If you follow the documentation, you find:
public void println(int x)
Prints an integer and then terminate the line. This method behaves as though it invokes
print(int) documentation says:
The string produced by
String.valueOf(int) is translated into bytes according to the platform’s default character encoding, and these bytes are written in exactly the manner of the
So it converts the integer to a String before converting that to bytes and printing it out.