When exactly do you need to import in java? - class

Question

The following unexpectedly compiled and ran without a problem:
import info.gridworld.actor.Actor;
import java.util.ArrayList;
public class ChameleonKid extends ChameleonCritter
{
public ArrayList<Actor> getActors()
{
ArrayList<Actor> actors = getGrid().getNeighbors(getLocation());
ArrayList<Actor> frontBack = new ArrayList<Actor>();
for(Actor i : actors)
if(getLocation().getDirectionToward(i.getLocation())==getDirection())
frontBack.add(i);
return frontBack;
}
}
The method getLocation() in the Actor class returns an instance of Location. And then I call the getDirectionToward() method of the Location class. getLocation().getDirectionToward(i.getLocation()). How does this work? I never imported the Location class. How am I able to work with it and call its methods? If that is how it works, when would I need to import a class? Only if I am instantiating it?
I am using Java 7.

Answer 1

Say you have two methods, one returning foo.Location and the other returning bar.Location (two completely different classes happening to have the same name, but in different packages - completely valid):
foo.Location getFooLocation();
bar.Location getBarLocation();
When you can both of these methods in the same class and chain some methods, you don't need an import:
if(getFooLocation().onlyInFoo()) {
//...
}
if(getBarLocation().onlyInBar()) {
//...
}
It works because the compiler is completely sure which version (from which package) of Location are you using and it knows where onlyInFoo() and onlyInBar are available.
But suppose you need a local variable:
Location location;
// much later
location = getFooLocation();
Now the compiler doesn't really know Location do you mean, so you must help him either by proceeding class name with package:
foo.Location location;
or by importing that class:
import foo.Location;
You should now ask: what if I want to have local variable of both foo.Location and bar.Location? Well, you can't import them both, obviously:
//WRONG
import foo.Location;
import bar.Location;
What you can do is again: either don't import at all and use fully qualified names:
foo.Location location1;
bar.Location location;
...or import just one location:
import foo.Location;
//...
Location location1; //foo.Location
bar.Location location2;

Answer 2

The reason why you don't need to import that class is because of the fact that you are not explicitly using that class. Actor is the one actually using the Location class locally. You are never holding a reference to the Location class and so, you are able to keep using it dynamically. However, if you wanted to hold a reference (eg Location l = getLocation();), you would have to import Location since the compiler has to link l with Location, but has no idea where to find it.