Question

Im using a list of objects (Area) in java, which i defined as so:

    public static List<Area> areaList = new ArrayList<Area>();

I add content to my list as so:

    areaList.add(new Area(px, py, pz, radius, wl));

then i access the list, to check each of the Area’s within it like so:

for (int i = 1; i < areaList.size(); i++) {
    System.out.println(areaList.get(i).somevariable));
}

(ignore the ‘somevariable’ and i also didnt use println(), this was for example, the way i accessed using:

areaList.get(i)

is whats important here)

But it returns all the objects inside the List as having the same values – that of the last one accessed.

Can anyone tell me where im going wrong?

Answer 1

I looked through your uploaded code and found the error.

You declared every field in the class Area as static:

public class Area {
    public static int posx;
    public static int posy;
    public static int posz;
}

The fields are therefore equals for all instances, because there is just one posx field for the class Area (read this question and the answers for details). Because of this every write to, e. g., posx overrides the old value. Remove the static keyword and then all instances of the class Area have their own instance variable.

You should also think about making them private and provide getter and setter methods.

I haven’t looked in detail through your code, but there are several places where you used static variables. You should revisit this.