import java.util.Vector;                 // Java container class
public class Holding {
  public Account account;                // part of primary key, but not a string
  public Stock stock;                    // part of primary key, reference to parent
  public int QTY;

  public Holding(Account account, Stock stock, int QTY) {
    this.account = account; this.stock = stock; this.QTY = QTY;
    account.holdings.addElement(this);   // add itself to the parent's list of children
  }
  public String toString() {
    return (account.ACCOUNT_NO + " " + stock.SYM + " " + QTY);  // access primary key string
  }
  public void remove() {
    account.holdings.removeElement(this); // remove itself when QTY is sold off 
  }
}