How to use Java to edit a template document (form letter) from a file?

Object[] arguments = {
     new Integer(7),
     new Date(System.currentTimeMillis()),
     "a disturbance in the Force"
 };

 String result = MessageFormat.format(
     "At {1,time} on {1,date}, there was {2} on planet {0,number,integer}.",
     arguments);

 output: At 12:30 PM on Jul 3, 2053, there was a disturbance
           in the Force on planet 7.

C:oreyessamplesjavareplace>type Simplistic.java
public class Simplistic{
    public static void main( String [] args ) {
        String template = "Dear _NAME_HERE_. I'm glad you...";
        System.out.println( template.replaceAll("_NAME_HERE_","Oscar Reyes"));
    }
}

C:oreyessamplesjavareplace>java Simplistic
Dear Oscar Reyes. I'm glad you...