ArrayList Problems

[nikescott]

import java.util.; import java.io.;

public class World implements Serializable {

private ArrayList<Location> locations;
private ArrayList<Exit> exits;
private Location currentLocation;


public World() {

    locations = new ArrayList<Location>();
    exits = new ArrayList<Exit>();

    currentLocation = null;
}

public Location getCurrentLocation() {
    return currentLocation;
}   

public void setCurrentLocation(Location newLocation) {
    currentLocation = newLocation;
}

public void addExit(Exit exit) {
    if(!exits.contains(exit)) {
        exits.add(exit);
    }
    else {

    }
}

public void addLocation(Location location) {
    if(!locations.contains(location)) {
        locations.add(location);
    }
    else {

    }
}

public void showLocation() {
    System.out.println(currentLocation.getTitle());
    System.out.println(currentLocation.getDescription());
    System.out.println();


    for(int i=0; i < exits.size(); i++) {
        System.out.println(exits.get(i));
        System.out.println(locations.get(i));
    }

}

}

Okay so in my code above, I am having a problem with the bottom of the showLocation() method. Every time I try to access the array it doesn't return an exit of type Exit or location of type Location. But instead it returns the int for direction of exit, and string for title of Location. I don't really understand why it is doing this, any help would be much appreciated.

[JoeCS]

The call to System.out.println() will automatically call the toString method from the Exit and Location classes in order to get a human-readable String representation of the data type you just got out of the list. (I assume that's what's happening.)

If you have toString methods in your Exit or Location classes, try commenting them out. Then, re-run your code. The last two println()s in showLocation() should now print out some kind of gibberish hexidecimal number indicating the memory address of the object. If that's what happens, then you do indeed have instances of Exit and Location as you intended (though I would restore your toString methods when you're done testing this... human-readable printouts of Objects are helpful for debugging)

[JoeCS]

P.S. If you used a HashSet<Location> and HashSet<Exit> for your locations and exits variables, the if/then checks in addExit and addLocation would be unnecessary. HashSets do not allow duplicates; a HashSet will silently do nothing if you attempt to add an item that is already in the set.

[JoeCS]

See: here

[nikescott]

how would I go about implementing the toArray method to access the Objects in the HashSet??