The condition class
java-not-an-array-error is signaled when an argument that needs to be an array is not an array, or when an argument that needs to be a primitive array is not a primitive array, or when an argument that needs to be an object array is not an object array.
You can use the java-bad-jobject readers
java-bad-jobject-object on these conditions.
LispWorks User Guide and Reference Manual - 13 Feb 2015