public boolean checkRootBySuperUserApk(){
  File suApk=new File(SU_APK);
  if (suApk != null && suApk.exists()) {
    return true;
  }
  return false;
}

public boolean checkRootBySuperUserApk ( ) { File suApk = new File ( SU_APK ) ; if ( suApk != null && suApk . exists ( ) ) { return true ; } return false ; }
returns true if the device contains superuser . apk which is stored into the device in the rooting process .
