java - Output on buffer write using serial monitor of arduino -

i trying send data serial monitor of arduino , make led on , of can't yet problem in code kindly check here arduino code

int led = 12; // led connected digital pin 13 int pts = 2;  // powertail switch 2 connected digital pin 2 int recv = 0; // byte received on serial port  void setup() { // initialize onboard led (led), powertail (pts) , serial port   pinmode(led, output);  pinmode(pts, output);  digitalwrite(led,low); serial.begin(9600); }  void loop() {    // if serial port available, read incoming bytes   if (serial.available() > 0) {   recv = serial.read();  // if 'y' (decimal 121) received, turn led/powertail on // other 121 received, turn led/powertail off if (recv == 121){   digitalwrite(led, high);   digitalwrite(pts,low); } else {   digitalwrite(led, low);   digitalwrite(pts,high); }  // confirm values received in serial monitor window serial.print("--arduino received: "); serial.println(recv);  }  } 

here java code

import java.awt.borderlayout; import java.awt.event.actionevent; import java.awt.event.actionlistener; import java.io.filenotfoundexception; import java.io.printwriter; import java.util.calendar; import java.util.date; import java.util.scanner; import javax.swing.jbutton; import javax.swing.jcombobox; import javax.swing.jframe; import javax.swing.jpanel;  import com.fazecast.jserialcomm.serialport;  import javax.swing.jlabel;  import javax.swing.imageicon;  import javax.swing.swingconstants;  public class connection {  static serialport chosenport;  public static void main(string[] args) throws filenotfoundexception {      // create , configure window     jframe window = new jframe();     window.settitle("automatic car wash");     window.setsize(1000, 600);     window.setdefaultcloseoperation(jframe.exit_on_close);     window.getcontentpane().setlayout(null);     date dateandtime = calendar.getinstance().gettime();     printwriter out = new printwriter("incom record save.txt");       // create drop-down box , connect button, place them @ top of window     jcombobox<string> portlist = new jcombobox<string>();     jbutton connectbutton = new jbutton("connect");     jpanel toppanel = new jpanel();     toppanel.setbounds(0, 0, 584, 33);     toppanel.add(portlist);     toppanel.add(connectbutton);     window.getcontentpane().add(toppanel);      jlabel stageone = new jlabel("stage 1 gif");     stageone.seticon(new imageicon("e:\\thesis\\first stage gif.gif"));     stageone.setbounds(76, 95, 160, 120);     stageone.setvisible(false);     window.getcontentpane().add(stageone);      jlabel stageoneimage = new jlabel("stage 1 image ");     stageoneimage.seticon(new imageicon("c:\\users\\dell\\desktop\\stagoneimage.jpg"));     stageoneimage.setbounds(76, 95, 160, 120);     window.getcontentpane().add(stageoneimage);      jlabel totalcars = new jlabel("number of cars");     totalcars.sethorizontalalignment(swingconstants.center);     totalcars.setbounds(156, 270, 138, 14);      window.getcontentpane().add(totalcars);      jlabel lbltotalcars = new jlabel("total cars=");     lbltotalcars.sethorizontalalignment(swingconstants.center);     lbltotalcars.setbounds(104, 270, 81, 14);     window.getcontentpane().add(lbltotalcars);      jlabel totalincome = new jlabel("0");     totalincome.sethorizontalalignment(swingconstants.center);     totalincome.setbounds(365, 270, 92, 14);      window.getcontentpane().add(totalincome);      jlabel rs = new jlabel("rs");     rs.sethorizontalalignment(swingconstants.center);     rs.setbounds(416, 270, 46, 14);     window.getcontentpane().add(rs);      jlabel datetime = new jlabel("todays date , time");     datetime.sethorizontalalignment(swingconstants.center);     datetime.setbounds(184, 294, 173, 25);     datetime.settext(dateandtime.tostring());     window.getcontentpane().add(datetime);      jbutton btnsave = new jbutton("  save");     btnsave.addactionlistener(new actionlistener() {         public void actionperformed(actionevent e) {             out.close();          }     });     btnsave.setbounds(26, 295, 89, 23);     window.getcontentpane().add(btnsave);      jlabel lbltotalincome = new jlabel("total income=");     lbltotalincome.sethorizontalalignment(swingconstants.center);     lbltotalincome.setbounds(304, 270, 92, 14);     window.getcontentpane().add(lbltotalincome);      jlabel = new jlabel("thanks");     thanks.sethorizontalalignment(swingconstants.center);     thanks.seticon(new imageicon("c:\\users\\dell\\desktop\\thanks.gif"));     thanks.setbounds(36, 333, 312, 218);     thanks.setvisible(false);     window.getcontentpane().add(thanks);      jlabel lblstagetwogif = new jlabel("stage 2 gif");     lblstagetwogif.setbounds(236, 95, 160, 120);     window.getcontentpane().add(lblstagetwogif);      jlabel stagetwoimage = new jlabel("stage2image");     stagetwoimage.seticon(new imageicon("c:\\users\\dell\\desktop\\stagetwoimage.jpg"));     stagetwoimage.setbounds(236, 95, 160, 120);     window.getcontentpane().add(stagetwoimage);      jlabel stage3gif = new jlabel("stage3gif");     stage3gif.setbounds(395, 95, 160, 120);     window.getcontentpane().add(stage3gif);      jlabel stage3image = new jlabel("stageimage3");     stage3image.seticon(new imageicon("c:\\users\\dell\\desktop\\stagethree.jpg"));     stage3image.setbounds(395, 95, 160, 120);     window.getcontentpane().add(stage3image);      jlabel stagefourimage = new jlabel("stagefourimage");     stagefourimage.seticon(new imageicon("c:\\users\\dell\\desktop\\stagefour.jpg"));     stagefourimage.setbounds(555, 95, 160, 120);     window.getcontentpane().add(stagefourimage);      jlabel stagefourgif = new jlabel("stagefourgif");     stagefourgif.setbounds(555, 95, 160, 120);     window.getcontentpane().add(stagefourgif);      jlabel stagefiveimage = new jlabel("stagefiveimage");     stagefiveimage.seticon(new imageicon("c:\\users\\dell\\desktop\\stage 5image.jpg"));     stagefiveimage.setbounds(715, 95, 160, 120);     window.getcontentpane().add(stagefiveimage);      jlabel stagefivegif = new jlabel("stagefivegif");     stagefivegif.setbounds(715, 95, 160, 120);     window.getcontentpane().add(stagefivegif);      // populate drop-down box     serialport[] portnames = serialport.getcommports();     for(int = 0; < portnames.length; i++)         portlist.additem(portnames[i].getsystemportname());         // configure connect button , use thread listen data     connectbutton.addactionlistener(new actionlistener(){         @override public void actionperformed(actionevent arg0) {             if(connectbutton.gettext().equals("connect")) {                 // attempt connect serial port                 chosenport = serialport.getcommport(portlist.getselecteditem().tostring());                 chosenport.setcomporttimeouts(serialport.timeout_scanner, 0, 0);                 if(chosenport.openport()) {                     connectbutton.settext("disconnect");                     portlist.setenabled(false);                 }                   thread thread = new thread(){                     @override public void run() {                         // wait after connecting, bootloader can finish                         try {thread.sleep(100); } catch(exception e) {}                          // enter infinite loop sends text arduino                         printwriter output = new printwriter(chosenport.getoutputstream());                         while(true) {                             output.println("y");                             output.flush();                             try {thread.sleep(100); } catch(exception e) {}                         }                     }                 };                 thread.start();                  // create new thread listens incoming text , populates graph                 thread thread2 = new thread(){                     @override public void run() {                         int count = 0;                         int total_income = 0;                         int car_price=300;                            scanner scanner = new scanner(chosenport.getinputstream());                         while(scanner.hasnextline()) {                              try {                                 string line = scanner.nextline();                                 int number = integer.parseint(line);                                 system.out.println(number);                                  if(number==1)                                 {                                     count++;                                     stageone.setvisible(true);                                     stageoneimage.setvisible(false);                                     total_income=count*car_price;                                     out.println("date= "+dateandtime+" number of cars="+count+" total income="+total_income);                                     totalcars.settext(string.valueof(count));                                     totalincome.settext(string.valueof( total_income));                                     thanks.setvisible(true);                                    }                                  } catch(exception e) {}                         }                         scanner.close();                      }                 };                 thread2.start();             } else {                 // disconnect serial port                 chosenport.closeport();                 portlist.setenabled(true);                 connectbutton.settext("connect");              }         }     });        // show window     window.setvisible(true); } } 

i sovled problem changing output.println("y"); output.write("y"); , worked chorm response