Printing unique strings in HashMap-CodePudding

i am currently making this code and it suppose to output the name of someone that a list of people didn't write his/her name. i just would like to ask how can i make the output like this using Map

Output: {Andrew}

Explanation : Jay wrote Susan , Susan wrote Jay, Andrew wrote Anna, Anna wrote Jay but nobody wrote Andrew.

Thanks!

public class Main {

        public static void main(String[] args) {

                Main func = new Main();

                System.out.println(func.test("Jay:Susan,Susan:Jay,Andrew:Anna,Anna:Jay"));
        }
        public PriorityQueue test(String c) {
                Map < String, String > hmap = new HashMap < > ();
                PriorityQueue a = new PriorityQueue();

                String b = c.replaceAll("[,]", "-");
                System.out.println(b);
                String[] d = b.split("-");

                for (int i = 0; i < d.length; i  ) {

                        String names = d[i];
                        String[] temp;
                        String splitter = ":";

                        temp = names.split(splitter);
                        String aName = temp[0];
                        String cName = temp[1];

                        hmap.put(aName, cName);

                }

                System.out.println(hmap);

                return a;
        }

}

CodePudding user response：

Just add this snippet before returning your priorityQueue:

 Set<String> keys= new HashSet<>( hmap.values());
        for(Map.Entry<String, String> map: hmap.entrySet())
        {
            String key=map.getKey();
            if(!keys.contains(key))
            {
                System.out.println(key);
                a.add(key);
            }
        }

I am simply checking which value is missing in the set which was supposed to be there.

CodePudding user response：

Another way, using the functionality of Collections, would be to add the following before returning:

//Extract all the voters into a new hashset, this will be modified
Set<String> missing = new HashSet<>( hmap.keySet());
//Use Collections.removeAll() to remove all the values from the keyset
missing.removeAll(hmap.values());
//Add the results to your queue
a.addAll(missing);

Have a look at: https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html#removeAll-java.util.Collection-