查找----基于无序链表

public class SequentialSearchST<Key,Value> {
    private  Node first;    //头指针
    private int size;     //链表结点数
	
    public SequentialSearchST() {size = 0;first = null;}
    //节点类
    private class Node{
        Key key;
        Value value;
        Node next;
        public Node(Key key,Value value,Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }
    }
    //get()方法，根据键查找值
    public Value get(Key key) {
        for(Node x = first;x!=null;x=x.next)
            if(key.equals(x.key))
                  return x.value;	//命中
        return null;	//未命中
    }
    //put()方法，加入键值对
    public void put(Key key,Value value,Node next) {
        for(Node x = first;x!=null;x=x.next)
            if(key.equals(x.key)) {
                x.value = value;return ;	//命中，更新
        }
        first = new Node(key,value,first);		//未命中，新建,连接到链表的最前面
        size++;
    }
    //返回键值对个数
    public int size() {return size;}
    //delete()方法，删除键值对
    public void delete(Key key) {
        for(Node x = first;x!=null;x=x.next)
            if(x.next.key.equals(key)) {
                x.next = x.next.next;
                break;
            }
    }  
    //获取链表中的所有key
    public Iterable<Key> keys()  {
        Queue<Key> queue = new Queue<Key>();
        for (Node x = first; x != null; x = x.next)
            queue.enqueue(x.key);
        return queue;
    }
}