Where do I need to use a Synchronized statement when using a FileBackupHelper

Question

Android's Data Backup guide says that reading and writing to internal storage is "not threadsafe" and therefore I need to use Synchronized statements when accessing the file. I've worked very little with file input/output so far, but my understanding is that Synchronized uses a static object to make sure multiple parts of the program don't try to edit a file at the same time.

What's not clear to me is where I need to use this statement. I use it, for example, in the onBackup and onRestore methods as instructed in the guide:

public void onBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
     ParcelFileDescriptor newState) throws IOException {
        synchronized (DBAdapter.dbBackupLockObject) {
                super.onBackup(oldState, data, newState);
        }
}

My question is, do I need to do the same thing everywhere I read/write the db in my code? My instinct says yes, but I want to confirm before I go adding this statement to the million places I access my db.

So should I change a snippet like this

db.open();
Semester curSemester = db.getSemester(curSemesterId);
db.close();

to

synchronized (DBAdapter.dbBackupLockObject) {
        db.open();
        Semester curSemester = db.getSemester(curSemesterId);
        db.close();
} 

? Is that what I should be doing? Surround every open/close with a synchronized statement?