I have following code. In this code CSClient is an interface. All methods of CSClient are implementaed in CSClientImpl class. Do I not need CS Client Impl imported in this code ?
How can I call getBranch() of CSClient, which is not implemented in CSClient as " this. getCsClient(). get Branch (new CSVPath(vpath), true);" ? This code works fine without any error in eclipse.
How can a method getBranch(), which is implemented in CSClientImpl class be used in this code without importing CSClientImpl ?
I'm working with Libgdx but I have a basic java question. I'm trying to access the overridden methods from and interface in another class via a call but I'm not sure how. This is what I've got so far :
Java Code:
public interface Controller { public void show (); } public class MainActivity extends AndroidApplication implements Controller { @Override public void showAd(boolean show) { System.out.println("TEST");
[Code] ....
Right now this code returns a null pointer at the call.
I'm wondering about the use of exceptions to handle errors that might occur during file I/O when the I/O is done by a method implementing an interface's method. The idea is for the interface to provide a uniform way for application code to read (and write, though I'm not addressing that in this post) a document from a file, given a File object that specifies the on-disk location of the document. The "document" can be an instance of any class the application programmer wants it to be, provided that it can be created from a file stored on disk. Here's the interface definition:
public interface DocumentRamrod<T> { public T openDocumentFile(File file) throws FileNotFoundException; }
A simple implementation, when T is a class that just holds a String, might look like this (Please overlook the fact that there is no call to the BufferedReader's close method, as it's not needed for this example.):
public class MyRamrod implements DocumentRamrod<OneLineOfText> { public OneLineOfText openDocumentFile(File file) throws FileNotFoundException { return new OneLineOfText(new BufferedReader(new FileReader(file)).readLine()); } }
But, that one line where the file is read (Line 5) might generate an IOException.To cope with it, I could add a try-catch to the implementation like this:
public class MyRamrod implements DocumentRamrod<OneLineOfText> { public OneLineOfText openDocumentFile(File file) throws FileNotFoundException { try { return new OneLineOfText(new BufferedReader(new FileReader(file)).readLine()); } catch (IOException ex) { Logger.getLogger(MyRamrod.class.getName()).log(Level.SEVERE, null, ex); } } }
Or, I could add that to the list of exceptions defined for the method in the interface, like this:
public interface DocumentRamrod<T> { public T openDocumentFile(File file) throws FileNotFoundException, IOException }
But that's where I'm getting nervous, as it makes me realize that, with an infinite number of possible implementations of openDocumentFile, I can't predict what all the exceptions thrown might be.should I have openDocumentFile simply throw Exception, and let the application programmer sort out which one(s) might actually be thrown, should I keep listing them as it become clear which ones are likely to be thrown, or should I not have openDocumentFile throw any exceptions and let the application programmer deal with it in the implementation of openDocumentFile (with try-catch blocks, etc.)? In Good Old C, I'd have passed back a null to indicate some general failure, with the various callers up the call-stack having to either deal with it or pass that back themselves (until some routine up the stack finally did deal with it), but that seems like an approach the whole exception mechanism was designed to avoid.
I'm thinking the right choice is to have openDocumentFile throw Exception, and let the application programmers decide which subclasses of Exception they really want to deal with. But I have learned to be humble about the things I think, where Java is concerned,
why interfaces inherit prototype of all the non final methods of the object class in itself? Object class is parent class of all the class and Interface is not the class.
I am writing a game in Java for Android (although my question isn't Android or Game Dev specific).
I have a SceneManager class and a Scene interface and then various other classes that implement the Scene interface (Code at the end of this post).
Basically, in my MainGame class (which also implements the Scene Interface for Touch Event capturing purposes) I hold the bulk of my game code. Methods in this class are then called from my Level classes. (most of these are needed in all levels so it makes sense to hold them here and call them from the levels to eliminate unnecessary code duplication)
So, I have Level1, Level2......... Level20 classes which all implement Scene.
Now, the problem comes because in only 2 of my Levels something can happen (that can't in the other 18) and I need to run a response method in these 2 levels (the method isn't exactly the same, the response to this event happening is different for both levels).
To run common methods from my classes, I use my Scene Manager like this:
This works great as all Level's have an updateLogic(); and render(); method.
So from my mainGame class, I am doing something like : (pseudo code)
public void checkIfSomethingHappened(){ if (something happens){ if (currentLevel==5){ Level5.response();}
[Code]....
The above would be called from my 2 level classes. So something like:
MainGame.checkIfSomethingHappened(); //Called in addition to the normal methods that make up that level
I don't really want to have this (second) 'if' statement here in the middle of my performance critical game loop.
What I'm after is something like this:
if (something happens){ SceneManager.getInstance().getCurrentScene().response(); }
However, this would require me to put stubs in the other 18 classes.
I'm thinking there must be a way to do this as the SceneManager already knows the current scene so it seems a waste checking it again via an if (or switch) statement. What is the best way to do this without having to put stubs into classes that don't require this method?
Variables defined in interface are public static and final so I was thinking that we should not be able to override the variables in a class thats implementing the interface. But when I am compiling the below class, it compiles fine and gives the correct values. but when I did disp.abhi = 35; it gives a compile error (cannot override final variable)
interface display{ int abhi = 10; void displayName();
I'm having trouble understanding the concept of the interface Connection, and PreparedStatement.
1) The simplest way to put it is how is it possible that this code is creating Connection and PreparedStatement objects? I was always under the impression that interfaces cannot be instantiated, but rather implemented. For example I don't see "public class Prepared implements Connection", or "public class Prepared implements PreparedStatement", But I see "Connection con = null;" and "PreparedStatement pst = null;". So it seems as if the interfaces are being used to create objects called con and pst.
2) If in fact these interfaces are being implemented, where are the method blocks in this code that should have been added in order to fulfill the contract?
I am not getting the concept of interfaces.I know they are used to implement multiple inheritances.I also know the example that we create an interface car with certain methods so that a class like bmw which implements the car interface has to implement these methods.But I don't know how interfaces come handy?I don't know the meaning of a class calls a method using an interface?(i know that an interface can not be instantiated).
public class Someone { String name; int age; ArrayList <Someone> listarr = new ArrayList <Someone>(); public Someone(String name1, int age1) { name = name1; age = age1;
[code]...
1. In the compare method, what happens when it returns one of the 0, -1, or 1? How does returning such values contribute to the sorting process? How does it take in information (like I know it does through the parameters, but how exactly)?
The program runs well , it adds the applet but it dosn't update the interface unless I press "_"(Minimize) . To be more clear , the object paints a spring wich goes through 4 stages , it is added to the JFrame but it dosn't uptade until I minimize the frame , that is when it goes to the next stage .
The main class which calls the spring to be added to the frame :
public class principal implements ActionListener ,Runnable{ JTextField field; JFrame frame; private class Action implements ActionListener { public void actionPerformed(ActionEvent event) { frame.repaint();
I know whats the interfaces and abstract class and also know that difference between interface and abstract class,but here my doubt is eventhough abstract class more advantage than the interface,then why should we use interfaces and when?
I am supposed to implement a custom Map interface and I'm having some trouble with this method:
// 1. From the interface /** * Gives an iterator iterating over the key set from the smallest key that is not less than the key provided. * @param key the key * @return the iterator * @throws NullPointerException if key == null */
public Iterator<Key> tailIterator(Key key);
[Code] .....
My implementation is wrong according to a JUnit test. Also, to get a full score this method should have a worst case running time of O(log N), which obviously isn't the case now. (My Map implementation is currently based on binary search in an ordered array, keeping a prallel array for the values).
Can i type cast a interface to ArrayList? suppose there is a interface Named Node.
public interface Node { public static final short ELEMENT_NODE=1; ...... ..... }
i want to typecast this interface to ArrayList and fetch all the value.You can use hashtable object class etc.my main moto is to take a value in ArrayList and traverse it.
class Super { static String ID = "QBANK"; } class Sub extends Super{ static { System.out.print("In Sub"); } } public class Test{ public static void main(String[] args){ System.out.println(Sub.ID); } }
According to me output should be "QBANK" In Sub...BECAUSE sub default constructor will call super() constructor.. below is the definition in jls which i am unable to understand ....
A class or interface type T will be initialized at its first active use, which occurs if:
T is a class and a method actually declared in T (rather than inherited from a superclass) is invoked.
T is a class and a constructor for class T is invoked, or T1 is an array with element type T, and an array of type T1 is created.
A non-constant field declared in T (rather than inherited from a superclass or superinterface) is used or assigned. A constant field is one that is (explicitly or implicitly) both final and static, and that is initialized with the value of a compile-time constant expression . Java specifies that a reference to a constant field must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field are never active uses.
All other uses of a type are passive. A reference to a field is an active use of only the class or interface that actually declares it, even though it might be referred to through the name of a subclass, a subinterface, or a class that implements an interface.
I have the following code that will make linked list and order its elements using self referential objects. but i have the following error: incompatible types
required: ListNode<T#2> found: ListNode<T#1> where T#1,T#2 are type-variables: T#1 extends Comparable declared in method <T#1>insertInOrder(T#1) T#2 extends Comparable declared in class OrderedList
import java.util.*; public class ListNode<T> { ListNode<T> nextNode; T data; public ListNode(T item) { this(item, null);
I need to implement the attached interface ("Locality"). In the attached UML diagram it has a 1 on 1 relationship with the class "Team". I don't know if this can be somehow implemented in Java. Can I create the attribute "team" in the Locality interface and let it be used by the "Town" and "City" classes? Could it be better to implement it as an abstract class instead?
I am making an app that would allow user to buy seat either by Price or Choice (Row and Column). I have Original code where it runs within JAVA IDE I am making same thing but rather in GUI now. I need putting my Buttons, textfield, and area in organize fashion.
I have not explain how these buttons will behave or act but right now putting them in order is priority then I will add action listeners to do the task we intend to do. A Wire Frame of the code looks like this :
I have a task to create a Java OOP program, I have a class Team which requires a comparable and iterable interface, the only way I know how to do this is either:
public class Team implements Iterable <Mechanic> or public class Team implements Comparable <Mechanic>
I'm trying to create a GUI interface in Netbeans that calculates a phone bill.
I created a GUI interface that input: - Account Name. - Account Number. - Number of Minutes the phone was used. (with a textarea so the user input the minutes) - 2 JRadioButtoms so the user can chose the regular or premium service. - Amount Due (+10% taxes) (also with a textarea) - Clear/Enter/Result/Done Buttoms
And I need to output: - Account Name. - Account Number. - Number of Minutes. - Taxes - Total Amount Due.
I have a couple of math formulas I have to add them to output the above however I'm new to java so I don't know which code to use.
