迭代器模式
文档查阅说明:
定义:它提供一种方法访问一个容器对象中各个元素,而又不需暴露该对象的内部细节
使用场景:
● 访问一个聚合对象的内容而无须暴露它的内部表示;
● 需要为聚合对象提供多种遍历方式;
● 为遍历不同的聚合结构提供一个统一的接口
注意事项:迭代器模式就是分离了集合对象的遍历行为,抽象出一个迭代器类来负责,这样既可以做到不暴露集合的内部结构,又可让外部代码透明地访问集合内部的数据
ps:迭代器模式已经被淘汰,java中已经把迭代器运用到各个聚集类(collection)中了,使用java自带的迭代器就已经满足我们的需求了
public abstract class Iterator {
public abstract Object first();
public abstract Object next();
public abstract boolean hasNext();
public abstract Object getCurrentItem();
}
public abstract class Aggregate {
public abstract Iterator createIterator();
}
public class ConCreateAggregate extends Aggregate{
private List<Object> items = new ArrayList<Object>();
@Override
public Iterator createIterator() {
return new ConCreateIterator(this);
}
public int count() {
return items.size();
}
public void add(Object name) {
items.add(name);
}
public Object get(int index) {
return items.get(index);
}
}
public class ConCreateIterator extends Iterator {
private ConCreateAggregate aggregate;
private int current = 0;
public ConCreateIterator(ConCreateAggregate aggregate) {
super();
this.aggregate = aggregate;
}
@Override
public Object first() {
return aggregate.get(0);
}
@Override
public Object next() {
if(current < aggregate.count()) {
return aggregate.get(current++);
}else {
return null;
}
}
@Override
public boolean hasNext() {
return current < aggregate.count();
}
@Override
public Object getCurrentItem() {
return aggregate.get(current);
}
}
public class Test {
public static void main(String[] args) {
ConCreateAggregate aggregate = new ConCreateAggregate();
aggregate.add("芒果柒");
aggregate.add("苹果八");
aggregate.add("榴莲一");
Iterator iterator = new ConCreateIterator(aggregate);
while(iterator.hasNext()) {
System.out.println("水果排名:"+iterator.next());
}
}
}