1.定義
迭代器模式:提供一種方法順序訪問一個聚合對象中的各個元素,而又不暴露其內部的表示。 把在元素之間遊走的責任交給迭代器,而不是聚合對象,這不僅簡化了聚合的接口和實現,也讓聚合更專注在它所應該專注的事情上,讓責任者各得其所。
2.結構類圖
3.代碼實現
聚合接口:
public interface Aggregate {
void add(Object obj);
void remove(Object obj);
Iterator iterator();
}
具體的聚合接口實現:
import java.util.ArrayList;
import java.util.List;
public class ConcreteAggregate implements Aggregate {
List list = new ArrayList();
@Override
public void add(Object obj) {
list.add(obj);
}
@Override
public void remove(Object obj) {
list.remove(obj);
}
@Override
public Iterator iterator() {
return new ConcreteIterator(list);
}
}
迭代器接口:
public interface Iterator {
boolean hasNext();
Object next();
}
具體的迭代器接口實現:
import java.util.ArrayList;
import java.util.List;
import java.util.NoSuchElementException;
public class ConcreteIterator implements Iterator{
private List list = new ArrayList();
private int cursor = 0;
public ConcreteIterator(List list) {
this.list = list;
}
@Override
public boolean hasNext() {
if(cursor == list.size()){
return false;
}
return true;
}
@Override
public Object next() {
if(cursor > list.size()){
throw new NoSuchElementException();
}
return list.get(cursor++);
}
}
client類(在這裏是個測試類):
public class Client {
public static void main(String[] args) {
Aggregate aggregate = new ConcreteAggregate();
aggregate.add("123");
aggregate.add("456");
aggregate.add("789");
aggregate.remove("123");
Iterator iterator = aggregate.iterator();
while (iterator.hasNext()){
System.out.println(iterator.next());
}
}
}