Question

I need to get a List of 10 consecutive database records from a random offset in the database each time.

The problem I see with this is overlapping the end boundary.

For example:

Let’s say my database only contains 20 records.

If I choose a random offset between 1 and 20 to start my read of 10 consecutive records and the random number happens to be, say, 15 – then I only get 5 records before I run into the end of the available range.

public getNext10RandomRecords() {

  int totalRecs = this.getTotalDatabaseRecordCount();
  Random rand = new Random();
  // ??
  int startOffSet = 15;
  int endOffSet = 25;
  query.setRange(startOffSet, endOffset); // oops! totalRecs == 20!

}

Answer 1

Choose your random offset to be in the range of 0 to totalRecs - 10. That way, the highest start offset will be totalRecs - 10 in which case your end offset will be equal to totalRecs.