Question

Class clazz = new Object(){}.getClass();

Why is this possible and what would it mean? Could someone please remind me?

For example:

public class Testing {
    public static void main(String[] args) {
        Class clazz = new Object(){}.getClass();
        System.out.println(clazz);
    }
}

The result is: class Testing$1

Answer 1

It creates an anonymous inner class subclassing Object. The main use I’ve seen with an empty body is in Guice, for TypeLiteral, where it’s used to capture generic type arguments:

key = new TypeLiteral<List<String>>() {};

This is useful because type erasure doesn’t apply to the superclass here, so Guice is able to get the List<String> part out, which can’t be expressed as a normal class literal.