java - How do I get object from HashMap respectively?

I make the personal profiles database,and I use HashMap to collect profile.

private HashMap database;

but I want to write profile data to text files

PrintWriter fileOut = new PrintWriter(new FileWriter(fileName));
fileOut.println(database.size());

for(int i = 0; i < database.size();i++){
 Profile eachProfile = database.get(key);
}

But I don't know how to get list of key to looping
How can I get data from HashMap respectively with another ways?

Answer

You could use Map.entrySet() and extended for:

for (Map.Entry e: database.entrySet())
{
    String s  = e.getKey();
    Profile p = e.getValue();
}