Help adding to an array

Question

Hello,
I've added an Add button to a GUI. This feature should enable users to add itemName, numberUnitsStock, unitPrice, and itemNumber(one more than the previous last item). Can anyone help? I'm thinking that I need to extend the array size first and then figure a way to get the aforementioned included in the array. Any help would be greatly appreciated.
public class DVD6
          protected int itemNumber; // item number
          protected String itemName; // name of product
          protected int numberUnitsStock; // number of units in stock
          protected double unitPrice; // price of each unit
        // constructor initializes DVD with int, String, and double as argument
        public DVD6 (int itemNumber, String itemName, int numberUnitsStock, double unitPrice)
        this.itemNumber = itemNumber; // initializes itemNumber
          this.itemName = itemName; // initializes itemName
          this.numberUnitsStock = numberUnitsStock; // initializes numberUnitsStock
          this.unitPrice = unitPrice; // initializes unitPrice
          } // end constructor
            // method to set the item number
          public void setitemNumber (int itemNumber)
          itemNumber = itemNumber; // store the item number
          } // end method setitemNumber
            // method to retrieve the item number
        public int getitemNumber()
        return itemNumber;
        } // end method getitemNumber
        // method to set the name of product
            public void setitemName (String itemName)
            itemName = itemName; // store the name of product
            } // end method setitemName   
            // method to retrieve the itemName
        public String getitemName()
        return itemName;
        } // end method getitemName
        // method to set the number of units in stock
            public void setnumberUnitsStock (int numberUnitsStock)
            numberUnitsStock = numberUnitsStock; // store the number of units in stock
            } // end method setnumberUnitsStock   
            // method to retrieve the number of units in stock
        public int getnumberUnitsStock()
        return numberUnitsStock;
        } // end method getnumberUnitsStock
        // method to set the price of each unit
            public void setunitPrice (double unitPrice)
            unitPrice = unitPrice; // store the price of each unit
            } // end method setunitPrice   
            // method to retrieve the price of each unit
        public double getunitPrice()
        return unitPrice;
        } // end method getunitPrice
            // method to retrieve the inventoryValue
            public double getinventoryValue()
            return (numberUnitsStock * unitPrice); // multiply numbers
            } // end method getinventoryValue   
            // method to get the value of entire inventory
            public static double getTotalValueOfAllInventory (DVD6 [] inv)
               double tot = 0.0;
                 for (int i = 0; i < inv.length; i++)
                    tot += inv.getinventoryValue();
               return tot;
          } // end method getTotalValueOfAllInventory
          public static DVD6[] sort(DVD6 [] inventory)
          DVD6 temp[] = new DVD6[1];
               // sort
               for (int j = 0; j < inventory.length - 1; j++)
               for (int k = 0; k < inventory.length - 1; k++)
                    if (inventory[k].getitemName().compareToIgnoreCase(inventory[k+1].getitemName()) > 0 )
                         temp[0] = inventory[k];
                              inventory[k] = inventory[k+1];
                              inventory[k+1] = temp[0];
                         } // end if
                    } // end for
          } // end for
          return inventory;
          public String toString()
          StringBuffer sb = new StringBuffer();
               sb.append("Item number: \t").append(itemNumber).append("\n");
               sb.append("DVD Title: \t").append(itemName).append("\n");
               sb.append("Units in stock: \t").append(numberUnitsStock).append("\n");
               sb.append("Price of unit: \t").append(String.format("$%.2f%n", unitPrice));
               sb.append("Inventory value of product: \t").append(String.format("$%.2f%n", getinventoryValue()));
               return sb.toString();
} // end class DVD6
public class DVDs6 extends DVD6
    private String genre; // genre of DVD
      private double restockingFee; // percentage added to product's inventory value
       //constructor
     public DVDs6(String genre, int itemNumber, String itemName,
                 int numberUnitsStock, double unitPrice)
           super(itemNumber, itemName, numberUnitsStock, unitPrice);
          this.genre = genre;
     // method to set the genre of DVD
     public void setgenre (String genre)
     genre = genre; // store the genre
     } // end method setgenre
     // method to retrieve the genre
     public String getgenre()
     return genre;
     } // end method getgenre
     // method to retrieve the restockingFee
     public double getrestockingFee()
     return (super.getunitPrice() * 0.05);
     } // end method getrestockingFee   
     // Inventory value + restocking fee
     public double getinventoryValue()
        return super.getinventoryValue() + (super.getunitPrice() * 0.05);
     // String representation
     public String toString()
        StringBuffer sb = new StringBuffer();
          sb.append("DVD Genre:   \t").append(genre).append("\n");
          sb.append("Restocking fee:   \t").append(String.format("$%.2f%n", getrestockingFee()));
          sb.append(super.toString());
          return sb.toString();
} // end class
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.*;
public class DVD6Test
     static int itemDisplay = 0; // ActionEvent variable 
     // main method begins execution of Java application  
   public static void main ( String args[] )
          double total = 0; // variable to get entire inventory value
          JPanel bttnJPanel; // panel to hold buttons
          JLabel label; // JLabel for company logo
          // instantiate object     
      final DVDs6[] a = new DVDs6[5];
      a[0] = new DVDs6("Action/Drama" , 041, "Rocky", 20, 15.00);
      a[1] = new DVDs6("Action" , 006, "Braveheart", 20, 20.00);
      a[2] = new DVDs6("Action" , 001, "Armageddon", 10, 10.00);
      a[3] = new DVDs6("Action" , 060, "Scarface", 15, 18.00);
      a[4] = new DVDs6("Action" , 021, "Goodfellas", 5, 15.00);
      DVDs6 temp[] = new DVDs6[1];
      // sort
      for (int j = 0; j < a.length - 1; j++)
         for (int k = 0; k < a.length - 1; k++)
            if (a[k].getitemName().compareToIgnoreCase(a[k+1].getitemName()) > 0 )
               temp[0] = a[k];
               a[k] = a[k+1];
               a[k+1] = temp[0];
            } // end if
         } // end for
      } // end for
          // value of entire inventory
          for (int i = 0; i < a.length; i++)
                    total += a.getinventoryValue();
          // setup buttons
          JButton firstBtn = new JButton("First"); // button to display first inventory item
          JButton prevBtn = new JButton("Previous"); // button to display previous inventory item
          JButton nextBtn = new JButton("Next"); // button to display next inventory item
          JButton lastBtn = new JButton("Last"); // button to display last inventory item
          JButton addBtn = new JButton("Add"); // button to add item to inventory
          JButton delBtn = new JButton("Delete"); // button to delete item from inventory
          JButton modBtn = new JButton("Modify"); // button to modify DVD item
          JButton saveBtn = new JButton("Save"); // button to save inventory to a .dat file
          JButton srchBtn = new JButton("Search"); // button to search for item by name
          // create and setup panel to hold buttons
          bttnJPanel = new JPanel();
          bttnJPanel.setLayout(new GridLayout(1, 4));
          bttnJPanel.add(firstBtn);
          bttnJPanel.add(prevBtn);
          bttnJPanel.add(nextBtn);
          bttnJPanel.add(lastBtn);
          bttnJPanel.add(addBtn);
          bttnJPanel.add(delBtn);
          bttnJPanel.add(modBtn);
          bttnJPanel.add(saveBtn);
          bttnJPanel.add(srchBtn);
          //JLabel constructor
Icon logo = new ImageIcon("C:/logo.jpg"); // load graphic
label = new JLabel(logo); // create logo label
label.setText("Java Solutions Inc."); // set company name          
          // text area and frame setup for product display
          final JTextArea textArea;      
          textArea = new JTextArea(a[0] + "\n");           
          textArea.append("\nValue of entire inventory: " + new java.text.DecimalFormat("$0.00").format(total) + "\n\n");
          textArea.setEditable(false); // uneditable text
          JFrame dvdFrame = new JFrame(); // JFrame container
          dvdFrame.setLayout(new BorderLayout()); // set layout
          dvdFrame.getContentPane().add(new JScrollPane(textArea), BorderLayout.CENTER); // add text area to frame
          dvdFrame.getContentPane().add(bttnJPanel, BorderLayout.SOUTH); // adds buttons to frame
          dvdFrame.getContentPane().add(label, BorderLayout.NORTH); // add company logo to JFrame
          dvdFrame.setTitle("DVD Inventory"); // title of frame
          dvdFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // terminate upon close
          dvdFrame.setSize(800, 575); // set size
          dvdFrame.setLocationRelativeTo(null); // set location
          dvdFrame.setVisible(true); // display the window     
     // inner class to handle button events
firstBtn.addActionListener(new ActionListener() // register event handler
public void actionPerformed(ActionEvent event) // process button event
itemDisplay = 0;
textArea.setText(a[itemDisplay] + "\n");
          prevBtn.addActionListener(new ActionListener() // register event handler
public void actionPerformed(ActionEvent event) // process button event
               --itemDisplay;
                    if (itemDisplay < 0)
                    itemDisplay = (itemDisplay + a.length) % a.length;
                    textArea.setText(a[itemDisplay]+"\n");
          nextBtn.addActionListener(new ActionListener() // register event handler
          public void actionPerformed(ActionEvent event) // process button event
                    itemDisplay++;
                    if (itemDisplay >= a.length)
                    itemDisplay = (itemDisplay) % a.length;
                    textArea.setText(a[itemDisplay]+"\n");     
          lastBtn.addActionListener(new ActionListener() // register event handler
          public void actionPerformed(ActionEvent event) // process button event
               itemDisplay = a.length-1;
                    textArea.setText(a[itemDisplay]+"\n");
          addBtn.addActionListener(new ActionListener() // register event handler
          public void actionPerformed(ActionEvent event) // process button event
                    DVDs6[] as = new DVDs6[a.length + 1]; // increase array length
                    textArea.setText(new String());
     } // end method main          
} // end class

Answer 1

check this link,
http://www.java2s.com/Tutorial/Java/0140__Collections/0160__ArrayList.htm
U have lot of collections. always user like this
List user=new ArrayList();
user.add("username");
This code helps u to make changes in future. In future, if u want to change from ArrayList to Vector then u can just easily make a modification like this.
List user=new Vector();
user.add("username");
need to make changes only in the declaration part.