搜索ArrayList的一个元素并返回包含该元素的所有对象的List

Question

The question seems trivial, but i can't find how to do it properly.

I have a Map<Node, Integer> memorized in a server, where each Node is defined by its hostName (a String) and its serviceList (a List of String), and port is obviously the port used by the Node. So every entry of the map gives me three informations: hostName, serviceList and port.

I'm looing for a way to search for an element, that is contained into one or more serviceLists already memorized into the map, and return a list of objects "serviceProviders". A serviceProvider is defined by hostName and port. So basically:

1. I have a Map with entries Node/Port <---- done
2. I want to look for a service contained into one (or more) serviceLists present in the map <---- to do
3. I want to return a List of ServiceProvider, that is basically a list of hostName and port of each Node whose serviceList contains the service i'm looking for <---- to do

I thought something like this might have worked, but it's not:

public List<ServiceProvider> getProvidersForService(String serviceName) throws TException {
    ServiceProvider serviceProvider = new ServiceProvider();
    List<ServiceProvider> result = new ArrayList<>();                       
    for(Map.Entry<Node, Integer> pair : nodePorts.entrySet()) {
            //problems start here               
        List<String> nodeService = pair.getKey().serviceList;
        for(String s : nodeService) {
            if(s.contains(serviceName))
                result.add(serviceProvider);
                break;
            }
        }
    return result;
}

which is the correct way to implement this?

Answer 1

Problem with your code is you are not updating your serviceProvider object before adding to the list, currently you are adding empty ServiceProvider objects:

public List<ServiceProvider> getProvidersForService(String serviceName) throws TException {
    ServiceProvider serviceProvider = new ServiceProvider();
    List<ServiceProvider> result = new ArrayList<>();                       
    for(Map.Entry<Node, Integer> pair : nodePorts.entrySet()) {
            //problems start here               
        List<String> nodeService = pair.getKey().serviceList;
        for(String s : nodeService) {
            if(s.contains(serviceName))
               // **update service provide before adding here by putting host/port**   
                result.add(serviceProvider);
                break;
            }
        }
    return result;
}

Hope this helps.