泛型相关请参考：http://www.cnblogs.com/lwbqqyumidi/p/3837629.html
uml：
Aggregate及其子类：
public abstract class Aggregate<T> {
public abstract Iterator<T> getIterator();
public abstract T get(int index);
public abstract int getLength();
public abstract void add(T e);
public abstract void remove(T e);
}
import java.util.ArrayList;
import java.util.List;
public class ConcreteAggregate<T> extends Aggregate<T> {
private List<T> list = new ArrayList<>();
@Override
public int getLength(){
return list.size();
}
@Override
public void add(T item) {
list.add(item);
}
@Override
public void remove(T item) {
list.remove(item);
}
@Override
public T get(int index){
return list.get(index);
}
@Override
public Iterator<T> getIterator() {
return new ConcreteIterator<T>(this);
}
}
Iterator及其子类：
public abstract class Iterator<T> {
public abstract boolean hasNext();
public abstract T next();
}
public class ConcreteIterator<T> extends Iterator<T> {
private ConcreteAggregate<T> aggr;
private int current = 0;
public ConcreteIterator(ConcreteAggregate<T> aggr) {
this.aggr = aggr;
}
@Override
public boolean hasNext() {
return current < aggr.getLength() ? true : false;
}
@Override
public T next() {
// TODO Auto-generated method stub
current++;
return aggr.get(current - 1);
}
}
Demo：
public class IteratorDemo {
public static void main(String[] args) {
Aggregate<Integer> aggregate = new ConcreteAggregate<>();
for(int i = 0; i < 10; i++){
aggregate.add(i);
}
Iterator<Integer> iterator = aggregate.getIterator();
while(iterator.hasNext()){
System.out.println(iterator.next());
}
}
}