J2SE 1.3.1 contains no changes to the API specifictation at the signature level. There are no changes to the signatures of any class or method, nor are there any new classes or class members in the J2SE 1.3.1 specification.
The J2SE 1.3.1 specification does not require a new Java Compatibility Kit (JCK). The JCK used for J2SE 1.3.0 applies also to J2SE 1.3.1.
The wording of the API specification has been amended in some places to clarify behavior. Many of these clarifications have been made in response to bug reports and requests submitted by our partners and J2SE users. In no case does the wording of the clarifications impact the JCK test suite.
The J2SE 1.3.1 specification contains clarifications to approximately 90 class members, counting clarifications to class-level and package-level specifications.
All J2SE 1.3.1 specification clarifications are viewable in the form of HTML differences to the Javadoc output. Download the archived Difference Pages.