Question

I have this method:

 private void unZipElementsTo(String inputZipFileName, String destPath) throws FileNotFoundException, IOException {

        OutputStream out = null;
        InputStream in = null;
        ZipFile zf = null;

        try {
            zf = new ZipFile(inputZipFileName);

            for (Enumeration<? extends ZipEntry> em = zf.entries(); em.hasMoreElements();) {
                ZipEntry entry = em.nextElement();
                String targetFile = destPath + FILE_SEPARATOR + entry.toString().replace("/", FILE_SEPARATOR);
                File temp = new File(targetFile);

                if (!temp.getParentFile().exists()) {
                    temp.getParentFile().mkdirs();
                }

                in = zf.getInputStream(entry);

                out = new FileOutputStream(targetFile);
                byte[] buf = new byte[4096];
                int len;
                while ((len = in.read(buf)) > 0) {
                    out.write(buf, 0, len);
                }
                out.flush();
                out.close();
                in.close();
            }
        }
        finally
        {
            if (out!=null) out.close();
            if (zf!=null) zf.close();
            if (in!=null) in.close();
        }
    }

For this method Sonar give me this Violation:

Bad practice – Method may fail to close stream on exception
unZipElementsTo(String, String) may fail to close stream on exception

But, I don’t see any violations there. Maybe, it is just a False-positive ?

Answer 1

That’s right.
The OutputStream.close() method can itself throw an exception.
If this happens, e.g. on the 1st line of your finally{} block, then the other streams will be left open.