Help comparing objects

Question

Hi,
My java app's purpose is to find out if I must update my simulated framework if the real framework has changed ( interfaces).
My app loads two jar files ( real framework and simulated framwork) and use bcel to make an static analysis of the classes ( bcel created 'JavaClass' to describe the class).
In order to determine if the classes are equal i create a 'DataClass' object with the following information:
className
Field [] fields (bcel 'Field' not java.lang.reflect.Field)
Method [] methods (bcel 'Method' not java.lang.reflect.Method)
I retrieve the information from JavaClass and put it in my 'DataClass'.
This is the code I use to create a Vector for each framework ( Listing 1). This is where I store the data describing my classes in the api (Listing 2). Then I compare each 'DataClass' contained in the Vector.
My intention is to compare the 'data' of the 'DataClass'. But since I get that all DataClass objects are NOT equal I guess I compare references. How can I do this.
All hints are vey much welcome.
cheers,
//mikael
Listing 1
==========
Note: ClassSet is a 'Set' of JavaClass' objects.
public static Vector makeDataObjects(ClassSet classes){
        Vector api = new Vector();
        JavaClass [] clazzes = classes.toArray();
        for (int i = 0; i < clazzes.length; i++) {
         JavaClass clazz = clazzes;
DataClass dc = new DataClass();
dc.setClassName(clazz.getClassName());
Field [] fields = clazz.getFields();
for(int j = 0; j < fields.length; j++){
dc.setField(fields[j].toString());
Method [] methods = clazz.getMethods();
for (int k = 0; k < methods.length; k++) {
dc.setMethod(methods[k].toString());
api.add(dc);
return api;
Listing 2
=========
import java.util.ArrayList;
public class DataClass implements Comparable{
    private String className = null;
    private ArrayList fields = new ArrayList();
    private ArrayList  methods = new ArrayList();
    public void setClassName(String className){
        this.className = className;
    public String getClassName(){
        return className;
    public void setField(String field){
        fields.add(field);
    public void setMethod(String method){
        methods.add(method);
    public int compareTo(Object o){
}This is where I compare the content of my two api:s
Listing 3
=========
public static void compare(Vector api1, Vector api2) {
for (Iterator iter = api1.iterator(); iter.hasNext();) {
   DataClass clazz1 = (DataClass) iter.next();
   String className = (String) clazz1.getClassName();
   DataClass clazz2 = (DataClass) toBeCompared(className, api2);
   // compare object values
   System.out.println("clazz1 is " + clazz1.toString());
   System.out.println("clazz2 is " + clazz2.toString());
   if (clazz1.equals(clazz2)) {
    System.out.println("Objects are the SAME" + className);
   } else {
    System.out.println("Objects are NOT the same" + className);
private static DataClass toBeCompared(String className, Vector api){
  DataClass dao = null;
  for (Iterator iter = api.iterator(); iter.hasNext();) {
    DataClass element = (DataClass) iter.next();
    String otherClassName = element.getClassName();
    if (className.equals(otherClassName)){
    dao = element;
return dao;

Answer 1

Your error is that you implement Comparable and the compareTo method instead of the equals method of Object class. Comparable is needed for ordering items. Equals instead is used to check if two objects are equal. Per convinience it is expected that there is no inconsistency if both equals and compateTo are implemented.
So you should implement a method in DataClass:
public boolean equals(Obejct o) {
  boolean result = false;
  if (o instanceof DataClass) {
    DataClass c = (DataClass) o;
    result = className.equals(c.className) &&
         fields.equals(c.fields) &&
         methods.equals(c.methods);
    // keep in mind here, that the arrays fields and
    // methods should be sorted / ordered. use Collections.sort(fields)
    // for this when you create or modify it
  return result;
}You could also simplify the compare(Vector api1, Vector api2) method when you keep these Vectors sorted for className or use Set (what i dont recommand because of properbly performance drawbacks):
public static void compare(Vector api1, Vector api2) {
  Collections.sort(api1, new ClassNameComparator());
  Collections.sort(api2, new ClassNameComparator());
  // you should possibly dont do this sorting here because the
  // method name does not state that the vectors are modified
  // but it's a precondition for make the following work properly:
  return api1.equals(api2);
}i did not compile the code, so i hope i did not make many errors.
regards
Sven