I would like to declare an enum Direction, that has a method that returns the opposite direction (the following is not syntactically correct, i.e, enums cannot be instantiat
Yes we do it all the time. You return a static instance rather than a new Object
static Direction getOppositeDirection(Direction d){
Direction result = null;
if (d != null){
int newCode = -d.getCode();
for (Direction direction : Direction.values()){
if (d.getCode() == newCode){
result = direction;
}
}
}
return result;
}