Iterator-迭代器

1. • package com.yjwang.Iterator;
     
   • public interface Aggregate {
   •     public abstract Iterator iterator();
   • }

1. package com.yjwang.Iterator;
   
3. public interface Iterator {
4.     public abstract boolean hasNext();
5.     public abstract Object Next();
6. }

1. package com.yjwang.Iterator;
   
3. public class Book {    
4.     private String name;
5.     
6.     public Book(String name){
7.         this.name = name;
8.     }
9.     
10.     public String getName(){
11.         return name;
12.     }
14.     public void setName(String name) {
15.         this.name = name;
16.     }
17. }

1. package com.yjwang.Iterator;
   
2. import java.util.Vector;
4. public class BookShelf implements Aggregate{
5.     //private Book[] books;
   
7.     private Vector books;
8.     private int last = 0;
9.     
10.     /**定义书架的长度***/
11.     public BookShelf(int maxsize) {
12.         //this.books = new Book[maxsize];
    
14.         this.books = new Vector(maxsize);
15.     }
16.     
17.     public Book getBookAt(int index){
18.         //return books[index];
    
20.         return (Book)books.get(index);
21.     }
22.     
23.     public void appendBook(Book book){
24.         //this.books[last] = book;
    
26.         books.add(book);
27.         //last++;
    
29.     }
30.     
31.     /**统计书的总数**/
32.     public int getLength(){
33.         //return last;
    
35.         return books.size();
36.     }
37.     
38.     public Iterator iterator(){
39.         return new BookShelfIterator(this);
40.     }
41. }

1. package com.yjwang.Iterator;
   
3. public class BookShelfIterator implements Iterator {
4.     private BookShelf bookShelf;
5.     private int index;
6.     
7.     public BookShelfIterator(BookShelf bookShelf){
8.         this.bookShelf = bookShelf;
9.         this.index = 0;
10.     }
11.     
12.     public boolean hasNext() {
13.         // TODO Auto-generated method stub
    
15.         if(index < bookShelf.getLength()){
16.             return true;
17.         }
18.         else{
19.         return false;
20.         }
21.     }
23.     public Object Next() {
24.         // TODO Auto-generated method stub
    
26.         Book book = bookShelf.getBookAt(index);
27.         index++;
28.         return book;
29.     }
30.     
31. }

1. package com.yjwang.Iterator;
   
3. public class MainTest {
4.     public static void main(String args[]){
5.         BookShelf bookShelf = new BookShelf(4);
6.         bookShelf.appendBook(new Book("A_book1"));
7.         bookShelf.appendBook(new Book("B_book2"));
8.         bookShelf.appendBook(new Book("C_book3"));
9.         bookShelf.appendBook(new Book("D_book4"));
10.         bookShelf.appendBook(new Book("E_book5"));
11.         Iterator it = bookShelf.iterator();
12.         while(it.hasNext()){
13.             Book book = (Book)it.Next();
14.             System.out.println(" " + book.getName());
15.         }
16.     }
17. }