HashMap example - looking for and printing out the same values

[adize]

Hello,
In my last lab assignment, I had to write a class which stores names and birthday dates in a HashMap. I managed to do this, as well as write methods to print only names, only dates and both key and value. However, I am struggling to complete the last part of an exercise.

I was asked to write a method which iterates through the map and looks for people with the same birthday date. If it finds the same values, it will print out a list of the names together with the shared date of birth.

I have written a method but I have a wrong output, as some values are printed twice. I would appreciate it so much, if you cold give me some advice how to tackle this problem.

Here is my code for a class:

/**
 * @author AP
 * @version 1.0 01/03/2012
 */
import java.util.*;


     public class Birthdays {
          
     //Fields
     private HashMap<String, String> birthdays;
     

     //Constructors
     public Birthdays()
     {
          birthdays = new HashMap<String, String>();
     }
     
     public void add(String name, String date)
     {
          birthdays.put(name,date);
     }
     
     public void printNames()
     {
          for(String name: birthdays.keySet())
          {
               System.out.println(name);
          }
     }
     
     public void printNames2()
     {
          Iterator it = birthdays.keySet().iterator();
          
          while (it.hasNext())
          {
               System.out.println(it.next());
          }
     
     }
     
     public void printDates()
     {
          for(String date : birthdays.values())
          {
               System.out.println(date);
          }
     }
         
     public void printDates2()
     {
          Iterator it = birthdays.values().iterator();
          
          while (it.hasNext())
          {
               System.out.println(it.next());
          }
     
     }
     
     public void printAll()
     {
          for (Map.Entry<String, String> entryPair:birthdays.entrySet())
          {
               System.out.println(entryPair.getKey() + ": " + entryPair.getValue());
          }
     }
     
     public void printAll2()
     {
          Iterator it = birthdays.entrySet().iterator();
          
          while (it.hasNext())
          {
               Map.Entry pair=(Map.Entry)it.next();
               System.out.println(pair.getKey() + ": " + pair.getValue());
          }
     }
     
     public void hasSameBday()
     {
          for (Map.Entry<String, String> entry:birthdays.entrySet())
          {
               for (Map.Entry<String, String> entry2:birthdays.entrySet())
               {
                    if(entry.getValue().equals(entry2.getValue()) && !entry.equals(entry2))
                    {
                         System.out.println(entry.getKey() + ": " + entry.getValue());
                    }
               }
          }
               

     }
}

Here is a test class:

/**
 * A class that tests Birthdays class
 * @author AP
 * @version 1.0 01/03/2012
 */
public class TestBirthdays {
     
      public static void main(String[] args) 
      {
           
           Birthdays b = new Birthdays();
           b.add("John", "1992/02/08");
           b.add("Sarah", "1987/03/07");
           b.add("David", "1987/03/07");
           b.add("Tom", "1992/07/06");
           b.add("Barbara", "1992/07/06");
           b.add("Samantha", "1992/07/06");
           
           b.hasSameBday();
   }
}

And it's my output:

> run TestBirthdays
Samantha: 1992/07/06
Samantha: 1992/07/06
Barbara: 1992/07/06
Barbara: 1992/07/06
David: 1987/03/07
Tom: 1992/07/06
Tom: 1992/07/06
Sarah: 1987/03/07
>

[KevinWorkman]

I suggest you print out the info for both entry and entry2, that way you can see what is matching with what.