java - 组合和泛型

Question

我正在尝试解决这种“组合 + 泛型”的情况，并使 PostCompany.send(msg) 与传递/注入(inject)类的类型兼容。

由于 Fexed 的发送方法需要字符串作为参数，而 FeexPlus 需要整数，所以我可以更改什么以允许 Fedex 和 FedexPlus 在 PostCompany 类中用作通用类型？

interface Poster<T> {
    void send(T msg);
}

class Fedex implements Poster<String> {

    @Override
    public void send(String msg) {
        // do something
    }
}

class FedexPlus implements Poster<Integer> {

    @Override
    public void send(Integer msg) {
        // do something
    }
}

class PostCompany<P extends Poster> {

    private final P poster;

    public PostCompany(P poster) {
        this.poster = poster;
    }

    public void send(??? msg) { // <-- Here 
        this.poster.send(msg);
    }
}

Answer 1

你错过了海报的类型

class PostCompany<T, P extends Poster<T>> {
    public void send(T msg) { // <-- Here 
        this.poster.send(msg);
    }
}

但实际上只输入对象的类型会更好

class PostCompany<T> {

    private final Poster<T> poster;

    public PostCompany(Poster<T> poster) {
        this.poster = poster;
    }

    public void send(T msg) { // <-- Here 
        this.poster.send(msg);
    }
}

因为您将始终使用 Poster 的接口(interface)方法