Java设计模式:迭代器模式
12 Oct 2014注:本文为译文,原文出处java-design-patterns-in-stories
迭代器模式应用于遍历对象的集合. 它是一个很常用的模式, 或许你之前已经用过他了. 只要你见过像hasNext()和next(), 它可能就是迭代器模式. 例如: 你可以遍历一个数据库查询记录的链表.
迭代器模式类图
迭代器模式Java代码
interface IIterator{
public boolean hasNext();
public Object next();
}
interface IContainer{
public IIterator createIterator();
}
class RecordCollection implements IContainer{
private String recordArray[] = {"first","second","third","fourth","fifth"};
public IIterator createIterator(){
RecordIterator iterator = new RecordIterator();
return iterator;
}
private class RecordIterator implements IIterator{
private int index;
public boolean hasNext(){
if (index < recordArray.length)
return true;
else
return false;
}
public Object next(){
if (this.hasNext())
return recordArray[index++];
else
return null;
}
}
}
public class TestIterator {
public static void main(String[] args) {
RecordCollection recordCollection = new RecordCollection();
IIterator iter = recordCollection.createIterator();
while(iter.hasNext()){
System.out.println(iter.next());
}
}
}
迭代器模式在JDK中的应用
在java.util包内, Iterator接口定义如下:
public interface Iterator<E> {
boolean hasNext();
E next();
void remove();
}
还有可以创建迭代器的类, 例如: TreeSet#iterator(), HashSet#iterator()等.