Package version identification

Question

I just completed going through the
http://developer.java.sun.com/developer/TechTips/1999/tt0414.html#tip2
article on "Package version identification" and based
on the results I got, unless I did something wrong,
I'd say that who ever implemented Java 1.4.1 on
windows left out a lot of stuff. Below is the code I
ran:
public class LoadClass {
     public static void main(String args[]) {
          // check argument
          if (args.length != 1) {
               System.err.println("missing classname");
               System.exit(1);
          // load class
          Class cls = null;
          try {
               cls = Class.forName(args[0]);
          catch (ClassNotFoundException e) {
               System.err.println(e);
               System.exit(1);
          // retrieve and check package information
          Package pkg = cls.getPackage();
          if ((pkg == null) || (pkg.equals(""))) {
               System.out.println("No version information");
          } else {
               System.out.println(pkg);
               System.out.println(pkg.getImplementationTitle());
               System.out.println(pkg.getImplementationVendor());
               System.out.println(pkg.getImplementationVersion());
               System.out.println(pkg.getSpecificationTitle());
               System.out.println(pkg.getSpecificationVendor());
               System.out.println(pkg.getSpecificationVersion());
               System.out.println("Sealed: "+pkg.isSealed());
               try {
                    if (pkg.isCompatibleWith("1.2")) {
                         System.out.println("Compatible with 1.2");
               } catch(NumberFormatException nfe) {
                    System.err.println("Empty version string");
                    //nfe.printStackTrace();
}and here's the results I got:
java LoadClass java.util.regex.Matcher
package java.util.regex
null
null
null
null
null
null
Sealed: false
Empty version string
java LoadClass java.nio.MappedByteBuffer
package java.nio
null
null
null
null
null
null
Sealed: false
Empty version string
java LoadClass java.util.ArrayList
package java.util
null
null
null
null
null
null
Sealed: false
Empty version string
java LoadClass java.lang.System
package java.lang
null
null
null
null
null
null
Sealed: false
Empty version string
Did I do something wrong or are the implementers taking
a lot of short cuts on windows or is the Package class not
really supported any more?

Answer 1

Check the manifest - Is this information provided?