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• C# Different class objects in one list

  - by jeah_wicer

  I have looked around some now to find a solution to this problem. I found several ways that could solve it but to be honest I didn't realize which of the ways that would be considered the "right" C# or OOP way of solving it. My goal is not only to solve the problems but also to develop a good set of code standards and I'm fairly sure there's a standard way to handle this problem. Let's say I have 2 types of printer hardwares with their respective classes and ways of communicating: PrinterType1, PrinterType2. I would also like to be able to later on add another type if neccessary. One step up in abstraction those have much in common. It should be possible to send a string to each one of them as an example. They both have variables in common and variables unique to each class. (One for instance communicates via COM-port and has such an object, while the other one communicates via TCP and has such an object). I would however like to just implement a List of all those printers and be able to go through the list and perform things as "Send(string message)" on all Printers regardless of type. I would also like to access variables like "PrinterList[0].Name" that are the same for both objects, however I would also at some places like to access data that is specific to the object itself (For instance in the settings window of the application where the COM-port name is set for one object and the IP/port number for another). So, in short something like: In common: Name Send() Specific to PrinterType1: Port Specific to PrinterType2: IP And I wish to, for instance, do Send() on all objects regardless of type and the number of objects present. I've read about polymorphism, Generics, interfaces and such, but I would like to know how this, in my eyes basic, problem typically would be dealt with in C# (and/or OOP in general). I actually did try to make a base class, but it didn't quite seem right to me. For instance I have no use of a "string Send(string Message)" function in the base class itself. So why would I define one there that needs to be overridden in the derived classes when I would never use the function in the base class ever in the first place? I'm really thankful for any answers. People around here seem very knowledgeable and this place has provided me with many solutions earlier. Now I finally have an account to answer and vote with too. EDIT: To additionally explain, I would also like to be able to access the objects of the actual printertype. For instance the Port variable in PrinterType1 which is a SerialPort object. I would like to access it like: PrinterList[0].Port.Open() and have access to the full range of functionality of the underlaying port. At the same time I would like to call generic functions that work in the same way for the different objects (but with different implementations): foreach (printer in Printers) printer.Send(message)

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• iPhone - Change app icon pointed to by info.plist within the application?

  - by Batgar

  Is there any way to change the 47x47 PNG, pointed to within info.plist, for the iPhone springboard icon from within code? I understand I can add a translation and change the springboard icon per language that the iPhone supports via a changed info.plist per language, but I would like to change the springboard icon for my iPhone app based on a user preference within the app. Any ideas? I haven't tried this, but can a file be copied over another within an app bundle? Could I ship with info.plist pointing to "base.png" then replace "base.png" with another PNG I package with my app from within code? Thanks. --Batgar

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• How have your coding values changed since graduating?

  - by Matt

  We all walked out of school with the stars in our eyes and little experience in "real-world" programming. How have your opinions on programming as a craft changed since you've gained more experience away from academia? I've become more and more about design a la McConnell : wide use of encapsulation, quality code that gives you warm fuzzy feelings when you read it, maintainability over execution performance, etc..., whereas many of my co-workers have followed a different path of fewer middlemen layers getting in the way, code that is right out in the open and easier to locate, even if harder to read, and performance-centric designs. What have you learned about the craft of software design which has changed the way you approach coding since leaving the academic world?

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• Process AJAX response with long runing tasks

  - by mpz

  I have long time task in controller action. I use delayed job for it. (Also in heroku it is good practice for perfomance - dyno must work for small time in each request) But my client need result of it work and users can wait on that task. It is more clear: no any addition models or records in it, simple view and js... I think about such way: On client run AJAX with very long timeout (5 min for example) Client make request to server as usual On controller in action1 def start_work (with delay work setup) i need NO any response to client After work performs (delay job finished) i need run new action2 with response to client Client recieve response after about 1-5 min It is possible?

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• Transitioning from C++ to C#

  - by Jim

  I am very experienced in C and C++ but am having problems finding current opportunities. I decided to switch to C# but noticed that while the syntax is very similar, the programming styles are very different (we don't have IEnumerable etc in C). So the problem I am having now is having 20 years of experience but is only a junior when it comes to interviewing for a C# job. Most of the problems are me not being able to answer questions like 1) How do you do XYZ in Sql Server? 2) What's the use of in Spring.NET In other words, the phone interviewers don;t care if you know DB programming or not - they want to know if you know SQL Server. I am frustrated because the guys who are doing the interviews seem to be so narrow sighted in knowing ONLY C#, .NET and SQL Server, that I don't know how to get past them.

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• On a Hudson master node, what are the .tmp files created in the workspace-files folder?

  - by Patrick Johnmeyer

  Question: In the path HUDSON_HOME/jobs/<jobname>/builds/<timestamp>/workspace-files, there are a series of .tmp files. What are these files, and what feature of Hudson do they support? Background Using Hudson version 1.341, we have a continuous build task that runs on a slave instance. After the build is otherwise complete, including archiving the artifacts, task scanner, etc., the job appears to hang for a long period of time. In monitoring the master node, I noted that many .tmp files were being created and modified under builds//workspace=files, and that some of them were very large. This appears to be causing the delay, as the job completed at the same time that files in this path stopped changing. Some key configuration points of the job: It is tied to a specific slave node It builds in a 'custom workspace' It triggers a downstream job that builds in the same custom workspace on the same slave node

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• C#: How to unit test a method that relies on another method within the same class?

  - by michael paul

  I have a class similar to the following: public class MyProxy : ClientBase<IService>, IService { public MyProxy(String endpointConfiguration) : base(endpointConfiguration) { } public int DoSomething(int x) { int result = DoSomethingToX(x); //This passes unit testing int result2 = ((IService)this).DoWork(x) //do I have to extract this part into a separate method just //to test it even though it's only a couple of lines? //Do something on result2 int result3 = result2 ... return result3; } int IService.DoWork(int x) { return base.Channel.DoWork(x); } } The problem lies in the fact that when testing I don't know how to mock the result2 item without extracting the part that gets result3 using result2 into a separate method. And, because it is unit testing I don't want to go that deep as to test what result2 comes back as... I'd rather mock the data somehow... like, be able to call the function and replace just that one call.

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• Is it stable to change I/O direction on microcontroller repeatedly?

  - by SS

  I'm new to microcontroller programming and I have interfaced my microcontroller board to another device that provides a status based on the command send to it but, this status is provided on the same I/O pin that is used to provide data. So basically, I have an 8-bit data line that is used as an output from the microcontroller, but for certain commands I get a status back on one of the data lines if I choose to read it. So I would be required to change the direction of this one line to read the status thus converting this line as an ouput to an input and then back to an output. Is this acceptable programming or will this changing of the I/O pin this frequently cause instability? Thanks.

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• Which "platform" should we use for a notifier-component?

  - by cwap

  Hi all We need to develop a notifier component. What it will do, is to scan a database at given intervals (say, every 15th minute), to see if any notifications needs to be sent out. We're running on Windows, and so we've been looking into either a Windows Service or the Windows Task Scheduler. Our biggest concern is the robustness of our implementation. If it, for some reason, crashes, can it be auto-restarted the next interval? Can we use custom logging logic, to take care of crashes? I'd like an educated guess on what to use here :) Feel free to say if you need additional info, to make such a guess.. Props will be given if someone could make a short listing of the pros n cons of a windows service vs. the windows task scheduler. Also, it should be noted, that we aren't set on either of these, so if you have any alternatives, please, do post away. Thanks in advance :)

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• Getting list of all existing vtables.

  - by Patrick

  In my application I have quite some void-pointers (this is because of historical reasons, application was originally written in pure C). In one of my modules I know that the void-pointers points to instances of classes that could inherit from a known base class, but I cannot be 100% sure of it. Therefore, doing a dynamic_cast on the void-pointer might give problems. Possibly, the void-pointer even points to a plain-struct (so no vptr in the struct). I would like to investigate the first 4 bytes of the memory the void-pointer is pointing to, to see if this is the address of the valid vtable. I know this is platform, maybe even compiler-version-specific, but it could help me in moving the application forward, and getting rid of all the void-pointers over a limited time period (let's say 3 years). Is there a way to get a list of all vtables in the application, or a way to check whether a pointer points to a valid vtable, and whether that instance pointing to the vtable inherits from a known base class?

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• Statically Init a derived class

  - by AC

  With c++, Is there a way to get a derived class to inherit its own static initializer? I am trying to do something like the following: class Base { public: class StaticInit { public: virtual StaticInit() =0; }; }; class Derived: public Base { public: virtual StaticInit::StaticInit() { //do something with the derived class } static StaticInit init; } static Derived::StaticInit init; it would also be nice if I didn't have to define the init var in each derived class. I am currently redefining the StaticInit internal class in each derived class but it seems redundant. Each derived class is a singleton, and I need the instance to be stored in a lookup table at program startup.

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• Filtering SQLAlchemy query on attribute_mapped_collection field of relationship

  - by bsa

  I have two classes, Tag and Hardware, defined with a simple parent-child relationship (see the full definition at the end). Now I want to filter a query on Tag using the version field in Hardware through an attribute_mapped_collection, eg: def get_tags(order_code=None, hardware_filters=None): session = Session() query = session.query(Tag) if order_code: query = query.filter(Tag.order_code == order_code) if hardware_filters: for k, v in hardware_filters.iteritems(): query = query.filter(getattr(Tag.hardware, k).version == v) return query.all() But I get: AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with Tag.hardware has an attribute 'baseband The same thing happens if I strip it back by hard-coding the attribute, eg: query.filter(Tag.hardware.baseband.version == v) I can do it this way: query = query.filter(Tag.hardware.any(artefact=k, version=v)) But why can't I filter directly through the attribute? Class definitions class Tag(Base): __tablename__ = 'tag' tag_id = Column(Integer, primary_key=True) order_code = Column(String, nullable=False) version = Column(String, nullable=False) status = Column(String, nullable=False) comments = Column(String) hardware = relationship( "Hardware", backref="tag", collection_class=attribute_mapped_collection('artefact'), ) __table_args__ = ( UniqueConstraint('order_code', 'version'), ) class Hardware(Base): __tablename__ = 'hardware' hardware_id = Column(Integer, primary_key=True) tag_id = Column(String, ForeignKey('tag.tag_id')) product_id = Column(String, nullable=True) artefact = Column(String, nullable=False) version = Column(String, nullable=False)

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• What's the deal with all of the abstract stuff?

  - by JustVenting

  I see a lot of talk about MVVM, MVC, Design Patterns etc... You know, some guy has a blog, and he spent the last six months learning about one these things and desiging a program centered around that concept and then he goes on and on about it like its better than sliced bread. I read all of this crap and I wonder, whatever happened to simple logical programming? Not self-absorbed huge frameworks of design patterns and mvc and whatever else you can think of... just simple linear programming, perhaps a few classes to encapsulate things here and there.

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• How to override [Authorize] attribute in the MVC Web API?

  - by NullReference

  I have a MVC Web Api Controller that uses the [Authorize] attribute at the class level. This makes all of the api methods require authorization but I'd like to create an attribute called [ApiPublic] that overrides the [Authorize] attribute. There is a similar technique described here for normal MVC controllers. I tried creating an AuthorizeAttribute based of the System.Web.Http.AuthorizeAttribute but none of the overridden events are called if I put it on a api method that has the [Authorize] at the class level. Anyone have an idea how to override the authorize for the web api? [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class ApiPublicAttribute : AuthorizeAttribute { protected override void HandleUnauthorizedRequest(System.Web.Http.Controllers.HttpActionContext actionContext) { base.HandleUnauthorizedRequest(actionContext); } public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext) { base.OnAuthorization(actionContext); } protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext) { return true; } }

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• Table Variables in SSIS

  - by aceinthehole

  In one SQL Task can I create a table variable DELCARE @TableVar TABLE (...) Then in another SQL Task or DataSource destination and select or insert into the table variable? The other option I have considered is using a Temp Table. CREATE TABLE #TempTable (...) I would prefer to use Table Variable so that it remains in memory. But can use temp table if it is not possible to use table variable. Also I cannot use the record set destination as I need to preform straight SQL tasks on it later on.

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• Ruby on Rails: create records for multiple models with one form and one submit

  - by notblakeshelton

  I have a 3 models: quote, customer, and item. Each quote has one customer and one item. I would like to create a new quote, a new customer, and a new item in their respective tables when I press the submit button. I have looked at other questions and railscasts and either they don't work for my situation or I don't know how to implement them. I also want my index page to be the page where I can create everything. quote.rb class Quote < ActiveRecord::Base attr_accessible :quote_number has_one :customer has_one :item end customer.rb class Customer < ActiveRecord::Base #unsure of what to put here #a customer can have multiple quotes, so would i use: has_many :quotes #<----? end item.rb class Item < ActiveRecord::Base #also unsure about this #each item can also be in multiple quotes quotes_controller.rb class QuotesController < ApplicationController def index @quote = Quote.new @customer = Customer.new @item = item.new end def create @quote = Quote.new(params[:quote]) @quote.save @customer = Customer.new(params[:customer]) @customer.save @item = Item.new(params[:item]) @item.save end end items_controller.rb class ItemsController < ApplicationController def index end def new @item = Item.new end def create @item = Item.new(params[:item]) @item.save end end customers_controller.rb class CustomersController < ApplicationController def index end def new @customer = Customer.new end def create @customer = Customer.new(params[:customer]) @customer.save end end quotes/index.html.erb <%= form_for @quote do |f| %> <%= f.fields_for @customer do |builder| %> <%= label_tag :firstname %> <%= builder.text_field :firstname %> <%= label_tag :lastname %> <%= builder.text_field :lastname %> <% end %> <%= f.fields_for @item do |builder| %> <%= label_tag :name %> <%= builder.text_field :name %> <%= label_tag :description %> <%= builder.text_field :description %> <% end %> <%= label_tag :quote_number %> <%= f.text_field :quote_number %> <%= f.submit %> <% end %> When I try submitting that I get an error: Can't mass-assign protected attributes: item, customer So to try and fix it I updated the attr_accessible in quote.rb to include :item, :customer but then I get this error: Item(#) expected, got ActiveSupport::HashWithIndifferentAccess(#) Any help would be greatly appreciated.

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• How can we use order by in SQLite

  - by Nidhi

  There is two field in my data base id(primary key) and name. I want arrange my data in descending order by using id

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• % confuses python raw sql query

  - by Jonathan

  Following this SO question, I'm trying to "truncate" all tables related to a certain django application using the following raw sql commands in python: cursor.execute("set foreign_key_checks = 0") cursor.execute("select concat('truncate table ',table_schema,'.',table_name,';') as sql_stmt from information_schema.tables where table_schema = 'my_db' and table_type = 'base table' AND table_name LIKE 'some_prefix%'") for sql in [sql[0] for sql in cursor.fetchall()]: cursor.execute(sql) cursor.execute("set foreign_key_checks = 1") Alas I receive the following error: C:\dev\my_project>my_script.py Traceback (most recent call last): File "C:\dev\my_project\my_script.py", line 295, in <module> cursor.execute(r"select concat('truncate table ',table_schema,'.',table_name,';') as sql_stmt from information_schema.tables where table_schema = 'my_db' and table_type = 'base table' AND table_name LIKE 'some_prefix%'") File "C:\Python26\lib\site-packages\django\db\backends\util.py", line 18, in execute sql = self.db.ops.last_executed_query(self.cursor, sql, params) File "C:\Python26\lib\site-packages\django\db\backends\__init__.py", line 216, in last_executed_query return smart_unicode(sql) % u_params TypeError: not enough arguments for format string Is the % in the LIKE making trouble? How can I workaround it?

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• undefined method `events' for #<ActiveRecord::Relation:0x4177518> -rails 3.0.3

  - by brg

  I am having this unexplained NoMethodError with undefined method `events' for #. I don't know why since my model association are well defined and the event table has the foreign keys for the user table. I tried using this fix but it failed: Rails 3 ActiveRecord::Relation random associations behavior event.rb class Event < ActiveRecord::Base belongs_to :user attr_accessible :event_name, :Starts_at, :finish, :tracks end user.rb class User < ActiveRecord::Base has_many :events, :dependent = :destroy attr_accessible :name, :event_attributes accepts_nested_attributes_for :events, :allow_destroy = true end schema.rb ActiveRecord::Schema.define(:version = 20101201180355) do create_table "events", :force = true do |t| t.string "event_name" t.string "tracks" t.datetime "starts_at" t.datetime "finish" t.datetime "created_at" t.datetime "updated_at" t.integer "user_id" end end error message NoMethodError in Users#index undefined method `events' for # Extracted source (around line #10): 7: <%= sortable "Tracks" % 8: 10: <% @users.events.each do |event| % 11: <% debugger % 12: 13: <%= event.starts_at % Trace of template inclusion: app/views/users/index.html.erb Rails.root: C:/rails_project1/events_manager Application Trace | Framework Trace | Full Trace app/views/users/_event_user.html.erb:10:in _app_views_users__event_user_html_erb__412443848_34308540_1390678' app/views/users/index.html.erb:7:in_app_views_users_index_html_erb___603337143_34316016_0'

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• what else to do to establish many-to-many associations in Ruby on Rails? thanks!

  - by john

  Hi, I have two classes and I want to establish a many-to-many assications, here is the code: class Category < ActiveRecord::Base has_and_belongs_to_many :events has_and_belongs_to_many :tips end class Tip < ActiveRecord::Base has_and_belongs_to_many :categories However, I kept getting the following errors and I would appreciate it if some one could educate me what is going wrong: PGError: ERROR: relation "categories_tips" does not exist : SELECT "categories".id FROM "categories" INNER JOIN "categories_tips" ON "categories".id = "categories_tips".category_id WHERE ("categories_tips".tip_id = NULL ) the viewer part: 4: <%= text_field :tip, :title %></label></p> 5: 6: <p><label>Categories<br/> 7: <%= select_tag('categories[]', options_for_select(Category.find(:all).collect {|c| [c.name, c.id] }, @tip.category_ids), :multiple => true ) %></label></p> 8: 9: <p><label>Location<br/> 10: <%= text_field_with_auto_complete :tip, :abstract %></label></p>

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• Where can C debugger tutorials be found?

  - by Ricky

  Is there any tutorial about using debuggers, when doing C programming on Linux (console mode)?

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• Check boxes for a has_many and belongs_to association.

  - by Thomas

  I have a has_many and belongs_to association. class Link < ActiveRecord::Base has_and_belongs_to_many :categories belongs_to :property end class Property < ActiveRecord::Base has_many :links end In the index and show I have <%= link.property.name %> and it will show the Property that I assigned to the link with the console just fine. I have a problem with figuring out how to show check boxes in the _form that assign a property to the link (a drop down would work as well). It seems everyone who has had this question before has ether a has_many :through or a HABTM relationship and I can't seem to adapt their answers.

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• Erlang Question - Time order of messages

  - by Aiden Bell

  Read (skimmed enough to get coding) through Erlang Programming and Programming Erlang. One question, which is as simple as it sounds: If you have a process Pid1 on machine m1 and a billion million messages are sent to Pid1, are messages handled in parallel by that process (I get the impression no) and(answered below) is there any guarantee of order when processing messages? ie. Received in order sent? If so, how is clock skew handled in high traffic situations for ordering? Coming from the whole C/Thread pools/Shared State background ... I want to get this concrete. I understand distributing an application, but want to ensure the 'raw bones' are what I expect before building processes and distributing workload. Also, am I right in thinking the whole world is currently flicking through Erlang texts ;)

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• Rspec and Rails 3 - Problem Validating Nested Attribute Collection Size

  - by MunkiPhD

  When I create my Rspec tests, I keep getting a validation of false as opposed to true for the following tests. I've tried everything and the following is the measly code that I have now - so if it's waaaaay wrong, that's why. class Master < ActiveRecord::Base attr_accessible :name, :specific_size # Associations ---------------------- has_many :line_items accepts_nested_attributes_for :line_items, :allow_destroy => true, :reject_if => lambda { |a| a[:item_id].blank? } # Validations ----------------------- validates :name, :presence => true, :length => {:minimum => 3, :maximum => 30} validates :specific_size, :presence => true, :length => {:minimum => 4, :maximum => 30} validate :verify_items_count def verify_items_count if self.line_items.size < 2 errors.add(:base, "Not enough items to create a master") end end end And here it the items model: class LineItem < ActiveRecord::Base attr_accessible :specific_size, :other_item_type_id # Validations -------------------- validates :other_item_type_id, :presence => true validates :master_id, :presence => true validates :specific_size, :presence => true # Associations --------------------- belongs_to :other_item_type belongs_to :master end The RSpec Tests: before(:each) do @master_lines = [] @master_lines << LineItem.new(:other_item_type_id => 1, :master_id => 2, :specific_size => 1) @master_lines << LineItem.new(:other_item_type_id => 2, :master_id => 2, :specific_size => 1) @attr = {:name => "Some Master", :specific_size => "1 giga"} end it "should create a new instance given a valid name and specific size" do @master = Master.create(@attr) line_item_one = @master.line_items.build(:other_item_type_id => 1, :specific_size => 1) line_item_two = @master.line_items.build(:other_item_type_id => 2, :specific_size => 2) @master.line_items.size === 2 @master.should be_valid end it "should have at least two items to be valid" do master = Master.new(:name => "test name", :specific_size => "1 mega") master_item_one = LineItem.new(:other_item_type_id => 1, :specific_size => 2) master_item_two = LineItem.new(:other_item_type_id => 2, :specific_size => 1) master.line_items << master_item_one master.should_not be_valid master.line_items << master_item_two master.line_items.size.should === 2 master.should be_valid end I'm very new to Rspec and Rails - and I've been failing at this for the past couple of hours. Thanks for any help in advance.

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• Overload and hide methods in Java

  - by Marco

  Hi, i have an abstract class BaseClass with a public insert() method: public abstract class BaseClass { public void insert(Object object) { // Do something } } which is extended by many other classes. For some of those classes, however, the insert() method must have additional parameters, so that they instead of overriding it I overload the method of the base class with the parameters required, for example: public class SampleClass extends BaseClass { public void insert(Object object, Long param){ // Do Something } } Now, if i instantiate the SampleClass class, i have two insert() methods: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object); sampleClass.insert(Object object, Long param); what i'd like to do is to hide the insert() method defined in the base class, so that just the overload would be visible: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object, Long param); Could this be done in OOP?

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