import java.util.Iterator;
import java.util.jar.Attributes;
import java.util.jar.JarFile;
import java.util.jar.Manifest;
public class Main {
public static void main(String[] argv) throws Exception {
JarFile jarfile = new JarFile("filename.jar");
Manifest manifest = jarfile.getManifest();
Attributes attrs = (Attributes) manifest.getMainAttributes();
for (Iterator it = attrs.keySet().iterator(); it.hasNext();) {
Attributes.Name attrName = (Attributes.Name) it.next();
String attrValue = attrs.getValue(attrName);
}
}
}