/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
interface I<T> {
    T doStuff();
}
 
class A implements I<Void> {
    @Override
    public Void doStuff() {
        return null; // ничего другого вернуть нельзя (если не хитрить с рефлексией, конечно)
    }
}
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone {
	public static void main (String[] args) throws java.lang.Exception {
		A a = new A();
	}
}

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