第一章--迭代器模式

• 类图
  

package com.designer.practice4;
import com.designer.practice4.Iterator;

//所要遍历的集合的接口
public interface Aggregate {


    //添加图书
    public void appendBook(Book book);
    //获取图书
    public Book getBook(int index);
    //获取当前书架的容量
    public int getLength();
    //遍历方法(返回一个迭代器)
    public Iterator iterator();
}

package com.designer.practice4;

import java.util.ArrayList;


//书架
public class BookShelf implements Aggregate{
    //当前书架书籍的数量

    //书籍
    private ArrayList<Book> books;
    //创建书架
    public BookShelf(){
        books=new ArrayList<>();
    }
    //添加图书
    @Override
    public void appendBook(Book book){
        books.add(book);

    }
    @Override
    //获取图书
    public Book getBook(int index){
        return (Book) books.get(index);
    }
    @Override
//获取当前书架的容量
    public int getLength(){
        return books.size();
    }

    @Override
    public Iterator iterator() {
        return new BookShelfIterator(this);
    }
}

package com.designer.practice4;

//书架迭代器
public class BookShelfIterator implements Iterator {
private BookShelf bookShelf;
private int index;//当前遍历到的元素的索引

    public BookShelfIterator(BookShelf bookShelf){
        this.bookShelf=bookShelf;
        this.index=0;
    }
    @Override
    public boolean hasNext() {
        //判断下一个元素是否存在
      if(index < bookShelf.getLength()){
          return true;
      }
        return false;
    }

    @Override
    public Object next() {
        //获取当前元素，并将Index指针后移一位
        Book book = bookShelf.getBook(index);
        index++;
        return book;
    }
}

package com.designer.practice4;

public interface Iterator {
    boolean hasNext();
    Object next();
}

package com.designer.practice4;

public class Book {
    private String name;

    public Book() {
    }

    public Book(String name) {
        this.name = name;
    }

    /**
     * 获取
     * @return name
     */
    public String getName() {
        return name;
    }

    /**
     * 设置
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }


}

package com.designer.practice4;

public class Main {
    public static void main(String[] args) {
        //创建图书
        Book book1 = new Book("Java");
        Book book2 = new Book("C++");
        Book book3 = new Book("Python");
        //创建书架
        Aggregate abstractBookShelf = new BookShelf();
        //添加图书
        abstractBookShelf.appendBook(book1);
        abstractBookShelf.appendBook(book2);
        abstractBookShelf.appendBook(book3);
        //遍历
        Iterator iterator = abstractBookShelf.iterator();//将图书注入到了书架遍历器当中
        while (iterator.hasNext()) {
            Book book = (Book) iterator.next();
            System.out.println(book.getName());
        }



    }
}