Create a Java source dynamically, compile and call

import java.io.*;
import java.util.*;
import java.lang.reflect.*;

public class MakeTodayClass {
       Date today = new Date();
       String todayMillis = Long.toString(today.getTime());
       String todayClass = "z_" + todayMillis;
       String todaySource = todayClass + ".java";

       public static void main (String args[]){
              MakeTodayClass mtc = new MakeTodayClass();
              mtc.createIt();
              if (mtc.compileIt()) {
                      System.out.println("Running " + mtc.todayClass + ":\n\n");
                      mtc.runIt();
                      }
              else
                      System.out.println(mtc.todaySource + " is bad.");
              }

       public void createIt() {
              try {
                     FileWriter aWriter = new FileWriter(todaySource, true);
                     aWriter.write("public class "+ todayClass + "{");
                     aWriter.write(" public void doit() {");
                     aWriter.write(" System.out.println(\""+todayMillis+"\");");
                     aWriter.write(" }}\n");
                     aWriter.flush();
                     aWriter.close();
                     }
              catch(Exception e){
                     e.printStackTrace();
                     }
              }

       public boolean compileIt() {
              String [] source = { new String(todaySource)};
              ByteArrayOutputStream baos= new ByteArrayOutputStream();

              new sun.tools.javac.Main(baos,source[0]).compile(source);
              // if using JDK >= 1.3 then use
              // public static int com.sun.tools.javac.Main.compile(source);
              return (baos.toString().indexOf("error")==-1);
              }

       public void runIt() {
              try {
                     Class params[] = {};
                     Object paramsObj[] = {};
                     Class thisClass = Class.forName(todayClass);
                     Object iClass = thisClass.newInstance();
                     Method thisMethod = thisClass.getDeclaredMethod("doit", params);
                     thisMethod.invoke(iClass, paramsObj);
                     }
              catch (Exception e) {
                     e.printStackTrace();
                     }
              }
}