The Long class includes a method named parseLong() that serves just this purpose. An example of a simple program that performs this conversion is shown below:

public class s2l {

   public static void main (String[] args) {

      // String s = "fred";    // do this if you want an exception

      String s = "100";

      try {
         long l = Long.parseLong(s.trim());
         System.out.println("long l = " + l);
      } catch (NumberFormatException nfe) {
         System.out.println("NumberFormatException: " + nfe.getMessage());
      }

   }

}

Other notes

• Long.toString(long l) is used to convert in the other direction, from long to String.
   
• If you're interested in converting a String to a Long object, use the valueOf() method of the Long class instead of the parseLong() method.