Annotation Interface Positive

The annotated expression evaluates to an integer greater than or equal to 1.

As an example of a use-case for this type, consider the following code:

 if (arr.length > 0) {
    int j = arr[arr.length - 1];
Without the knowing that arr.length is positive, the Index Checker cannot verify that accessing the last element of the array is safe - there might not be a last element!
See the Checker Framework Manual:
Index Checker