code: private static final synchronized void setIVS16(byte[] key) {
          if (ivs16 == null) {
              byte[] iv16 = new byte[16];
              for (int i = 0; i < 16; i++) {
                  iv16[i] = key[i];
              }
              ivs16 = new IvParameterSpec(iv16);
          }
      }
docs: /*
  Set the 16-byte initialization vector.
  
  @param key The key