The RecordEnumeration interface is used to retrieve and iterate through records from a record store. It maintains a sequence of record IDs using an optional record comparator for sorting. A record filter can select a subset of records for searching. The interface provides methods to navigate the sequence, check for next/previous records, and rebuild the index when records are added or removed from the store.

1. Interface RecordEnumeration
Interface RecordEnumeration

2. • It is used to retrieve data from the record store
• It also helps us to sort the records and searching the
records
• RecordEnumeration is build by calling
enumerateRecords() method
• An interface representing a bidirectional record store
Record enumerator. The RecordEnumeration logically
maintains a sequence of the recordId's of the records
in a record store. The enumerator will iterate over all
(or a subset, if an optional record filter has been
supplied) of the records in an order determined by an
optional record comparator.
Interface RecordEnumeration

3. • By using an optional RecordFilter, a subset of the records can be
chosen that match the supplied filter. This can be used for providing
search capabilities.
• By using an optional RecordComparator, the enumerator can index
through the records in an order determined by the comparator. This
can be used for providing sorting capabilities.
• If, while indexing through the enumeration, some records are
deleted from the record store, the recordId's returned by the
enumeration may no longer represent valid records. To avoid this
problem, the RecordEnumeration can optionally become a listener
of the RecordStore and react to record additions and deletions by
recreating its internal index. Use special care when using this option
however, in that every record addition, change and deletion will
cause the index to be rebuilt, which may have serious performance
impacts.
Interface RecordEnumeration

4. •
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If the RecordStore used by this RecordEnumeration is closed, this
RecordEnumeration becomes invalid and all subsequent operations performed on
it may give invalid results or throw a RecordStoreNotOpenException, even if the
same RecordStore is later opened again. In addition, calls
to hasNextElement() and hasPreviousElement() will return false.
The first call to nextRecord() returns the record data from the first record in the
sequence. Subsequent calls to nextRecord() return the next consecutive record's
data. To return the record data from the previous consecutive from any given point
in the enumeration, call previousRecord(). On the other hand, if after creation, the
first call is to previousRecord(), the record data of the last element of the
enumeration will be returned. Each subsequent call to previousRecord() will step
backwards through the sequence until the beginning is reached.
Final note, to do record store searches, create a RecordEnumeration with no
RecordComparator, and an appropriate RecordFilter with the desired search
criterion.
Interface RecordEnumeration

5. hasNextElement()
• It checks whether there is next
record(another) available in Record
Enumeration.
• It returns boolean ‘true’, if next record exists,
false otherwise
• Generally it is used in the looping statements
Interface RecordEnumeration

6. Rebuild()
• A RecordEnumeration can be rebuild by
explicitly calling the rebuild().
• This method is required, when automatic
updation mode is disabled and record store is
updated.
Interface RecordEnumeration

7. keepUpdated()
• This method sets the RecordEnumeration to
automatic updation mode, wherein the
enumeration is rebuilt whenever the records
are updated
Interface RecordEnumeration