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  • Java: design problem with final-value and empty constructor

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; // Design Problem? // I feel the initialization problem is just due to bad style. InitInt(){} InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } } public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Partial Solutions and Suggestions use "this" to access methods in the class, instead of creating empty constructor change final to non-final with final field value: initialize all final values in every constructor remove the empty constructor, keep your code simple and clean

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  • Unreachable statement when using return in finally?

    - by abson
    this compiles class ex1 { public int show() { try { int a=10/10; return 10; } catch(ArithmeticException e) { System.out.println(e); } finally { System.out.println("Finally"); } System.out.println("hello"); return 20; } } on the other hand this doesn't class ex15 { public int show() { try { int a=10/0; return 10; } catch(ArithmeticException e) { System.out.println(e); } finally { System.out.println("Finally"); return 40; } System.out.println("hello"); return 20; } } and gives unreachable statement System.out.println("hello"); error. why is it so?

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  • Should I use Python or Assembly for a super fast copy program

    - by PyNEwbie
    As a maintenance issue I need to routinely (3-5 times per year) copy a repository that is now has over 20 million files and exceeds 1.5 terabytes in total disk space. I am currently using RICHCOPY, but have tried others. RICHCOPY seems the fastest but I do not believe I am getting close to the limits of the capabilities of my XP machine. I am toying around with using what I have read in The Art of Assembly Language to write a program to copy my files. My other thought is to start learning how to multi-thread in Python to do the copies. I am toying around with the idea of doing this in Assembly because it seems interesting, but while my time is not incredibly precious it is precious enough that I am trying to get a sense of whether or not I will see significant enough gains in copy speed. I am assuming that I would but I only started really learning to program 18 months and it is still more or less a hobby. Thus I may be missing some fundamental concept of what happens with interpreted languages. Any observations or experiences would be appreciated. Note, I am not looking for any code. I have already written a basic copy program in Python 2.6 that is no slower than RICHCOPY. I am looking for some observations on which will give me more speed. Right now it takes me over 50 hours to make a copy from a disk to a Drobo and then back from the Drobo to a disk. I have a LogicCube for when I am simply duplicating a disk but sometimes I need to go from a disk to Drobo or the reverse. I am thinking that given that I can sector copy a 3/4 full 2 terabyte drive using the LogicCube in under seven hours I should be able to get close to that using Assembly, but I don't know enough to know if this is valid. (Yes, sometimes ignorance is bliss) The reason I need to speed it up is I have had two or three cycles where something has happened during copy (fifty hours is a long time to expect the world to hold still) that has caused me to have to trash the copy and start over. For example, last week the water main broke under our building and shorted out the power.

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  • Java: startingPath as "public static final" exception

    - by HH
    [Updated] Thanks to polygenelubricants's reply, the real problem is the exception from the method getCanonicalPath() because I cannot include try-catch-loop there. $ cat StartingPath.java import java.util.*; import java.io.*; public class StartingPath { public static final String startingPath = (new File(".")).getCanonicalPath(); public static void main(String[] args){ System.out.println(startingPath); } } $ javac StartingPath.java StartingPath.java:5: unreported exception java.io.IOException; must be caught or declared to be thrown public static final String startingPath = (new File(".")).getCanonicalPath(); ^ 1 error

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  • Connect to Mongodb in python

    - by SpawnCxy
    I'm a little confused by the document when I tried to connect to the Mongodb.And I find it's different from mysql.I want to create a new database named "mydb" and insert some posts into it.The follows is what I'm trying. from pymongo.connection import Connection import datetime host = 'localhost' port = 27017 user = 'ucenter' passwd = '123' connection = Connection(host,port) db = connection['mydb'] post = {'author':'mike', 'text':'my first blog post!', 'tags':['mongodb','python','pymongo'], 'date':datetime.datetime.utcnow()} posts = db.posts posts.insert(post) #print str(db.collection_names()) And I got an error as pymongo.errors.OperationFailure: database error: unauthorized.How can I do the authorizing part?Thanks.

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  • ActionScript 3.0: placing code on stage/MC timelines a la AS2 instead of in classes

    - by BoltClock
    I'm aware that ActionScript 3.0 is designed from the ground up to be a largely object-oriented language and using it means less or even no timeline code in Flash documents. I'm quite experienced with OOP and am comfortable writing classes. However, since I mostly use Flash for animations, I hardly ever need to write ActionScript code other than for preloaders, subtitles, quality controls, website links and so on. In fact, I still set my Flash movies to use AS2 to this day because I'm used to gotoAndPlay()/gotoAndStop(), AS2 preloaders, subtitles, quality controls and even getURL(). Of course, I really want to move on now that practically everyone's on Flash Player 9 or 10 and now that I've dabbled with other OO languages like Java, C# and Objective-C too. I'm a complete newcomer to AS3 and am not very learned with AS2 either. Considering my current use of ActionScript, are there any cases where it's still OK to use very simple AS3 code in the timeline instead of moving code to a class, especially since moving to a class might mean unnecessarily increasing the number of LOC from 4 to 40? (Heck, is the latter case ('instead of ...') even a valid concern at all?)

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  • Why are Python exceptions named "Error"?

    - by Elena
    Why are Python exceptions named "Error" (e.g. ZeroDivisionError, NameError, TypeError etc) and not "Exception" (e.g. ZeroDivisionException, NameException, TypeException etc). I come from a Java background and started to learn Python recently, as such this is confusing because in java there is a distinction between error and exception. Is there a difference in Python also or not? Can someone explain or point me to some documentation explaining it? Thank you!

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  • Java: dangerous self-returning-recursive function by IOException?

    - by HH
    I had very errorsome Exception handling with if-clauses. An exception occurs if not found path. An exception returns the function again. The function is recursive. Safe? $ javac SubDirs.java $ java SubDirs Give me an path. . HELLO com TOASHEOU google common annotations base collect internal Give me an path. IT WON'T FIND ME, SO IT RETURNS ITSELF due to Exception caught Give me an path. $ cat SubDirs.java import java.io.*; import java.util.*; public class SubDirs { private List<File> getSubdirs(File file) throws IOException { List<File> subdirs = Arrays.asList(file.listFiles(new FileFilter() { public boolean accept(File f) { return f.isDirectory(); } })); subdirs = new ArrayList<File>(subdirs); List<File> deepSubdirs = new ArrayList<File>(); for(File subdir : subdirs) { deepSubdirs.addAll(getSubdirs(subdir)); } subdirs.addAll(deepSubdirs); return subdirs; } public static void search() { try{ BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); String s; System.out.println("Give me an path."); while ((s = in.readLine()) != null && s.length() != 0){ SubDirs dirs = new SubDirs(); List<File> subDirs = dirs.getSubdirs(new File(s)); for ( File f : subDirs ) { System.out.println(f.getName()); } System.out.println("Give me an path."); } }catch(Exception e){ // Simple but is it safe? search(); } } public static void main(String[] args) throws IOException { search(); } }

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  • Can't find ant in the Android SDK

    - by StormShadow
    Hey all, I'm working my way through APress's Beginning Android 2 and I've made it all the way to chapter 3, where we build a skeleton app. The book tells me to compile my application by typing "ant" in the command line, but my pc doesn't know what "ant" is yet. I checked in the SDK files and it looks like it wasn't included with the Android SDK. Does anybody know where ant is? Thanks

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  • Why can't I find `len(list)` in Python?

    - by FarmBoy
    I'm new to Python. I have a method that begins: def foo(self, list): length = len(list) I've called len() successfully in other cases, but here I get: TypeError: object of type 'type' has no len() How do I convince Python that this object passed in is a list? What am I missing?

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  • How do I create and use a junction table in Rails?

    - by Thierry Lam
    I have the following data: A post called Hello has categories greet Another post called Hola has categories greet, international My schema is: create_table "posts", :force => true do |t| t.string "name" t.datetime "created_at" t.datetime "updated_at" end create_table "categories", :force => true do |t| t.string "name" t.datetime "created_at" t.datetime "updated_at" end create_table "posts_categories", :force => true do |t| t.integer "post_id" t.integer "category_id" t.datetime "created_at" t.datetime "updated_at" end After reading the Rails guide, the most suitable relationship for the above seems to be: class Post < ActiveRecord::Base has_and_belongs_to_many :categories end class Category < ActiveRecord::Base has_and_belongs_to_many :posts end My junction table also seems to have a primary key. I think I need to get rid of it. What's the initial migration command to generate a junction table in Rails? What's the best course of action, should I drop posts_categories and re-create it or just drop the primary key column? Does the junction table have a corresponding model? I have used scaffold to generate the junction table code, should I get rid of the extra code? Assuming all the above has been fixed and is working properly, how do I query all posts and display them along with their named categories in the view. For example: Post #1 - hello, categories: greet Post #2 - hola, categories: greet, international

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  • Changing classes on multiple divs when selecting specific radio buttons

    - by Rob
    Hey everyone I got a javascript problem I can't seem to find a specific solution for on the web. What I want to be able to do is select one of the radio buttons and have that change the class of #home-right to either .rackmount or .shipping and add the class of .displaynone to the type of dimensions I don't want shown. <div id="home-right" class="rackmount"> <h4 class="helvneuebcn">Case Finder</h4> <div class="cta-options"> <input type="radio" value="Shipping and Storage" name="" checked> Shipping and Storage<br/> <input type="radio" value="Rackmount Enclosures" name=""> Rackmount Enclosures<br/> </div> <div class="shipping-dimensions displaynone"> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">H x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">W x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">L</span></div> </div> <div class="rackmount-dimensions"> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">U Height x </span></div> <div class="dimensions"><input type="text" class="size"><span class="helvneuemd">Rack Depth</span></div> </div> <div class="clear"></div> <input type="button" value="Submit" class="findcase"> </div>

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  • How can ported code be detected?

    - by NiallJG
    If you port code over from one language to another, how can this be detected? Say you were porting code from c++ to Java, how could you tell? What would be the difference between a program designed and implemented in Java, and a near identical program ported over to Java?

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  • Django and Google App Engine Helper not finding the ipaddr module.

    - by Phil
    I'm trying to get Django running on GAE using this tutorial. When I run python manage.py runserver I get the stacktrace below. I'm new to both django and python so I don't know what my next steps are (This is Ubuntu Jaunty btw). It seems django isn't finding the GAE module ipaddr which comes with SDK 1.3.1. How do I get django to find this module? /home/username/bin/google_appengine/google/appengine/api/datastore_file_stub.py:40: DeprecationWarning: the md5 module is deprecated; use hashlib instead import md5 /home/username/bin/google_appengine/google/appengine/api/memcache/__init__.py:31: DeprecationWarning: the sha module is deprecated; use the hashlib module instead import sha Traceback (most recent call last): File "manage.py", line 18, in <module> InstallAppengineHelperForDjango() File "/home/username/Development/GAE/myapp/appengine_django/__init__.py", line 543, in InstallAppengineHelperForDjango InstallDjangoModuleReplacements() File "/home/username/Development/GAE/myapp/appengine_django/__init__.py", line 260, in InstallDjangoModuleReplacements import django.db File "/home/username/Development/GAE/myapp/django/db/__init__.py", line 57, in <module> 'TIME_ZONE': settings.TIME_ZONE, File "/home/username/Development/GAE/myapp/appengine_django/db/base.py", line 117, in __init__ self._setup_stubs() File "/home/username/Development/GAE/myapp/appengine_django/db/base.py", line 128, in _setup_stubs from google.appengine.tools import dev_appserver_main File "/home/username/bin/google_appengine/google/appengine/tools/dev_appserver_main.py", line 82, in <module> from google.appengine.tools import appcfg File "/home/username/bin/google_appengine/google/appengine/tools/appcfg.py", line 53, in <module> from google.appengine.api import dosinfo File "/home/username/bin/google_appengine/google/appengine/api/dosinfo.py", line 25, in <module> import ipaddr ImportError: No module named ipaddr

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  • Java: how to initialize private final int value with if-else in constructor?

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; InitInt(){} public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? InitInt test = new InitInt(); System.out.println(test.getRight()); // later assiging a value } public int getRight(){return right;} } Initialization problem with Constructor, due to if-else -loop InitInt{ // Still the error, "may not be initialized" // How to initialise it, without removing if-else? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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  • Getting the first result from a LINQ query - why does ElementAt<T>(0) fails when First<T>() succeeds

    - by Mr Roys
    I have a method AddStudent() which looks for a student with the same name and returns an existing student from the database if there is a student with the same name, otherwise it creates a new student and adds it to the database. I'm curious why se = students.First<StudentEntity>(); succeeds when se = students.ElementAt<StudentEntity>(0); fails when I try to get the first result from the LINQ query. Aren't the two methods the same? The full code for the method is shown below. public Student AddStudent(string name) { using (SchoolEntities db = new SchoolEntities()) { // find student with same name via LINQ var students = from s in db.StudentEntitySet where s.name == name select s; StudentEntity se = default(StudentEntity); // if student with the same name is already present, return // that student if (students.Count<StudentEntity>() > 0) { // if i use ElementAt, if fails with a "LINQ to Entities does not // recognize the method 'StudentEntity ElementAt[StudentEntity] // (System.Linq.IQueryable`1[StudentEntity], Int32)' method, // and this method cannot be translated into a store expression.", // but not when I use First. Why? // se = students.ElementAt<StudentEntity>(0); se = students.First<StudentEntity>(); } else { // passing 0 for first parameter (id) since it's represented by // a BigInt IDENTITY field in the database so any value // doesn't matter. se = StudentEntity.CreateStudentEntity(0, name); db.AddToStudentEntitySet(se); db.SaveChanges(); } // create a Student object from the Entity object return new Student(se); } } Thanks!

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  • How to do REST securely and with sensitive data?

    - by Earlz
    Hello, we are implementing a new web service. The web service will be a store of sensitive data and there are multiple users types with different permissions. So some user types can't access(and some can't change, and so on) certain types of data. How would this work in REST? I'm very new to REST, so sorry if this sounds noobish.

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  • Java compiler error: "cannot find symbol" when trying to access local variable

    - by HH
    $ javac GetAllDirs.java GetAllDirs.java:16: cannot find symbol symbol : variable checkFile location: class GetAllDirs System.out.println(checkFile.getName()); ^ 1 error $ cat GetAllDirs.java import java.util.*; import java.io.*; public class GetAllDirs { public void getAllDirs(File file) { if(file.isDirectory()){ System.out.println(file.getName()); File checkFile = new File(file.getCanonicalPath()); }else if(file.isFile()){ System.out.println(file.getName()); File checkFile = new File(file.getParent()); }else{ // checkFile should get Initialized at least HERE! File checkFile = file; } System.out.println(file.getName()); // WHY ERROR HERE: checkfile not found System.out.println(checkFile.getName()); } public static void main(String[] args) { GetAllDirs dirs = new GetAllDirs(); File current = new File("."); dirs.getAllDirs(current); } }

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  • Java: define terms initialization, declaration and assignment

    - by HH
    I find the defs circular statements, the subjects are defined by their verbs but the verbs are undefined! So how do you define them? The question is central to understand the term final, related. The Circular Definitions itialization: to initilise a variable. It can be can be done at the time of declaration. assignment: to assign value to a variable. It can be done anywhere. declaration: to declare value to a variable.

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  • Add New Gist using the Github API

    - by Ben Shelock
    I'm making a small app in Adobe Air which I need to interact with the Github Gist API. However I'm kind of stuck. If you're not familiar with Adobe Air you can still help, the XMLHttpRequest javascript object can do cross domain requests, as there is no domain as such. So theres nothing Adobe Air specific here. Where I'm stuck is I think I need to authenticate myself then make the POST. I just don't understand it

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  • Adding negative and positive numbers in java without BigInt.

    - by liamg
    Hi, i'm trying to write a small java class. I have an object called BigNumber. I wrote method that add two positive numbers, and other method that subract two also positive numbers. Now i want them to handle negative numbers. So the i wrote couple of 'if' statements eg. if (this.sign == 1 /* means '+' */) { if (sn1.sign == 1) { if (this.compare(sn1) == -1 /* means this < sn1 */ ) return sn1.add(this); else return this.add(sn1); } etc. Unfortunately the code looks just ugly. Like a bush of if's and elses. Is there a better way to write that kind of code? Edit i can't just do this.add(sn1) beacuse sometimes i want to add positive number to negative one or negitve to negative. But add can handle only positive numbers. So i have to use basic math and for example: instead of add negative number to negative number i add this.abs() (absolute value of number) to sn1.abs() and return the result with opposite sign. Drew: this lines are from method _add. I use this method to decide what to do with numbers it receive. Send them to add method? Or send them to subract method but with different order (sn1.subtract(this))? And so on.. if (this.sign == 1) { if (sn1.sign == 1) { if (this.compare(sn1) == -1) return sn1.add(this); else return this.add(sn1); } else if (wl1.sign == 0) return this; else { if (this.compare(sn1.abs()) == 1) return this.subtract(sn1.abs()); else if (this.compare(sn1.abs()) == 0) return new BigNumber(0); else return sn1.abs().subtract(this).negate(); // return the number with opposite sign; } } else if (this.sign == 0) return sn1; else { if (wl1.sign == 1) { if (this.abs().compare(sn1) == -1) return sn1.subtract(this.abs()); else if (this.abs().compare(sn1) == 0) return new BigNumber(0); else return this.abs().subtract(sn1).negate(); } else if (sn1.sign == 0) return this; else return (this.abs().add(wl1.abs())).negate(); } As you can see - this code looks horrible..

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