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  • Hibernate and mssql inner join rowcount

    - by ez2sarang
    I am struggling with Hibernate Criteria. My aim is to create the following request using Hibernate Criteria : select count(*) as y0_ from PInterface this_ inner join Product product2_ on this_.product_id=product2_.id where this_.product_interface_type_id=? Here is my code: @Entity @Table(name = "PInterface") public class PInterface { @Id @GeneratedValue @Column(name = "id", nullable = false, insertable = false, updatable = false) private int id; @Column(name = "product_id") private int productId; @Column(name = "product_interface_type_id") private int type; @ManyToOne(optional=false) @JoinColumn(name = "product_id", referencedColumnName = "id", insertable=false, updatable=false) private Product product; } @Entity @Table(name = "Product") public class Product { @Id @GeneratedValue @Column(name = "id", nullable = false, insertable = false, updatable = false) private int id; private String name; } //Criteria is : Object criteria = sessionFactory.getCurrentSession() .createCriteria(PInterface.class) .add(Restrictions.eq("type", 1)) .setProjection(Projections.rowCount()) .uniqueResult() ; However, the results ... select count(*) as y0_ from PInterface this_ where this_.product_interface_type_id=? Where Inner join? Thank you for help!

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  • SQL: Join multiple tables and get a grouped sum

    - by Scienceprodigy
    I have a database with 3 tables that have related data. One table has transactions, and the other two relate to transaction categories. Basically it's financial data, so each transaction has a category (i.e. "gasoline" for a gas purchase transaction). A short version of my Transactions table looks like this- Transactions Table: ________________________________ | ID | Type | Amount | Category | --------------------------------- I also have two more tables relating a category to a categories parent. So basically, every Category entry in the Transactions Table belongs to a parent category (i.e. "gasoline" would belong to say "Automotive Expenses"). For categories, and their parent, I have two tables - Category Children: ____________________________________________ | ID | Parent Category ID | Child Category | -------------------------------------------- Category Parent: ________________________ | ID | Parent Category | ------------------------ What I'm trying to do is query the database and have it return a total spending by parent category. To get "spending" the Type of transactions must be "Debit". I tried the following statement: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category = 'category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id = category_parents._id WHERE trans_type = 'Debit' GROUP BY parent_category ORDER BY totals DESC but it gives me the following exception: 12-31 13:51:21.515: ERROR/Exception on query(4403): android.database.sqlite.SQLiteException: no such column: category_children.parent_category_id: , while compiling: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category='category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id=category_parents._id where trans_type='Debit' group by parent_category order by totals desc Any help is appreciated. (EXTRA CREDIT: I also need to make another statement to do spending by child category, given the parent category)

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  • The Best Websites for Free Online Courses, Certificates, Degrees, and Educational Resources

    - by Lori Kaufman
    Have you thought about expanding your knowledge by taking some courses? There are several colleges and other sites that offer free online courses, certificate programs, some degree programs, and education resources for teachers and professors. How to Banish Duplicate Photos with VisiPic How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It?

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  • Object model design: collections on classes

    - by Luke Puplett
    Hi all, Consider Train.Passengers, what type would you use for Passengers where passengers are not supposed to be added or removed by the consuming code? I'm using .NET Framework, so this discussion would suit .NET, but it could apply to a number of modern languages/frameworks. In the .NET Framework, the List is not supposed to be publicly exposed. There's Collection and ICollection and guidance, which I tend to agree with, is to return the closest concrete type down the inheritance tree, so that'd be Collection since it is already an ICollection. But Collection has read/write semantics and so possibly it should be a ReadOnlyCollection, but its arguably common sense not to alter the contents of a collection that you don't have intimate knowledge about so is it necessary? And it requires extra work internally and can be a pain with (de)serialization. At the extreme ends I could just return Person[] (since LINQ now provides much of the benefits that previously would have been afforded by a more specified collection) or even build a strongly-typed PersonCollection or ReadOnlyPersonCollection! What do you do? Thanks for your time. Luke

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  • Using IComparable<T> Interface

    - by Pawan_Mishra
    Level : Beginner to Intermediate C# language has constantly evolved over a constant period of time.Each new version introduced new features which changed the way we programmed and solved the problems. Whether it was introduction of generics in C# 2.0 , LINQ in C# 3.0 or concept of dynamic programming in C# 4.0 , each of them had or will have greater impact on our programming style.As a developer we don’t have much option but to evolve and redefine our self in this constantly changing environment...(read more)

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  • Changing CSS classes when different strings are displayed in a text element with jQuery

    - by Nick Maddren
    I'm just wondering if this method would be possible using jQuery HTML and PHP. Basically I have a filtering system were products are listed, some have different attribute values such as Hatchback for example. The text element that holds these PHP echo's also have a css class that implements an icon. I'm just wondering can I alter class's that are added to a html element just by looking at the string? So for example if the string displays "Pick-up" then jQuery alters the class and adds the one associated with the "Pick-up" string? Thanks sorry if this is a little confusing, I can explain more if needed.

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  • how to double buffer in multiple classes with java

    - by kdavis8
    I am creating a Java 2D video game. I can load graphics just fine, but when it gets into double buffering I have issues. My source code package myPackage; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class GameView extends JFrame { private BufferedImage backbuffer; private Graphics2D g2d; public GameView() { setBounds(0, 0, 500, 500); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); backbuffer = new BufferedImage(getHeight(), getWidth(), BufferedImage.TYPE_INT_BGR); g2d = backbuffer.createGraphics(); Toolkit tk = Toolkit.getDefaultToolkit(); Image img = tk.getImage(this.getClass().getResource("cage.png")); g2d.setColor(Color.red); //g2d.drawString("Hello",100,100); g2d.drawImage(img, 100, 100, this); repaint(); } public static void main(String args[]) { new GameView(); } public void paint(Graphics g) { g2d = (Graphics2D)g; g2d.drawImage(backbuffer, 0, 0, this); } }

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  • Is it appropriate for a class to only be a collection of information with no logic?

    - by qegal
    Say I have a class Person that has instance variables age, weight, and height, and another class Fruit that has instance variables sugarContent and texture. The Person class has no methods save setters and getters, while the Fruit class has both setters and getters and logic methods like calculateSweetness. Is the Fruit class the type of class that is better practice than the Person class. What I mean by this is that the Person class seems like it doesn't have much purpose; it exists solely to organize data, while the Fruit class organizes data and actually contains methods for logic.

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  • Class Design and Structure Online Web Store

    - by Phorce
    I hope I have asked this in the right forum. Basically, we're designing an Online Store and I am designing the class structure for ordering a product and want some clarification on what I have so far: So a customer comes, selects their product, chooses the quantity and selects 'Purchase' (I am using the Facade Pattern - So subsystems execute when this action is performed). My class structure: < Order > < Product > <Customer > There is no inheritance, more Association < Order has < Product , < Customer has < Order . Does this structure look ok? I've noticed that I don't handle the "Quantity" separately, I was just going to add this into the "Product" class, but, do you think it should be a class of it's own? Hope someone can help.

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  • Deserialize inherited classes into the same list in XNA

    - by M0rgenstern
    I am writing a Gui for a game (for what else ...). Therefor I wrote a class GuiElement which has some serializeable fields. From this class I deflect a Class "Button" which has one serializeable field more. Furthermore, I have a Class GuiWindow, which is as well deflected from "GuiElement". An Object of this Class has a Field "HandledElements" of the type "List". To know the layout of the Menues, I use XML-Files, which look like that (for example): <?xml version="1.0" encoding="utf-8" ?> <XnaContent xmlns:Generic="System.Collections.Generic"> <Asset Type="System.Collections.Generic.List[GUI.GuiWindow]"> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>MainMenu</Name> <HandledElements> <Item> <Position>100 100</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>Optionen</Name> <Caption>Optionen</Caption> </Item> </HandledElements> </Item> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>false</IsActive> <Name>Options</Name> <HandledElements> </HandledElements> </Item> </Asset> </XnaContent> As you can see, the first window has in its "HandledElements" List an Item with the Field . This is a field which only a Button has. The Problem is now: I can't deserialize this XML file, because GuiElement does not have this Field, it only has the few fields above. I thought it would know automatically which Class to use,but it doesn't. Do I really have to give my windows a list for each child class of GuiElement? Or can I do another workaround?

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  • Liskov substitution and abstract classes / strategy pattern

    - by Kolyunya
    I'm trying to follow LSP in practical programming. And I wonder if different constructors of subclasses violate it. It would be great to hear an explanation instead of just yes/no. Thanks much! P.S. If the answer is no, how do I make different strategies with different input without violating LSP? class IStrategy { public: virtual void use() = 0; }; class FooStrategy : public IStrategy { public: FooStrategy(A a, B b) { c = /* some operations with a, b */ } virtual void use() { std::cout << c; } private: C c; }; class BarStrategy : public IStrategy { public: BarStrategy(D d, E e) { f = /* some operations with d, e */ } virtual void use() { std::cout << f; } private: F f; };

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  • Entity Framework 4.0 POCO Classes and Data Services

    If you've flipped on the POCO (Plain Ol' CLR Objects) code generation T4 templates for Entity Framework to enable testing or just 'cuz you like the code better, you might find that you lack the ability to expose that same model via Data Services as OData (Open Data). If you surf to the feed, you'll likely see something like this: The XML page cannot be displayed Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Entity Framework 4.0 POCO Classes and Data Services

    If you've flipped on the POCO (Plain Ol' CLR Objects) code generation T4 templates for Entity Framework to enable testing or just 'cuz you like the code better, you might find that you lack the ability to expose that same model via Data Services as OData (Open Data). If you surf to the feed, you'll likely see something like this: The XML page cannot be displayed Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Data Education: Great Classes Coming to a City Near You

    - by Adam Machanic
    In case you haven't noticed, Data Education (the training company I started a couple of years ago) has expanded beyond the US northeast; we're currently offering courses with top trainers in both St. Louis and Chicago , as well as the Boston area. The courses are starting to fill up fast—not surprising when you consider we’re talking about experienced instructors like Kalen Delaney , Rob Farley , and Allan Hirt —but we have still have some room. We’re very excited about bringing the highest quality...(read more)

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  • Using T4 to generate Configuration classes

    - by Justin Hoffman
    I wanted to try to use T4 to read a web.config and generate all of the appSettings and connectionStrings as properties of a class.  I elected in this template only to output appSettings and connectionStrings but you can see it would be easily adapted for app specific settings, bindings etc.  This allows for quick access to config values as well as removing the potential for typo's when accessing values from the ConfigurationManager. One caveat: a developer would need to remember to run the .tt file after adding an entry to the web.config.  However, one would quickly notice when trying to access the property from the generated class (it wouldn't be there).  Additionally, there are other options as noted here. The first step was to create the .tt file.  Note that this is a basic example, it could be extended even further I'm sure.  In this example I just manually input the path to the web.config file. <#@ template debug="false" hostspecific="true" language="C#" #><#@ output extension=".cs" #><#@ assembly Name="System.Configuration" #><#@ assembly name="System.Xml" #><#@ assembly name="System.Xml.Linq" #><#@ assembly name="System.Net" #><#@ assembly name="System" #><#@ import namespace="System.Configuration" #><#@ import namespace="System.Xml" #><#@ import namespace="System.Net" #><#@ import namespace="Microsoft.VisualStudio.TextTemplating" #><#@ import namespace="System.Xml.Linq" #>using System;using System.Configuration;using System.Xml;using System.Xml.Linq;using System.Linq;namespace MyProject.Web { public partial class Configurator { <# var xDocument = XDocument.Load(@"G:\MySolution\MyProject\Web.config"); var results = xDocument.Descendants("appSettings"); const string key = "key"; const string name = "name"; foreach (var xElement in results.Descendants()) {#> public string <#= xElement.Attribute(key).Value#>{get {return ConfigurationManager.AppSettings[<#= string.Format("{0}{1}{2}","\"" , xElement.Attribute(key).Value, "\"")#>];}} <#}#> <# var connectionStrings = xDocument.Descendants("connectionStrings"); foreach(var connString in connectionStrings.Descendants()) {#> public string <#= connString.Attribute(name).Value#>{get {return ConfigurationManager.ConnectionStrings[<#= string.Format("{0}{1}{2}","\"" , connString.Attribute(name).Value, "\"")#>].ConnectionString;}} <#} #> }} The resulting .cs file: using System;using System.Configuration;using System.Xml;using System.Xml.Linq;using System.Linq;namespace MyProject.Web { public partial class Configurator { public string ClientValidationEnabled{get {return ConfigurationManager.AppSettings["ClientValidationEnabled"];}} public string UnobtrusiveJavaScriptEnabled{get {return ConfigurationManager.AppSettings["UnobtrusiveJavaScriptEnabled"];}} public string ServiceUri{get {return ConfigurationManager.AppSettings["ServiceUri"];}} public string TestConnection{get {return ConfigurationManager.ConnectionStrings["TestConnection"].ConnectionString;}} public string SecondTestConnection{get {return ConfigurationManager.ConnectionStrings["SecondTestConnection"].ConnectionString;}} }} Next, I extended the partial class for easy access to the Configuration. However, you could just use the generated class file itself. using System;using System.Linq;using System.Xml.Linq;namespace MyProject.Web{ public partial class Configurator { private static readonly Configurator Instance = new Configurator(); public static Configurator For { get { return Instance; } } }} Finally, in my example, I used the Configurator class like so: [TestMethod] public void Test_Web_Config() { var result = Configurator.For.ServiceUri; Assert.AreEqual(result, "http://localhost:30237/Service1/"); }

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  • Should I use a Class or Dictionary to Store Form Values

    - by Shamim Hafiz
    I am working on a C# .NET Application, where I have a Form with lots of controls. I need to perform computations depending on the values of the controls. Therefore, I need to pass the Form values to a function and inside that function, several helper functions will be called depending on the Control element. Now, I can think of two ways to pass all the Form values: i) Save everything in a Dictionary and pass the Dictionary to the function or ii) Have a class with attributes that corresponds to each of the Form element. Which of these two approaches , or any other, is better?

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  • designing classes with similar goal but widely different decisional core

    - by Stefano Borini
    I am puzzled on how to model this situation. Suppose you have an algorithm operating in a loop. At every loop, a procedure P must take place, whose role is to modify an input data I into an output data O, such that O = P(I). In reality, there are different flavors of P, say P1, P2, P3 and so on. The choice of which P to run is user dependent, but all P have the same finality, produce O from I. This called well for a base class PBase with a method PBase::apply, with specific reimplementations of P1::apply(I), P2::apply(I), and P3::apply(I). The actual P class gets instantiated in a factory method, and the loop stays simple. Now, I have a case of P4 which follows the same principle, but this time needs additional data from the loop (such as the current iteration, and the average value of O during the previous iterations). How would you redesign for this case?

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  • Calling functions from different classes

    - by A Ron Hubbard Clevenger
    I'm writing a program and I'm supposed to check and see if a certain object is in the list before I call it. I set up the contains() method which is supposed to use the equals() method of the Comparable interface I implemented on my Golfer class but it doesn't seem to call it (I put print statements in to check). I can't seem to figure out whats wrong with the code, the ArrayUnsortedList class I'm using to go through the list even uses the correct toString() method I defined in my Golfer class but for some reason it won't use the equals() method I implemented. //From "GolfApp.java" public class GolfApp{ ListInterface <Golfer>golfers = new ArraySortedList<Golfer> (20); Golfer golfer; //..*snip*.. if(this.golfers.contains(new Golfer(name,score))) System.out.println("The list already contains this golfer"); else{ this.golfers.add(this.golfer = new Golfer(name,score)); System.out.println("This golfer is already on the list"); } //From "ArrayUnsortedList.java" protected void find(T target){ location = 0; found = false; while (location < numElements){ if (list[location].equals(target)) //Where I think the problem is { found = true; return; } else location++; } } public boolean contains(T element){ find(element); return found; } //From "Golfer.java" public class Golfer implements Comparable<Golfer>{ //..irrelavant code sniped..// public boolean equals(Golfer golfer) { String thisString = score + ":" + name; String otherString = golfer.getScore() + ":" + golfer.getName() ; System.out.println("Golfer.equals() has bee called"); return thisString.equalsIgnoreCase(otherString); } public String toString() { return (score + ":" + name); } My main problem seems to be getting the find function of the ArrayUnsortedList to call my equals function in the find() part of the List but I'm not exactly sure why, like I said when I have it printed out it works with the toString() method I implemented perfectly. I'm almost positive the problem has to do with the find() function in the ArraySortedList not calling my equals() method. I tried using some other functions that relied on the find() method and got the same results.

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  • Pygame: Save a list of objects/classes/surfaces

    - by Sam Tubb
    I am working on a game, in which you can create mazes. You place blocks on a 16x16 grid, while choosing from a variety of block to make the level with. Whenever you create a block, it adds this class: class Block(object): def __init__(self,x,y,spr): self.x=x self.y=y self.sprite=spr self.rect=self.sprite.get_rect(x=self.x,y=self.y) to a list called instances. I tried shelving it to a .bin file, but it returns some error dealing with surfaces. How can I go about saving and loading levels? Any help is appreciated! :) Here is the whole code for reference: import pygame from pygame.locals import * #initstuff pygame.init() screen=pygame.display.set_mode((640,480)) pygame.display.set_caption('PiMaze') instances=[] #loadsprites menuspr=pygame.image.load('images/menu.png').convert() b1spr=pygame.image.load('images/b1.png').convert() b2spr=pygame.image.load('images/b2.png').convert() currentbspr=b1spr curspr=pygame.image.load('images/curs.png').convert() curspr.set_colorkey((0,255,0)) #menu menuspr.set_alpha(185) menurect=menuspr.get_rect(x=-260,y=4) class MenuItem(object): def __init__(self,pos,spr): self.x=pos[0] self.y=pos[1] self.sprite=spr self.pos=(self.x,self.y) self.rect=self.sprite.get_rect(x=self.x,y=self.y) class Block(object): def __init__(self,x,y,spr): self.x=x self.y=y self.sprite=spr self.rect=self.sprite.get_rect(x=self.x,y=self.y) while True: #menu items b1menu=b1spr.get_rect(x=menurect.left+32,y=48) b2menu=b2spr.get_rect(x=menurect.left+64,y=48) menuitems=[MenuItem(b1menu,b1spr),MenuItem(b2menu,b2spr)] screen.fill((20,30,85)) mse=pygame.mouse.get_pos() key=pygame.key.get_pressed() placepos=((mse[0]/16)*16,(mse[1]/16)*16) if key[K_q]: if mse[0]<260: if menurect.right<255: menurect.right+=1 else: if menurect.left>-260: menurect.left-=1 else: if menurect.left>-260: menurect.left-=1 for e in pygame.event.get(): if e.type==QUIT: exit() if menurect.right<100: if e.type==MOUSEBUTTONUP: if e.button==1: to_remove = [i for i in instances if i.rect.collidepoint(placepos)] for i in to_remove: instances.remove(i) if not to_remove: instances.append(Block(placepos[0],placepos[1],currentbspr)) for i in instances: screen.blit(i.sprite,i.rect) if not key[K_q]: screen.blit(curspr,placepos) screen.blit(menuspr,menurect) for item in menuitems: screen.blit(item.sprite,item.pos) if item.rect.collidepoint(mse): if pygame.mouse.get_pressed()==(1,0,0): currentbspr=item.sprite pygame.draw.rect(screen, ((255,0,0)), item, 1) pygame.display.flip()

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  • Entity Framework 4.0 POCO Classes and Data Services

    If you've flipped on the POCO (Plain Ol' CLR Objects) code generation T4 templates for Entity Framework to enable testing or just 'cuz you like the code better, you might find that you lack the ability to expose that same model via Data Services as OData (Open Data). If you surf to the feed, you'll likely see something like this: The XML page cannot be displayed Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Share Mulitple Classes as one dll or a lib with Mulitple Projects

    - by JNL
    Currently I have some shared class files(.cpp and .h) which I include them in around 20 Projects. Currently I have to include them in all of the projects. So if I get some business requirments and I change some of the shared(.cpp or .h) files I have to include them in all the 20 Projects which is kind of tedious. Is there a way where I can create a shared dll or library and include it all of my Projects. So if I have to change it, I just have to change it once and then just Add Reference to include that dll or library which contains all the shared(.cpp, .h) files. Any help/recommendations regarding the same, will be highly appreciated. I am using VS2012 for VC++.

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  • How do I separate codes with classes?

    - by Trycon
    I have this main class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; public class tests extends BasicGameState{ public boolean render=false; tests1 test = new tests1(); public tests(int test) { // TODO Auto-generated constructor stub } @Override public void init(GameContainer arg0, StateBasedGame arg1) throws SlickException { // TODO Auto-generated method stub } @Override public void render(GameContainer arg0, StateBasedGame arg1, Graphics g) throws SlickException { // TODO Auto-generated method stub if(render==true) { g.drawString("Hello",100,100); } } @Override public void update(GameContainer gc, StateBasedGame s, int delta) throws SlickException { // TODO Auto-generated method stub test.render=render; test.update(gc, s, delta); } @Override public int getID() { // TODO Auto-generated method stub return 1000; } } and its sub-class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class tests1 { public boolean render; public void update(GameContainer gc, StateBasedGame s, int delta) { Input input = gc.getInput(); if(input.isKeyPressed(Input.KEY_X)) { render=true; } } } I was finding a way to prevent many codes in one class. I'm new to java. When I try running my game, then when I press X, it does not work. How am I suppose to fix that?

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  • Functional programming compared to OOP with classes

    - by luckysmack
    I have been interested in some of the concepts of functional programming lately. I have used OOP for some time now. I can see how I would build a fairly complex app in OOP. Each object would know how to do things that object does. Or anything it's parents class does as well. So I can simply tell Person().speak() to make the person talk. But how do I do similar things in functional programming? I see how functions are first class items. But that function only does one specific thing. Would I simply have a say() method floating around and call it with an equivalent of Person() argument so I know what kind of thing is saying something? So I can see the simple things, just how would I do the comparable of OOP and objects in functional programming, so I can modularize and organize my code base? For reference, my primary experience with OOP is Python, PHP, and some C#. The languages that I am looking at that have functional features are Scala and Haskell. Though I am leaning towards Scala. Basic Example (Python): Animal(object): def say(self, what): print(what) Dog(Animal): def say(self, what): super().say('dog barks: {0}'.format(what)) Cat(Animal): def say(self, what): super().say('cat meows: {0}'.format(what)) dog = Dog() cat = Cat() dog.say('ruff') cat.say('purr')

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  • What is the use of Association, Aggregation and Composition (Encapsulation) in Classes

    - by SahilMahajanMj
    I have gone through lots of theories about what is encapsulation and the three techniques of implementing it, which are Association, Aggregation and Composition. What i found is, Encapsulation Encapsulation is the technique of making the fields in a class private and providing access to the fields via public methods. If a field is declared private, it cannot be accessed by anyone outside the class, thereby hiding the fields within the class. For this reason, encapsulation is also referred to as data hiding. Encapsulation can be described as a protective barrier that prevents the code and data being randomly accessed by other code defined outside the class. Access to the data and code is tightly controlled by an interface. The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this feature Encapsulation gives maintainability, flexibility and extensibility to our code. Association Association is a relationship where all object have their own lifecycle and there is no owner. Let’s take an example of Teacher and Student. Multiple students can associate with single teacher and single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. Both can create and delete independently. Aggregation Aggregation is a specialize form of Association where all object have their own lifecycle but there is ownership and child object can not belongs to another parent object. Let’s take an example of Department and teacher. A single teacher can not belongs to multiple departments, but if we delete the department teacher object will not destroy. We can think about “has-a” relationship. Composition Composition is again specialize form of Aggregation and we can call this as a “death” relationship. It is a strong type of Aggregation. Child object dose not have their lifecycle and if parent object deletes all child object will also be deleted. Let’s take again an example of relationship between House and rooms. House can contain multiple rooms there is no independent life of room and any room can not belongs to two different house if we delete the house room will automatically delete. The question is: Now these all are real world examples. I am looking for some description about how to use these techniques in actual class code. I mean what is the point for using three different techniques for encapsulation, How these techniques could be implemented and How to choose which technique is applicable at time.

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