Java基础编程-泛型

本文全文参考 https://www.bilibili.com/video

自定义泛型结构：泛型类、泛型接口、泛型方法

自定义泛型类

@Getter
@Setter
@ToString
public class Order<T> {

    String orderName;
    int orderId;
    T orderT;
    public Order() {
    }
    public Order(String orderName, int orderId, T orderT) {
        this.orderName = orderName;
        this.orderId = orderId;
        this.orderT = orderT;
    }
}

    @Test
    public void test01(){
        Order<Integer> order = new Order<>();
        order.setOrderId(11);
        order.setOrderName("张三");
        order.setOrderT(1);
        System.out.println(order);
    }

自定义泛型方法

    public <E> List<E> copyArray(E[] arr){
        ArrayList<E> list = new ArrayList<>();
        
        Iterator<E> iterator = list.iterator();
        while (iterator.hasNext()){
            E next = iterator.next();
            list.add(next);
        }
        
        return list;
    }

通配符的使用

    @Test
    public void test02(){
        List<Object> list1 = null;
        List<String> list2 = null;
        List<?> list = null;
        
        //list1 = list2; // 错误
        list = list1;
        list = list2;
    }