How to dinamically populate a String array?

[miguel lisboa]

i can query this pupils table to obtain an ArrayList with their email adresses
from javamail api the method to send to more then one adress at the same time is:

String [] para = { "a@a", "b@b"};
Address[] to = new InternetAddress[para.length];
for(int i = 0; i < para.length; i++)
	to[i] = new InternetAddress(para[i]);
msg.setRecipients(Message.RecipientType.TO,to);
 

how can i dinamically populate the para[] String array?

[Efrain Morales]

I think you could simply use something like String [] para = myArrayList.toArray(); , as long as your ArrayList is declared as <String> type.

Doing it without that <String> type could also work, but I don't think it's safe to do it.

You could also do it manually by using

   
//String [] para = { "a@a", "b@b"};   
ArrayList myArrayList = whateverYouGotFromQuery;

Address[] to = new InternetAddress[myArrayList.size()];   
for(int i = 0; i < myArrayList.size(); i++)   
    to[i] = new InternetAddress( (String) myArraList.get(i) );   
msg.setRecipients(Message.RecipientType.TO,to);

 

[miguel lisboa]

that worked nicely

thanks a lot!

[Siva Masilamani]

 to[i] = new InternetAddress( (String) myArraList.get(i) );

I would recommend to use instanceof operator before you cast array list element to String.

E.g.

 if(myArrayList.get(i) instanceof String){
    to[i] = new InternetAddress( (String) myArraList.get(i) );
}
  

[John de Michele]

Or, just use an ArrayList<String>.

John.

[Rob Spoor]

Efrain Morales wrote:I think you could simply use something like String [] para = myArrayList.toArray(); , as long as your ArrayList is declared as <String> type.

Not quite; the array returned by ArrayList.toArray() is always an Object[]. When you try to cast that to String[] you will get a ClassCastException. The following will work though:

String[] para = myArrayList.toArray(new String[myArrayList.size()]);

As the Javadoc of Collection.toArray(T[]) says, it will make sure the runtime type of the returned array is the same as the type of the array argument.