[BCEL-info]BCEL query on helloify.java

[Derek M. <d.j...@sm...>]

 I am currently undertaking a project to animate java=20
programs by  analysing bytecode method calls and attribute updates. I=20
have been studying the BCEL API as a means of implementing my design. I=20
am however having difficulty understanding results when running the=20
program on the latest JDK virtual machine. I wonder if anyone could help =

clarify this.

I have been experimenting with the helloify.java program which I can=20
get working in most cases but I get the following error when executing=20
it on the java program which i have included below.

"Exception in thread "main" java.lang.VerifyError: (class:=20
ComplexNumber_hello, method: add signature:=20
(LComplexNumber;)LComplexNumber;) Incompatible type for getting or=20
setting field"

My java program simply creates two complexNumber objects and adds them=20
together. This compiles and runs successfully on "Java(TM) 2 Runtime=20
Environment, Standard Edition (build 1.4.2_02-b03), Java HotSpot(TM)=20
Client VM (build 1.4.2_02-b03, mixed mode)".  The=20
ComplexNumber_hello.class file produces the error above and I cannot=20
understand why. It seems to happen when trying to return the sum of the=20
two complex numbers. I have tried to rectify this problem with no=20
success. When using the Kaffe JVM supplied with RedHat Linux 7.2 I get=20
no errors when running ComplexNumber_hello or ComplexNumber classes. Is=20
this an issue with the latest JVM or am I missing something important?

Thanks.



/*
*    Class ComplexNumber specify Complex Number object and
*      associated functions
*
*/


class ComplexNumber {

   // Private data fields for the complex number:
   // realPart + imagPart * i
   private double realPart;
   private double imagPart;
 =20
 =20
   /**
    * initializes the
    * the complex number to be zero.
    */
   ComplexNumber() {
   realPart =3D 0;
   imagPart =3D 0;
   }

   /**
    * Constructor that allows the real and imaginary
    * parts of the complex number to be initialized
    * to arbitrary values.
    */
   ComplexNumber(double realPart, double imagPart) {
   this.realPart =3D realPart;
   this.imagPart =3D imagPart;
   }


   /**
    * Set the value of a complex number by specifying its
    * real and imaginary parts.
    */
   public void setValue(double realPart, double imagPart) {
   this.realPart =3D realPart;
   this.imagPart =3D imagPart;
   }


   /**
    * Return a new complex number with its value equal
    * to the sum of the invoking ComplexNumber and
    * the Complex Number argument.
    */
   public ComplexNumber add(ComplexNumber theNum) {
   return new ComplexNumber(realPart + theNum.realPart,
                imagPart + theNum.imagPart);
   }                    =20




   /**
    * Convert the complex number into a string representation.
    * The string representation is realPart + imagPart i.
    */
   public String toString() {

   // If the imagPart is >=3D 0 print out a + b i
   if (imagPart >=3D 0) {
       return realPart + " + " + imagPart + " i";
   }
   // If the imagPart is < 0 print out a - b i
   else {
       return realPart + " - " + (-imagPart) + " i";
   }
   }


  =20
//***********************************************************************=
**
   //  Test the above methods

     =20
   public static void main(String args[]) {
         =20
   //  Create 3 complex number objects and initialize
   ComplexNumber A =3D new ComplexNumber();
   ComplexNumber B =3D new ComplexNumber();
   ComplexNumber result =3D new ComplexNumber();

   System.out.println("Testing ComplexNumber.java...");
 =20
   A.setValue(5,1);
   B.setValue(2,3);
     =20
   // Test the add method
   result =3D A.add(B);  =20
 =20
   // output the result
   System.out.println(A.toString() + "    +    " + B.toString() + "    =20
=3D " + result.toString());
 =20
   }
}