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  • Please explain how Trial Division works for Primality Test

    - by mister_dani
    I came across this algorithm for testing primality through trial division I fully understand this algorithm static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i <= Math.sqrt(N); i++) if (N % i == 0) return false; return true; } It works just fine. But then I came across this other one which works just as good but I do not fully understand the logic behind it. static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i * i<N; i++) if (N % i == 0) return false; return true; } It seems like i *i < N behaves like i <= Math.sqrt(N). If so, why?

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  • When to use new layouts and when to use new activities?

    - by cmdfrg
    I'm making a game in Android and I'm trying to add a set of menu screens. Each screen takes up the whole display and has various transitions available to other screens. As a rough summary, the menu screens are: Start screen Difficult select screen Game screen. Pause screen. Game over screen. And there are several different ways you can transition between screen: 1 - 2 2 - 3 3 - 4 (pause game) 4 - 1 (exit game) 4 - 3 (resume game) 3 - 5 (game ends) Obviously, I need some stored state when moving between screens, such as the difficulty level select when starting a game and what the player's score is when the game over screen is shown. Can anyone give me some advice for the easiest way to implement the above screens and transitions in Android? All the create/destroy/pause/resume methods make me nervous about writing brittle code if I'm not careful. I'm not fond of using an Activity for each screen. It seems too heavy weight, having to pass data around using intents seems like a real pain and each screen isn't a useful module by itself. As the "back" button doesn't always go back to the previous screen either, my menu layout doesn't seem to fit the activity model well. At the moment, I'm representing each screen as an XML layout file and I have one activity. I set the different buttons on each layout to call setContentView to update the screen the main activity is showing (e.g. the pause button changes the layout to the pause screen). The activity holds onto all the state needed (e.g. the current difficulty level and the game high score), which makes it easy to share data between screens. This seems roughly similar to the LunarLander sample, except I'm using multiple screens. Does what I have at the moment sound OK or am I not doing things the typical Android way? Is there a class I can use (e.g. something like ViewFlipper) that could make my life easier? By the way, my game screen is implemented as a SurfaceView that stores the game state. I need the state in this view to persist between calls to setContentView (e.g. to resume from paused). Is the right idea to create the game view when the activity starts, keep a reference to it and then use this reference with setContentView whenever I want the game screen to appear?

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  • HTML/CSS Rendering to Image

    - by Steve
    Is there a library or tool that can take an html page and some css, and then render an image? I would like to define some templates server side using html code snippets, and some CSS to define the layout. Then using the template and CSS, I would like to essentially render an image of how this would display in a browser, and pass the image back to the client. Thanks.

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  • red5: how can i extend ISharedObject ?

    - by ufk
    Hiya. Red5 uses ISharedObject interface to create shared objects and to operate them. because ISharedObject is an interface I'm having issues extending it. I would like to extend the getAttribute, setAttribute, get{Int/String/Map}Attribute so the values will be checked before entered or pulled out. how is it possible to do so ? thanks

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  • Creating Linear Layout with TextViews using a for loop

    - by cad8
    Hi all, I was wondering if there is a way to dynamically create an additional linear layout with a textview within a predefined liner layout. THis is my code so you get the gist of what I am asking: LinearLayout MainLL= (LinearLayout) findViewById(R.id.myLayoutId); for(int i=0; i<5; i++) { LinearLayout childLL= new LinearLayout(this); childLL.setOrientation(LinearLayout.VERTICAL); childLL.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT)); childLL.setGravity(Gravity.LEFT); TextView text = new TextView(this); text.setText("The Value of i is :"i); text.setTextSize(12); text.setGravity(Gravity.LEFT); text.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); childLL.addView(text); MainLL.addView(childLL); } My problem is that I am only getting "The Value of i is :0" as the output, i.e. the first instance. Any help would be much appreciated

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  • Manually manipulating ArrayList

    - by jsan
    I have an assignment where I have to create a deque, however I am not allowed to use any built-in classes or interfaces. I am implementing my deque using an array list. My problem is that when I have to, for instance, add to the beginning of the array list (beginning of the queue), i am not allowed to do this: public void addFirst(ArrayList<Integer> array) { array.add(0, int); } Is there a way to do this without using the add() function? Such as manually adding to the front and shifting the rest of the array to the right? Or maybe creating a new array list and copying...I'm not sure. Any help would be great; I have a bunch of functions to write, and getting the first one done will definitely put me in the right direction. Thanks

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  • calling a service layer method to my presentation layer

    - by Josepth Vodary
    Ok I feel really dumb asking this but I seem to be missing something really simple here. I have the following code in a class in my service layer - public Items getItems(String category, float amount, String color, String type) The code reads from a database and returns the results - I plan on placing it in a jframe. Nice and simple. But no matter how I call it from the jframe I get errors in eclipse that the code is wrong - either that their are illegal modifiers or such. So obviously I am calling it completely wrong, so my stupid question is how do you call that method into a jframe? For example - if I try to call it this way: public Items getItems(); I get told that getItems is an illegal parameter. If I call this.. Items getItems(); I am told its undefined

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  • Not reaction to pressing button

    - by Orange91
    I have a ring in primefaces: <h:form> <p:ring id="ring" value="#{ringBean.images}" var="image" styleClass="image-ring" easing="easeInOutBack"> <p:graphicImage value="./../../images/#{image.image}" width="150" height="150"/> <p:commandButton value="#{image.name}" action="#{image.action}" /> </p:ring> </h:form> My RingBean: @ManagedBean @RequestScoped public class RingBean implements Serializable{ private List<PersonImage> images; private PersonImage selectedPerson; public RingBean() { images = new ArrayList<PersonImage>(); images.add(new PersonImage("person3.png", "Pacjent", "patientList")); images.add(new PersonImage("person4.png", "Admin", "adminList")); images.add(new PersonImage("person5.png", "Lekarz", "doctorList")); images.add(new PersonImage("person6.png", "Sekretarka", "secretaryList")); images.add(new PersonImage("person7.png", "Nieaktywni", "inactiveList")); } public List<PersonImage> getImages() { return images; } public PersonImage getSelectedPerson() { return selectedPerson; } public void setSelectedPerson(PersonImage selectedPerson) { this.selectedPerson = selectedPerson; } } PersonImage class: public class PersonImage { String image; String name; String action; public PersonImage() { } public PersonImage(String image, String name, String action) { this.image = image; this.name = name; this.action = action; } public String getImage() { return image; } public void setImage(String image) { this.image = image; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAction() { return action; } public void setAction(String action) { this.action = action; } } faces-config: <navigation-case> <from-outcome>adminList</from-outcome> <to-view-id>/protected/admin/adminList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>doctorList</from-outcome> <to-view-id>/protected/admin/doctorList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>patientList</from-outcome> <to-view-id>/protected/admin/patientList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>secretaryList</from-outcome> <to-view-id>/protected/admin/secretaryList.xhtml</to-view-id> <redirect/> </navigation-case> When i pressed my button, not reaction. Why? I added the action in button: And in Ring I add: images.add(new PersonImage("person4.png", "Admin", "adminList")); action is adminList. Why this not work? When i changed in button: <p:commandButton value="#{image.name}" action="adminList" /> all work. Why? Both construction returned identical string.

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  • Designing DAOs for data sources other than a database

    - by James P.
    Hi, Until now I've been used to using DAOs to retrieve information from databases. Other sources of data are possible though and I'm wondering if and how the pattern could be applied in general. For example, I'm now working on an application that fetches XML on the web. The XML file could be considered as a data source and the actual fetching is similar in principle to a database request. I'm not quite sure how the DAO could be structured though. Any views on the subject are welcome.

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  • android: getting rid of "warning: unmappable character for encoding ascii"

    - by Lo'oris
    I'm compiling using android tools without eclipse. I compile launching "ant debug" from command line. I have found many many instructions around the web about how to remove with annoying warning, but I haven't been able to make any of them work. I've tried -D option, I've tried randomly tweaking build.* files, I've tried exporting an environment variable... nothing. I guess some of these methods just don't work, and some others would work but I've been doing them incorrectly. Anything is possible and I can't stand it any more: any advice on how to do it?

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  • DocumentBuilder.parse() / Parsing Entities

    - by stormin986
    I'm new to parsing XML and am having an issue with entities. (Am doing this on Android, if it makes a difference). Is there a way to have it turn an entity into the character it represents? I have this in the child of an element: "isn&#39;t" (minus quotes). I would prefer it parse it and the end result be a single text node. However, right now this is turned in to TEXT, ENTITY, TEXT. Is there a way to automatically have it parse the entity into text, or a manual way to do it?

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  • Is this technically thread safe despite being mutable?

    - by Finbarr
    Yes, the private member variable bar should be final right? But actually, in this instance, it is an atomic operation to simply read the value of an int. So is this technically thread safe? class foo { private int bar; public foo(int bar) { this.bar = bar; } public int getBar() { return bar; } } // assume infinite number of threads repeatedly calling getBar on the same instance of foo.

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  • How to introduce multi-column constraint with JPA annotations?

    - by plouh
    I am trying to introduce a multi-key constraint on a JPA-mapped entity: public class InventoryItem { @Id private Long id; @Version private Long version; @ManyToOne @JoinColumn("productId") private Product product; @Column(nullable=false); private long serial; } Basically (product, serial) pair should be unique, but I only found a way to say that serial should be unique. This obviously isn't a good idea since different products might have same serial numbers. Is there a way to generate this constraint via JPA or am I forced to manually create it to DB?

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  • Major inconsistencies in Zend Framework

    - by John Nall
    Okay first of all let me just say Zend Framework is the greatest tool I have ever used in 30+ years of programming (well, for web development, Qt wins the desktop market). However, through my use I have noticed some glaring and annoying inconsistencies. For instance, Zend_Form_Element's have a setAttrib() method. Now why the hell is this the only method in that API which is abbrev.? Why then am I using setRequired() instead of setReq()? I have more examples, I am extremely nerd raged about this. It is completely ruining what could have been God's gift to web development. FOR FUTURE REFERENCE NEVER ABBREV. THINGS WHEN MAKING AN API. also always filter data before storing it i m o Who do we talk to about this, where something will actually get done about it?

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  • Good article about File- and Folder Permissions on production server?

    - by Camran
    I have a classifieds website, and users may post classifieds, add images, remove classifieds etc etc... I have no idea what to set the permissions to on folders. For instance, a php script which I have uploads a file to a directory. What would you have set the directory permissions to? Nobody need access to the directory, only the php script... Just wonder if anybody has a good (brief) article about setting the "right" permissions? Thanks

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  • from Hibernate hbm to JPA annotations, a challenging one

    - by nodje
    Hi, I've been struggling with this one for quite some time already. It appears a lot less simple than I thought it'd be: This is included in the "COTISATION" table mapping an uses SynchroDataType, extending Hibernate UserType. This works really great, and I can't find a way to translate it to proper JPA, while keeping the convenience of it. Does someone has a solution for that kind of one-to-one mapping? cheers

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  • get a different file name

    - by Power-Mosfet
    Hi, How do i get a different file name on a webserver by requesting the url. for example "file" click url link and get "file.bin" the "file" is located on a webserver by requesting the url, user can download "file.bin" instead of "file" something like (file + .bin)

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  • Is there some way to assume @Nullable as default? (using FindBugs or any other free tool).

    - by alex2k8
    Consider such code public void m1(String text) { if(text == null) text = "<empty>"; System.out.println(text.toLowerCase()); } And this is a buggy version: public void m1(String text) { System.out.println(text.toLowerCase()); } If null value passed, the NullPointerException may be thrown. I would like the static-analysis tool (e.g. FindBugs) to report this issue. Unsuccessfully the FindBugs (at least by default) requires me to specify @Nullable annotation explicitly. public void m1(@Nullable String text) { System.out.println(text.toLowerCase()); // FindBugs: text must be nonnull but is marked as nullable } The problem is that if I forget to annotate it, the bug will be missed!!! How can I make the FindBugs (or any other free tool) to assume @Nullable by default?

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