I am currently undertaking a project to animate java
programs by  analysing bytecode method calls and attribute updates. I
have been studying the BCEL API as a means of implementing my design. I
am however having difficulty understanding results when running the
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
get working in most cases but I get the following error when executing
it on the java program which i have included below.

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

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

  /**
   * initializes the
   * the complex number to be zero.
   */
  ComplexNumber() {
  realPart = 0;
  imagPart = 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 = realPart;
  this.imagPart = imagPart;
  }

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

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

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

//*************************************************************************
  //  Test the above methods

  public static void main(String args[]) {

  //  Create 3 complex number objects and initialize
  ComplexNumber A = new ComplexNumber();
  ComplexNumber B = new ComplexNumber();
  ComplexNumber result = new ComplexNumber();

  System.out.println("Testing ComplexNumber.java...");

  A.setValue(5,1);
  B.setValue(2,3);

  // Test the add method
  result = A.add(B);

  // output the result
  System.out.println(A.toString() + "    +    " + B.toString() + "
= " + result.toString());

  }
}