How to print the key of the values in HashMap by using stream

Question

Please Help me with this code below

I am getting an output like this

Enter name:Chaya
[455-567-8888, 655-884-4557, 811-115-5556]
Enter phone: 7666644556
7666644556 = [Chaya]
I need to get an output like this
Enter name: Chaya
455-567-8888
655-884-4557
811-115-5556
Enter phone: 7666644556
7666644556 = Bhanu

I not able to resolve the issue of name output it is printing 'Chaya' instead of 'Bhanu'. Can I use a toString method to print the phone number values
Please Elaborate.....

public class PhNo 
{
    private static String name;
    private static long phno;

    public static void main(String[] args) 
    {
            HashMap<String, List<Long>> map = new HashMap<String, List<Long>>();
            List<Long> One = new ArrayList<Long>();
            One.add(1111111111L);
            One.add(9444445555L);

            List<Long> Two = new ArrayList<Long>();
            Two.add(7666644556L);

            List<Long> Three = new ArrayList<Long>();
            Three.add(4555678888L);
            Three.add(6558844557L);
            Three.add(8111155556L);

            List<Long> Four = new ArrayList<Long>();
            Four.add(4555678899L);
            Four.add(6558844566L);
            Four.add(8666655556L);

            map.put("Arya", One);
            map.put("Bhanu", Two);            
            map.put("Chaya", Three);
            map.put("Dhamu", Four);

            System.out.println("Enter name: ");
            Scanner userInput = new Scanner(System.in); 
            name = userInput.nextLine();

            List<Long> phoneNum = map.get(name);
            System.out.println(String.valueOf(phoneNum).replaceAll("(\\d{3})(\\d{3})(\\d+)", "$1-$2-$3"));                    

            System.out.println("Enter phone: ");              
            phno = userInput.nextLong();    

            System.out.println(phno+" = "+ getKeysByValue(map));

     }

    static List<String> getKeysByValue(Map<String, List<Long>> map) 
    {
     return map.entrySet()
              .stream()
              .filter(entry -> Objects.equals(entry.getKey(), name))
              .map(Map.Entry::getKey)
              .collect(Collectors.toList());        
    }
}

Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. See: [How to create a Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve). — Lino, Jul 03 '18 at 14:22
Possible duplicate of [How do I print out all keys in hashmap?](https://stackoverflow.com/questions/26847081/how-do-i-print-out-all-keys-in-hashmap) which is a duplicate of [Printing HashMap In Java](https://stackoverflow.com/questions/5920135/printing-hashmap-in-java) — LuCio, Jul 03 '18 at 14:37

Youcef LAIDANI · Answer 1 · 2018-07-03T14:50:33.807

You can use :

static String getName(Map<String, List<Long>> users, Long phone) throws Exception {
    return users.entrySet()
            .stream()
            .filter(entry -> entry.getValue().contains(phone))
            .findFirst()
            .map(user -> user.getKey())
            .orElseThrow(() -> new Exception("No result found"));
}

Note :

Your method name should be significant name (Instead change it to getName)
I assume that your method should return a String(name of user who have this phone number) and not a list of Long
What if your method not find any result? (You can throw an exception)
The code would be more readable if the phno value would be passed as a second argument to the method (thank you Conffusion), then call your method like this getName(map, phno)
The design you are using is not good at all, instead I would suggest to create a class of users which hold username, and a List of phone numbers, It will be easy to read and to manipulate.
Name of variables should be in lower case not upper case

Of If you want to get all the name of users which have that phone number you can use :

static List<String> getNameOfUsersByPhoneNumber(Map<String, List<Long>> map, Long phone) {
    return map.entrySet()
            .stream()
            .filter(entry -> entry.getValue().contains(phone))
            .map(entry->entry.getKey())
            .collect(Collectors.toList());
}

The code would be more readable if the phno value would be passed as a second argument to the method. (+1 for the use of Optional :) — Conffusion, Jul 03 '18 at 14:34
Instead of `if (result.isPresent()) { ... } else { throw ... }` in the first code sample you can continue method chaining: `findFirst().map(entry -> entry.getKey())..orElseThrow(() -> new Exception("No result found"));` — LuCio, Jul 03 '18 at 14:44
@LuCio I'm using `result.get().getKey();` not just `result.get();` In this case how you can continue chaining? — Youcef LAIDANI, Jul 03 '18 at 14:46
@LuCio yes this is correct I forgot the `map(..)` thank you I changed my code — Youcef LAIDANI, Jul 03 '18 at 14:49

How to print the key of the values in HashMap by using stream

1 Answers1