# 迭代器(Iterator)
# Intent
提供一种顺序访问聚合对象元素的方法,并且不暴露聚合对象的内部表示。
# Class Diagram
- Aggregate 是聚合类,其中 createIterator() 方法可以产生一个 Iterator;
- Iterator 主要定义了 hasNext() 和 next() 方法;
- Client 组合了 Aggregate,为了迭代遍历 Aggregate,也需要组合 Iterator。
# Implementation
public interface Aggregate {
Iterator createIterator();
}
public class ConcreteAggregate implements Aggregate {
private Integer[] items;
public ConcreteAggregate() {
items = new Integer[10];
for (int i = 0; i < items.length; i++) {
items[i] = i;
}
}
@Override
public Iterator createIterator() {
return new ConcreteIterator<Integer>(items);
}
}
public interface Iterator<Item> {
Item next();
boolean hasNext();
}
public class ConcreteIterator<Item> implements Iterator {
private Item[] items;
private int position = 0;
public ConcreteIterator(Item[] items) {
this.items = items;
}
@Override
public Object next() {
return items[position++];
}
@Override
public boolean hasNext() {
return position < items.length;
}
}
public class Client {
public static void main(String[] args) {
Aggregate aggregate = new ConcreteAggregate();
Iterator<Integer> iterator = aggregate.createIterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
}
}
}