what is the reason for "java.lang.NoClassDefFoundError: com.estimote.sdk.BeaconManager" ?Please help me to rseolve : java.lang.NoClassDefFoundError: com.estimote.sdk.BeaconManager

	at com.campus.ReadingBeaconService.onStart(ReadingBeaconService.java:50)
	at android.app.Service.onStartCommand(Service.java:450)
	at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2702)
	at android.app.ActivityThread.access$2100(ActivityThread.java:135)
	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293)
	at android.os.Handler.dispatchMessage(Handler.java:102)
	at android.os.Looper.loop(Looper.java:136)
	at android.app.ActivityThread.main(ActivityThread.java:5017)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at java.lang.reflect.Method.invoke(Method.java:515)
	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
	at dalvik.system.NativeStart.main(Native Method)