Finding implementations of an interface programmatically

Hi... would anyone know how to find programmatically all classes that implement an interface?
Ideally, I would like to query on an interface and end up with a list of Class objects (i.e. the implementations of said interface).
Thanks
Message was edited by:
javaBoy

can't be done. this gets asked all the time, and it's impossible. Yes - technically correct.
However, in many contexts where you know what classloaders are at play (and lets face it, many of us do work on projects where we use known classloaders, and dont have some random loading off the net on demand going on), it is possible, useful, and very much do-able - if you accept the limitations and constraints.
So, OP, do a search and you'll probably find something useful to you.
~D

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Where are the implementations for some interfaces in the search_sdk.jar?

Hi,
Is the source code for the implementation of some interfaces (DocumentMetadata etc) available to public?
Thanks.
Jun
Message was edited by:
Alwaysthink

Source code is not available. The javadoc is distributed with the installation media. On my machine I can find the javadoc for DocumentMetadata here:
file:///F:/SES_1018_WIN32_DVD2/doc/search.1018/b32260/toc.htm

Why the HashMap implements the Map interface twice

See the type hierarchy below:
HashMap<K,V>
┃
┣AbstractMap<K,V>
┃┃
┃┗Map<K,V>
┗Map<K,V>
The HashMap extends AbstractMap, which implements Map. So the HashMap has already implements Map, and has the Map type. But the HashMap's declaration still contains "implements Map".
So why the HashMap implements the Map interface twice?
Thanks in advance.

georgemc wrote:
Maybe the guy who wrote HashMap wanted to make it clear that HashMap implemented Map, rather than rely on you looking further up the hierarchy to find outYes, it does make the Javadoc clearer. If they hadn't done that then there would have been legions of newbies who couldn't tell that HashMap implemented Map and thousands of "I have a doubt, does HashMap implement Map" questions here.

The XElement class explicitly implements the IXmlISerializable interface?

I see a sentence on a training book.
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Implementing two generic interfaces

I have a generic interface,
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class X implements Callback<Type1>, Callback<Type2> {
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   public void result(Type2 r) {};
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mlk has the correct answer, but here's some more explanation:
Generics are only used at compile time. The actual bytecode specifies the base object type (aka type erasure), in this case Object. When you implement a generified interface, the compiler will generate a bridge method from the erased type to the specific type.
Some examples should make this clearer.
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Code that invokes the interface, like this:
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Is it true that when specifing a number of business interfaces for a bean class with an annotation (@Remote) it not require that the bean class implement the interfaces ??
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thanks in advanced.

If your bean doesn't implement the business interface, you'll need to use annotations (@Remote on the session bean class) or the deployment descriptor to let the container know what the business interfaces are used by the session bean.
For example,
// BusinessIF1.java
package myejbs;
public interface BusinessIF1 { public void doSomething(); }
// BusinessIF2.java
package myejbs;
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// MySessionBean.java
package myejbs;
@Remote({BusinessIF1.class, BusinessIF2.class})
@Stateless
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BUILD FAILED
weblogic.Deployer$DeployerException: weblogic.deploy.api.tools.deployer.DeployerException: Task 0 failed: [Deployer:149026]deploy application smap.war on AdminServer.
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Hi,
I am not sure - given the information you provide - that you posted to the right forum
Frank

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How to name implementation of an interface

Hi there
is there any standard for naming concrete implementation of interfaces?
So if I have an interface
A
in package "interfaces"
is it sensful to call the concrete implementation of the interface interfaces.A A, too?
class A implements interfaces.A{
}? Or should it be called ConcreteA, or or or....?
Thx for your tips.
Sincerely
Karlheinz Toni

JebeDiAH heres a very interesting reading.
Class and Interface Names
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When using multiple words in a class name, the words should be concatenated with no separating characters between them. The first letter of each word should be capitalized.
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Hi guys,
I have a conceptual question about implementing the Serializable interface - since it's only a marker interface (i.e. - it doesn't have any abstract methods) why does Java demand an object to implement this interface in order to be written into a file? What I'm asking is why wouldn't they make the writeObject method's signature
public void writeObject(*Object* o)
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So that serialization requires the explicit consent of the class or superclass/superinterface.

Passing implementation of Java interfaces

Hi
I have a static function which I want to be supplied with a another class. Now the passed class needs to be an implementation of that class. How can I make sure?
Thanks
Saaransh

an example:
Lets say I have an interface :
public interface foo
//some methods
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How do i do this?
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Thanks

Implementation of the interface IF_EX_XSS_TIM_PER_INTERFACE.

Dear Guru's,
I need an example of implementation of the interface IF_EX_XSS_TIM_PER_INTERFACE.
for methods
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-PROVIDE_DROPDOWN_ENTRIES
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la idea es poder configurar la seleccion de periodos.
regards.
icemanirc
Edited by: Juan Carlos De La Fuente Fuentes on Jul 12, 2011 11:08 PM

excellent, now I can understand how to implement it.
thanks
Yugandhar Reddy

Cann't extend a inner class where as can Implement a nested Interface

i cann't extend a inner class in some other outer class . Where as i can implement the nested Interface in some other class. Why????
for example:-
class ABC
class Inner
/* class body */
interface TempInterface
/* interfacebody */
class OuterClass
class InnerTwo extends ABC.inner //(line 1)Will give error
class InnerTwo implements ABC.TempInterface //(line 2)Will run fine
the line 1 is going to give compilation error i.e not in the scope but the line 2 will run fine .
Both of the things are in the same class but giving 2 other results.
I am not getting sufficient reasons for it.
Can any one help me????
Reagrds
Arunabh

As far as the language is concerned, the classonly
exists in the context of an instance of theenclosing
class.This still exhibits a class/object confusion to me.
It should be 'instance only exists ...' or 'instance
can only exist'. The class only exists in the
scope of the enclosing class, but this is another
issue.I'm not following what you're saying. The second sentence sounds like you're disagreeing with me. The last sentence sounds like you're agreeing with me.
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Why the ArrayList implements the List interface

Why the ArrayList implements the List interface even though it extends the AbstractList class. Is it only for clarity of interface implemented?

899440 wrote:
Why the ArrayList implements the List interface even though it extends the AbstractList class. Is it only for clarity of interface implemented?I dont think there's any specific reason for that. In my opinion its redundant. May be its added for clarity so that from the documentation its obivous that ArrayList implements List.
May be there's something which I am missing regarding this?

How to find classes implementing a certain interface at runtime

I am making an Application and I want have a plug-in nature for the different tools I have.
My App is packaged in a package with subpackages for the individual tools. I want to beable to remove/add subpackages without crashing the app.
The only way I can see this working is for the App to search its sub packages for a certain interface (eg an 'AddOnTool' interface) and build a set of available AddOnTools.
I just dont know if this is possible, but pretty sure it must be!....
Once I have the set of available AddOnTools I also realise that I have to Construct the one chosen, this I see as my other hurdle!
If I can be helped with these I'll be mighty Happy!

You can use getClassLoader() in the Class class to get the ClassLoader, then use getPackages() to get an array of all packages available to your class. How to get a list of all classes, however, I can't find in the documentation; perhaps you can do more research.

Finding implementations of an interface programmatically

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