Sun has a (now unsupported) download of their collections classes that were added for JDK 1.2 that are 1.1 compatible. You can download them from the old Infobus web page. At the bottom of the page is a link to the JDK1.1 Collections package which is (from the readme):
This package was mechanically constructed from the JDK1.2 source for the Collections API's using a sed script to substitute the new package name (com.sun.java.util.collections) for the existing JDK1.2 package name(s) (java.util and java.lang). Therefoe they are bug for bug compatible!!!