Displaying an array list item by item in GUI

Question

I am trying to display an array list with multiple types, item by item. So I suppose this is a two part question. First, how do I convert this array list to a string in order to print it out (I am not sure how important this is). And second how do I move from item to item using an ActionEvent.

My Array list has String, int, int, double. I have already figured out how to format the double to be a string, however how do I do this for the entire arraylist? The arraylist is already sorted in order to display it in alphabetical order.

Below is my array list and the sorting

inventory.add(new inventoryItem("Pencil", 1111, 50, .25));
    inventory.add(new inventoryItem("Pen", 2222, 50, 1.00));
    inventory.add(new inventoryItem("Marker", 3333, 5, 2.00));
    inventory.add(new inventoryItem("Notebook", 4444, 10, 2.50));
    inventory.add(new officeSupplyItem("Mechanical Pencil", 1112, 25, .50));
    inventory.add(new officeSupplyItem("Lead Pencil", 1113, 25, .25));
    inventory.add(new officeSupplyItem("Blue Pen", 2221, 25, 1.00));
    inventory.add(new officeSupplyItem("Black Pen", 2223, 5, 1.00));
    inventory.add(new officeSupplyItem("Red Pen", 2224, 20, 1.00));
    inventory.add(new officeSupplyItem("Steno Notebook", 4441, 5, 2.50));
    inventory.add(new officeSupplyItem("Legal Pad", 4442, 5, 2.50));

    inventory = sortInventory(inventory);
    for (int i = 0; i < inventory.size(); i++) {
        inventory.get(i).output(outputText);
    }
    inventoryTotal(inventory, outputText);
    sortInventory(inventory);
}

static ArrayList sortInventory(ArrayList<inventoryItem> unsorted) {
    ArrayList<inventoryItem> sorted = new ArrayList<>(); //create new array list to sort
    inventoryItem alpha = null;
    int lowestIndex = -1;
    while (unsorted.size() > 0) { //while my unsorted array is less than 0 do the following
        for (int i = 0; i < unsorted.size(); i++) { //increment through 
            if (alpha == null) {
                alpha = unsorted.get(i); //get the next line in the inventoryItem array
                lowestIndex = i;
            } else if (unsorted.get(i).itemName.compareToIgnoreCase(alpha.itemName) < 0) { //compare items to determine which has a higher value
                alpha = unsorted.get(i);
                lowestIndex = i;
            }

        }
        sorted.add(alpha); //reset the index so it will loop until there are no more items in the unsorted array
        unsorted.remove(lowestIndex);
        alpha = null;
        lowestIndex = -1;
    }
    return sorted; //return the sorted arraylist

}

My buttons are set up like this

 nextButton.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            outputText.append("\n this should move me forward in the list");

        }
    });
    previousButton.addActionListener(new ActionListener(){

        @Override
        public void actionPerformed(ActionEvent e) {
            outputText.append("\n this should move me backward in the list");

        }
    });

    exitButton.addActionListener(new ActionListener() { //setup listener for the exit button

        @Override
        public void actionPerformed(ActionEvent ae) {
            System.exit(0); //once the exit button is pressed, exit the program

        }

    });
    thePanel.add(nextButton); //move forward in the arraylist
    thePanel.add(previousButton); //move to previous item in the arraylist
    thePanel.add(exitButton); //add exit button to the panel

Any help would be greatly appreciated.

It is really two parts. I think that I have to use a list iterator in order to move through my arraylist item by item in both directions, forward and backward, and to do so it should be in string correct? So my first question is how do I convert my arraylist to one string per line? The second question is how do I use the list Iterator in conjunction with gui buttons to move through the list? — kerinr
– kerinr, Commented Nov 27, 2013 at 3:59
"convert my arraylist to one string " iterate over it and call toString() on each element — vandale
– vandale, Commented Nov 27, 2013 at 4:00

Paul Samsotha · Accepted Answer · 2013-11-27 04:31:24Z

2

Object#toString() should be overridden in InventoryItem to get your desired display result. Example:

public class InventoryItem {
    String type;
    int id;
    int quantity;
    double cost;

    public InventoryItem(String type, int id, int quantity, double cost){
        this.type = type;
        this.id = id;
        this.quantity = quantity;
        this.cost = cost;
    }

    // override toString
    @Override
    public void toString(){
        return "Type: " + type
               + ", Id: " + id
               + ", Qty: " + quantity
               + ", Cost: " + cost;
    }
}

When you print an InventoryItem it will look something like this

Output: Type: pencil, Id: 1111, Qty: 50, Cost: .25

To move from index to index, you can keep a currentIndex variable

int currentIndex = 0;

ArrayList<InventoryItem> inventory = new ArraList<>();

previousButton.addActionListener(new ActionListener(){

    @Override
    public void actionPerformed(ActionEvent e) {
        if (currentIndex > 0) {
            currentIndex--;

            outputText.append(inventory.get(currentIndex) + "\n");
        }
    }
});

Note: consider Java naming conventions. Class names should begin with capital letters

edited Nov 27, 2013 at 4:31

answered Nov 27, 2013 at 4:13

Paul Samsotha

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6 Comments

kerinr Over a year ago

This seems to be working great, with the exception of not being able to get the currentIndex working. I either get a problem with it being called from a static context or it cannot find the variable. Should it not go in the main class?

Paul Samsotha Over a year ago

Place it the same location you declared ArrayList<InventoryItem> inventory = new ArraList<>();. I'm not exactly how your code looks, but if the first doesn't work, try and make currentIndex static. Though it's hard to tell without seing your code is structured. If you're trying to call currentIndex from a static method, it should also be static.

Paul Samsotha Over a year ago

currentIndex should be within a global scope, if that helps at all.

kerinr Over a year ago

I have declared it in my public class Testing which is prior to my main - if that helps at all. I declared it private, but I am not sure that is right.

Paul Samsotha Over a year ago

What is not working? There may other problems in your code. For one, I see in your sortInventory() method, you are creating a new Arrayist instead of modify the original. Then you try an call it in a static way, (without assigning a variable to it and using that variable) sortInventory(inventory);. There could be multiple things wrong. It may not be the modifications you made from my suggestions.

|

Pratik Shelar · Accepted Answer · 2013-11-27 04:06:38Z

0

To display the properties of your objects you need to implement the 'toString()' merthod of your inventoryItem Object (Please note in JAVA class names should start with Capital Letter)
In the toString method you can create a string as you wish to be displayed like you can even concatenate property names. For e.g you can display it like this Item Name: Pen, Item Id: 1111 ..
Since you need to traverse forward and backward direction, you should consider using linkedlist or a doublylinkedlist collection.

answered Nov 27, 2013 at 4:06

Pratik Shelar

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