[Jesdisciple]

What's the result (output or compile/runtime error/exception) of this?

Code:

class B {
    String value;
    B(String value){
        this.value = value;
    }
    public String toString(){
        return value;
    }
    static void test(A<? extends Object> a){
        a.set(new B("foo"));
        System.out.println(a.get());
    }
    public static void main(String[] args){
        A<B> a = new A<B>();
        test(a);
    }
}
class A<T> {
    private T o;
    void set(T o){
        this.o = o;
    }
    T get(){
        return o;
    }
}