question: public final byte [ ] update ( byte [ ] input ) { if ( mode != ENCRYPT_MODE && mode != DECRYPT_MODE ) { throw new IllegalStateException ( ) ; } if ( input == null ) { throw new IllegalArgumentException ( "input == null" ) ; } if ( input . length == 0 ) { return null ; } return spiImpl . engineUpdate ( input , 0 , input . length ) ; }
target:  Continues a multi-part transformation (encryption or decryption). The transformed bytes are returned.