Binary upward compatibility

Question

Hi,
It's writtern on this page (http://java.sun.com/javase/technologies/compatibility.jsp#incompatibilities) that Java5.0 is upward compatible with v1.4.2 except for the list of specified imcompatibilities. Part of the list, is the new keyword enum used for typsafe enumeartions in Java 5.0.
Nevertheless, I've tried to run some 1.4 compiled bytecode making use of the enum keyword with the 5.0 JRE and I haven't noticed any issues. So the upward compatibility seems to work, even for the enum keyword.
Does anybody have some more details on this issue ?
Thks,
Tristan

Answer 1

Thanks for your answer. What do you mean by: "if you were using it in a manner that is consistent with version 5 requirements". enum is a reserved keyword in java 5 so I don't see how it is possible to make use of it in a consistent way to java 5.
To illustrate my first post, here is what I tested. The simple following code is compiled with 1.4.2:
String enum = "enum";
System.out.println(enum);
Then I tried to execute it with 5.0 JRE, and it works fine. But of course, if you try to re-compile the code with 5.0, it will fail as enum is now a reserved keyword for enums ...
Is there a logical explanation why this 1.4.2 byte code would work in 5.0 without needing a fix and a recompilation ?