Unexpected behavior when creating Objects in a Vector

Question

I have a situation where Objects in a Vector appear to be getting corrupted. The context is this: I obtain a ResultSet from a database, create a Vector of Strings for each row, and a Vector of these row vectors for the entire ResultSet. This is passed to a method where a POJO is created for each row. This method returns a Vector of these POJOs. In the Object constructor, a String array of initial values is created and also values are assigned to individual variables. Here is a snippet with the Object constructor
public class RefAuthorItem {
     private final String refKey;
     private String authorKey, firstName, lastName, itemKey;
     private int authorPosition;
     private boolean isDeleted, isNew;
     // Keep a copy of the original values
     private final String[] oldValues;
      * The constructor for the data object item.
      * @param dataVals     a String array of the data values
      * @param isNewVal     boolean true if this is a new item, false if it is
      *                                              an existing item
     public RefAuthorItem(final String[] dataVals, final boolean isNewVal) {
          oldValues = dataVals;
          authorKey = dataVals[RefQueryBuilder.AUTH_NUM];
          firstName = dataVals[RefQueryBuilder.AUTH_FIRST_NAME];
          itemKey = dataVals[RefQueryBuilder.AUTH_PKEY];
          lastName = dataVals[RefQueryBuilder.AUTH_LAST_NAME];
          refKey = dataVals[RefQueryBuilder.AUTH_REF_FKEY];
          isNew = isNewVal;
          isDeleted = false;
          // the author position integer value is used to sort the display
          authorPosition =
                    Integer.parseInt(dataVals[RefQueryBuilder.AUTH_POS]);
     }It seems the oldValues[] values should be identical to the corresponding individual variable values. When the following code is used to create the objects, they are not.
          final boolean isNew = isNewVal;
          Vector<RefAuthorItem> returnSet = new Vector<RefAuthorItem>();
          final String queryString = QueryBuilder
               .getRefQuery(keyString, tableName);
          Vector<Vector> dataSet = QueryDB.getResultSet(queryString);
          int columnTot = dataSet.firstElement().size();
                String[] itemVals = new String[columnTot];
          for (Iterator iter = dataSet.iterator(); iter.hasNext();) {
               Vector element = (Vector) iter.next();
               for (int i = 0; i < columnTot; i++) {
                    itemVals[i] = (String) element.get(i);
               RefAuthorItem item = new RefAuthorItem(itemVals, isNew);
               returnSet.add(item);
          }What happens is this. I returned four rows from the database and the oldValues[] array for each of the four corresponding objects contains the data from the fourth row. However, when I retrieve the corresponding individual values (e.g., authorLastName) from the Object, it is correct. I checked the object values (oldValues versus individual values retrieved via getters) right after the object is created (the line: RefAuthorItem item = new RefAuthorItem(itemVals, isNew);) and get the correct results. Also, results are correct when the itemVals constructor is moved within the loop, as below
          int columnTot = dataSet.firstElement().size();
          for (Iterator iter = dataSet.iterator(); iter.hasNext();) {
               Vector element = (Vector) iter.next();
               String[] itemVals = new String[columnTot];
               for (int i = 0; i < columnTot; i++) {
                    itemVals[i] = (String) element.get(i);
               RefAuthorItem item = new RefAuthorItem(itemVals, isNew);
               returnSet.add(item);
          } There is a problem here. Am I missing a subtle Java issue with instantiating the String array within the loop? Or is there a problem with Vectors? Thanks!

Answer 1

Dear ejp,
In the non-working code, I rewrite the itemVals[], create a new RefAuthorItem using the itemVals[] and repeat. I checked the RefAuthorItem immediately after it was created (with println()) and the oldValues and individual String values in the object are concordant. However, after the loop is completed (all RefAuthorItems are created and added to the Vector), the oldValues[] in the objects all have the values from the last row. The individual String variables in the object all have the correct value from the ResultSet row.