Question

Hello I am creating a application that uses arraylists ( practice purposes not real app )
I have created a method that gives me the answer of a math but only if the arraylist contains no object. for some reason I always see the else in my if/else construction.

Here is how I check if the array list contains objects

public void sluitRegistratie() {

    aantalBezoekers = bezoeker.size();

    if(!(aantalBezoekers >= 0)) {

        String str = "Gemiddelde tijd bezoekers: " + (gesommeerdeTijd / aantalBezoekers);

        JOptionPane.showMessageDialog(null, str);
    }
    else {
        JOptionPane.showMessageDialog(null, "Bezoekers zijn nog niet weg");
    }

}

Answer 1

if(!(aantalBezoekers >= 0)) {

Basically means that only execute if when aantalBezoekers is NOT greater than zero.

If you want to check if your list is of size zero use something like below:

if(bezoeker.size()>0){
  System.out.pritnln("bezoeker is greater than zero " + bezoeker..size());
 } 
 else {
  System.out.pritnln("Mahn, my bezoeker is Empty " + bezoeker..size());
  }

you could also simply use ArrayList.isEmpty() method to check if an arraylist is empty.

if(bezoeker.isEmpty()) {