在for循环中如何将数据写入字符串

Question

So basically I have this database that is a for loop. It gives a different score every time, which I need to save to a String (or file, but I guess a string would be easier, because I need it to be empty at every new call for the database).

I want to store all the scores by going through the loop, and then adding a , after each score (to keep them seperate) but my code isn't working because a part of the code is outside the for loop. How do I fix this? Or are there better/other methods to do what I want to create?

DatabaseHandler db = new DatabaseHandler(camera.this);
List<Database> contacts = db.getAllContacts();
for (Database contact : contacts) {
    String test = contact.getMP();
    StringWriter stringWriter = new StringWriter();
    PrintWriter printWriter = new PrintWriter(stringWriter);
    printWriter.println(test);
}  
printWriter.flush();
printWriter.close();
return stringWriter.toString();

Answer 1

Try this:

StringBuilder sb = new StringBuilder();
for (Database contact : contacts) { 
    if(sb.length > 0) {
        sb.append(", ");
    }
    sb.append(contact.getMP());
}
...
sb.toString();

Answer 2

Try this

DatabaseHandler db = new DatabaseHandler(camera.this);
List<Database> contacts = db.getAllContacts();
StringWriter stringWriter = new StringWriter();
PrintWriter printWriter = new PrintWriter(stringWriter);
boolean first = true;
for (Database contact : contacts) {
   if(!first) printWriter.print(", ");
   else first = false;
   String test = contact.getMP();
   printWriter.print(test);      
}      
printWriter.flush();
printWriter.close();
return stringWriter.toString();

Hope this helps and enjoy your work