LinkedBag

简书 賈小強
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package com.lab1.test1;

import java.util.Iterator;

public class LinkedBag<Item> implements Iterable<Item> {
    private int n;
    private Node first;

    private class Node {
        private Item item;
        private Node next;
    }

    @Override
    public Iterator<Item> iterator() {
        return new ListIterator();
    }

    private class ListIterator implements Iterator<Item> {
        Node current = first;

        @Override
        public boolean hasNext() {
            return current != null;
        }

        @Override
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }

    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        for (Item item : this) {
            builder.append(item + " ");
        }
        return builder.toString();
    }

    private boolean isEmpty() {
        return first == null;
    }

    private int size() {
        return n;
    }

    private void add(Item item) {
        Node oldfirst = first;
        first = new Node();
        first.item = item;
        first.next = oldfirst;
        n++;
    }

    public static void main(String[] args) {
        LinkedBag<String> bag = new LinkedBag<>();
        System.out.println(bag);
        System.out.println(bag.size());
        System.out.println(bag.isEmpty());
        
        bag.add("bill");
        bag.add("jack");
        bag.add("lucy");
        System.out.println(bag);
        System.out.println(bag.size());
        System.out.println(bag.isEmpty());
    }

}

输出

0
true
lucy jack bill 
3
false

Happy learning !!