带头节点的双链表及其基本操作（Java实现）

package lwh.linearlist.linklist;

public class DbNode {

    protected int e;
    protected DbNode next;
    protected DbNode previous;

    public DbNode(){}

    public DbNode(int e){
        this.e = e;
    }

    public int getE() {
        return e;
    }
    public void setE(int e) {
        this.e = e;
    }
    public DbNode getNext() {
        return next;
    }
    public void setNext(DbNode next) {
        this.next = next;
    }
    public DbNode getPrevious() {
        return previous;
    }
    public void setPrevious(DbNode previous) {
        this.previous = previous;
    }
}

package lwh.linearlist.linklist;

//带头节点的双链表
public class DbLinkedList {

    private DbNode head;

    public DbLinkedList(){
        head = new DbNode();
        head.next = null;
        head.previous = null;
    }

    //在头节点后面插入节点
    public void insertHead(int num){
        DbNode node = new DbNode(num);
        DbNode p = head.next;
        if(p != null){
            node.next = p;
            p.previous = node;
            node.previous = head;
            head.next = node;
        }else{
            head.next = node;
            node.previous = head;
        }
    }

    //求表长,不包括表头节点
    public int length(){
        int len = 0;
        DbNode p = head.next;
        while(p != null){
            len++;
            p = p.next;
        }
        return len;
    }

    //删除i处的节点
    public boolean delete(int i){
        if(i < 1 || i > length()){
            System.out.println("Delete index wrong");
            return false;
        }
        DbNode q = head.next;
        int j = 1;
        while(j < i){
            q = q.next;
            j++;
        }
        DbNode r = q.next;
        DbNode p = q.previous;
        if(r != null){
            p.next = r;
            r.previous = p;
            q = null;
        }else{
            p.next = null;
            q = null;
        }
        return true;
    }

    public void print() {
        if(head.next == null){
            System.out.println("No num");
            return;
        }
        System.out.print("[");
        for(DbNode node = head.next; node != null; node = node.next){
            if(node.next != null)
                System.out.print(node.e + ",");
            else
                System.out.print(node.e + "]");
        }
        System.out.println();
    }
}