Adding objects to an arraylist using object elements

Question

I am trying to add objects to my arraylist with which I can then implement a few methods referencing an element of the object. I have two classes Balloons and MyPark (both implement other interfaces but that's irrelavant). In the balloon class there is:

public class Balloons implements Balloon { private int area; private int position; public void Balloon(int area, int position) { this.area = area; this.position = position; } @Override public int getArea() { return area; } }

And in the MyPark I have created my Arraylist of balloons:

import java.util.*; public class MyPark implements Park { public Balloons balloon = new Balloons; public ArrayList <Balloon> a = new ArrayList <Balloon>(); public int index; @Override public void addBalloon (int barea){ a.add(new Balloons (barea, index)); } }

But obviously this isn't the way to do it. Any suggestions? I also want to be able to eventually sort the list by area......

public class Balloons implements Balloon { public void Balloon(...: are you engaged in an obfuscation contest or what? Don't use the same name for everything. And respect the Java naming conventions. — JB Nizet
– JB Nizet, Commented Nov 3, 2013 at 15:30
Noted. I have been told about that before by my professor. Bit of a nasty habit sorry. — user2950071
– user2950071, Commented Nov 3, 2013 at 15:46

Bernhard Barker · Accepted Answer · 2013-11-03 15:34:17Z

public void Balloon(int area, int position) isn't a constructor, it's a method - presumably you want it to be a constructor.

To make it a constructor, it should have the same name as your class (Balloons, not Balloon) and you should remove void.

public Balloons(int area, int position)

To sort the list, you basically have two options:

Use the sort method that takes a Comparator.
Have your Balloons class implement Comparable and just use the normal sort.

This fixed the problem I had with adding an object to the array thank you. How would I then retrieve the area of the balloon from a specified position in the array?

upog · Accepted Answer · 2013-11-03 15:35:20Z

you can you comparator to sort your list

Collections.sort(SortList, new Comparator<Balloon>(){ public int compare(Balloon b1, Balloon b2) { return b1.area- b2.area; } });

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