I've never been so good at design because there are so many different possibilities and they all have pros and cons and I'm never sure which to go with. Anyway, here's ... |
I saw in the apache camel source code that
public class DefaultCamelContext extends ServiceSupport implements CamelContext, Service
My question is why this definition since
public interface CamelContext extends Service
and also
public abstract ... |
Basically I want to do this:
public interface A {
void a();
}
public interface B {
void b();
}
public class SomeClass {
public SomeClass(<A&B> e) ...
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If we have:
public interface Foo{}
public class Bar implements Foo{...}
Is there a difference between:
public class BarBar extends Bar implements Foo{..}
and
public class BarBar extends Bar{..}
I see a lot of code like this and ... |
I have two questions regarding interfaces in Java.
1) If a class happens to implement all the interface methods of interface I, without declaring itself as implementing them, can it still ... |
I just want to inject some design patterns into my Java code, but I don't know which style to use -- is inheritance or interface preferred? And why?
Thanks!
Kind regards!
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I have a little problem.
Class ll:
interface jj{
public class ll implements gg{
public static String j ="C:\\";
//some ...
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I am reading "The Java Tutorial" (for the 2nd time). I just got through the section on Interfaces (again), but still do not understand how Java Interfaces simulate multiple inheritance. Is ... |
I can make abstract class equivalent to interface by putting all abstract methods within abstract class. Why did Java's designers choose to provide support for interfaces and single inheritance instead of ... |
I have two interfaces, HasClickHandlers and DoesFancyFeedback. Then I have some UI objects that implement both interfaces - for example, a Button that implements both has click handlers and also ... |
I am trying to learn inheritance and interface in Java. I have three different classes: Customer, SilverCustomer and GoldCustomer. Both SilverCustomer and GoldCustomer extend Customer.
In the application, the customer get ... |
I have a basic question with Java interfaces.
Say if I have a interface IA
and interface IB extends IA
now,
class CK implements IB,
class CL implements IB,
class CM implements IB,
... etc
void foo(IA iFace) ...
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If the objects being decorated implement different combinations of other interfaces, how do you implement a decorator without losing the extra interface methods? For example, say we have the following ... |
I have one main interface and an abstract class implementing all "derivable" methods (that can be written using only abstract methods) of it:
public interface Main {
public void ...
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I'd like to implement the Decorator design pattern using inheritance (Decorator extends Component) because i need access to the protected fields/methods of the Component class.
The problem is that the ... |
I.e. why is the following "cyclic dependency" not possible?
public class Something implements Behavior {
public interface Behavior {
// ...
...
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Suppose we have a method inside an interface and a class implements the interface.
As per the rule, the methods inside the interface should be implemented in the class that implements the ... |
i'm very confused...
I have a class which directly implements an interface:
public class Device implements AutocompleteResult
{...}
Here is proof that I'm looking at the right variables:
Object match = ...;
log.debug(match.getClass()); // Outputs 'Device'
log.debug(match.getClass().getInterfaces()[0]); // ...
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I'm writing some code to create a Swing 'wizard' type component. I have an interface called WizardPage, which represents the features of an individual page, such as getNextPage(), getPrevPage(), etc. I have a WizardController class that manages a list of WizardPages and selects the next one to show. My problem is that each of the WizardPages needs to be a subclass ... |
Hi Frnds, class A is the parent class which implements Serializable interface. Class B is the child class which extends Class A. Now my question is I don't want class B as Serializable, So can make class B as non Serializable class .. Is it possible? I think one way is we can mark all variables as transient. Is there any ... |
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Hi Alok, Prashanth is correct. In order to support the answer I can point to the AWT classes. If you have noticed that all AWT classes are subclasses of Component. Component implements Serializable Button doesn't implicitly implement any interface Yet from experience and/or books we know that all AWT components are serializable! Therefore you have real proof that subclasses inherit all ... |
I have a question about interface. For example I have Interface A with two functions: getName() and getAddress(). Than interface B with function getSalary(). Interface B is instance of interface A. Than class Professor that is subclass or instance of interface B. I did the UML diagram on TogetherJ 4.02. My question is does is legal for class C implement the ... |
One big problem with mulitple inheritance is what to do when both base classes implement a particular method differently. If the subclass doesn't override this method, what code should be called? This situation often arises when both base classes themselves extend from a common ancestor. In this case, a class hierarchy diagram would show a diamond pattern of classes. This conflict ... |
I often see the statement that the problem with multiple inheritence (in other languages) is that you can end up with two methods with same signature in the same class. Then it is stated that interfaces solve this problem. But why couldn't the class trying to implement the interface encounter the same problem? Is it just because that the compiler will ... |
It's simple, actually. First, when you inherit from a superclass, you automatically inherit all of its methods (except in the case of an abstract class) and have all of the default implementation. For example, when extend Applet, you get methods like add() and repaint() which are immediately usable by you with no coding. When you impliment an interface, you are saying ... |
Hi, welcome to the ranch! In this forum we often encourage you to answer your own questions a little bit at a time. For this one, why not just try it? Make an interface I with one method, a class A that implements I and a class B that extends A. Then see if ( B instanceOf I ). Also try ... |
An interface is basically a list of methods (with their arguments - the signiature). You are stating in the interface what an object must do in order to be considered that. in other words, if i have public interface Comedian{ public void tellJoke(string wifesName); public void waitForApplause(int delaySeconds); public int getSalary(); } then anything that wants to be a Comedian has ... |
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - ... |
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Bon jour, coding associates! Not a minute ago was a friend of mine here, and I was trying to explain to him some basics about Java, because he desires to do well in a test he has to take as part of the process of applying for a Job, anyways ....................... He made think hard about something I hadn't thought before, ... |
public interface Arithmetic { /** * Increases the value stored by adding this number to it, eg 1 + 2 = 3 *@param i The number to add */ void add(int i); void subtract(int i); void multiply(int i); void divide(int i); } public interface WackyArithmetic { /** * Adds the number passed to make a new number by appending the digits ... |
Could someone explain why the following code shouldn't compile (it doesn't compile, but I don't see a good reason why it shouldn't)? interface Test { interface TestA extends Test {TestA test();} interface TestB extends Test {TestB test();} interface TestAB extends TestA, TestB {TestAB test();} } The compile error is "types TestB and TestA are incompatible. Both define test() but with unrelated ... |
Which is not true about interfaces and Abstract classes? (at least mark two answers) (a) Abstract class support to the inheritance relationship but not realization relationship. (b) Interface supports to the realization relationship but not inheritance relationship. (c) Both Abstract class and Interface are supporting inheritance relationship. (d) All above statements are correct. |
an interface is a contract - nothing else. When you have Interface A {} you are saying "here are the rules for what it means to implement the 'A' interface. When you say "implements A", you are saying "This class/abstract class will implement everything required by the A interface" so, interface B extends A is just saying "here are the rules ... |
What is the real use of interface in java apart from Multiple inheritance I don't really agree with the title of this topic. I don't think that a "use" of interfaces is to do "multiple inheritance". It is true that with interfaces, you can accomplish one big advantage of multiple inheritance, in that, you can have an class that IS-A many ... |
I recently attended one interview, there was one question that was asked. Interviewer: Forget that java can extend only one class.Let suppose it supports multiple inheritance through class extension. Now why should i use interface.We can create a base class and give a default implementation of our function. And the child classes can choose to override our method. Still why would ... |
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class MyException extends Exception { } class MyException2 extends Exception { } interface Hello1 { public String sayHello() throws MyException; public void greet(); } interface Hello2 { public String sayHello() throws MyException2; public Object greet(); } public class InheritanceTest implements Hello1, Hello2 { // what goes here for method signature, return type and Exception thrown for: // 1) for method name ... |
Hi, I am looking in to the source code for JDK (6.0), and have the following question over the List interface. Please clarify on what is wrong in my understanding. List interface inherits Collection interface. Hence all the public/package-private methods declared in Collection interface would be inherited in the List interface and would be required to be implemented in the concrete ... |
I'm confused. In an exam I took, I think it was the ExamLab diagnostic, there was a question that said "An Interface IS-A Object", and my answer was false because obviously, an interface cannot inherit from a class. My answer was wrong, and the explanation said an Interface really IS-A Object, because any interface reference can be assigned to an Object. ... |
Hi everyone ! My name is Akshay Sahu and I have a serious issue on my mind. I say "Java supports multiple inheritance" and I came to this conclusion based on the following points: 1. Every class in java inherits itself and the java.lang.Object class. (Reference Kathy Sierra and Bert Bates OCJP 6). This statement alone is enough to prove it. ... |
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I'm trying to get my head around interfaces and how they can be used for inheritance. If I had a class for example called Lion, which I wanted to inherit from a class, Cat, containing int numTeeth, and from a class killer, containing int numKills. Do I need a seperate class for killer and cat, as well as two interfaces, or ... |
// instance variables // constructor // methods } Or this public class Club extends { } Can't figure out how to get the Goalkeeper information as well for the Club class. I'm going to use an ArrayList to add the information, then sort it using the Collections framework. Thanks for any help on this. |
dunc, I know diddly about JavaCC, but from what I read at https://javacc.dev.java.net/ it would appear that it generates some parser code, which in turn generates a parse tree, which you can may then manipulate. You are attempting to smartify? the generated classes by introducing unforseen and convoluted OO-relationships... which IMHO is likely to be problematic... ala you're (understandably) stuck to ... |
I didn't think that I needed to override it either, and preferably I wouldn't. When in the Employee class, if I change Employee to object in the method header, I don't get a clean compile. I'm sorry for being so frusterating, but I am new to this and I need some more specific clarification |
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In other news: I wish people would stop using type "names" like A B, interface1, and method names like myM, when trying to explain their question (or at all, come to think of it). It makes it all the more awkward to visualise what they're on about. But no, I'm not entirely sure what this dude's asking, either. Probably something wholly ... |
Hi, I know that interfaces are used to create an empty class which cannot be instantiated as it is not implemented. The user will have to eventually implement all or some of the methods defined. Now my problem lies here...cant' the user simply use inheritance and then override the method/s which he/she wants to behave differently from the parent class? I ... |
I've read that "The Java programming language does not permit multiple inheritance , but interfaces provide an alternative." But I also read contradictory information-There are no method bodies in an interface. Java interfaces only contain empty methods? Apparently, if I want to share a method among classes, I have to re-write the methods in each class that implements the interface. That ... |
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Hi, I'm new to java and have only a little experience with programming languages. I can't seem to figure out what the differences and uses are for Inherited classes and interfaces. I understand Interfaces set a list of methods and variables that must exist in implemented classes and that Super classes can define a default method. What i want to understand ... |
suvojit168 wrote: I tentatively made a program and found that multiple inheritance problem of C++ persists even with interfaces. Although this is definetely a special case but I want to know what is this problem known as( i know that this is perhaps known as diamond problem in C++). And is there a way out of this thing. This is not ... |
1) How does interfaces overcome the problem of single inheritance? Can anyone give an example of how it works? 2) In a Java book, I read: "Interfaces are implemented and used throughout the Java class library when behavior is expected to be implemented by a number of disparate classes." Why does different classes require to implement a Java class library? Can ... |
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calmanFischer wrote: @pm_kirkham: that is correct, but that's just what I wanted to avoid - giving up compile-time safety and instead raising a stupid exception in the middle of program flow You missed my point - I said nothing about compile time safety. If you have two interfaces, Porcine { goOink() } and Flighted { fly () ; } , then ... |
Multiple inheritance has some inherent difficulties like the diamond-shaped inheritance problem (when inheriting the same members through several paths) etc. It was a design decision to avoid these in Java and to have only the simplest, least problematic part covered by the multiple inheritance among interfaces. I am sure this has been discussed to the tilt every now and then. |
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class bb implements inf.... Now, inf i = new aa(); inf i = new bb(); Answer 2: We can extends as many interface as we want in the ... |
Just wondering if this is possible... Can I make a type reference to classes that both descend from a specific class AND implement another, specific interface? A case where this could be useful would be for making an ArrayList of JPanels that implement MyHandyInterface... This would allow me to take extend descendants of JPanel, add MyHandyInterface to them, and use them. ... |
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