServletFilter with Guice. But I think this would conflict with wickets object creation strategy.

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  • how can I handle user defined exceptions and after handling them resume the flow of program. here is

    - by fari
    /** * An exception thrown when an illegal side pit was * specified (i.e. not in the range 1-6) for a move */ public class IllegalSidePitNumException extends RuntimeException { /** * Exception constructor. * @param sidePitNum the illegal side pit that was selected. */ public IllegalSidePitNumException(int sidePitNum) { super("No such side pit number: "+sidePitNum); } } how do i use this ina program and then resume for there. I do not want the program to end but want to handle the exception and continue.

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  • How mature is apache sshd (MINA)?

    - by Yaneeve
    Has anyone ever used apache sshd (based on Apache MINA)? I would like to get some user input. Is it mature? Does it have (annoying) bugs? How is the API? Can useful documentation/tutorials be found? etc. Thanks all for your feedback.

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  • How to avoid serializing zero values with Simple Xml

    - by Bram Vandenbussche
    I'm trying to serialise an object using simple xml (http://simple.sourceforge.net/). The object setup is pretty simple: @Root(name = "order_history") public class OrderHistory { @Element(name = "id", required = false) public int ID; @Element(name = "id_order_state") public int StateID; @Element(name = "id_order") public int OrderID; } The problem is when I create a new instance of this class without an ID: OrderHistory newhistory = new OrderHistory(); newhistory.OrderID = _orderid; newhistory.StateID = _stateid; and I serialize it via simple xml: StringWriter xml = new StringWriter(); Serializer serializer = new Persister(); serializer.write(newhistory, xml); it still reads 0 in the resulting xml: <?xml version='1.0' encoding='UTF-8'?> <order_history> <id>0</id> <id_order>2</id_order> <id_order_state>8</id_order_state> </order_history> I'm guessing the reason for this is that the ID property is not null, since integers can't be null. But I really need to get rid of this node, and I'd rather not remove it manually. Any clues anyone?

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  • Mismatched coordinate systems in LWJGL with Mouse and Textures

    - by Braains
    I'm not really sure how to expand on this other than to say that it appears that my LWJGL seems to have different coordinate systems for the Mouse and for painting Textures. It seems that Textures have the usual Java2D way of putting (0, 0) in the upper-left corner, while the Mouse goes by the more sensible way of having the origin in the lower-left corner. I've checked my code a bunch but I don't see anything modifying the values between where I read them and where I use them. It's thrown me for a loop and I can't quite figure it out. I'll post all the code that involves the Mouse input and Texture painting for you guys to look at. private static void pollHelpers() { while(Mouse.next()) { InputHelper.acceptMouseInput(Mouse.getEventButton(), Mouse.getEventX(), Mouse.getEventY()); } while (Keyboard.next()) { if (Keyboard.getEventKeyState()) { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), true); } else { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), false); } } } public static void acceptMouseInput(int mouseButton, int x, int y) { for(InputHelper ie: InputHelper.instances) { if(ie.checkRectangle(x, y)) { ie.sendMouseInputToParent(mouseButton); } } } private void sendMouseInputToParent(int mouseButton) { parent.onClick(mouseButton); } public boolean checkRectangle(int x, int y) { //y = InputManager.HEIGHT - y; See below for explanation return x > parent.getX() && x < parent.getX() + parent.getWidth() && y > parent.getY() && y < parent.getY() + parent.getHeight(); } I put this line of code in because it temporarily fixed the coordinate system problem. However, I want to have my code to be as independent as possible so I want to remove as much reliance on other classes as possible. These are the only methods that touch the Mouse input, and as far as I can tell none of them change anything so all is good here. Now for the Texture methods: public void draw() { if(!clicked || deactivatedImage == null) { activatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(activatedImage, x, y, width, height); } glEnd(); } else { deactivatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(deactivatedImage, x, y, width, height); } glEnd(); } } public static void drawGLQuad(Texture texture, float x, float y, float width, float height) { glTexCoord2f(x, y); glVertex2f(x, y); glTexCoord2f(x, y + texture.getHeight()); glVertex2f(x, y + height); glTexCoord2f(x + texture.getWidth(), y + texture.getHeight()); glVertex2f(x + width, y +height); glTexCoord2f(x + texture.getWidth(), y); glVertex2f(x + width, y); } I'll be honest, I do not have the faintest clue as to what is really happening in this method but I was able to put it together on my own and get it to work. my guess is that this is where the problem is. Thanks for any help!

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  • I create a JPanel and GridBagLayout within an object but when I get it in the main object, attributes are missing

    - by chickeneaterguy
    public oijoij() { String name = "Jackie"; int priority = 50; int minPriority = 90; setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setBounds(100, 100, 450, 300); contentPane = new JPanel(); contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); contentPane.setLayout(new BorderLayout(0, 0)); setContentPane(contentPane); JPanel panel = new JPanel(); GridBagLayout gbc_panel = new GridBagLayout(); gbc_panel.columnWidths = new int[]{0,0,0}; gbc_panel.rowHeights = new int[]{0, 0, 0, 0, 0, 0}; gbc_panel.columnWeights = new double[]{0.0, 0.0, Double.MIN_VALUE}; gbc_panel.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE}; panel.setBorder(new LineBorder(new Color(0,0,0),1)); panel.setLayout(gbc_panel); panel.setAlignmentX(Component.LEFT_ALIGNMENT); panel.setMinimumSize(new Dimension(110,110)); panel.setPreferredSize(new Dimension(110, 110)); panel.setSize(new Dimension(110,110)); JLabel lblNewLabel = new JLabel("Process ID:"); GridBagConstraints gbc_lblNewLabel = new GridBagConstraints(); gbc_lblNewLabel.gridheight = 2; gbc_lblNewLabel.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel.gridx = 0; gbc_lblNewLabel.gridy = 0; panel.add(lblNewLabel, gbc_lblNewLabel); JLabel lblNewLabel_1 = new JLabel(name); GridBagConstraints gbc_lblNewLabel_1 = new GridBagConstraints(); gbc_lblNewLabel_1.gridheight = 2; gbc_lblNewLabel_1.insets = new Insets(0, 0, 5, 0); gbc_lblNewLabel_1.gridx = 1; gbc_lblNewLabel_1.gridy = 0; panel.add(lblNewLabel_1, gbc_lblNewLabel_1); JLabel lblNewLabel_2 = new JLabel("Priority:"); GridBagConstraints gbc_lblNewLabel_2 = new GridBagConstraints(); gbc_lblNewLabel_2.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel_2.gridx = 0; gbc_lblNewLabel_2.gridy = 2; panel.add(lblNewLabel_2, gbc_lblNewLabel_2); JLabel lblNum = new JLabel(Integer.toString(priority)); GridBagConstraints gbc_lblNum = new GridBagConstraints(); gbc_lblNum.insets = new Insets(0, 0, 5, 0); gbc_lblNum.gridx = 1; gbc_lblNum.gridy = 2; panel.add(lblNum, gbc_lblNum); JLabel lblNewLabel_3 = new JLabel("Min Priority:"); GridBagConstraints gbc_lblNewLabel_3 = new GridBagConstraints(); gbc_lblNewLabel_3.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel_3.gridx = 0; gbc_lblNewLabel_3.gridy = 3; panel.add(lblNewLabel_3, gbc_lblNewLabel_3); JLabel lblMp = new JLabel(Integer.toString(minPriority)); GridBagConstraints gbc_lblMp = new GridBagConstraints(); gbc_lblMp.insets = new Insets(0, 0, 5, 0); gbc_lblMp.gridx = 1; gbc_lblMp.gridy = 3; panel.add(lblMp, gbc_lblMp); JLabel lblTimeSlice = new JLabel("Time Slice:"); GridBagConstraints gbc_lblTimeSlice = new GridBagConstraints(); gbc_lblTimeSlice.insets = new Insets(0, 0, 0, 5); gbc_lblTimeSlice.gridx = 0; gbc_lblTimeSlice.gridy = 4; panel.add(lblTimeSlice, gbc_lblTimeSlice); Random r = new Random(System.currentTimeMillis()); panel.setBackground(new Color( r.nextInt(255 - 210) + 210, r.nextInt(255 - 210) + 210, r.nextInt(255 - 210) + 210)); } I have accessor methods for the GridBagLayout and the JPanel. When calling the functions in another file, it looks like I just get the JPanel (but without any labels or the layout or other GridBagLayout features). Help?

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  • How to remove the file suffix/extension (.jsp and .action) using the Stripes Framework?

    - by Dolph Mathews
    I'm looking to use pretty / clean URL's in my web app. I would like the following URL: http://mydomain.com/myapp/calculator .. to resolve to: com.mydomain.myapp.action.CalculatorActionBean I tried overwriting the NameBasedActionResolver with: public class CustomActionResolver extends NameBasedActionResolver { public static final String DEFAULT_BINDING_SUFFIX = "."; @Override protected String getBindingSuffix() { return DEFAULT_BINDING_SUFFIX; } @Override protected List<String> getActionBeanSuffixes() { List<String> suffixes = new ArrayList<String>(super.getActionBeanSuffixes()); suffixes.add(DEFAULT_BINDING_SUFFIX); return suffixes; } } And adding this to web.xml: <servlet-mapping> <servlet-name>StripesDispatcher</servlet-name> <url-pattern>*.</url-pattern> </servlet-mapping> Which gets me to: http://mydomain.com/myapp/Calculator. But: A stray "." is still neither pretty nor clean. The class name is still capitalized in the URL..? That still leaves me with *.jsp..? Is it even possible to get rid of both .action and .jsp?

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  • Highlight field in source code pane of Findbugs UI

    - by Ryan Fernandes
    I'm using a class that extends BytecodeScanningDetector to check for some problematic fields in a class. After detecting whether the field is problematic, I add it to the bug report like below: Once I run findbugs, it identifies the bug, lists it in the left pane, but does not highlight the corresponding source line. Any hints/help on this will be very appreciated. public void visit(Field f) { if (isProblematic(getXField())) { bugReporter.reportBug(new BugInstance(this, tBugType, HIGH_PRIORITY) .addClass(currentClass) //from visit(JavaClass) .addField(this)); } } public void visit(JavaClass someObj) { currentClass = someObj.getClassName(); } P.S. I tried posting this on the findbugs list but... no joy.

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  • With the introduction of the HTML5 <canvas> element, could Swing be implemented in GWT?

    - by knorv
    With the introduction of the HTML5 <canvas> element, could Swing theoretically be implemented in Google Web Toolkit (GWT) by using the <canvas> tag for drawing? I'm aware of efforts to port source code from using Swing calls to GWT calls, but what I'm after is a pure behind the scenes port where a Swing application would compile under GWT without any source code modifications. Is that theoretically possible? Why? Why not?

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  • JPA - Performance with using multiple entity manager

    - by Nguyen Tuan Linh
    My situation is: The code is not mine I have two kinds of database: one is Dad, one is Son. In Dad, I have a table to store JNDI name. I will look up Dad using JNDI, create entity manager, and retrieve this table. From these retrieved JNDI names, I will create multiple entity managers using multiple Son databases. The problem is: Son have thousands of entities. It takes each Son database around 10 minutes to load all entities. If there is 4 Son databases, it will be 40 minutes. My question: Is there any way to load all entities and use them for all entity manager? Please look at the code below For each Son JNDI: Map<String, String> puSonProperties = new HashMap<String, String>(); puSonProperties.put("javax.persistence.jtaDataSource", sonJndi); EntityManagerFactory emf = Persistence.createEntityManagerFactory("PUSon", puSonProperties); PUSon - All of them use the same persistence unit log.info("Verify entity manager for son: {0} - {1}", sonCode, emSon.find(Son_configuration.class, 0) != null ? "ok" : "failed!"); This is the actual code where the loading of all entities begins. 10 mins.

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  • Object Slicing, Is it advantage ?

    - by harigm
    Object slicing is some thing that object looses some of its attributes or functions when a child class is assigned to base class. Some thing like Class A{ } Class B extends A{ } Class SomeClass{ A a = new A(); B b = new B(); // Some where if might happen like this */ a = b; (Object slicing happens) } Do we say Object slicing is any beneficial in any ways? If yes, can any one please tell me how object slicing be a helpful in development and where it might be helpful?

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  • Python code translation to JVM

    - by jldupont
    Is there such a thing as a "translator" (for lack of a better word in my mind now) that translates Python code directly to JVM / Dalvik bytecode? Would be great for writing Android applications in Python! NOTE: I know about the scripting capabilities of the Android platform but I am looking for something that would generate a '.apk' without having to install the 'scripting' package... annoying for end-users.

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