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Check if a Type is an interface or class - Uses BCel Api

Posted on 2004-10-15
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Last Modified: 2010-03-31
I have a JavaClass class under the following Bcel API

http://jakarta.apache.org/bcel/apidocs/index.html

class.getFields gets the fields
 
I have a field f I want to see if its INHERITED class (not declared class) is an interface or a regular class.
 - Inherited being if in Class1, I have field F initiialized as HashTable F = .... I want to get HashTable.

I can do this by doing f.getType() however now this returns a Type.  How do I check if this is an interface, etc.  or convert  this to a Class or something.
(Use the above link for the API)

Please help.

Thanks.
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Question by:bcsmess
19 Comments
 
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Expert Comment

by:cjjclifford
ID: 12318381
The Field[] returned by the getFields() method contains objects that extend org.apache.bcel.classfile.AccessFlags (i.e. the Field class extends AccessFlags) - there is a suite of methods in this class, including "isInterface()" which you can use to decide the type of the field...

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LVL 18

Expert Comment

by:armoghan
ID: 12318522
correctly said by cjjclifford Class.inTnterface() method returns that it is a class or interface
see this link for details
http://java.sun.com/developer/technicalArticles/DataTypes/ObjectsConscious/
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Author Comment

by:bcsmess
ID: 12318576
Does isInterface() check if the class that declares it  is an inteface or if it's the initialized type class (HashTab).  I did it and it returns false for when getType is a Set though Set is an inteface.
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Expert Comment

by:armoghan
ID: 12318716
see this simple example

  Class c = null;
  try {
    c = Class.forName("java.util.Set");
  }
  catch (ClassNotFoundException ex) {
  }
   if(c.isInterface())
   {
     System.out.println("Is a interface");
   }
   else
     System.out.println("Is a class");
0
 

Author Comment

by:bcsmess
ID: 12318718
I also tried,

String f = field.getType().toString();
Class c = Class.forName(f);
return c.isInterface();

But it says it can't find the class that has the name f.  Do I need to crop the string somehow?
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Author Comment

by:bcsmess
ID: 12318766
Your example works but how do you put a field.getType() into that String format.
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Expert Comment

by:expertmb
ID: 12318805
f
need to be fulll package path
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Accepted Solution

by:
armoghan earned 500 total points
ID: 12318808
if you are talking about such code, It will return class as the object is instanceof a Class,
Set s = new HashSet();
   Class c = null;
   c = s.getClass();

   if (c.isInterface()) {
     System.out.println("Is a interface");
   }
   else
    {
 System.out.println("Is a class");
   Class cl[] = c.getInterfaces();
}


so what you can do is call
   Class cl[] = c.getInterfaces();

and get all the interfaces
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Author Comment

by:bcsmess
ID: 12318852
Well again, I don't want the declared class but the class Set to be checked.  s.getClass() returns the class that declares it, I think.  Is there anyway to do it like my example.  Thanks again.
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Expert Comment

by:armoghan
ID: 12318860
you need to do
field.getType().getName();
to get the full name
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Expert Comment

by:armoghan
ID: 12318875
Why dont you do simply
return  field.getType().isInterface();
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Author Comment

by:bcsmess
ID: 12318943
There's no such method isInterface for Type.
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Expert Comment

by:armoghan
ID: 12318971
field is java.lang.reflect.Field?
it has method
public Class getType()
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Author Comment

by:bcsmess
ID: 12319027
No.  In my original question, it gives you the API for the class file I"m talking about.  It's under a Bcel api.
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Expert Comment

by:armoghan
ID: 12319081
ohh sorry, I forgot about the original question :(
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Expert Comment

by:armoghan
ID: 12319099
Have you tried getSignature() ?
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Expert Comment

by:armoghan
ID: 12319112
Doesnot seem to have a method to get the Class object back
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Author Comment

by:bcsmess
ID: 12319224
i can't tell what getsignature does.
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