Hi, This is functioning as expected. The input array of bytes is interpreted in little-endian order. The first byte in the input array is the smallest part of the output binary string interpreted as a binary number. So if you pass two bytes the output string will start with the second byte and end with the first byte when reading left to right.
You can see how this works by looking at the test for the method here: https://gitbox.apache.org/repos/asf?p=commons-codec.git;a=blob;f=src/test/java/org/apache/commons/codec/binary/BinaryCodecTest.java;h=2e3e6380bcc08d913f514deaebbdfa3a325600ed;hb=HEAD#l296 As you set more bits in each byte (filling from the lowest bit first) the output string fills up from the right. The output order is a format for data transfer. The key point is that the output string will be correctly converted back to the original bytes using the complementary BinaryCodec.fromAscii method. Regards, Alex On Thu, 4 Mar 2021 at 14:20, t_liang <t_liang1...@qq.com> wrote: > System.out.println(BinaryCodec.toAsciiString(new byte[] { 'a' })); // > output 01100001 System.out.println(BinaryCodec.toAsciiString(new byte[] { > 'b' })); // output 01100010 > System.out.println(BinaryCodec.toAsciiString(new byte[] { 'a', 'b' })); // > output 0110001001100001(ba), why not 0110000101100010(ab)?
