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  • Java Inheritance - Getting a Parameter from Parent Class

    - by Aaron
    I'm trying to take one parameter from the parent class of Car and add it to my array (carsParked), how can i do this? Parent Class public class Car { protected String regNo; //Car registration number protected String owner; //Name of the owner protected String carColor; /** Creates a Car object * @param rNo - registration number * @param own - name of the owner **/ public Car (String rNo, String own, String carColour) { regNo = rNo; owner = own; carColor = carColour; } /** @return The car registration number **/ public String getRegNo() { return regNo; } /** @return A String representation of the car details **/ public String getAsString() { return "Car: " + regNo + "\nColor: " + carColor; } public String getColor() { return carColor; } } Child Class public class Carpark extends Car { private String location; // Location of the Car Park private int capacity; // Capacity of the Car Park - how many cars it can hold private int carsIn; // Number of cars currently in the Car Park private String[] carsParked; /** Constructor for Carparks * @param loc - the Location of the Carpark * @param cap - the Capacity of the Carpark */ public Carpark (String locations, int room) { location = locations; capacity = room; } /** Records entry of a car into the car park */ public void driveIn() { carsIn = carsIn + 1; } /** Records the departure of a car from the car park */ public void driveOut() { carsIn = carsIn - 1; } /** Returns a String representation of information about the carpark */ public String getAsString() { return location + "\nCapacity: " + capacity + " Currently parked: " + carsIn + "\n*************************\n"; } }

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  • Any way to allow classes implementing IEntity and downcast to have operator == comparisons?

    - by George Mauer
    Basically here's the issue. All entities in my system are identified by their type and their id. new Customer() { Id = 1} == new Customer() {Id = 1}; new Customer() { Id = 1} != new Customer() {Id = 2}; new Customer() { Id = 1} != new Product() {Id = 1}; Pretty standard scenario. Since all Entities have an Id I define an interface for all entities. public interface IEntity { int Id { get; set;} } And to simplify creation of entities I make public abstract class BaseEntity<T> : where T : IEntity { int Id { get; set;} public static bool operator ==(BaseEntity<T> e1, BaseEntity<T> e2) { if (object.ReferenceEquals(null, e1)) return false; return e1.Equals(e2); } public static bool operator !=(BaseEntity<T> e1, BaseEntity<T> e2) { return !(e1 == e2); } } where Customer and Product are something like public class Customer : BaseEntity<Customer>, IEntity {} public class Product : BaseEntity<Product>, IEntity {} I think this is hunky dory. I think all I have to do is override Equals in each entity (if I'm super clever, I can even override it only once in the BaseEntity) and everything with work. So now I'm expanding my test coverage and find that its not quite so simple! First of all , when downcasting to IEntity and using == the BaseEntity< override is not used. So what's the solution? Is there something else I can do? If not, this is seriously annoying. Upadate It would seem that there is something wrong with my tests - or rather with comparing on generics. Check this out [Test] public void when_created_manually_non_generic() { // PASSES! var e1 = new Terminal() {Id = 1}; var e2 = new Terminal() {Id = 1}; Assert.IsTrue(e1 == e2); } [Test] public void when_created_manually_generic() { // FAILS! GenericCompare(new Terminal() { Id = 1 }, new Terminal() { Id = 1 }); } private void GenericCompare<T>(T e1, T e2) where T : class, IEntity { Assert.IsTrue(e1 == e2); } Whats going on here? This is not as big a problem as I was afraid, but is still quite annoying and a completely unintuitive way for the language to behave. Update Update Ah I get it, the generic implicitly downcasts to IEntity for some reason. I stand by this being unintuitive and potentially problematic for my Domain's consumers as they need to remember that anything happening within a generic method or class needs to be compared with Equals()

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  • Partial class or "chained inheritance"

    - by Charlie boy
    Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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  • A "Trig" Calculating Class

    - by Clinton Scott
    I have been trying to create a gui that calculates trigonometric functions based off of the user's input. I have had success in the GUI part, but my class that I wrote to hold information using inheritance seems to be messed up, because when I run it gives an error saying: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - constructor ArcTrigCalcCon in class TrigCalc.ArcTrigCalcCon cannot be applied to given types; required: double,double,double,double,double,double found: java.lang.Double,java.lang.Double,java.lang.Double reason: actual and formal argument lists differ in length at TrigCalc.TrigCalcGUI.(TrigCalcGUI.java:31) at TrigCalc.TrigCalcGUI.main(TrigCalcGUI.java:87) Java Result: 1 and says it is the object causing the problem. Below Will be my code. First I will put up my inheritance class with cosecant secant and cotangent and then my original class with the original 3 trig functions: { public ArcTrigCalcCon(double s, double cs, double t, double csc, double sc, double ct) { // Inherit from the Trig Calc class super(s, cs, t); cosecant = 1/s; secant = 1/cs; cotangent = 1/t; } public void setCsc(double csc) { cosecant = csc; } public void setSec(double sc) { secant = sc; } public void setCot(double ct) { cotangent = ct; } } Here is the first Trigonometric class: public class TrigCalcCon { public double sine; public double cosine; public double tangent; public TrigCalcCon(double s, double cs, double t) { sine = s; cosine = cs; tangent = t; } public void setSin(double s) { sine = s; } public void setCos(double cs) { cosine = cs; } public void setTan(double t) { tangent = t; } public void set(double s, double cs, double t) { sine = s; cosine = cs; tangent = t; } public double getSin() { return Math.sin(sine); } public double getCos() { return Math.cos(cosine); } public double getTan() { return Math.tan(tangent); } } and here is the demo class to run the gui: public class TrigCalcGUI extends JFrame implements ActionListener { // Instance Variables private String input; private Double s, cs, t, csc, sc, ct; private JPanel mainPanel, sinPanel, cosPanel, tanPanel, cscPanel, secPanel, cotPanel, buttonPanel, inputPanel, displayPanel; // Panel Display private JLabel sinLabel, cosLabel, tanLabel, secLabel, cscLabel, cotLabel, inputLabel; private JTextField sinTF, cosTF, tanTF, secTF, cscTF, cotTF, inputTF; //Text Fields for sin, cos, and tan, and inverse private JButton calcButton, clearButton; // Calculate and Exit Buttons // Object ArcTrigCalcCon trC = new ArcTrigCalcCon(s, cs, t); public TrigCalcGUI() { // title bar text. super("Trig Calculator"); // Corner exit button action. setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Create main panel to add each panel to mainPanel = new JPanel(); mainPanel.setLayout(new GridLayout(3,2)); displayPanel = new JPanel(); displayPanel.setLayout(new GridLayout(3,2)); // Assign Panel to each variable inputPanel = new JPanel(); sinPanel = new JPanel(); cosPanel = new JPanel(); tanPanel = new JPanel(); cscPanel = new JPanel(); secPanel = new JPanel(); cotPanel = new JPanel(); buttonPanel = new JPanel(); // Call each constructor buildInputPanel(); buildSinCosTanPanels(); buildCscSecCotPanels(); buildButtonPanel(); // Add each panel to content pane displayPanel.add(sinPanel); displayPanel.add(cscPanel); displayPanel.add(cosPanel); displayPanel.add(secPanel); displayPanel.add(tanPanel); displayPanel.add(cotPanel); // Add three content panes to GUI mainPanel.add(inputPanel, BorderLayout.NORTH); mainPanel.add(displayPanel, BorderLayout.CENTER); mainPanel.add(buttonPanel, BorderLayout.SOUTH); //add mainPanel this.add(mainPanel); // size of window to content this.pack(); // display window setVisible(true); } public static void main(String[] args) { new TrigCalcGUI(); } private void buildInputPanel() { inputLabel = new JLabel("Enter a Value: "); inputTF = new JTextField(5); inputPanel.add(inputLabel); inputPanel.add(inputTF); } // Building Constructor for sinPanel cosPanel, and tanPanel private void buildSinCosTanPanels() { // Set layout and border for sinPanel sinPanel.setLayout(new GridLayout(2,2)); sinPanel.setBorder(BorderFactory.createTitledBorder("Sine")); // sinTF = new JTextField(5); sinTF.setEditable(false); sinPanel.add(sinTF); // Set layout and border for cosPanel cosPanel.setLayout(new GridLayout(2,2)); cosPanel.setBorder(BorderFactory.createTitledBorder("Cosine")); cosTF = new JTextField(5); cosTF.setEditable(false); cosPanel.add(cosTF); // Set layout and border for tanPanel tanPanel.setLayout(new GridLayout(2,2)); tanPanel.setBorder(BorderFactory.createTitledBorder("Tangent")); tanTF = new JTextField(5); tanTF.setEditable(false); tanPanel.add(tanTF); } // Building Constructor for cscPanel secPanel, and cotPanel private void buildCscSecCotPanels() { // Set layout and border for cscPanel cscPanel.setLayout(new GridLayout(2,2)); cscPanel.setBorder(BorderFactory.createTitledBorder("Cosecant")); // cscTF = new JTextField(5); cscTF.setEditable(false); cscPanel.add(cscTF); // Set layout and border for secPanel secPanel.setLayout(new GridLayout(2,2)); secPanel.setBorder(BorderFactory.createTitledBorder("Secant")); secTF = new JTextField(5); secTF.setEditable(false); secPanel.add(secTF); // Set layout and border for cotPanel cotPanel.setLayout(new GridLayout(2,2)); cotPanel.setBorder(BorderFactory.createTitledBorder("Cotangent")); cotTF = new JTextField(5); cotTF.setEditable(false); cotPanel.add(cotTF); } private void buildButtonPanel() { // Create buttons and add events calcButton = new JButton("Calculate"); calcButton.addActionListener(new CalcButtonListener()); clearButton = new JButton("Clear"); clearButton.addActionListener(new ClearButtonListener()); buttonPanel.add(calcButton); buttonPanel.add(clearButton); } @Override public void actionPerformed(ActionEvent e) { } private class CalcButtonListener implements ActionListener { public void actionPerformed(ActionEvent ae) { // Declare boolean variable boolean incorrect = true; // Set input variable to input text field text input = inputTF.getText(); ImageIcon newIcon; ImageIcon frowny = new ImageIcon(TrigCalcGUI.class.getResource("/Sad_Face.png")); Image gm = frowny.getImage(); Image newFrowny = gm.getScaledInstance(100, 100, java.awt.Image.SCALE_FAST); newIcon = new ImageIcon(newFrowny); // If boolean is true, throw exception if(incorrect) { try{Double.parseDouble(input); incorrect = false;} catch(NumberFormatException nfe) { String s = "Invalid Input " + "/n Input Must Be a Numerical value." + "/nPlease Press Ok and Try Again"; JOptionPane.showMessageDialog(null, s, "Invalid", JOptionPane.ERROR_MESSAGE, newIcon); inputTF.setText(""); inputTF.requestFocus(); } } // If boolean is not true, proceed with output if (incorrect != true) { /* Set each text field's output to the String double value * of inputTF */ sinTF.setText(input); cosTF.setText(input); tanTF.setText(input); cscTF.setText(input); secTF.setText(input); cotTF.setText(input); } } } /** * Private inner class that handles the event when * the user clicks the Exit button. */ private class ClearButtonListener implements ActionListener { public void actionPerformed(ActionEvent ae) { // Clear field sinTF.setText(""); cosTF.setText(""); tanTF.setText(""); cscTF.setText(""); secTF.setText(""); cotTF.setText(""); // Clear textfield and set cursor focus to field inputTF.setText(""); inputTF.requestFocus(); } } }

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  • Naming Exception when bounding to the home interface

    - by Nila
    Hi! I'm new to ejb. I'm trying to call the ejb from the servlet. But, I'm getting the NamingException. I'm directly running the servlet from the netbeans to check whether it is calling the ejb. But, it is not working. I'm getting the exception as home interface not bound. What is the solution for this?

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  • Dependency issue in inheritance chain

    - by Razer
    I have a class in coffeescript a class layout like the following. class @A foo: -> console.log('foo') class @B extends A fooB: -> @foo() class @C extends B fooC: -> @foo() I tried this in interpreters, it works. However it raises errors, when executing this in the browser (all of them are in separate coffee files, and are used in a global context. Therefore the @ before the class): Uncaught ReferenceError: B is not defined application.js It seems that B is defined after the definition of C. How can this happen?

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  • Inheritance and type parameters of Traversable

    - by Jesper
    I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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  • Tapestry5 : No service implements the interface org.springframework.context.ApplicationContext

    - by Joel
    I'm using the Tapestry5 tapx template library to send an html email, as per this example. When I run the example I get the following error: Caused by: java.lang.RuntimeException: No service implements the interface org.springframework.context.ApplicationContext. at org.apache.tapestry5.ioc.internal.RegistryImpl.getService(RegistryImpl.java:560) at org.apache.tapestry5.ioc.internal.ObjectLocatorImpl.getService(ObjectLocatorImpl.java:44) All the tapestry-* jars, including tapestry-spring-5.1.05.jar are in my classpath. Any clues as to what I'm missing?

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  • Rails STI validation inheritance

    - by KARASZI István
    Dear Rails users! I have STI models in my Rails application. The ancestor model has validations with the validates_... methods which are working fine. But I have custom validations as well, and I would like to add more different custom validations in the descendants. These custom validations would depend on the class. If I write class DescendantA < Ancestor protected def validate # ... end end It simply overwrites the original validations. Is there a convention to do this in Rails?

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  • Good books and resources on user interface testing

    - by josefx
    I am looking for good books and articles on user-interface testing. What they should contain (one or more of): different test methods/strategies examples, use cases naming pros and cons for different methods something important I might have forgotten :-) What they should not be: Only about general tests and not gui tests describing a test framework limited to a single language What are the best resources you know of? (preferably language agnostic)

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  • Inheritance in tables - structure problem

    - by Naor
    I have 3 types of users in my system. each type has different information I created the following tables: BaseUser(base_user_id, username, password, additional common data) base_user_id is PK and Identity UserType1(user_id, data related to type1 only) user_id is PK and FK to base_user_id UserType2(user_id, data related to type2 only) user_id is PK and FK to base_user_id UserType3(user_id, data related to type3 only) user_id is PK and FK to base_user_id Now I have relation from each type of user to warehouses table. Users from type1 and type2 should have only warehouse_id and users from type3 should have warehouse_id and customer_id. I thought about this structure: WarehouseOfUser(base_user_id,warehouse_id) base_user_id is FK to base_user_id in BaseUser WarehouseOfTyp3User(base_user_id,warehouse_id, customer_id) base_user_id is FK to base_user_id in BaseUser The problem is that such structure allows 2 things I want to prevent: 1. add to WarehouseOfTyp3User data of user from type2 or type1. 2. add to WarehouseOfUser data of user from type3. what is the best structure for such case?

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  • Transfer ADOBE licence after inheritance

    - by Vilius
    Hello there! After my aunts death, I have inherited an iMac with several Adobe software on it (= Photoshop, Illustrator, InDesign, etc.). Is ist possible to sell (or better to overwrite the licence) the software to other persons in the name of my aunt? Or whom does the software belong now? Thanks in advice! :)

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  • Why `is_base_of` works with private inheritance?

    - by Alexey Malistov
    Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class B {}; class D : private B {}; //Exspression is true. int test[is_base_of<B,D>::value && !is_base_of<D,B>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

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  • iPhone SDK development obj-C vs interface builder

    - by Amy
    I'm new to the iOS platform. I'm not clear on the purpose of the interface builder. It looks like I can avoid using it entirely and just write all the code in objective c. am I right? is there anything that IB can do but obj-c cannot? It reminds me of visual basic 6.

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  • CSS LESS class inheritance

    - by Haradzieniec
    Here is a css description of properties for my #myform1 .btn1 class: #myform1 .btn1 { ... } #myform1 .btn1:hover { ... } #myform1 .btn1.active { ... } #myform1 .btn1.disabled { ... } Is it possible to add absolutely the same properties for my #myform2 .btn2 class using LESS (any way is OK) without writing #myform1 .btn1 ,#myform2 .btn2 { ... } #myform1 .btn1:hover, #myform2 .btn2:hover { ... } #myform1 .btn1.active, #myform2 .btn2.active { ... } #myform1 .btn1.disabled, #myform2 .btn2.disabled { ... } Is it possible?

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  • what would be the output?

    - by Abhishek Jain
    Please explain me below situation What would be the output? interface A{} class B implements A{} class C extends B{} Class D extends C{} class E extends D{ public static void main(String args[]){ C c = new C(); B b = c; A a = (E)c; A a = (B)c; C c = (C)(B)c; } }

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  • Inheritance - initialization problem

    - by dumbquestion
    I have a c++ class derived from a base class in a framework. The derived class doesn't have any data members because I need it to be freely convertible into a base class and back - the framework is responsible for loading and saving the objects and I can't change it. My derived class just has functions for accessing the data. But there are a couple of places where I need to store some temporary local variables to speed up access to data in the base class. mydata* MyClass::getData() { if ( !m_mydata ) { // set to NULL in the constructor m_mydata = some_long_and complex_operation_to_get_the_data_in_the_base() } return m_mydata; } The problem is if I just access the object by casting the base class pointer returned from the framework to MyClass* the ctor for MyClass is never called and m_mydata is junk. Is there a way of only initializing the m_mydata pointer once?

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  • Adding an inheritance to an Qt designed object

    - by Jaguar
    Hello, I have a problem and I want to implement the MVC pattern to my QT application, that's why I need for example to inherite in my QTableWidget about another class like myClass { myMethod(); } but our QTableWidget is contained by our Mainwidows that is designed by the QT designer and generate an ui_MainWindow class ! Do you know how to do that ? Is that a method inside the Qt Designer to do that ? or another method ? Thank you for your answer !

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