code: public static boolean isBlockOrSF(String s) {
          // we currently only support DSA and RSA PKCS7 blocks
          if (s.endsWith(".SF") || s.endsWith(".DSA") ||
                  s.endsWith(".RSA") || s.endsWith(".EC")) {
              return true;
          }
          return false;
      }
docs: Utility method used by JarVerifier and JarSigner
  to determine the signature file names and PKCS7 block
  files names that are supported
  
  @param s file name
  @return true if the input file name is a supported
  Signature File or PKCS7 block file name