New to Graphics, trying to display array output in a single window

Question

I am trying to figure out how to use the GUI components of JAVA.
What I am trying to do is take my packaged array output and list it in a single window. All that ever prints is last array data set. The last keeps overwritting the previous. How do I keep the previous data shown while listing the next in the array?
Below are my three classes. The Frame Class is the class containing the display method. It is called near the bottom of the Product Class.
Product.java
// Inventory Program Part 4
/* This program will store multiple entries
for office supplies, give the inventory value,
sort the data by Product Name,
and output the results using a GUI */
import javax.swing.text.JTextComponent;
import javax.swing.JLabel;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JOptionPane; //Uses class JOptionPane
import java.util.Scanner; //Uses class Scanner
import java.util.Arrays; //Uses class Arrays
public class Product
     private String productBrand[]; // Declares the array
     public void setProductBrand( String brand[] ) // Declare setProductBrand method
          productBrand = brand; // stores the productbrand
     } // End setProductBrand method
     public String getProductBrand( int counter )  // Declares getProductBrand method
          return productBrand[ counter ]; // Returns data using counter to define the element
     } // End method getProductBrand
     public double restockingFee( double value ) // Declares restocking Fee method
          double fee = 0; // Declares variable fee
          fee = value * 0.05; // Calculates the sum of values
          return fee;  // Returns the restocking fee
     } // End method restockingFee     
     public String inventoryValue( double value[] , int number, String name[] ) // Declares inventoryValue method
          OfficeSupplies myOfficeSupplies = new OfficeSupplies();  //Creates OfficeSupplies Object
          Product myProduct = new Product();
          double total = 0; // Declares variable total
          for ( int counter = 0; counter < number ; counter++ )
               total += ( value[ counter ] + myProduct.restockingFee( value[ counter ] ) ); // Calculates the sum of values
                    return String.format( "%s$%.2f", "Total Inventory Value: " , total );  // Returns the total value
     } // End method inventoryValue
     // main method begins execution
     public static void main( String args[] )
          Scanner input = new Scanner( System.in ); //Creates Scanner object to input from command window
          Product myProduct = new Product(); //Creates Product object
          OfficeSupplies myOfficeSupplies = new OfficeSupplies();  //Creates OfficeSupplies Object          
          //Prompt for maxNumber using JOptionPane
          String stringMaxNumber =
               JOptionPane.showInputDialog( "Enter the number of products you wish to enter" );
          int maxNumber = Integer.parseInt( stringMaxNumber );     
          String prodName[] = new String[ maxNumber ]; // Declares prodName array
          int numberUnits[] = new int[ maxNumber ]; // Declares maxNumber array          
          float unitPrice[] = new float[ maxNumber ]; // Declares unitPrice array
          double value[] = new double[ maxNumber ]; // Declares value array
          String brand[] = new String [ maxNumber ]; // Declares brand array
          String stringNumberUnits[] = new String [ maxNumber]; // Declares array
          String stringUnitPrice[] = new String [ maxNumber ]; // Declares array
          int productNumber[] = new int[ maxNumber ]; // Declares array
          for ( int counter = 0; counter < maxNumber; counter++ ) // For loop for the number of products to enter
               productNumber[ counter ] = counter;
               myOfficeSupplies.setProductNumber( productNumber ); // Sends the Product name to method setProductNumber                         
               //Prompt for product name using JOptionPane
               prodName[ counter ] =
                    JOptionPane.showInputDialog( "Enter the Product Name" );
               myOfficeSupplies.setProductName( prodName ); // Sends the Product name to method setProductName
               //Prompt for brand name using JOptionPane
               brand[ counter ] =
                    JOptionPane.showInputDialog( "Enter the Brand name of the Product" );
               myProduct.setProductBrand( brand ); // Sends the Brand name to method setProductBrand
               //Prompt for number of units using JOptionPane
               stringNumberUnits[ counter ] =
                    JOptionPane.showInputDialog( "Enter the Number of Units" );
               numberUnits[ counter ] = Integer.parseInt( stringNumberUnits[ counter ] );
               myOfficeSupplies.setNumberUnits( numberUnits ); // Sends the Number Units to the method setNumberUnits
               //Prompt for unit price using JOptionPane
               stringUnitPrice[ counter ] =
                    JOptionPane.showInputDialog( "Enter the Unit Price" );
               unitPrice[ counter ] = Float.parseFloat( stringUnitPrice[ counter ]);
               myOfficeSupplies.setUnitPrice( unitPrice ); // Sends the Unit Price to the method setUnitPrice
               value[ counter ] = numberUnits[ counter ] * unitPrice[ counter ]; // Calculates value for each item
               myOfficeSupplies.setProductValue( value ); // Sends the product value to the method setProductValue
          Arrays.sort( prodName, String.CASE_INSENSITIVE_ORDER ); // Calls method sort from Class Arrays
               Frame myFrame = new Frame();
               myFrame.displayData( myProduct, myOfficeSupplies, maxNumber );
          // Outputs Total Inventory Value using a message dialog box
          JOptionPane.showMessageDialog( null, myProduct.inventoryValue( value, maxNumber, prodName ),
               "Total Inventory Value", JOptionPane.PLAIN_MESSAGE );
     } // End method main
} // end class ProductOfficeSupplies.java ----> This is the data container
// Inventory Program Part 4
/* Stores the array values */
public class OfficeSupplies // Declaration for class Payroll
     private int productNumber[];
     public void setProductNumber( int number[] ) // Declare setProductNumber method
          productNumber = number; // stores the product number
     } // End setProductNumber method
     public int getProductNumber( int counter )  // Declares getProductNumber method
          return productNumber[ counter ];
     } // End method getProductNumber
     private String productName[];
     public void setProductName( String name[] ) // Declare setProductName method
          productName = name; // stores the Product name
     } // End setProductName method
     public String getProductName( int counter )  // Declares getProductName method
          return productName[ counter ];
     } // End method getProductName
     private int numberUnits[];
     public void setNumberUnits( int units[] ) // Declare setNumberUnits method
          numberUnits = units; // stores the number of units
     } // End setNumberUnits method
     public int getNumberUnits( int counter )  // Declares getNumberUnits method
          return numberUnits[ counter ];
     } // End method getNumberUnits
     private float unitPrice[];
     public void setUnitPrice( float price[] ) // Declare setUnitPrice method
          unitPrice = price; // stores the unit price
     } // End setUnitPrice method
     public float getUnitPrice( int counter )  // Declares getUnitPrice method
          return unitPrice [ counter ];
     } // End method getUnitPrice
     private double productValue[];
     public void setProductValue( double value[] ) // Declare setProductValue method
          productValue = value; // stores the product value
     } // End setProductValue method
     public double getProductValue( int counter )  // Declares getProductValue method
          return productValue[ counter ];
     } // End method getProductValue
} // end class OfficeSuppliesFrame.java ------> Contains the display method
import java.awt.Color;
import javax.swing.text.JTextComponent;
import javax.swing.JLabel;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JOptionPane; //Uses class JOptionPane
public class Frame extends JFrame
     public Frame() //Method declaration
          super( "Products" );
     } // end frame constructor
     public void displayData( Product myProduct, OfficeSupplies myOfficeSupplies, int maxNumber )
          //Here I attempted to use an array to output all of the array data in a single window
//          JTextArea myTextArea[] = new JTextArea[ maxNumber ]; // Declares myTextArea array to display output
          JTextArea myTextArea = new JTextArea(); // textarea to display output
          // For loop to display data array in a single Window
          for ( int counter = 0; counter < maxNumber; counter++ )  // Loop for displaying each product
//               myTextArea[ counter ].setText( packageData( myProduct, myOfficeSupplies, counter ) + "\n" );
//                add( myTextArea[ counter ] ); // add textarea to JFrame
               myTextArea.setText( packageData( myProduct, myOfficeSupplies, counter ) + "\n" );
               add( myTextArea ); // add textarea to JFrame
          } // End For Loop
          setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          setSize( 450, maxNumber*400 ); // set frame size
          setVisible( true ); // display frame
     public String packageData( Product myProduct, OfficeSupplies myOfficeSupplies, int counter ) // Method for formatting output
          return String.format( "%s: %d\n%s: %s\n%s: %s\n%s: %s\n%s: $%.2f\n%s: $%.2f\n%s: $%.2f\n%s: $%.2f",
          "Product Number", myOfficeSupplies.getProductNumber( counter ),
          "Product Name", myOfficeSupplies.getProductName( counter ),
          "Product Brand",myProduct.getProductBrand( counter ),
          "Number of Units in stock", myOfficeSupplies.getNumberUnits( counter ),
          "Price per Unit", myOfficeSupplies.getUnitPrice( counter ),
          "Total Value of Item in Stock is", myOfficeSupplies.getProductValue( counter ),
          "Restock charge this product is", myProduct.restockingFee( myOfficeSupplies.getProductValue( counter ) ),
          "Total Value of Inventory plus restocking fee", myOfficeSupplies.getProductValue( counter )+
               myProduct.restockingFee( myOfficeSupplies.getProductValue( counter ) ) );
     } // end method packageData
}

Answer 1

Lets pretend that your assignment was to manage a list of employees of a store, and that each employee is identified by their name, position, and hourly wage. If you created a program along the lines of your current product program, I picture you creating three separate ArrayLists (or arrays), one for each variable, something like this:
import java.util.ArrayList;
public class MyEmployees1
    private ArrayList<String> names = new ArrayList<String>();
    private ArrayList<String> positions = new ArrayList<String>();
    private ArrayList<Double> hourlyWages = new ArrayList<Double>();
    public void add(String name, String position, double wage)
        names.add(name);
        positions.add( position);
        hourlyWages.add(wage);
    public void removed()
        // TODO: I am nervous about trying to manage this!
    //.......... more
}This program tries to manage three separate parallel arrays (arraylists actually). They are parallel because the 3rd item in the names list corresponds to the 3rd item in the positions list and also the hourlywages list. If I wanted to delete data, I'd have to be very careful to delete the correct item in all three lists. If I tried to sort one list, I'd have to sort the other two in exactly the same way. It is extremely easy to mess this sort of program up.
Now lets look at a different approach. Say we created a MyEmployee class that contains the employee's name, position, and wage, along with the appropriate constructors, getters, setters, toString method, etc... something like so:
import java.text.NumberFormat;
public class MyEmployee
    private String name;
    private String position;
    private double hourlyWage;
    public MyEmployee(String name, String position, double hourlyWage)
        this.name = name;
        this.position = position;
        this.hourlyWage = hourlyWage;
    public String getName()
        return name;
    public String getPosition()
        return position;
    public double getHourlyWage()
        return hourlyWage;
    public String toString()
        // don't worry about these methods here.  They're just to make the output look nice
        NumberFormat currency = NumberFormat.getCurrencyInstance();
        return String.format("Name: %-15s    Position: %-15s    Wage: %s",
                name, position, currency.format(hourlyWage));
}Now I can create a MyEmployees2 class that holds a single list of MyEmployee objects, like so:
import java.util.ArrayList;
public class MyEmployees2
    private ArrayList<MyEmployee> employeeList = new ArrayList<MyEmployee>();
    public boolean add(MyEmployee employee)
        return employeeList.add(employee);
    public boolean remove(MyEmployee employee)
        return employeeList.remove(employee);
    public void display()
        for (MyEmployee employee : employeeList)
            System.out.println(employee);
    public static void main(String[] args)
        MyEmployees2 empl2 = new MyEmployees2();
        empl2.add(new MyEmployee("John Smith", "Salesman", 20));
        empl2.add(new MyEmployee("Jane Smyth", "Salesman", 25));
        empl2.add(new MyEmployee("Fred Flinstone", "Janitor", 15));
        empl2.add(new MyEmployee("Barney Rubble", "Supervisor", 35));
        empl2.add(new MyEmployee("Mr. Spacely", "The Big Boss", 45));
        empl2.display();
}Now if I want to add an Employee, I only add to one list. Same if I want to remove, only one list, and of course, the same for sorting. It is much safer and easier to do things this way. Make sense?