question: public void testIntbyInt1 ( ) { byte aBytes [ ] = { 10 , 20 , 30 , 40 } ; byte bBytes [ ] = { 1 , 2 , 3 , 4 } ; int aSign = 1 ; int bSign = - 1 ; byte rBytes [ ] = { - 11 , - 41 , - 101 , 55 , 5 , 15 , 96 } ; BigInteger aNumber = new BigInteger ( aSign , aBytes ) ; BigInteger bNumber = new BigInteger ( bSign , bBytes ) ; BigInteger result = aNumber . multiply ( bNumber ) ; 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:  Multiply two numbers of 4 bytes length.