Assign subclasses to each array element (run-time type)

Question

I have a base class Building and subclasses House and School. I have declared an array of Building objects the following way. I am not sure how to assign subclasses to each array element (run time type).

Building[] House = new Building[3];
Building[] School = new School[2];

What issues are you running into? Are you getting compiler errors? — Whymarrh
– Whymarrh, Commented Mar 10, 2014 at 18:27
Java's convention is to use lowerCamelCase for variables and CamelCase for classes. Following these conventions will make the code easier to work with for all developers. — unholysampler
– unholysampler, Commented Mar 10, 2014 at 18:31
Is School a variable name or a class name? You're using it both different ways in the same statement. — ajb
– ajb, Commented Mar 10, 2014 at 18:32

Salah · Accepted Answer · 2014-03-10 18:27:47Z

2

You can use instanceof to determine the subclass

if (building instanceof House) {
    House[0] = building;
}

answered Mar 10, 2014 at 18:27

Salah

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eebbesen · Accepted Answer · 2014-03-10 18:32:22Z

1

I'm not sure if you are asking how to check types at runtime or to populate with types at runtime. If the latter then see @Salah's answer using instanceof. In particular, why the House array is being populated with Building objects while the School array is being populated with School objects is confusing me.

To assign:

Building[] house = new House[3];
Building[] school = new School[2];

You could also populate the array with Building objects and then use type checking when you need to down the road.

answered Mar 10, 2014 at 18:32

eebbesen

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