Question

Let’s say I have this simple class structure:

Vehicle
|-- Bus
`-- Car

Bus and Car extends Vehicle

I have List<Vehicle>. How can I get only buses or cars? I would like to avoid instanceof operator. Do I have to use Visitor pattern or is there any simpler solution?

Answer 1

Well something will need to use instanceof or an equivalent (such as Class.isInstance).

Guava has a method which does exactly this though: Iterables.filter. So you could use:

List<Bus> buses = Lists.newArrayList(Iterables.filter(vehicles, Bus.class));