...
These methods are often used to read a byte or character from a stream. Unfortunately many programmers prematurely convert the resulting int back to a byte or char before checking whether they have reached the end of the stream (signaled by a return value of -1). Programs must check for end of stream (e.g., -1) before narrowing the return value to a byte or char.
This guideline rule applies to any InputStream or Reader subclass that provide an implementation of the read() method. This guideline rule is a specific instance of NUM15-J. Ensure conversions of numeric types to narrower types do not result in lost or misinterpreted data.
...
FindBugs version 1.3.9 can detect violations of this guideline rule with the INT: Bad comparison of nonnegative value with negative constant detector.
...
Search for vulnerabilities resulting from the violation of this guideline rule on the CERT website.
Related Guidelines
...