I am working on a project and it asks me to "Provide appropriate names and data types for each of the instance variables. Maintain two GVdie objects" under class fields. I am unsure as to what is being asked when asking for two objects as instance variables and how I would write that...
Let's pretend I'm working on an RPG. Like in all RPGs, there are items found all throughout the imaginary world. Each player and NPC can obtain an item. My question will concern those items.
In other words, I'd like to use instances of a class in multiple places of the code. Each instance will have its own, individual values of instance variables, with one obvious exception: itemQuantity should have a different value in playerInventory, npcInventory, etc. Also, I'd like a list of all items that can be found in the game. This list doesn't need itemQuantity at all.
class Items { String itemName; float itemWeight; int itemQuantity;
[Code] ....
The question is: should I really make itemQuantity an instance variable of the Item class? It seems as though for each copy of the Item class I should create a separate copy with different value of itemQuantity, but that's not very efficient. Where is the error in my logic?
What's important is that there may be plenty items in a game and a player may be given power to create new items during the course of the game.
I'm just wondering why variables in interface can't be instance scope?
interface Test{ int a; }
And then
Test test = new TestImpl(); test.a=13;
Yes, it violates OO, but I don't see why this is not possible? Since interface is not an implementation, therefore it can;t have any instance scope variable. I can't find the correlation of interface being abstract and being able to hold instance scope variable. There's gotta be another reason. I'm just curious about any programmatic limitation, not deliberate design constraint. the example of programmatic limitation is like when Java forbids multiple inheritance since when different parents have the exact same method, then the child will have trouble determining which method to run at runtime.
Alright, I have a JavaFX gui that is creating a new instance of data calculation to graph in a chart; however, the data is not updating each time the Platform.runLater() feature executes. Each time an event occurs, a new instance with the same variable name occurs. I use to get methods to retrieve the data I want, so shouldn't the values update each time the new instance is created? This is a very condensed version of what happens with the event, but this is what is not working correctly.
Event: solarPlot = new SolarTracker(); solarPlot.getElevation(); solarPlot.getAzimuth(); Class constructor : public SolarTracker() {
As web server has multiple threads to serve client requests in Thread Pool & to ensure Thread Safety we should not use any variables or Objects at Instance/Class level.But in case of Session Variable which one is the Best Practice as the Session object is used by all the requests to have the same Session ID.
My Code :
public class MyServlet extends HttpServlet { private static Logger log = Logger.getLogger(ClientRegistrationServlet.class); private HttpSession session; /* This is used at Instance Level*/ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
I am trying to simplify my constructor by using "this" reference variable. I am aware how to use this reference when making constructors that involve fields of primitive data types; however, not so sure fields involving objects. I have made the following constructors and haver placed a question mark in the last parameter. How I can use this reference that involves objects.
public class RetailItem { //Create the fiels for item. //You need item name and item number. then you would need //cost private String description; private int Item_Number; private CostData cost;
Say I have two classes, Author and Book, and I have 2 author objects and 10 book objects. I would like to know how to do two things:
1) Make some sort of connection that makes clear that author X wrote books A, B and F. 2) Call a method from a book object that is connected to an author.
Seeing as I don't know which books will be connected to an author, is there some way to call a method of an object bases on a variable object name? Something like call the getFirstPage() method for every book that is linked to author X?
The term "Local variable" is related to scope. That is a local variable is one which is defined in a certain block of code, and its scope is confined inside that block of code.And a "Member variable" is simple an instance variable.
I read in a discussion forum that when local variables are declared (example code below), their name reservation takes place in memory but they are not automatically initialized to anything. On the other hand, when member variables are declared, they are automatically initialized to null by default.
Java Code: public void myFunction () { int [] myInt; // A local, member variable (because "static" keyword is not there) declared } mh_sh_highlight_all('java');
So it seems that they are comparing local variables and member variables. While I think a member variable can also be be local in a block of code, isn't it?
I am currently working on a project where I need to return data from a database over RMI to a client who requests it. Some of the fields in the Data Object can not be seen by the client so I need to create another object to send over the network instead. The method I use is this...
public static SerializableObject createSerializableObjectFromDataObject(DataObject dataObject){ SerializableObject serializableObject = new SerializableObject(); serializableObject.setField(dataObject.getField()); serializableObject.setAnotherField(dataObject.getAnotherField()); return serializableObject; }
Is there a better way of doing this? I am creating many subclasses DataObject which all require this static method to be implemented and I can't push it into the superclass because each one needs custom behaviour.
when we create another variable and set it equal to the first : Car c2 = c1;
we're pointing c2 at the same car object that c1 points to (as opposed to pointing c2 at c1, which in turn points at the car). So if we have code like,
Car c1 = new Car(); Car[] cA = {c1, c1, c1, c1};
are we doing the same? Are we creating four *new* reference variables, each of which points at the same car (again as opposed to pointing them at c1 itself)? I think so, but want to make sure I'm understanding this correctly.
I have a JFrame jf and JPanel jp on it. jp has five TextFields named cel1, cel2.. cel5. I wish to construct a String Cel + for loop index and run a for loop to reset the values of all the text fields using a single statement such as cel1.SetText("abc"). Similar things can be done in foxfro. How does one do it in java?
in a set of instructions they keep referring to instance versions of things I've heard of before ie "private instance array of String references" (wtf is a string reference?) or "instance string variable" so what does all this mean?
.I was reading head first java book and saw a barbell question on page no. 280,question-"what if you want to write a class in such a way that only one instance of it can be created,and anyone who wants to use an instance of the class will always use that one,single instance?"
I have a method that accepts JSONArray as parameter and returns the values of it as ArrayList Object. My question which of these ways is appropriate in populating the ArrayList object this method populates the arraylist upon creation of object (I don't know what the right term to use, but as netbeans IDE suggest, JSONArray object should be final since it was used in inner class.).
private List<String> getStringList(final JSONArray jsonArr) { return new ArrayList<String>() { { try { for (int i = 0; i < jsonArr.length(); i++) { add(jsonArr.getString(i)); } } catch (JSONException ex) { ex.printStackTrace(); } } }; }
this second method is the usual way of populating collection
private List<String> getStringList(JSONArray jsonArr) { List<String> strList = new ArrayList<String>(); try { for (int i = 0; i < jsonArr.length(); i++) { strList.add(jsonArr.getString(i)); } } catch (JSONException ex) { ex.printStackTrace(); } }
What are the advantages and disadvantages between the two? like which is faster? or which consumed larger memory?
I have been working on a program that is meant to use a class' instructions in a program to add a value to a variable, save it, and present it. This is my class
public class Car { //FIELDS private int yearModel; private String make; private int speed; //METHODS public Car(int carYearModel, String carMake)
[Code] .....
Whenever I call the accelerate method, a value of 5 is to be added to the speed variable. But whenever I call accelerate, it doesn't increase! I just don't understand why not. I've tried different renditions of adding 5 to speed and it doesn't quite work. I don't get any errors when I compile, just runtime, when it doesn't add 5 to speed.
So far in my assignment I have successfully opened a text file. However I am required to do more:
1) As each line of text (containing names and ages) is read a new Runner object is created with its instance variables set thus: ! (Runner class already created )!
- name : set directly set from the value in the file - agaGroup : can be worked out from the given ages: < 18 should be 'junior' > 55 should be 'senior' the rest should be 'standard'
2) the instance of Runner should be added to the list referenced by the instance variable runners.
I have used if statements to create the junior list, however I do not see the full list of names and ages in the variable runners as I am requested to.
I am sure there is a for loop involved somewhere but I do not know how to:
a) use the for loop in my method add a new Runner object with the variable mentioned.
I include the code I have done so far as a file - p.s I use Bluej.
public class MarathonAdmin { // instance variables private String runners; private String age;
I have 1 textfield and 1 button on a JFrame and having 10 such frames stored in ArrayList al and getting the JFrame instance from traversing the ArrayList at execution time ,So is there a way to access textfield using JFrame instance or i have to name the textfield diffrently 10 times for each frame .