• There are disadvantages with making significant changes to a language.
  • There is more for people to learn.
  • Existing books and courses will need to be updated.
  • Developers cannot avoid the changes for long as future APIs will use the new features.
  • Some language changes need support from new classes.
    Source code written to use these features need Java 5 JRE.
    Best to avoid generating Java 5 code when producing applets.