public class Test {

    static ThreadLocal<iA> cache = new ThreadLocal<iA>();
    
    static interface iA {}
    static class B {
        public B(iA a) {}
    }


    static class MyClass implements iA {}

    static class MyB extends B {
        private iA a;

        public MyB() {
            super(set(new MyClass()));
            synchronized (this){
                this.a = cache.get();
                cache.remove();
            }
        }

        private static iA set(MyClass a) {
            cache.set(a);
            return a;
        }
    }

}