双链表实现

双链表可以通过前后两个节点来进行两个方向的查找，而单链表只能单方向查找。

package collection;

public class SetLinkedList/*implements List*/ {
private Node first;
private Node last;

private int size;

public void add(Object obj){
if(first == null){
Node n = new Node();
n.setPrevious(null);
n.setObj(obj);
n.setNext(null);

first = n;
last = n;
}else{
//直接往last节点后增加新的节点
Node n = new Node();
n.setPrevious(last);
n.setObj(obj);
n.setNext(null);

last.setNext(n);

last = n;
}
}

public int size(){
return size;
}

public static void main(String[] args) {
SetLinkedList list = new SetLinkedList();
list.add("aaa");
list.add("bbb");
list.add("ccc");
System.out.println(list.size());
}

}

package collection;


class Node{
private Object previous;
private Object obj;
private Object next;

public Node() {

}

public Node(Object previous, Object obj, Object next) {
super();
this.previous = previous;
this.obj = obj;
this.next = next;
}
public Object getPrevious() {
return previous;
}
public void setPrevious(Object previous) {
this.previous = previous;
}
public Object getObj() {
return obj;
}
public void setObj(Object obj) {
this.obj = obj;
}
public Object getNext() {
return next;
}
public void setNext(Object next) {
this.next = next;
}





}