java.io.BufferedReader; import java.io.FileReader;

public List<String> getLikes(String user)

This will take a String representing a user (like "Mike") and return a unique List containing all of the users that have liked the user "Mike."

public List<String> getLikedBy(String user)

This will take a String representing a user (like "Tony") and return a unique List containing each user that "Tony" has liked.

create a Main to test your work.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class FacebookLikeManager {
public List<String> facebookMap;
private Set<String> likesSets;

public FacebookLikeManager() {
facebookMap = new ArrayList<>();
likesSets = new HashSet<>(Arrays.asList("Mike","Kristen","Bill","Sara"));
}

public void buildMap(String filePath) {
try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
String line = reader.readLine();

while (line != null) {
String[] lineWords = line.split("[\\s,%$]+");
for (String word : lineWords) {

String cleanWord = word.replaceAll("[^A-Za-z]", "").toUpperCase();

facebookMap.add(cleanWord);

}
line = reader.readLine();
}

} catch (IOException ex) {
System.err.format("IOException: %s%n", ex);
}
}

public List<String> getAllUsers(){
List<String> userList = new ArrayList<>();
Set<String> users = new HashSet<>();
for(String usersName: facebookMap){
users.add(usersName);
}
userList.addAll(users);
return userList;
}

public List<String> getLikes(String user) {

}
public List<String> getLikedBy(String user) {

}

}

public class Main {

public static void main(String[] args) {

FacebookLikeManager main = new FacebookLikeManager();

main.buildMap(args[0]);

System.out.println(main.getAllUsers());

}

}

users.txt

Mike: Kristen, Sara, Nate, Anthony, Randy
Kristen: Mike, John, Steve, Bill
Bill: Sara, Nate
Sara: Nate, Anthony