. . . at present. That might change in future. Try this little class, which you must execute with three command*#x2011;line arguments, like thisThe character corresponding to 0x20 is space.
the javap call will allow you see the inner workings of the bytecode, and you can verify from that whether it uses a StringBuilder. Presumably Java1.4 and older versions used a StringBuffer.
subject: How “String” concatenation uses “StringBuilder/StringBuffer” internally?