Detect changes in an instance

Question

Hello,
how can I detect changes in an instantiated object? I could serialize the object and write it into a file. After some minutes I could write it a second time into a file. Now I could compare the two files. But I thing this is not the best way for doing this, isnt't it.
Any suggestions?
Thanks

Answer 1

it can be of any help, here's how I implement object changes:
/** Interface for object instances comparison */
interface ContentComparable {
   /** Returns a string describing the object instance for comparison */
   public String getCompareString();
/** Custom class sample */
public class CustomClass implements ContentComparable {
   private String    customField1;
   private int       customField2;
   /** Constructor */
   private CustomClass(String field1, int field2) {
      this.customField1 = field1;
      this.customField2 = field2;
   //------------------------------------------------------------ ContentComparable ---
   /** Returns a string describing the object instance for comparison */
   public String getCompareString() {
      String content = this.getClass().getName() + "["
                       + "customField1='" + this.customField1 + "', "
                       + "customField2=" + this.customField2 + "]";
       return content;          
   /** Returns TRUE if the object is equal to an other object
    * @param   otherobj  the other object
    * @return  TRUE or FALSE
    * @see #getCompareString()
   public boolean equals(Object otherobj) {
      if (otherobj instanceof CustomClass) {
         CustomClass classobj = (CustomClass)otherobj;
         return this.getCompareString().equals(classobj.getCompareString());
      return false;
}With that, you just have to keep a copy of the getCompareString() of the object before any changes are made.
When you want to test changes, call this method:
   // private member to hold copy of unchanged object string
   private String oldObjectValue;
   // Returns TRUE if object has changed
   private boolean testDataChanged() {
      if (oldObjectValue == null) oldObjectValue = object.getCompareString();
      String newObjectValue = object.getCompareString();
      return !oldObjectValue.equals(newObjectValue);  
   //...Hope this helped,
Regards.