Is there a data structure in java can hold different type of objects? For example, if you need use Stack, the element in stack should be in the same type. What if I want a container has different objects inside it?
2 Answers
This sounds like a perfect opportunity for inheritance. Most broadly you could have a List of objects and any type of object can go in. More specifically if you need a list of vehicles you would possibly have the following:
interface Vehicle{
}
class Car implements Vehicle{
}
class Truck implements Vehicle{
}
List<Vehicle> list = new ArrayList<Vehicle>();
list.add(new Car());
list.add(new Truck());
7 Comments
user2372074
This sounds like a perfect example for re-heating my understanding on inheritance, thanks
Michael
Its a super useful concept and very important in java. Glad to help!
Compass
Good answer microsby0. For posterity's sake, you could also mention how we get the Car and the Truck back out using
instanceof. :)Michael
What do you mean "get the Car and Truck back out"?
Compass
@TheLostMind well, when he wants the
Airplane that will be invented 2 chapters down the road to fly() we're going to have some funny situations then :P |
Whatever data structure you are defining can just hold items Object since EVERY class implicitly inherits from Object. However this take a load on your memory be sure to find a way to handle Garbage collection.
E.g. List<Object> or HashMap<Object,Object> obj; or something of that sort.
Maybe if you know all the kinds of Objects that will be held in that data structure you can use the method getClass() within a switch statement to find out what class the Object belongs to. Hope this is of help to you. Please implement this solution only if there is no inheritance between the Objects you plan to use otherwise use @microsby0 's answer
1 Comment
Manny265
what I actually meant was items of type
Object take up alot of memory. It is useful to assign them to null when you are done with them so that they become eligible for Gcollection
Objectif you want it to hold anything, or use a parent class for all the objects you want to store. Then you can useinstanceofto process each individual element as intended.instanceofwould lead me to believe the design is potentially wonky.