Java9 以上なら、
java.io.InputStream.transferTo(OutputStream out) throws IOException 使えば、
List<String> list; // list に送信するものを入れてから try(ByteArrayOutputStream out = new ByteArrayOutputStream()){ ScriptExecutor.runStream(()->"python script/test.py" , ()->list.stream().map(e->Unicodes.encode(e) + "\n").collect(Collectors.toList()) , ThrowableConsumer.of(i->i.transferTo(out)) , (t, e)->{ System.out.println("stderr : " + t ); e.printStackTrace(); }); String response = out.toString(); }catch(IOException ex){ ex.printStackTrace(); }finally{ }