Question

I have a strong python background and a total newbie with Java, so I try to do things in Pythonic way in java and end up struggling. Currently I have a problem to figure out how to do store objects, indexed by coordinates, so that they are iterable. I could create an 2-dimensional array of the objects, but I’m afraid that would take a lot of memory AND I would have to iterate over all the indexes every time (when I only want to do it occasionally) to get all the objects.

In python, I would use a dictionary with tuples as keys, but looks like such thing is not possible in Java.

E.g.

class bar()
    pass

bar1 = bar()
bar2 = bar()
# etc

foo = { (0,1): bar1, (100,30): bar2 }

for x in foo.values():
    do_something()

Answer 1

1. Do not hesitate for memory (not now, maybe later)

2. The Java equivalent “class” is a Map. As Map is an interface take a HashMap class for the moment.

3. Map has a method values() to get all values of the map.

4. As your key is not scalar you may create your own Coordinates class. Be aware to override equals() and hashCode().