private JobStore(Context context,File dataDir){
  mContext=context;
  mDirtyOperations=0;
  File systemDir=new File(dataDir,"system");
  File jobDir=new File(systemDir,"job");
  jobDir.mkdirs();
  mJobsFile=new AtomicFile(new File(jobDir,"jobs.xml"));
  mJobSet=new ArraySet<JobStatus>();
  readJobMapFromDisk(mJobSet);
}

private JobStore ( Context context , File dataDir ) { mContext = context ; mDirtyOperations = 0 ; File systemDir = new File ( dataDir , "system" ) ; File jobDir = new File ( systemDir , "job" ) ; jobDir . mkdirs ( ) ; mJobsFile = new AtomicFile ( new File ( jobDir , "jobs.xml" ) ) ; mJobSet = new ArraySet < JobStatus > ( ) ; readJobMapFromDisk ( mJobSet ) ; }
construct the instance of the job store . this results in a blocking read from disk .
