How to use Java Extends Keyword in Graphql

[KushagraBindal]

I am new to GraphQL and so tried to search on Google but couldn't found any reasonable solution of my query.

I have two class Foo and Boo.

public class Foo{
String a;
}
public class Foo extends Boo{
String b;
}

Boo will be my output object in .graphqls

type getBoo : Boo

type Boo{
b:String
}

I am able to get the response of Boo in this. But if I wanted to get the a also as the output of above query then how can we define the type and graphqls.