背包抽象数据类型

一代码

package common;

import java.util.Iterator;
import java.util.NoSuchElementException;


public class Bag<Item> implements Iterable<Item> {
    private Node<Item> first;    // beginning of bag
    private int n;               // number of elements in bag

    // helper linked list class
    private static class Node<Item> {
        private Item item;
        private Node<Item> next;
    }

    public Bag() {
        first = null;
        n = 0;
    }

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

    public int size() {
        return n;
    }

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

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

    // an iterator, doesn't implement remove() since it's optional
    private class ListIterator implements Iterator<Item> {
        private Node<Item> current;


        public ListIterator(Node<Item> first) {
            current = first;
        }

        public boolean hasNext()  { return current != null;                     }
        public void remove()      { throw new UnsupportedOperationException();  }
        public Item next() {
            if (!hasNext()) throw new NoSuchElementException();
            Item item = current.item;
            current = current.next;
            return item;
        }
    }

    public static void main(String[] args) {
        Bag<String> bag = new Bag<String>();
        while (!StdIn.isEmpty()) {
            String item = StdIn.readString();
            bag.add(item);
        }

        StdOut.println("size of bag = " + bag.size());
        for (String s : bag) {
            StdOut.println(s);
        }
    }
}

二测试

F:\Algorithm\target\classes>more tobebag.txt
to be or not to be that is


F:\Algorithm\target\classes>java common.Bag < tobebag.txt
size of bag = 8
is
that
be
to
not
or
be
to

来源：CSDN

作者：cakincheng

链接：https://blog.csdn.net/chengqiuming/article/details/104227413

标签

抽象数据类型

iterator