图解设计模式Iterator模式

Iterator设计模式UML图

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Iterator(迭代器)

//负责定义按顺序遍历各个元素的接口
package me.maweiyi;


/**
 * Created by MWY
 * Date: 1/10/17
 * Time: 22:10
 */
public interface Iterator {
    public abstract boolean hasNext();
    public abstract Object next();
}

ConcreteIterator(具体的迭代器)

//负责实现具体的迭代器
package me.maweiyi;

/**
 * Created by MWY
 * Date: 1/10/17
 * Time: 22:21
 */
public class BookShelfIterator implements Iterator {
    private BookShelf bookShelf;
    private int index;
    public BookShelfIterator(BookShelf bookShelf) {
        this.bookShelf = bookShelf;
        this.index = 0;
    }
    @Override
    public boolean hasNext() {
        //return false;
        if (index < bookShelf.getLength()) {
            return true;
        } else {
            return false;
        }
    }

    @Override
    public Object next() {
        //return null;
        Book book = bookShelf.getBookAt(index);
        index++;
        return book;
    }
}

Aggregate(集合)

//负责定义创建Iterator的接口
package me.maweiyi;

/**
 * Created by MWY
 * Date: 1/10/17
 * Time: 22:09
 */
public interface Aggregate {
    public abstract Iterator iterator();
}

ConcreteAggregate(具体的集合)

//实现Aggregate创建的接口，创建出具体的Iterator
package me.maweiyi;

/**
 * Created by MWY
 * Date: 1/10/17
 * Time: 22:15
 */
public class BookShelf implements Aggregate {

    private Book[] books;
    private int last = 0;

    public BookShelf(int maxSize) {
        this.books = new Book[maxSize];

    }

    public Book getBookAt(int index) {
        return books[index];
    }

    public void appendBook(Book book) {
        this.books[last] = book;
        last++;
    }

    public int getLength() {
        return last;
    }

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

Iterator设计模式的优点

• 将遍历和实现分开