java 在java中将元素添加到iterable
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add element to iterable in java
提问by ovod
I have the following code:
我有以下代码：
public class Router {
private Iterable<Route> routes;
public Router(Iterable<Route> routes) {
this.routes = routes;
}
public void addRoute(Route route) {
routes.add(route);\problem is here
}
}
I highlighted the line which is not working. Here I try to add a new object to the routes. In main file routes are:
我突出显示了不起作用的行。在这里，我尝试向路线添加一个新对象。在主要文件路由是：
public class RouterMain
{
public static void main(String[] arg) throws IllegalArgumentException
{
List<Route> routes = new ArrayList<Route>();
Router router = new Router(routes);
}
}
The task is to add an object in iterable object in Routerclass. As I understood Iterablecan iterate, not add something. So what should I do, convert routes in Routerclass to a List, add an element and go back?
任务是在Router类中的可迭代对象中添加一个对象。据我了解Iterable可以迭代，而不是添加一些东西。那么我该怎么做，将Routerclass 中的路由转换为 a List，添加一个元素并返回？
采纳答案by Mustafa J
If you want to add to it you could create a new list and add all the current elements to that list and then just add the object you would like after e.g
如果您想添加到它，您可以创建一个新列表并将所有当前元素添加到该列表中，然后只需添加您想要的对象，例如
public class Router {
private Iterable<Route> routes;
public Router(Iterable<Route> routes) {
this.routes = routes;
}
public void addRoute(Route route) {
//create new list
ArrayList<Route> myList = new ArrayList<Route>();
//iterate through current objects and add them to new list
Iterator<Route> routeIterator = routes.iterator();
while(routeIterator.hasNext()){
myList.add(routeIterator.next());
}
//add object you would like to the list
myList.add(route);
}
}
回答by Eran
Iterable<Router>is used to enable iterating over the Routerelements contained in your class. It is not a Collection, though many collections implement this interface. It doesn't have the addmethod. It only has a method that returns an Iterator<Router>.
Iterable<Router>用于启用对Router类中包含的元素的迭代。它不是一个集合，尽管许多集合实现了这个接口。它没有add方法。它只有一个返回Iterator<Router>.
You should use some Collection (List, Set, etc...) to store your routes. Those collections have addmethod.
您应该使用一些集合（列表、集合等...）来存储您的路线。那些集合有add方法。
public class Router {
private List<Route> routes = new ArrayList<Route>();
public Router(Iterable<Route> routes) {
for (Route route : routes)
this.routes.add(route);
}
}
回答by Ernesto Campohermoso
Iterable doesn't has the method add. Maybe you need an AbstractCollection
Iterable 没有 add 方法。也许你需要一个 AbstractCollection
http://docs.oracle.com/javase/7/docs/api/java/util/AbstractCollection.html
http://docs.oracle.com/javase/7/docs/api/java/util/AbstractCollection.html
回答by Aaron Digulla
Iterableis a type which is mostly used in loops and utility functions - you should avoid it in general. I suggest to change the constructor to Router(Collection<Route> routes)and use the Collectioninterface internally. That way, you can use almost any collection type (sets, and lists).
Iterable是一种主要用于循环和实用函数的类型 - 通常应该避免使用它。我建议将构造函数更改为Router(Collection<Route> routes)并在Collection内部使用该接口。这样，您几乎可以使用任何集合类型（集合和列表）。
For additional safety, make a copy of the collection - then you can't be hurt by someone making changes to the collection outside of your code.
为了更加安全，请复制该集合 - 这样您就不会因为有人在您的代码之外对集合进行更改而受到伤害。
回答by Mikhail
Use Listinterface instead of Iterable. It has a method listIterator. Which returnes an instance of ListIterator. In this interface you can both add and remove items. Iterable does not look to fit in your task.
使用Listinterface 而不是Iterable. 它有一个方法listIterator。它返回ListIterator. 在此界面中，您可以添加和删除项目。Iterable 看起来不适合您的任务。
