When verifying a signed JAR, the bytes of the Manifest are read twice:

- In JarFile.getManifestFromReference():

            JarEntry manEntry = getManEntry();

            // If found then load the manifest
            if (manEntry != null) {
                if (verify) {
                    byte[] b = getBytes(manEntry);
                   ...

and then again in JarFile.initializeVerifier(), when it is being read in this loop:

            for (String name : names) {
                JarEntry e = getJarEntry(name);
                if (e == null) {
                    throw new JarException("corrupted jar file");
                }
                if (mev == null) {
                    mev = new ManifestEntryVerifier
                        (getManifestFromReference());
                }
                byte[] b = getBytes(e);

Since the raw bytes were previously stored in the manifestRawBytes field of the Manifest, they could be used above instead of reading them again.