Java 回调

public interface CallBack {

    public void solve(String result);

}

public class Wang implements CallBack {

    public String result;
    private Li li;

    public Wang(Li li) {
        this.li = li;
    }

    @Override
    public void solve(String result) {
        this.result = result;
        System.out.println("the result is : -->" + result);
    }

    public void askQuestion(final String question) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                li.executeMessage(Wang.this, question);
            }
        }).start();

        play();
    }

    public void play() {
        System.out.println("I am go  shopping.");
    }
}

public class Li {

    public void executeMessage(CallBack callBack, String question) {
        System.out.println("xiao wang's question? -->" + question);
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        String result = "the answer is 2";
        callBack.solve(result);
    }

}

public class Client {

    public static void main(String []args) {

        Li li = new Li();
        Wang wang = new Wang(li);
        wang.askQuestion("1 + 1 = ?");

        System.out.println("after shopoing : ->" + wang.result);

    }

}