DESKTOP-P665UA2_20200910-石家雨

1、遇到的问题

public boolean add( E e ) {
        if( first == null ) {
            first =new Node<>( null , e , null  );  
            last = first;
        }else {
            final Node<E> old = this.last;
            Node<E> n = new Node<>( old , e , null );
            old.next = n;
            this.last = n;
        }
        count++;
        return true ;
    }

此时

first =new Node<>( null , e , null  );  
Node<E> n = new Node<>( old , e , null );

报了一个错误 Cannot infer type arguments for Node 无法推断Node的类型参数

2、解决

private Node(Node<X> previous, Node<X> next, X item) {
            super();
            this.previous = previous;
            this.next = next;
            this.item = item;
}

因为我把构造方法里的参数列表调换了顺序，应该写成

first =new Node<>( null , null , e ); 
Node<E> n = new Node<>( old , null , e );

3、吐槽

今天讲的内容没怎么听懂，很蒙