链表简单实现栈与队列

链表方式实现栈

public class StackImpl<Item> implements Iterable<Item> {
    
    private Node first;
    private int N;
    /**
     * 内部类实现链表节点定义
     * @author feng
     *
     */
    private class Node{
        Item item;
        Node next;
    }
    
    public boolean isEmpty(){
        return first == null;
    }
    public int size(){
        return N;
    }
    
    public void push(Item item){
        Node oldFirst = first;
        first = new Node();
        first.item = item;
        first.next = oldFirst;
        N++;
    }
    public Item pop(){
        Item item = first.item;
        first = first.next;
        N--;
        return item;
    }

    /**
     * 迭代器
     * @author feng
     *
     */
    @Override
    public Iterator<Item> iterator() {
        return new ListIterator();
    }
    /**
     * 内部类实现迭代器
     * @author feng
     *
     */
    private class ListIterator implements Iterator<Item>{
        private Node current = first;
        @Override
        public boolean hasNext() {
            // TODO Auto-generated method stub
            return current != null;
        }
        public void remove(){}
        @Override
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }
    }

}

链表方式实现队列

public class QueueImpl<Item> implements Iterable<Item> {

    private Node first;
    private Node last;
    private int N;
    
    private class Node{
        Item item;
        Node next;
    }
    
    public boolean isEmpty(){
        return first == null;
    }
    
    public int size(){
        return N;
    }
        
    public void enqueue(Item item){
        Node oldlast = last;
        last.item = item;
        last.next = null;
        if(isEmpty()){
            first = last;
        }else{
            oldlast.next = last;
        }
        N++;
    }
    
    public Item dequeue(){
        Item item = first.item;
        first = first.next;
        if(isEmpty()){
            last = null;
        }
        N--;
        return item;
    }
    /**
     * 迭代器
     */
    @Override
    public Iterator<Item> iterator() {
        // TODO Auto-generated method stub
        return new ListIterator();
    }
    
    /**
     * 迭代器实现类
     * @author feng
     *
     */
    private class ListIterator implements Iterator<Item>{
        private Node current = first;
        @Override
        public boolean hasNext() {
            // TODO Auto-generated method stub
            return current != null;
        }
        public void remove(){}
        @Override
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }
    }
}