Simplification of Android's AsyncTask using functionaljava

Async.java

import android.app.Activity;
import android.os.AsyncTask;

import fj.F;
import fj.function.Effect1;

public class Async<A, B> extends AsyncTask<A, Void, B> {

    private final F<A, B> f;
    private Effect1<B> e = new Effect1<B>() {
        @Override
        public void f(B b) {
        }
    };

    public Async(F<A, B> f) {
        this.f = f;
    }

    @Override
    protected void onPostExecute(B b) {
        e.f(b);
    }

    @Override
    protected final B doInBackground(A... params) {
        return f.f(params[0]);
    }

    public <C> Async<A, C> andThen(final F<B, C> g) {
        return new Async<>(new F<A,C>() {
            @Override
            public C f(A a) {
                return g.f(f.f(a));
            }
        });
    }

    public Async<A, B> andFinally(final Effect1<B> effect) {
        this.e = effect;
        return this;
    }

    public Async<A, B> andFinallyInTheUI(final Activity a, final Effect1<B> effect) {
        this.e = new Effect1<B>() {
            @Override
            public void f(final B b) {
                a.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        effect.f(b);
                    }
                });
            }
        };
        return this;
    }

}