The following was added to the JDK Providers Guide regarding the Cipher transformation defaults:

"If the mode/padding are omitted, the SunJCE and SunPKCS11 providers use ECB as the default mode and PKCS5Padding as the default padding for many symmetric ciphers.

It is recommended to use transformations that fully specify the algorithm, mode, and padding instead of relying on the defaults. The defaults are provider specific and can vary among providers."

That recommendation (or something similar) should also be included in the Cipher javadoc.