question: public void testShiftLeft5 ( ) { byte aBytes [ ] = { 1 , - 128 , 56 , 100 , - 2 , - 76 , 89 , 45 , 91 , 3 , - 15 , 35 , 26 } ; int aSign = - 1 ; int number = 45 ; byte rBytes [ ] = { - 49 , - 8 , - 13 , 96 , 41 , 116 , - 38 , 84 , - 97 , - 127 , - 37 , - 100 , - 64 , 0 , 0 , 0 , 0 , 0 } ; BigInteger aNumber = new BigInteger ( aSign , aBytes ) ; BigInteger result = aNumber . shiftLeft ( number ) ; byte resBytes [ ] = new byte [ rBytes . length ] ; resBytes = result . toByteArray ( ) ; for ( int i = 0 ; i < resBytes . length ; i ++ ) { assertTrue ( resBytes [ i ] == rBytes [ i ] ) ; } assertEquals ( "incorrect sign" , - 1 , result . signum ( ) ) ; }
target:  shiftLeft(int n) a negative number, n > 0