unable to create service java.lang.NullPointerException

I implement a sensorEventListener which on shake changes ringer mode. I am using a service so that i can change the ringer mode from outside the activity whenever i like. This is my code for the service i am using- ``` package com.nadeem.shakeit; import android.app.Service; import android.content.Intent; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.media.AudioManager; import android.os.IBinder; public class service extends Service implements SensorEventListener { private SensorManager sensorManager; private long lastUpdate; AudioManager am; @Override public void onCreate() { super.onCreate(); sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); } /*@Override public int onStartCommand(Intent intent, int flags, int startId) { if (intent == null) { sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); } return Service.START_REDELIVER_INTENT; }*/ @Override public void onDestroy() { sensorManager.unregisterListener(this); } @Override public void onSensorChanged(SensorEvent event) { if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) { getAccelerometer(event); } } private void getAccelerometer(SensorEvent event) { float[] values = event.values; // Movement float x = values[0]; float y = values[1]; float z = values[2]; float accelationSquareRoot = (x * x + y * y + z * z) / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH); long actualTime = System.currentTimeMillis(); if (accelationSquareRoot >= 5) // { if (actualTime - lastUpdate < 200) { return; } lastUpdate = actualTime; int ringerMode = am.getRingerMode(); if (ringerMode == AudioManager.RINGER_MODE_NORMAL) { am.setRingerMode(AudioManager.RINGER_MODE_VIBRATE); } else if (ringerMode == AudioManager.RINGER_MODE_VIBRATE) { am.setRingerMode(AudioManager.RINGER_MODE_SILENT); } else { am.setRingerMode(AudioManager.RINGER_MODE_NORMAL); } } } @Override public void onAccuracyChanged(Sensor sensor, int accuracy) { } @Override public IBinder onBind(Intent intent) { // TODO for communication return IBinder implementation return null; } } ``` when i open the app it force closes. Logcat shows:- ``` 07-15 12:04:02.800: E/AndroidRuntime(22092): FATAL EXCEPTION: main 07-15 12:04:02.800: E/AndroidRuntime(22092): java.lang.RuntimeException: Unable to create service com.nadeem.shakeit.service: java.lang.NullPointerException 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2076) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.access$2500(ActivityThread.java:123) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:993) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.os.Handler.dispatchMessage(Handler.java:99) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.os.Looper.loop(Looper.java:130) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.main(ActivityThread.java:3835) 07-15 12:04:02.800: E/AndroidRuntime(22092): at java.lang.reflect.Method.invokeNative(Native Method) 07-15 12:04:02.800: E/AndroidRuntime(22092): at java.lang.reflect.Method.invoke(Method.java:507) 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 07-15 12:04:02.800: E/AndroidRuntime(22092): at dalvik.system.NativeStart.main(Native Method) 07-15 12:04:02.800: E/AndroidRuntime(22092): Caused by: java.lang.NullPointerException 07-15 12:04:02.800: E/AndroidRuntime(22092): at com.nadeem.shakeit.service.onCreate(service.java:21) 07-15 12:04:02.800: E/AndroidRuntime(22092): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2066) 07-15 12:04:02.800: E/AndroidRuntime(22092): ... 10 more ``` Edit-After instantiating the sensorManager again i am getting a nullPointerException. The stack trace is- ``` 07-15 12:35:45.280: E/AndroidRuntime(22469): FATAL EXCEPTION: main 07-15 12:35:45.280: E/AndroidRuntime(22469): java.lang.NullPointerException 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.nadeem.shakeit.service.getAccelerometer(service.java:64) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.nadeem.shakeit.service.onSensorChanged(service.java:43) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.hardware.SensorManager$ListenerDelegate$1.handleMessage(SensorManager.java:529) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.os.Handler.dispatchMessage(Handler.java:99) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.os.Looper.loop(Looper.java:130) 07-15 12:35:45.280: E/AndroidRuntime(22469): at android.app.ActivityThread.main(ActivityThread.java:3835) 07-15 12:35:45.280: E/AndroidRuntime(22469): at java.lang.reflect.Method.invokeNative(Native Method) 07-15 12:35:45.280: E/AndroidRuntime(22469): at java.lang.reflect.Method.invoke(Method.java:507) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 07-15 12:35:45.280: E/AndroidRuntime(22469): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 07-15 12:35:45.280: E/AndroidRuntime(22469): at dalvik.system.NativeStart.main(Native Method) ```