Unchecked unsafe operations
<p>I am getting a warning about unchecked unsafe operations. I am not quite sure why I am getting this warning, but does anyone know what exception I should be trying to catch and where? I am assuming that I getting this warning because I am not checking for possible exceptions.</p>

<pre><code>import java.awt.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;

public class Tokenizer{

public static String split( String string )
{
    TreeSet tree = new TreeSet();
    StringTokenizer tokenizer =
    new StringTokenizer( string );

    while ( tokenizer.hasMoreTokens() )
    tree.add( tokenizer.nextToken() );

    String result = tree.toString();

    return result;
}//end of split

public static void main( String args[] )
{
    String str;
    Scanner input = new Scanner(System.in);
    System.out.println("Please input a string:");
    str = input.nextLine();
    split(str);

}//end of main
}//end of tokenizer
</code></pre>
