java - Variable null pointer exception -

I have a main address that stores the stable main variable (app's calculator). Therefore, after pausing the app (home button or calling)

  06-21 00: 43: 14.916: E / Android Random (26676): Extra exception: Asinka Task # 1 06-21 00 : 43: 14.916: e / AndroidRuntime (26,676): java.lang.RuntimeException: 43 :: 14.916: e / AndroidRuntime (26,676): to android.os.AsyncTask $ 3.done (AsyncTask an error doInBackground () 06-21 00 occurred while performing .java: 29 9) 06-21 00: 43: 14.916: e / Android Rentaim (26,676) on java.util.concurrent.FutureTask $ Sync.innerSetException (FutureTask.java .73) 06-21 00: 43: 14.916: e / AndroidRuntime (26,676): 43 :: 14.916: e / AndroidRuntime (26,676): java.util.concurrent.FutureTask $ sync java.util.concurrent.FutureTask.setException (FutureTask.java:124 ) 06-21 00. Intern (Future Task .Java 307) 06-21 00: 43: 14.916: E / Android Runtimem (26676): On Java. Util.company Fucrtskkrn (Fucrtskkjawa Projer 37) 06-21 00: 43: 14.916: 06-21 00 E / AndroidRuntime (26,676): android.os.AsyncTask $ SerialExecutor $ 1.run (AsyncTask.java:230): 43: 14.916: e / AndroidRuntime (26,676): eadPoolExecutor.runWorker on java.util.concurrent.Thr (ThreadPoolExecutor.java:1076) 06-21 00: 43: 14.916: e / AndroidRuntime (26,676): java.util.concurrent .ThreadPoolExecutor $ Worker.run (ThreadPoolExecutor.java:569) at 06-21 00: 43: 14.916: e / AndroidRuntime (26,676): at java.lang.Thread.run (Thread.java:856) 06-21 00: 43: 14.916: E / AndroidRuntime (26,676): Because of: java.lang.NullPointerException 06-21 00: 43: 14.916: E / Android Runtime (26676): Com. com. Calc Task. Do Inackger (AMain.java:106) 06-21 00: 43: 14.916: E / Android Time (26676): On Ru. Ps.horoscope.amain $ CalcTask.doInBackground (06/06/2016: 43: 14.916: E / AndroidRuntime (26676): android.os.AsyncTask 06.Cal (AsyncTask.java:287) 06 - 21 00: 43: 14.916: E / Android Runtime (26676): $ Sync.innerRun on java.util.concurrent.FutureTask (FutureTask.java.355) 06-21 00: 43: 14.916: E / Androindertime (26676) :. ..5 more   
 106 string:  if (! _c.Calculated) CALCULATE _ ();   
  _   
 How can this be decided?  
  @ Override Protected Voice Doignbackground (Zero ... arg0) {// TODO Auto-Generated Method Stub if (! _c.Calc.Calculated) CALCULATE_ (); Return tap; }    
 
 
  _  or  calc  Is empty    You will need to post the code to get more information from this