Stream not closed (ARCH4081)

Key java.performance.stream-not-closed · Severity error · Category performance

If a Reader, Writer, or stream is opened and not closed, its underlying file handle stays held. Once enough handles leak, the app crashes with “too many open files”.

Incorrect

public String read(Path file) throws IOException {
    BufferedReader r = Files.newBufferedReader(file);
    return r.readLine();
}

Correct

public String read(Path file) throws IOException {
    try (BufferedReader r = Files.newBufferedReader(file)) {
        return r.readLine();
    }
}

Fix

Open streams and readers inside try-with-resources so they are closed in all cases.