Sorting Arraylist by an object variable

Question

Any ideas on how to apply Collections.sort method to sort my arraylist by priority of each grocItem object within the itemData ArrayList?

public class GroceryProgram {

    private final static int GROC_SIZE = 6;
    private final List<ItemData> itemData = new ArrayList<ItemData>();

    private void setUpList() {

        Scanner keyboard = new Scanner(System.in);

        for (int i = 0; i < GROC_SIZE; i++)  {

           System.out.print("\nEnter item name (" + i + ") : ");               
           String name = keyboard.next();

           System.out.print("\nEnter the price of item (" + i + ") : ");
           double cost = keyboard.nextDouble();

           System.out.print("\nEnter Priority Number (" + i + ") : ");
           int priority = keyboard.nextInt();

           ItemData grocItem = new ItemData(name, cost, priority);
           itemData.add(grocItem); // add grocery items to itemData ArrayList

           Collections.sort(grocItem);
           for (Int priority : priority) {
               System.out.println(integer);

Thomas W · Accepted Answer · 2013-07-20 05:20:22Z

2

Call sort() with a Comparator. For example, a Comparator in ascending-order of priority could look like this.

Collections.sort( items, new Comparator<ItemData>() {
    public int compare (ItemData o1, ItemData o2) {
        int comp = o1.getPriority() - o2.getPriority();
        return comp;
    }
});

PS: 'itemData' is bad variable naming -- it would refer to a single item, not a list. 'groceryItems', 'stockItems' or 'itemList' would be better.

Variable names should enable you to speak in meaningful, clear, concise English about your software.

Hope this helps.

answered Jul 20, 2013 at 5:20

Thomas W

14.2k4 gold badges64 silver badges77 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

sbrattla · Accepted Answer · 2013-07-20 05:19:30Z

0

Could you use Collections.sort(List list, Comparator c) to deal with this? You could simply do the following :

Collections.sort(itemData, new Comparator() {
  public int compare(Object o1, Object o2) {
    // Return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.
  }
}

answered Jul 20, 2013 at 5:19

sbrattla

5,4264 gold badges45 silver badges68 bronze badges

Comments

Mehul Joisar · Accepted Answer · 2013-07-20 05:49:18Z

0

You can use custom comparator as below:

Collections.sort(itemData ,new PriorityComparator());

        //print sorted arraylist,it will print the data in ascending order (low priority->high priority).feel free to modify if you want to go for descending order
        System.out.println(itemData );

PriorityComparator class definition:

private static class PriorityComparator implements Comparator{

    @Override
    public int compare(ItemData object1, ItemData object2) {
        return (object1.priority< object2.priority) ? -1: (object1.priority> object2.priority) ? 1:0 ;
    }

}

Reference:

how-to-sort-arraylist-in-java-example

I hope it will be helpful !!

answered Jul 20, 2013 at 5:49

Mehul Joisar

15.3k6 gold badges50 silver badges57 bronze badges

Collectives™ on Stack Overflow

Sorting Arraylist by an object variable

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related