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From David Hovemeyer <dav...@cs.umd.edu>
Subject Re: how to get the type info from this small code snippet?
Date Wed, 26 Jan 2005 19:31:34 GMT
On Wed, Jan 26, 2005 at 12:12:32PM -0700, Hiller, Dean D (Dean) wrote:
> package mod.fieldrefdepend;
> import mod.dummy.DummyClass;
> public class ClassDependsOnReferenceInFieldDeclaration {
>             private Class c = DummyClass.class; 
> }
> Anyone know how to process the ConstantPool or the instruction code to
> find out DummyClass.class is used in this context(ie. Class c =
> DummyClass.class).  I don't care about other contexts.

If the code was generated by javac from JDK 1.5, just look
for a LDC instruction that refers to a Constant_Class.

I believe that for javac from JDK 1.4 and earlier, SomeClass.class
expressions are compiled to

 - check a synthetic static field which caches the Class

 - if the field contains null, call a synthetic static method
   (called "class$", judging from the code you posted),
   passing the name of the class as a param.  The return value
   of this method is the Class object.

So, I think you can find out what classes are involved in
SomeClass.class expressions by scanning method bytecode for sequences of

  LDC "com.foobar.SomeClass"
  INVOKESTATIC "java.lang.Class class$(java.lang.String)"

You will probably want to use ConstantPoolGen/ClassGen/MethodGen
to produce an InstructionList for each method, unless you want
to write code to disassemble the actual bytecodes.  As a side
benefit, these classes make it easier to extract constants from
the constant pool (e.g., symbolic information for particular

Other compilers (e.g., jikes, Eclipse) may generate different

Hope that helps,


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