question: public static byte [ ] decode2 ( String encoded ) { if ( encoded == null ) { return null ; } char [ ] base64Data = encoded . toCharArray ( ) ; int len = removeWhiteSpace ( base64Data ) ; if ( len % FOURBYTE != 0 ) { return null ; } int numberQuadruple = ( len / FOURBYTE ) ; if ( numberQuadruple == 0 ) { return new byte [ 0 ] ; } byte decodedData [ ] = null ; byte b1 = 0 , b2 = 0 , b3 = 0 , b4 = 0 ; char d1 = 0 , d2 = 0 , d3 = 0 , d4 = 0 ; int i = 0 ; int encodedIndex = 0 ; int dataIndex = 0 ; decodedData = new byte [ ( numberQuadruple ) * 3 ] ; for ( ; i < numberQuadruple - 1 ; i ++ ) { if ( ! isData ( ( d1 = base64Data [ dataIndex ++ ] ) ) || ! isData ( ( d2 = base64Data [ dataIndex ++ ] ) ) || ! isData ( ( d3 = base64Data [ dataIndex ++ ] ) ) || ! isData ( ( d4 = base64Data [ dataIndex ++ ] ) ) ) { return null ; } b1 = base64Alphabet [ d1 ] ; b2 = base64Alphabet [ d2 ] ; b3 = base64Alphabet [ d3 ] ; b4 = base64Alphabet [ d4 ] ; decodedData [ encodedIndex ++ ] = ( byte ) ( b1 << 2 | b2 > > 4 ) ; decodedData [ encodedIndex ++ ] = ( byte ) ( ( ( b2 & 0xf ) << 4 ) | ( ( b3 > > 2 ) & 0xf ) ) ; decodedData [ encodedIndex ++ ] = ( byte ) ( b3 << 6 | b4 ) ; } if ( ! isData ( ( d1 = base64Data [ dataIndex ++ ] ) ) || ! isData ( ( d2 = base64Data [ dataIndex ++ ] ) ) ) { return null ; } b1 = base64Alphabet [ d1 ] ; b2 = base64Alphabet [ d2 ] ; d3 = base64Data [ dataIndex ++ ] ; d4 = base64Data [ dataIndex ++ ] ; if ( ! isData ( ( d3 ) ) || ! isData ( ( d4 ) ) ) { if ( isPad ( d3 ) && isPad ( d4 ) ) { if ( ( b2 & 0xf ) != 0 ) { return null ; } byte [ ] tmp = new byte [ i * 3 + 1 ] ; System . arraycopy ( decodedData , 0 , tmp , 0 , i * 3 ) ; tmp [ encodedIndex ] = ( byte ) ( b1 << 2 | b2 > > 4 ) ; return tmp ; } else if ( ! isPad ( d3 ) && isPad ( d4 ) ) { b3 = base64Alphabet [ d3 ] ; if ( ( b3 & 0x3 ) != 0 ) { return null ; } byte [ ] tmp = new byte [ i * 3 + 2 ] ; System . arraycopy ( decodedData , 0 , tmp , 0 , i * 3 ) ; tmp [ encodedIndex ++ ] = ( byte ) ( b1 << 2 | b2 > > 4 ) ; tmp [ encodedIndex ] = ( byte ) ( ( ( b2 & 0xf ) << 4 ) | ( ( b3 > > 2 ) & 0xf ) ) ; return tmp ; } else { return null ; } } else { b3 = base64Alphabet [ d3 ] ; b4 = base64Alphabet [ d4 ] ; decodedData [ encodedIndex ++ ] = ( byte ) ( b1 << 2 | b2 > > 4 ) ; decodedData [ encodedIndex ++ ] = ( byte ) ( ( ( b2 & 0xf ) << 4 ) | ( ( b3 > > 2 ) & 0xf ) ) ; decodedData [ encodedIndex ++ ] = ( byte ) ( b3 << 6 | b4 ) ; } return decodedData ; }
target:  Decodes Base64 data into octects