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  • static block instance block java Order

    - by Rollerball
    Having read this question In what order are the different parts of a class initialized when a class is loaded in the JVM? and the related JLS. I would like to know in more detail why for example having class Animal (superclass) and class Dog (subclass) as following: class Animal { static{ System.out.println("This is Animal's static block speaking"): } { System.out.println("This is Animal's instance block speaking"); } class Dog{ static{ System.out.println("This is Dog's static block speaking"); } { System.out.println("This is Dog's instance block speaking"); } public static void main (String [] args) { Dog dog = new Dog(); } } Ok before instantiating a class its direct superclass needs to be initialized (therefore all the statics variables and block need to be executed). So basically the question is: Why after initializing the static variables and static blocks of the super class, control goes down to the subclass for static variables initialization rather then finishing off the initialization of also the instance member? The control goes like: superclass (Animal): static variables and static blocks subclass (Dog): static variables and static blocks superclass (Animal): instance variables and instance blocks sublcass (Dog):instance variables and instance blocks What is the reason why it is in this way rather than : superclass -> static members superclass -> instance members subclass -> static members sublcass-> instance members

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  • What is a good use case for static import of methods?

    - by Miserable Variable
    Just got a review comment that my static import of the method was not a good idea. The static import was of a method from a DA class, which has mostly static methods. So in middle of the business logic I had a da activity that apparently seemed to belong to the current class: import static some.package.DA.*; class BusinessObject { void someMethod() { .... save(this); } } The reviewer was not keen that I change the code and I didn't but I do kind of agree with him. One reason given for not static-importing was it was confusing where the method was defined, it wasn't in the current class and not in any superclass so it too some time to identify its definition (the web based review system does not have clickable links like IDE :-) I don't really think this matters, static-imports are still quite new and soon we will all get used to locating them. But the other reason, the one I agree with, is that an unqualified method call seems to belong to current object and should not jump contexts. But if it really did belong, it would make sense to extend that super class. So, when does it make sense to static import methods? When have you done it? Did/do you like the way the unqualified calls look? EDIT: The popular opinion seems to be that static-import methods if nobody is going to confuse them as methods of the current class. For example methods from java.lang.Math and java.awt.Color. But if abs and getAlpha are not ambiguous I don't see why readEmployee is. As in lot of programming choices, I think this too is a personal preference thing. Thanks for your response guys, I am closing the question.

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  • Constructor parameter validation in C# - Best practices

    - by MPelletier
    What is the best practice for constructor parameter validation? Suppose a simple bit of C#: public class MyClass { public MyClass(string text) { if (String.IsNullOrEmpty(text)) throw new ArgumentException("Text cannot be empty"); // continue with normal construction } } Would it be acceptable to throw an exception? The alternative I encountered was pre-validation, before instantiating: public class CallingClass { public MyClass MakeMyClass(string text) { if (String.IsNullOrEmpty(text)) { MessageBox.Show("Text cannot be empty"); return null; } else { return new MyClass(text); } } }

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  • Why is my eth0 getting a dynamic ip when it is configured to be static?

    - by sdek
    For some reason our office linux box is being assigned an ip address via dhcp and I don't know why. What is confusing to me is that when I check system-config-network it shows that my eth0 is setup to be a static ip address. And /etc/sysconfig/network-scripts/ifcfg-eth0 also shows it is setup to be a static ip, yet it is getting a different ip address than the one specified in the ifcfg-eth0. Let me know if you have any suggestions on or ideas on where I can look next. Here are a few details that might help you figure out what an idiot I am :) Fedora 11 Router in front of this box is running dhcp, starting at 10.42.1.100 This box is configured to be 10.42.1.50 (at least I think it is!), subnet 255.255.255.0 (which is same as the router's lan subnet) Instead of having the static IP, this box is getting assigned 10.42.1.100. Here are the ifcfg-eth0 details DEVICE=eth0 BOOTPROTO=none ONBOOT=yes TYPE=Ethernet USERCTL=no NM_CONTROLLED=no NETMASK=255.255.255.0 IPADDR=10.42.1.50 GATEWAY=10.42.1.1

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  • How do i mitigate DDOS attacks on static servers?

    - by acidzombie24
    Here is a slightly different take on DDOS attacks. Rather than a server with dynamic content being attack i was curious how to deal with attacks on servers with STATIC CONTENT. This means cpu tends to not be an issue. Its either bandwidth or connection problems. How would i mitigate a DDOS attack knowing nothing about the attacker (for example country, ip address or anything else). I was wondering is shorting the timeout and increasing amount of connections is an acceptable solution? Or maybe that is completely useless? Also i would limit the amount of connections per IP address. Would the above help or be pointless? Keeping in mind everything is static checking for multiple request of the same page (html, css, js, etc) could be a sign of a attack. What are some measures i can take on a static content server?

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  • Two routers, one off-site, same ISP-assigned static IP. A recipe for conflict?

    - by boost
    This is the situation I've inherited: There are two routers, one off-site. Both are connected to the ISP. The ISP assigns both of them the same static IP (or so it seems). Presumably, the network problems we're having are related to the idea that you can't have two instances of the same IP. So we rang up the folk off-site and told them to turn off the router. Now everything's working okay here. How do I get around this? Get another static IP? Figure out how to get the router to ask for a dynamic IP (as we're not using the static IP for anything)?

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  • Using new to allocate an array of class elements with an overloaded constructor in C++.

    - by GordoN
    As an example say I have a class foo that does not have a default constructor but one that looks like this foo:foo(int _varA,int _varB) { m_VarA = _varA; m_VarB = _varB; } How would I allocate an array of these. I seem to remember trying somthing like this unsuccessfully. foo* MyArray = new foo[100](25,14). I don't think this will work either. foo* MyArray = new foo[100](25,14) Can this be done? I typically do this by writing the default constructor using some preset values for _varA and _varB. Then adding a function to reset _varA and _varB for each element but that will not work for this case. Thanks for the help.

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  • class classname(value); & class classname=value; difference when constructor is explicit

    - by Mahesh
    When constructor is explicit, it isn't used for implicit conversions. In the given snippet, constructor is marked as explicit. Then why in case foo obj1(10.25); it is working and in foo obj2=10.25; it isn't working ? #include <iostream> class foo { int x; public: explicit foo( int x ):x(x) {} }; int main() { foo obj(10.25); // Not an error. Why ? foo obj2 = 10.25; // Error getchar(); return 0; } error: error C2440: 'initializing' : cannot convert from 'double' to 'foo'

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  • Publish Static Content to WebLogic

    - by James Taylor
    Most people know WebLogic has a built in web server. Typically this is not an issue as you deploy java applications and WebLogic publishes to the web. But what if you just want to display a simple static HTML page. In WebLogic you can develop a simple web application to display static HTML content. In this example I used WLS 10.3.3. I want to display 2 files, an HTML file, and an xsd for reference. Create a directory of your choice, this is what I will call the document root. mkdir /u01/oracle/doc_root Copy the static files to this directory  In the document root directory created in step 1 create the directory WEB-INF mkdir WEB-INF In the WEB-INF directory create a file called web.xml with the following content <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/j2ee/dtds/web-app_2_3.dtd"> <web-app> </web-app> Login to the WebLogic console to deploy application Click on Deployments Click on Lock & Edit Click Install and set the path to the directory created in step 1 Leave default "Install this deployment as an application" and click Next Select a Managed Server to deploy to and click Next Accept the defaults and click Finish  Deployment completes successfully, now click the Activate Changes You should now see the application started in the deployments You can now access your static content via the following URL http://localhost:7001/doc_root/helloworld.html

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  • Managing JS and CSS for a static HTML web application

    - by Josh Kelley
    I'm working on a smallish web application that uses a little bit of static HTML and relies on JavaScript to load the application data as JSON and dynamically create the web page elements from that. First question: Is this a fundamentally bad idea? I'm unclear on how many web sites and web applications completely dispense with server-side generation of HTML. (There are obvious disadvantages of JS-only web apps in the areas of graceful degradation / progressive enhancement and being search engine friendly, but I don't believe that these are an issue for this particular app.) Second question: What's the best way to manage the static HTML, JS, and CSS? For my "development build," I'd like non-minified third-party code, multiple JS and CSS files for easier organization, etc. For the "release build," everything should be minified, concatenated together, etc. If I was doing server-side generation of HTML, it'd be easy to have my web framework generate different development versus release HTML that includes multiple verbose versus concatenated minified code. But given that I'm only doing any static HTML, what's the best way to manage this? (I realize I could hack something together with ERB or Perl, but I'm wondering if there are any standard solutions.) In particular, since I'm not doing any server-side HTML generation, is there an easy, semi-standard way of setting up my static HTML so that it contains code like <script src="js/vendors/jquery.js"></script> <script src="js/class_a.js"></script> <script src="js/class_b.js"></script> <script src="js/main.js"></script> at development time and <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script> <script src="js/entire_app.min.js"></script> for release?

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  • Add static ARP entries when network is brought up

    - by jozzas
    I have some pretty dumb IP devices on a subnet with my Ubuntu server, and the server receives streaming data from each device. I have run into a problem in that when an ARP request is issued to the device while it is streaming data to the server, the request is ignored, the cache entry times out and the server stops receiving the stream. So, to prevent the server from sending ARP requests to these devices altogether, I would like to add a static ARP entry for each, something like arp -i eth2 -s ip.of.the.device mac:of:the:device But these "static" ARP entries are lost if networking is disabled / enabled or if the server is rebooted. Where is the best place to automatically add these entries, preferably somewhere that will re-add them every time the interface eth2 is brought up? I really don't want to have to write a script that monitors the output of arp and re-adds the cache entries if they're missing. Edit to add what my final script was: Created the file /etc/network/if-up.d/add-my-static-arp With the contents: #!/bin/sh arp -i eth0 -s 192.168.0.4 00:50:cc:44:55:55 arp -i eth0 -s 192.168.0.5 00:50:cc:44:55:56 arp -i eth0 -s 192.168.0.6 00:50:cc:44:55:57 And then obviously add the permission to allow it to be executed: chmod +x /etc/network/if-up.d/add-my-static-arp And these arp entries will be manually added or re-added every time any network interface is brought up.

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  • get_called_class hack not working with eval-code.

    - by Ekampp
    Hi there. I am using a ge_called_class hack for allowing late static binding in php version 5.2 (found here). I have the following in my code: # db_record.php $ac = "ForumThread"; $objects = $ac::find("all"); This will not work in php 5.2 for some reason, so I have done this: # db_record.php $ac = "ForumThread"; eval("\$objects = {$ac}::find('all');"); This on the other hand will not work with the get_called_class function. I get an error that the file function can't read the evaled section of code. So how do I solve this problem? Best regards.

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  • Compilation Error related

    - by aparna
    Given: 11. public static void test(String str) { 12. int check = 4; 13. if (check = str.length()) { 14. System.out.print(str.charAt(check -= 1) +", "); 15. } else { 16. System.out.print(str.charAt(0) + ", "); 17. } 18. } and the invocation: 21. test("four"); 22. test("tee"); 23. test("to"); What is the result? A. r, t, t, B. r, e, o, C. Compilation fails. D. An exception is thrown at runtime. Answer: C Can you explain why the compilation fails please?

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  • Why does a sub-class class of a class have to be static in order to initialize the sub-class in the

    - by Alex
    So, the question is more or less as I wrote. I understand that it's probably not clear at all so I'll give an example. I have class Tree and in it there is the class Node, and the empty constructor of Tree is written: public class RBTree { private RBNode head; public RBTree(RBNode head,RBTree leftT,RBTree rightT){ this.head=head; this.head.leftT.head.father = head; this.head.rightT.head.father = head; } public RBTree(RBNode head){ this(head,new RBTree(),new RBTree()); } public RBTree(){ this(new RBNode(),null,null); } public class RBNode{ private int value; private boolean isBlack; private RBNode father; private RBTree leftT; private RBTree rightT; } } Eclipse gives me the error: "No enclosing instance of type RBTree is available due to some intermediate constructor invocation" for the "new RBTree()" in the empty constructor. However, if I change the RBNode to be a static class, there is no problem. So why is it working when the class is static. BTW, I found an easy solution for the cunstructor: public RBTree(){ this.head = new RBNode(); } So, I have no idea what is the problem in the first piece of code.

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  • Performing user authentication in a CodeIgniter controller constructor?

    - by msanford
    In "The Clean Code Talks -- Unit Testing" (http://youtu.be/wEhu57pih5w), Miško Hevery mentions that "as little work as possible should be done in constructors [to make classes more easily testable]'. It got me thinking about the way I have implemented my user authentication mechanism. Having delved into MVC development through CodeIgniter, I designed my first web application to perform user authentication for protected resources in controllers' constructors in cases where every public function in that controller requires the user to be authenticated. For controllers with public methods having mixed authentication requirements, I would naturally move the authentication from the constructor to each method requiring authentication (though I don't currently have a need for this). I made this choice primarily to keep the controller tight, and to ensure that all resources in the controller are always covered. As for code longevity and maintainability: given the application structure, I can't foresee a situation in which one of the affected controllers would need a public method that didn't require user authentication, but I can see this as a potential drawback in general with this implementation (i.e., requiring future refactoring). Is this a good idea?

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  • problem on static link to libsmbclient.a

    - by Rex
    I've tried to develop a library using libsmbclient-dev to access net share folders. I wish to static link libsmbclient.a in my project , but a lot of error happens when I tried to static link it, it seems that the libsmbclient.a doesn't include some objects it needed , while everything goes well with libsmbclient.so. Because my project need to support various linux versions like centOS , Ubuntu ..., we wish not to install libsmbclient-dev everywhere. Can anybody tell me that if I can static link this libsmbclient.a in an easy way ? Or what kind of installation strategy should I take to cause less trouble to users? If anyone have use this library to develop projects before , can you tell me how you deal with this case? Thank you very much!!!

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  • constructor should not call methods

    - by Stefano Borini
    I described to a colleague why a constructor calling a method is an antipattern. example (in my rusty C++) class C { public : C(int foo); void setFoo(int foo); private: int foo; } C::C(int foo) { setFoo(foo); } void C::setFoo(int foo) { this->foo = foo } I would like to motivate better this fact through your additional contribute. If you have examples, book references, blog pages, or names of principles, they would be very welcome. Edit: I'm talking in general, but we are coding in python.

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  • Constructor should generally not call methods

    - by Stefano Borini
    I described to a colleague why a constructor calling a method can be an antipattern. example (in my rusty C++) class C { public : C(int foo); void setFoo(int foo); private: int foo; } C::C(int foo) { setFoo(foo); } void C::setFoo(int foo) { this->foo = foo } I would like to motivate better this fact through your additional contribute. If you have examples, book references, blog pages, or names of principles, they would be very welcome. Edit: I'm talking in general, but we are coding in python.

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  • Naming convention: Final fields (not static)

    - by Zeeker
    Today I had a discussion with a co-worker about the naming of final fields in Java classes. In his opionion final fields should also be considered constants since their values won't change after the creation of the instance. This would lead to the following naming convention for final fields: public class Foo { private static final String BLA_BLA = "bla"; private final String BAR_BATZ; ... } In my opinion only static final fields should be considered constants while fields which are only final should follow the usual camelCase naming convention. public class Foo { private static final String BLA = "bla"; private final String barBatz; ... } Now I'm a bit uncertain since he is a far more experienced programmer than I am and I usually agree with his opinions and consider him a very good developer. Any input on this?

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  • Resuming from hibernation shows a fuzzy "static" screen

    - by Ross
    When I resume from hibernation in Ubuntu 10.10 the screen shows static, very similar to what you see on an analogue TV that hasn't been tuned properly. This also occurs on boot from shut down, but only for a moment after the Plymouth boot screen. The static lasts for at least 5 minutes. An odd thing that happens is that the mouse pointer, as a lighter square of static, becomes visible and you can move it around. Attempting to change into a terminal (i.e. Ctrl+Alt+F1) doesn't seem to work (and I'm not sure if that can be done from the login screen). Resuming from suspend has different issues - vertical lines appearing for a second before appearing to be in terminal mode (blinking cursor) and then going to the lock screen. I'm running Ubuntu 10.10 on a Dell Studio 15 with ATI graphics, however I'm not using the proprietary drivers as I had issues with dual-screen support, so it's the generic X.org drivers being used.

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  • does class reference itself static anti pattern in prism

    - by Michael Riva
    I have an application and my desing approach look like this: class Manager { public int State; static Manager _instance = null; public static Manager Instance { get { return _instance; } set { if (_instance == value) return; _instance = value; } } public Manager() { State = 0; Instance=this; } } class Module1 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module2 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module3 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } Manager class already registered in Bootstrapper like : protected override void ConfigureContainer() { base.ConfigureContainer(); Container.RegisterType<Manager>(new ContainerControlledLifetimeManager()); } protected override void InitializeModules() { Manager man= Container.Resolve<Manager>(); } Question is do I need to define my manager object as static in its field to be able to reach its state? Or this is anti pattern or bad for performance?

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