设计模式之组合模式

例题：餐厅菜单新需求导致的遍历困难

组合模式设计方案

类图

迭代器

public class ComposeIterator implements Iterator
{
private Stack<Iterator> stack=new Stack<Iterator>();

public ComposeIterator(Iterator iterator)
{
stack.push(iterator);
}

@Override
public boolean hasNext()
{
if(stack.empty())
{
return false;
}
Iterator iterator=stack.peek();
if(!iterator.hasNext())
{
stack.pop();
return hasNext();
}
else
{
return true;
}
}

@Override
public Object next()
{
if(hasNext())
{
Iterator iterator=stack.peek();
MenuComponent menuComponent=(MenuComponent)iterator.next();
stack.push(menuComponent.getIterator());
return menuComponent;
}
return null;
}

}

SubMenu里面
public Iterator getIterator() {
return new ComposeIterator(menuItems.iterator());
}