Java HashMap, One key multiple Values, One map

Question

As the question reads.... and I do NOT want to use multiple maps, just one map.

My goal is to get a list of the names I enter in the input. I have tried like a hundred different for-loops, but I always tend to end up with a list of the whole map and/or that the duplicate key is overridden.

    import java.util.*;

public class Another {
public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);

    String name;

    HashMap<String, ToA>wordkey = new HashMap<String, ToA>();

    ToA a = new ToA("Doolin", "Bill", "18580824-1464");
    ToA b = new ToA("Dalton", "Bob", "18701005-2232");
    ToA c = new ToA("James", "Jesse", "18470905-2401");
    ToA d = new ToA("Dalton", "Emmet", "18710713-0818");

    wordkey.put("Doolin", a);
    wordkey.put("Dalton", b);
    wordkey.put("James", c);
    wordkey.put("Dalton", d);

    System.out.println("Efternamn:");
    name = scan.next();
}
}


    public class ToA{
    private String fname, lname, dob;

public ToA(String fname, String lname, String dob){
    this.fname = fname;
    this.lname = lname;
    this.dob = dob;
}
public String getFname(){
    return fname;
}
public String getLname(){
    return lname;
}
public String getDob(){
    return dob;
}
public String toString(){
    return "\nFirstname: " + fname + "\nSurname: " + lname + "\nDateOfBirth: " + dob;
}
}

For inputting Dalton, I would like the output Firstname: Bill Surname: Dalton DateOfBirth: 18701005-2232

Firstname: Emmet Surname: Dalton DateOfBirth: 18710713-0818

I'm really stuck with this so any help is highly appreciated, Thanks

Answer 1

To post my comment as an answer: use a Map<String, List<ToA>> like this:

Map<String, List<ToA>> wordkey = new HashMap<>();

ToA a = new ToA("Doolin", "Bill", "18580824-1464");
ToA b = new ToA("Dalton", "Bob", "18701005-2232");
ToA c = new ToA("James", "Jesse", "18470905-2401");
ToA d = new ToA("Dalton", "Emmet", "18710713-0818");

wordkey.put("Doolin", Arrays.asList(a));
wordkey.put("James", Arrays.asList(c));
wordkey.put("Dalton", Arrays.asList(b, d));

To print the names based on the input, you can do something like this:

System.out.println("Efternamn:");
name = scan.next();

List<ToA> toas = wordkey.get(name);
if (toas != null) {
  System.out.println("ToAs");
  for (ToA toa : toas) {
    System.out.println("ToA: " + toa);
  }
}
else {
  System.out.println("No ToAs found for input: " + name);
}

Answer 2

There are several possibilities for what you are trying to achieve. A simple one would be to use Guavas Multimap or to use Apaches MultiMap .

Another possibility is to "wrap" the Map in a class and keep a List<ToA> as Value of the Map. You'd override the put , remove and get methods to what you need