泛型中再放泛型的設計

譬如List包Map這樣子：List<Map<String, String>>
首先先設計個像Map的泛型：

class Chess<K, V> {
    private K key;
    private V value;

    public Chess(K key, V value) {
        this.setKey(key);
        this.setValue(value);
    }

    public K getKey() {
        return key;
    }

    public void setKey(K key) {
        this.key = key;
    }

    public V getValue() {
        return value;
    }

    public void setValue(V value) {
        this.value = value;
    }
}

然後再設計個像List的泛型

class Msg<T> {
    private T info;

    public Msg(T m) {
        this.setInfo(m);
    }

    public T getInfo() {
        return info;
    }

    public void setInfo(T info) {
        this.info = info;
    }
}

寫個測試類：

Chess<String, Integer> chess = new Chess<>("象棋", 32);
Msg<Chess<String, Integer>> msg = new Msg<>(chess);

System.out.print(msg.getInfo().getKey() + "有");
System.out.println(msg.getInfo().getValue() + "顆棋子！");

結果： 象棋有32顆棋子！