null pointer exception processing error

Hello i am currently working my thesis (creation of BCI with emotiv, arduino,servo and processing). My goal is to send r and l keystrokes to move the servo right or left with emotiv. For start i have create a code in processing (actually i try to combine things that i found here in the forum) and to arduino. I get a null pointer exception error on valtowrite when i try to hit r or l keystrokes. The goal is to identify automatically the port .Please advise.

Here is the processing code:

import processing.serial.*;

Serial ser_port;                // for serial port
PFont fnt;                      // for font
int num_ports;
boolean device_detected = false;
String[] port_list;
String detected_port = "";

void setup() {
    size(400, 200);                         // size of application window
    background(0);                          // black background
    fnt = createFont("Arial", 16, true);    // font displayed in window

    println(Serial.list());

    // get the number of detected serial ports
    num_ports = Serial.list().length;
    // save the current list of serial ports
    port_list = new String[num_ports];
    for (int i = 0; i < num_ports; i++) {
        port_list[i] = Serial.list()[i];
    }
}

void draw()
{
    background(0);
    // display instructions to user
    textFont(fnt, 14);
    text("1. Arduino or serial device must be unplugged.", 20, 30);
    text("   (unplug device and restart this application if not)", 20, 50);
    text("2. Plug the Arduino or serial device into a USB port.", 20, 80);

    // see if Arduino or serial device was plugged in
    if ((Serial.list().length > num_ports) && !device_detected) {
        device_detected = true;
        // determine which port the device was plugge into
        boolean str_match = false;
        if (num_ports == 0) {
            detected_port = Serial.list()[0];
        }
        else {
            // go through the current port list
            for (int i = 0; i < Serial.list().length; i++) {
                // go through the saved port list
                for (int j = 0; j < num_ports; j++) {
                    if (Serial.list()[i].equals(port_list[j])) {
                        break;
                    }
                    if (j == (num_ports - 1)) {
                        str_match = true;
                        detected_port = Serial.list()[i];
                    }
                }
            }
        }
    }
    // calculate and display serial port name
    if (device_detected) {
        text("Device detected:", 20, 110);
        textFont(fnt, 18);
        text(detected_port, 20, 150);
        textFont(fnt, 14);
        text("3.  Now think Right or Left in this Window",20,190);

    }
}

char valToWrite = 'r' & 'l'; //a value to send as a single byte

void keyPressed(){
  valToWrite = key;
  ser_port.write(valToWrite);
}

void keyReleased(){
  valToWrite = 'r' & 'l';
  ser_port.write(valToWrite);
}

AND here is the arduino code:

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

#define SERVO_PIN 9


int pos = 0;    // variable to store the servo position
int lastMotionMillis = 0;

void setup() {
  Serial.begin(9600);
  myservo.attach(SERVO_PIN);  // attaches the servo on pin 9 to the servo object
  delay(300);
  myservo.write(90);
}

void loop() {
   if (Serial.available() ) {
     char c = Serial.read();
     if (c=='r') {
       pos = pos +25;
       myservo.write(pos);
       lastMotionMillis = millis();
     }
     if (c=='l') {
       pos = pos -25;
       myservo.write(pos);
       lastMotionMillis = millis();
     }

     }
   }