根据对象得到索引的方法

根据对象得到索引的方法

int indexOf(Object o)： 从头遍历找

public int indexOf(Object o) {
        int index = 0;
        if (o == null) {
            //从头遍历
            for (Node x = first; x != null; x = x.next) {
                if (x.item == null)
                    return index;
                index++;
            }
        } else {
            //从头遍历
            for (Node x = first; x != null; x = x.next) {
                if (o.equals(x.item))
                    return index;
                index++;
            }
        }
        return -1;
    }

int lastIndexOf(Object o)： 从尾遍历找

public int lastIndexOf(Object o) {
        int index = size;
        if (o == null) {
            //从尾遍历
            for (Node x = last; x != null; x = x.prev) {
                index--;
                if (x.item == null)
                    return index;
            }
        } else {
            //从尾遍历
            for (Node x = last; x != null; x = x.prev) {
                index--;
                if (o.equals(x.item))
                    return index;
            }
        }
        return -1;
    }