What is single inheritance, multiple inheritance, and describe Java's notio

What is single inheritance, multiple inheritance, and describe Java's notion of an interface?
Can you give me example or reference link? thx

Single inheritance is getting features like data and methods (functions) from a so called parent class. multiple inheritance is the same but you derive features from multiple parent classes (not supported by java). Interfaces are a way around this because you can inherit multiple interfaces. Inheriting from interfaces is like a promise to implement certain methods that these interfaces define but doesn't implement themselves.
check around java.sun.com in the tutorials section, you can probably find a text that describes object oriented program and how it is implemented in java.

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Enumerate multiple inheritance scenarios and their java equivalents?

hi,
ppl have often said things like
"java doesn't support multiple inheritance but this is ok, since there are other mechanisms for doing the same thing (by which we nearly always mean interfaces)"
how solid a statement is this? are there any formal methods available eg smt like "over all possible inheritance trees over all possible classes, only a handful of cases are distinct when viewed from the converting-to-single-inheritance scheme"?
the two things mentioned as harder to workaround are mixins and the diamond problem - are there more?
also what other mechanism apart from interfaces (if any) are useful?
any help appreciated,
asjf

What I say is that it doesn't matter since there is
almost never any need for MI. Most of the time it is
used it is used because the developer/designer did not
understand what they were doing and it should not have
been used in the first place.
That leaves one with very few cases where it should
ever be used. And that coupled with the fact that a
developer should never use it unless they are very
experienced (so that they actually know that it should
be used,) means that practicing programmers should
leave discussion of such usages to scholarly
journals.thanks :) I guess my problem is that often with computer stuff you don't have to rely on other peoples experience about things - you can go and test it yourself
I've done very little C++ development, and so have never come across real-world multiple inheritance. I bumped into the first situation with some java code where it might've been a neat solution recently but this could easily fit into the "designer did not understand what they were doing" category from above..
will have a casual look around the scholarly journals if I can find any that look promising :)
asjf

Alternative for multiple inheritance (AbstractQueue and AbstractList)

Hello all,
What is the best alternative for multiple inheritance? I want to make a list, which supports queue operations. Both AbstractQueue en AbstractList are useful, so I would like to use them both, instead of implementing the methods myself or copying the code.
thanks

Do you mean you want a class just like LinkedList?
Why don't you look at the code for LinkedList. Perhaps you could even use it.
Most Queue methods have trivial implmentations using a List.
From the source for LinkedList
public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Queue<E>, Cloneable, java.io.Serializable

Multiple inheritance and super

How to I get to a super function when using multiple inheritance? For example, the code below doesn't compile if Human extends Job, but works fine if Human only extends Animal.
package test;
import java.lang.System;
public class Job {
public class Animal {
public attribute isStanding:Boolean = false;
public function printStatus():Void {
System.out.println( if (isStanding) "Standing up" else "Laying down");
public class Human extends Animal, Job {
public attribute isAtWork:Boolean = false;
public function printStatus():Void {
System.out.println( if (isAtWork) "At the office" else "At home");
super.printStatus();
var person:Human = Human{};
person.printStatus();

Thanks! Works great. I never even tried that since my brain is wired to only use that syntax for calling a static method/function/field.
Note: If you change the class definition in the original sample from
public class Human extends Animal, Job {topublic class Human extends Animal {The original compiles and runs as you'd expect. So the 'super' keyword exists in some form and has the expected result for singular inheritance when used to call parent methods. I think you are thinking of using it to call constructors. In that usage I think you are right that it doesn't work at all in JavaFX.

Multiple inheritance, delegation and syntactic sugar

Given that delegation of an interface to a class member gives you most of the effect of multiple inheritance, why isn't there any syntactic sugar in the language to make this easy?
For example, you could have:
class B extends A implements I delegate i { I i = new IAdapter(); }
The semantics is simple: for each method in each delegated interface, if there is no method with that signature defined in the class then create one with a body that delegates the call to the given member. If there is an ambiguity from multiple interfaces, just flag it at compile time so that the programmer must add an explicit method.
This doesn't impact the class file format as it isn't doing anything that can't be done longhand in the code. It would even provide some protection from interface changes, as a recompile would pass the problem on to the delegate (which would likely inherit from some standard adapter class which would be modified at the same time as the interface).
Why isn't this done (apart from because MI is inherently evil and just suggesting this addition means I'm a bad person). It would make the language a tiny bit bigger, but at least when people ask why Java doesn't have proper MI you could answer 'it does and you do it like this' with an almost straight face.
Jonty

The only problem with this is that with multiple
delegates it kinda falls apart.
When yourFunc() is called on an instance of A, which
function is called?original> If there is an ambiguity from multiple interfaces, just flag it at compile
original> time so that the programmer must add an explicit method.
My suggestion was that if there is any ambiguity then no delegation is made, forcing the programmer to do it manually.
Normally in Java it's no big deal when multiple
interfaces have the same methods in them.Actually, I find it a bit of an odd choice by the language designers allowing same signature functions defined in different interfaces to not generate a name clash. Normally this indicates that there is, or soon will be, a bug. I can't think of any situation where this is good programming - if you want the method to exist in both interfaces then it should be defined in a third and inherited into both. This makes it clear that it really is the same method.
Not saying that delegates are a bad idea, but simple
examples don't prove that delegates are a worthwhile
feature to add.The point is that delegation is a commonly used pattern, and is almost always trotted out as a good way of getting most of multiple inheritance. The comments so far are about the problems with this pattern, not with my suggestion to make it easier to use.

Question about multiple inheritance

Why does java not support multiple inheritance, but also give you the ability to use interfaces?
I've done a quick search on here which turned up the same thing as the books on java I've read - they tell me that java doesn't support multiple inheritance, and that it supports interfaces, but not why.
And from what I can see, the between multiple inheritance and single inheritance + interfaces make them seem almost equivalent, especially when you consider abstract classes. So why did the java designers make this decision?
Edit: Just to say I've never programmed in an OO language that supports multiple inheritance, so I've never had to deal with it. Also, single inheritance has never crippled any of my designs (not that there have been that many), I'm not whingeing, just asking.
Message was edited by:
Dross

Why does java not support multiple
inheritance, but also give you the ability to use
interfaces?It does support MI, just not MI of Implementation.
why.
class Beasty { }
class Horse extend Beasty {
public void gallop() { System.out.println( "horse" ); }
class Donkey extend Beasty {
public void gallop() { System.out.println( "donkey" ); }
class Mule extend House, Donkey {
Mule mule = new Mule();
mule.gallop();what would this print out.
MI of implementation makes life harder, but adds very little to the party. So why add it?

Multiple Inheritance problem persists in Interfaces

Hi,
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.
interface one
     int i=10;
interface two
     int i=20;
interface z extends one,two
public class xyz implements z
     public static void main(String [] a)
     System.out.println(i);
}O/P
D:\Education\Java\JavaStudyRoom\Applets>javac xyz.java
xyz.java:16: reference to i is ambiguous, both variable i in one and variable i
in two match
System.out.println(i);
*^*
*1 error*
Thanks for replying

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 the so called diamond inheritance problem. What you have here is an ordinary name clash. And as has been noted you can resolve it by qualifying which constant you're referring to, like
System.out.println(one.i);
For the diamond inheritance problem to apply both the one and the two interfaces would need to inherit a common ancestor (that's how the diamond is formed). Furthermore the common anscestor would need to carry implementation which would then be inherited two ways, once via one and once via two. This is the diamond inheritance problem Java is avoiding by allowing single inheritance of implementation only.
P.S. My previous post was posted my mistake.

ERROR: RUL-00025:fact class multiple inheritance not supported

I am receiving this erro message when trying to invoke a rule (assert, execute ruleset,retrieve results) on a XML Fact structure that has demo element as parent with a ref to two child elements: invoice and po.
I simply used the wizards to deploy the decide activity so I have no clue what this might be.
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     at jess.DefinstanceList.assertObject(DefinstanceList.java:570)
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RL only supports single inheritance, either from an interface or a class. JAXB 1.0 generates a set of classes that inherit and implement each other. If the RL code is generated in the wrong order and child classes are generated before parent classes, then you get the indicated exception. In most cases, not importing the element class will prevent this from happening, and in the rest not importing the ObjectFactory class will prevent it (or unchecking the "supportsXpath" option). You can't use the element class in the rules anyway since the properties it inherits from it's parent don't show up in lists.
So, it's not the complexity of the XSD that matters in processing, only that a single inheritance chain is specified. If you follow the original instructions with your complex XSD, I believe you will see it work correctly.
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Is there (REAL) multiple inheritance ?

Hi brothers,
how r u..
let us discuss about one property of java, what do you think ..
The ability of multiple inheritance is one famous property of java, and that is done by interface, but I think that is not multiple inheritance really in contrast with C++ especially about inheriting of methods.
If a class M implements interface I and class C, M or its subclasses must implement all methods of I, i.e., the bodies of those methods are made in in M class; then where is the multiple inheritance or even the linear inheritance?
Is the multiple inheritance for methods prototypes only?
I[b] suggest that you put those methods in M class directly instead than putting them indirectly.
C++ provides real multiple inhritance for all members.
May be if the interface contains constants, we can see multiple inheritance clearly, OR :
in use APIs, but I dont have much experince in APIs?
What do you think in what I said?

Hi brothers,Hi :)
how r u..fine thanks, and you?
let us discuss about one property of java, what do
you think ..I'll do my best :$
If a class M implements interface I and class C, M or
its subclasses must implement all methods of I, i.e.,
the bodies of those methods are made in in M class;
then where is the multiple inheritance or even the
linear inheritance?
Is the multiple inheritance for methods prototypes
only?Inheritance is there to make your code more understandable I guess.
An Interface is there to define what the object is about. Persoanally I always felt that true inheritance in java is done when using the 'extends' word rather then the 'implements' keyword. When extending a class you no longer have to declare that method in your class or subclass (unless it is an abstract class).
I am not a genious in Java, however I always felt that an interface is there to specify the type of the object.
I suggest that you put those methods in M class
directly instead than putting them indirectly.But then your set of classes would not longer be understandable, and your objects can no longer have logical meaning. For example imagine haveing an class called 'John' I would never want to have all the methods and properties that describe 'John' to be lofically named only in 'John'! I would want an interface that describes to me that John needs to have two legs and two arms. An other interface that describes to me that John can walk, run, sit, etc, and another interface that tells me that John has a name, surname, id number and so on.
C++ provides real multiple inhritance for all
members.Then I guess C++ is the language for you ;)
May be if the interface contains constants, we can
see multiple inheritance clearly, OR :An interface can contain constants as much as I know!
What do you think in what I said?was gona ask the same thing, but now I am afraid I wrote a bunch of sh*t :$ :(

More about multiple inheritance

OK, you can solve problems where multiple inheritance is needed by using interfaces. But im facing a problem where it cant help me. Im constructing a system where there are componentes that need to extend JTextField as well Observable. I dont have interfaces above it in the hierarchy to substitute multiple inheritance. What can I do?
When you have a scenario that you have to use two (or more) third party classes, and need to inherit from both, how do interfaces can help? If ate least I had multiple inheritance from classes...

<< Begin Rant >>
I have seen more inherited code that is terribly designed because multiple inheritence was available.
The example provided is a perfect example of this: At first blush, it seems easy to combine the UI and data components by combining Observable and JTextArea. If you were able to do this, the person inheriting your code in 3 years will curse your name.
Nothing pisses me off more (well, I'm sure there are other things, but...) than attempting to debug C++ source code and finding that function calls are being made to multiple super classes.
Here's a fun one: try adding an innocuous method getInfo() to a class you've inherited, only to find that someone uses getInfo() in one of the super-classes, and it has been declared as 'friend' because the design is piss poor and it was the only way they could make the function available. Now, I have to go on a goose chase searching for all the places in the entire type hierarchy that getInfo() is used and change the code to explicitly call the other base class.
It gets to the point where its easier to name it getInfo2() (like that's good design) and get on with things.
MI is evil, evil, evil in any environment where you are trying to have code re-use and multiple teams.
I find that most programmers who insist that multiple inheritence is a good thing just don't know how to use the Composite design pattern.
Sun's decision to not support MI in Java is a sound one: the result is code that can be easily read and understood.
<< End Rant >>
Whew... I feel much better having said that...
- K

How java support multiple inheritance by the use of interface.

As per my understanding, Interface is just having the signatures of the methods not the implementation.
So How java support multiple inheritance by the use of interface?
Answer 1: we can institate interface reference by its implemented
class.
          �� interface inf...
          �� class aa implements inf..
          �� 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
single
           interface.
           i.e. interface infFirst....
           interface infSecond....
           interface infThird....
           Now ,
           interface ingMulti extends infFrist, infThird...
By above two answers its not prity clear as per the multiple inheritance in C or C++.
           i.e.
           class first{
           method abc();....}
           class second{
           method bbc()......}
           class multi::first::second{
           we can call to abc();.....as well as bbc();
-Please give your important suggstion on the same.(Hope I explain it well.)
-Jeff

The keyword implement is used only for interfaces not
for abstract class. If i am wrong correct me.I believe your right, but I will double check.
As for the multiple inheritence think about the following code:
class Animal {
    // Animal generic stuff in this class
interface Eat {
    // Generic stuff that models eating behavior
interface Runs {
    // generic methods that model running behavior
public class Horse extends Animal implements Eat, Runs {
    // Stuff specific to a horse
}The Animal class is generic but has stuff in it common to all animals.
The Eat interface models behavior that is generic to eating, all living things have to eat something to survive. Herbavore are different from carnivores.
The Runs interface models generic behavior to running, such as speed. A cheeta definately runs faster than a human.
This brings us to the Horse class. It extends the Animal class because it "is-a" animal, and it implements the eat and runs interface because they are behaviors a horse has.
I hope that helps.
Extending an abstract class is the same as extending a regular class with the exception you MUST override all abstract methods in the abstract class. Thats not too difficult but I believe when designing classes, designing an abstract can be more diffecult than modeling the base class, and generic behaviors in interfaces. JMO.
JJ

Alternatives to multiple inheritance for my architecture (NPCs in a Realtime Strategy game)?

Coding isn't that hard actually. The hard part is to write code that makes sense, is readable and understandable. So I want to get a better developer and create some solid architecture.
So I want to do create an architecture for NPCs in a video-game. It is a Realtime
Strategy game like Starcraft, Age of Empires, Command & Conquers, etc etc.. So I'll have different kinds of NPCs. A NPC can have one to many abilities (methods) of these: Build(), Farm() and Attack().
Examples:
Worker can Build() and Farm()
Warrior can Attack()
Citizen can Build(), Farm() and Attack()
Fisherman can Farm() and Attack()
I hope everything is clear so far.
So now I do have my NPC Types and their abilities. But lets come to the technical / programmatical aspect.
What would be a good programmatic architecture for my different kinds of NPCs?
Okay I could have a base class. Actually I think this is a good way to stick with the DRY principle.
So I can have methods like WalkTo(x,y) in
my base class since every NPC will be able to move. But now lets come to the real problem. Where do I implement my abilities? (remember: Build(), Farm() and Attack())
Since the abilities will consists of the same logic it would be annoying / break DRY principle to implement them for each NPC (Worker,Warrior, ..).
Okay I could implement the abilities within the base class. This would require some kind of logic that verifies if a NPC can use ability X. IsBuilder, CanBuild,
.. I think it is clear what I want to express.
But I don't feel very well with this idea. This sounds like a bloated base class with too much functionality.
I do use C# as programming language. So multiple inheritance isn't an opinion here. Means: Having extra base classes like Fisherman
: Farmer, Attacker won't work.

Hi
PandoraElite，
You can inherit from multiple interfaces (and use explicit interface implementation), but not from classes in C#. You can almost simulate it:
In C# we don't support multiple inheritance
http://blogs.msdn.com/b/csharpfaq/archive/2004/03/07/why-doesn-t-c-support-multiple-inheritance.aspx
What would be a good programmatic architecture for my different kinds of NPCs?
In your scenario, we can define some interface ,An interface contains only the signatures of methods, properties, events or indexers. A class or struct that implements the interface must implement the members of the interface that are specified
in the interface definition.
How to use? Please refer to the following article.
http://www.codeproject.com/Articles/18743/Interfaces-in-C-For-Beginners
Best of luck!
Kristin
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Replacement for multiple inheritance in MovieClip class

Hello
I need your opinion about a problem.
Commonly, when you need to replace multiple inheritance, you do it by making an aggregation with one of the class involved.
But in case of MovieClip attached class, there is one more class involved in the process : the MovieClip class, and this class can't be the one aggregated because every class attached to a MovieClip need to inherits from it.
The problem is if the other class can't be also aggregated because it has some abstract class behaviour, for instance, call of a virtual function.
A solution could be making the abstract class inherit from the MovieClip class, but what if you want to reuse its behaviour in a class which have nothing to do with MovieClip ?

This is Not Supported in WebLogic that the Remote Interface extends other Interfaces. Because Annotation Processor just looks up inside the implemented interface methods. The actual interface which is Implemented by the Bean Class. So the Methods declared inside the Interface B and Interface C will be ignored and will not be available as part of the generated Stubs. Thats why u are getting NoSuchMethodError.
You can even contact Oracle Support on this...there are 3-4 Cases on it. And the Solution is Work As Designed.
Workaround is : edit your interface A as following
Declare all the Business Methods only in the Remote Interface and not inside it's Super Interfaces.
Example:
@Stateless(name="A")
@Remote({A.class})
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public class AImpl implements A {
@Override
public void writeA() {
System.out.println("A");
@Override
public void writeB() {
System.out.println("B");
@Override
public void writeC() {
System.out.println("C");
@Remote
@JNDIName(A.JNDI_NAME)
public interface A extends B, C {
public static String JNDI_NAME = "A_JNDI_NAME";
void writeA();
void writeB();
void writeC();
Thanks
Jay SenSharma
http://jaysensharma.wordpress.com (WebLogic Wonders Are Here)

What is single inheritance, multiple inheritance, and describe Java's notio

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