Ant -- Another Neat Tool

<?xml version = "1.0"?>
<project name = "Hello" default = "compile">
     <target name = "compile" description = "compile the Java source code to class files">
          <mkdir dir = "classes"/>
          <javac srcdir = "." destdir  = "classes"/>
     </target>
     <target name = "jar" depends ="compile" description = "create a Jar file">
          <jar destfile = "hello.jar">
               <fileset dir = "classes" includes ="* * /*.class"/>
               <manifest>
                    <attribute name = "Main-Class" valus = "HelloProgram"/>
               </manifest>
          <jar>
     </target>
</project>