Inserting Node at the beginning of a linked list

问题

I have to insert a new Node at the beginning of my linked list. After I switched the Data Packages I try to overwrite the Data of my first Node with the new Data. But if I do that, my Program changes the data-values of my first and second Node.

void insert(String iv_name, String iv_name_first, String iv_title, int iv_earning) {
    if (this.first == null) {
        this.first = new Node(new Data(iv_name, iv_name_first, iv_title, iv_earning, 0));
    } else {
        Node n = this.first;
        Data last_n_data = getLast().data;
        Data[] datas = new Data[getLast().data.getId()];
        int j = 0;
        while (n.next != null) {
            datas[j] = n.data;
            j++;
            n = n.next;
        }
        j = 0;
        n = this.first;
        while (n.next != null) {
            n.next.data = datas[j];
            n.next.data.setId(datas[j].getId() + 1);
            j++;
            n = n.next;
        }
        n.next = new Node(new Data(last_n_data.getName_last(), last_n_data.getName_first(), last_n_data.getTitle(),
                last_n_data.getEarning(), last_n_data.getId() + 1));
        n.next.next = null;

        this.first.data.setName_last(iv_name);
        this.first.data.setName_first(iv_name_first);
        this.first.data.setTitle(iv_title);
        this.first.data.setEarning(iv_earning);
        this.first.data.setId(0);
    }
}

回答1:

I think you're making this unnecessarily complex. To insert to the beginning of a linked list all you need to do is this:

void insert(String iv_name, String iv_name_first, String iv_title, int iv_earning) {
    Node toCreate = new Node(new Data(iv_name, iv_name_first, iv_title, iv_earning, 0));
    toCreate.next = this.first;
    this.first = toCreate;
}

This code simply creates a new node, makes it the new first node, and makes it point to all of the nodes that already exist. So if you had nodes B->C->D, your end result will be A->B->C->D

来源：https://stackoverflow.com/questions/36678677/inserting-node-at-the-beginning-of-a-linked-list

标签

java

linked-list