I have a problem where I want to give each subclass of a certain class an index number (I don't care what index numbers are given, as long as there is a one-to-one relationship between subclasses and index numbers and the index numbers don't skip). This number will be used to sort the subclasses as an intermediate step to what I want to achieve. I know I could do this:
interface Superclass {
int index();
}
class Subclass implements Superclass {
int index() {
return 0; //or 1, or 2, ...
}
}
But this quickly gets tedious when I'm looking at lots of subclasses. Plus, there's the off chance that I could mess up and assign an index twice to two different subclasses by accident. Is there a better way to do this? I read about Annotations.
how to get access from variables in a super class or a subclass. Here is what I got:
1) I have a super class that is in Jar file, I created a link in Eclipse, I know that the link is created correctly, I am going to concentrate just in one variable, so I don’t have to put all the code here firstName; in the super class(the one that is define in the path)
public class CommissionEmployee { // Field descriptor #6 Ljava/lang/String; private java.lang.String firstName;
I need programming Quad-Tree for indexing line segments. what is difference between standard Quad-Tree (for indexing points) and PMR Quad-Tree (for indexing line segments) ?
As of now am using icefaces 1.8.2 provided tags for downloading data into excel sheet where i can download all the data from a data table. But now the requirement is like need to download the data into excel sheet based on values passed from UI as parameters to the action class method.
I am working with an Adjacency Matrix to try to find the MST of a graph. Along the way I have hit a snag that I am not sure how to get around. When running the program I will parse through each row of the matrix and find the smallest weight. However when trying to reset the row at the end of the lowest sort I cannot move to the next row.
The graph looks like this:
My Matrix was created from the graph and I have determined by starting at Vertex W my path should looks like this: W->R->D->H->G->S->C->B->A
I am trying to prepare for the next installment Java course. I found a syllabus online from last year. All I'm trying to say is that I am not in this course but will be shortly. I tried the first project but I am having subclass issues. I want to access the getStock method in the Executive subclass from the client. I keep getting a cannot find symbol: method getStock from class Employee. I don't know why won't access Executive.
Main:
import java.util.*; public class EmployeeClient extends Employee { public static void main(String[] args) { Scanner input = new Scanner(System.in); //variables String name = " "; int totalSalary = 0; int stock = 0;
I'm having a difficult time running this piece of my program. I can't run the method findSmallest() in subclass NEW because I receive an error that says I have to declare the variable "smallest" as final, but then I won't be able to continue my code because "smallest" when I happen to use "smallest" again, it will always be set to 0.
package FindYourCourseGrades; import java.util.Scanner; public class FindYourGrades { public static void main (String[] args){ int number = 0; int counter = 0; int sum = 0; double average = 0; double smallest = 0;
There are a few things lacking in the TableView's keyboard navigation handlers. In tracing the code, the behavior is handled via TableViewBehavior and its super classes. If I want to augment that behavior, how do I do it?
Ideally, I would like to subclass TableViewBehavior, but I don't see how I can do it. This gets created in the TableViewSkin ctor:
public TableViewSkin(final TableView<T> tableView) { super(tableView, new TableViewBehavior<T>(tableView)); ... }
but as you can see there is no factory method to create the behavior class. If there was, I could subclass TableViewSkin and override the factory method.
I am trying to display the getCommands() method from my subclasses but I do not know how to cast them both. At the moment I can only display one animals getCommands() method.
public class Test { public static void main(String[] args) { Pet [] pet = new Pet[5]; pet[0] = new Dog("Scamp", 1, "run"); pet[1] = new Dog("Molly", 2, "fetch"); pet[2] = new Dog("Rover", 3, "dig");
So far I thought that setting superclass member variables as protected would allow the subclasses to access them using this. and that this was a good approach. However now after further reading am finding that actually these variables are better set as private and then accessed by the subclasses using public method (getters and setters) or constructor.
So my question is do you recommend setting them as private instead of protected and what would be the best way to access these variables from the subclasses ?
I have a class called Sprite which extends its several subclasses. Therefore, there are a lot of different Sprite classes, the thing is however, most of those subclasses have unique types of variables which I want to only be included in those particular subclasses, not anywhere else. For instance, I might have a variable measuring distance in one subclass, and in another subclass there might be a height variable inherent. I don't want the first subclass to have both variables, neither the second or the main class. Because before I initialize my subclasses, I need to create the constructors of those subclasses in the main Sprite class first because it doesn't have the unique variables which those classes consist of. How do I prevent that? Now I have to create the unique constructors and variables for every subclass, when I only want them in their associated classes.
The super keyword when used explicitly in a subclass constructor must be the first statement but what about if i have a this(parameters) statements ? As the this one must also be the first statement... Does this means that i can have only one or the other ? What about when the super constructor is not explicit (aka implicit ) , can i use the this( parameters) in the same constructor ?
I'm working on a program design for a multimedia application its really just a learning process for myself about exploring application development, however there is a slight hiccup in the class inheritance hierarchy I think, and I'm not really sure why.
The problem being I cant set the constructor of subclass AnimatIntervalKeyFrame to be structured the same way as of the constructor of super class AnimatKeyFrame
This is the error given of the constructor of the subclass
public AnimatIntervalKeyFrame(int id, String category, Text text, ImageView image, int x, int y, int width, int height){ required: int,String,Text,ImageView,int,int,int,int found: no arguments
[Code] ....
package multimediasoftware.appComponent; import javafx.scene.image.ImageView; import javafx.scene.text.Text; // notes // class is declared abstract public abstract class AppComponent { // variables
I am creating a set of 3 subclasses, 1 superclass, and an application. In my instructions it says to make set methods in my super and subclass by using dialog boxes. In the application you have 3 different arrays where you create objects and are supposed to call the methods from the subclasses to be used in the application. I don't know how to make the dialog boxes from my subclasses to show up in my application.
I am trying to put a reference to a given subclass object into a linked list, and then come back later, and invoke a method of the subclass object that is in a given spot in the linked list. This produces an error because Object does not have that method. Is it necessary to cast the object to the correct subclass every time I want to use one of its methods, or is there a way to convince the JVM to treat it as always of type MySubclass?
I have studied about the hierarchy of exception classes in which Throwable class comes at the top and two of its direct subclasses are Error and Exception..I just want to ask if in some code snippet we throw an instance of Error or its subclass within the try catch block then will that be also called "exception handling" ? I am asking this because Error class is not a child class of Exception therefore cant be said an Exception, therefore handling the same should not be called exception handling
How do you declare methods for a class within the class whilst objects of the class are declared else where?
Say for instance, I have a main class Wall, and another class called Clock, and because they are both GUI based, I want to put a Clock on the Wall, so I have declared an instance object of Clock in the Wall class (Wall extends JFrame, and Clock extends JPanel).
I now want to have methods such as setClock, resetClock in the Clock class, but im having trouble in being able to refer to the Clock object thats been declared in the Wall class.
Is this possible? Or am I trying to do something thats not possible? Or maybe I've missed something really obvious?
Regarding the lifecycle of servlet , in headfirst servlet i can find :
You normally will NOT override the service() method, so the one from HttpServlet will run. The service() method figures out which HTTP method (GET, POST, etc.) is in the request, and invokes the matching doGet() or doPost() method. The doGet() and doPost() inside HttpServlet don’t do anything, so you have to override one or both. This thread dies (or is put back in a Container-managed pool) when service() completes.
How can I call the doGet method of the subclass from the superclass. i am not getting this .
I have a quick polymorphism question. I have a parent class and a sub class that extends the parent class. I then declare an array of parent class but instantiate an index to the sub class using polymorphism. Do I have to have all the same methods in the child class that I do in the parent class? Here is an example of what I mean.
public class ParentClass { public ParentClass(....){ } public String doSomething(){ } } public class ChildClass extends ParentClass { public ChildClass(....)
[Code] ....
Is polymorphism similar to interfaces where the child class needs all the same methods?
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{ public void hello(){ System.out.println("hello"); } } class B extends A{ public void hello(){ //super.hello(); System.out.println("hello1");
i want to write a class in such a way that i should get the current execution time of another class which is running. I searched in net but it shows only how to calculate the time duration of the current class which is running. But as per my way, i need the execution time of one class from another class. How to do this ?
I am working on a program that simulates a bug moving along a horizontal line, My code works correctly when I test it in it's own class but when I tried testing my constructor and methods in a test class I received an error saying, "package stinkBug does not exist" on lines with my methods. However, stinkbug is not a package.
Java Code:
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