title: java.lang.RuntimeException: Unable to instantiate activity
body: <p>how can I fix bellow errors from my logcat</p>
  
  <pre><code>   java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{hesh.ballc/hesh.ballc.MainActivity}: java.lang.IllegalAccessException: hesh.ballc.MainActivity() is not accessible from class android.app.Instrumentation
          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
          at android.app.ActivityThread.access$800(ActivityThread.java:151)
          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
          at android.os.Handler.dispatchMessage(Handler.java:102)
          at android.os.Looper.loop(Looper.java:135)
          at android.app.ActivityThread.main(ActivityThread.java:5257)
          at java.lang.reflect.Method.invoke(Native Method)
          at java.lang.reflect.Method.invoke(Method.java:372)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)    
  
  
  
  Caused by: java.lang.IllegalAccessException: hesh.ballc.MainActivity() is not accessible from class android.app.Instrumentation
          at java.lang.Class.newInstance(Class.java:1603)
          at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
  </code></pre>
  
  <p>There is no errors in code as I can see, after running my program  it stops in my emulator and I get bellow errors, should I import some libary ? </p>
  
  <p>            </p>