Java IIFE and shared scoped variables

Test.java

interface Function {
    Object call(Object argument);
}

interface A {
    void   set(String object);
    String get();
}

interface B {
    void   set(String object);
    String get();
}

class Pair {
    A a; B b;
    Pair(A a, B b) {
        this.a = a;
        this.b = b;
    }
    void puts(java.io.PrintStream stream) {
        stream.println(String.format("a:%s, b:%s", a.get(), b.get()));
    }
}

public class Test {
    public static void main(String[] args) {
        Pair pair = pair("foo");
        pair.puts(System.out);
        pair.a.set("bar");
        pair.puts(System.out);
        pair.b.set("baz");
        pair.puts(System.out);
    }

    private static Pair pair(String string) {
        return (Pair)(new Function() {

            String shared;

            public Object call(Object argument) {

                shared = (String) argument;

                A a = new A() {
                    public void set(String object) {
                        shared = object;
                    }
                    public String get() {
                        return shared;
                    }
                };

                B b = new B() {
                    public void set(String object) {
                        shared = object;
                    }
                    public String get() {
                        return shared;
                    }
                };

                return new Pair(a, b);
            }
        }).call(string);
    }
}

Test.java output

> javac Test.java && java Test

a:foo, b:foo
a:bar, b:bar
a:baz, b:baz