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MID Profile: Interface RecordEnumeration
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javax.microedition.rms</FONT>
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Interface RecordEnumeration</H2>
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<DT>public interface <B>RecordEnumeration</B></DL>
<P>
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. <p>By using an optional <code>RecordFilter</code>, a subset of the records can be chosen that match the supplied filter. This can be used for providing search capabilities.</p> <p>By using an optional <code>RecordComparator</code>, the enumerator can index through the records in an order determined by the comparator. This can be used for providing sorting capabilities.</p> <p>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through the enumeration, some records are deleted from the record store, the recordId's returned by the enumeration may no longer represent valid records.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.</p> <p>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 <code>hasNextElement()</code> and <code>hasPreviousElement()</code> will return false.</p> <p>The first call to <code>nextRecord()</code> returns the record data from the first record in the sequence. Subsequent calls to <code>nextRecord()</code> return the next consecutive record's data. To return the record data from the previous consecutive from any given point in the enumeration, call <code>previousRecord()</code>. On the other hand, if after creation, the first call is to <code>previousRecord()</code>, the record data of the last element of the enumeration will be returned. Each subsequent call to <code>previousRecord()</code> will step backwards through the sequence until the beginning is reached.</p> <p>Final note, to do record store searches, create a RecordEnumeration with no RecordComparator, and an appropriate RecordFilter with the desired search criterion.</p>
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<DT><B>Since: </B><DD>MIDP 1.0</DD>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#destroy()">destroy</A></B>()</CODE>
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Frees internal resources used by this RecordEnumeration.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#hasNextElement()">hasNextElement</A></B>()</CODE>
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Returns true if more elements exist in the <em>next</em> direction.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#hasPreviousElement()">hasPreviousElement</A></B>()</CODE>
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Returns true if more elements exist in the <em>previous</em> direction.</TD>
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<CODE> boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#isKeptUpdated()">isKeptUpdated</A></B>()</CODE>
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Returns true if the enumeration keeps its enumeration current with any changes in the records.</TD>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#keepUpdated(boolean)">keepUpdated</A></B>(boolean keepUpdated)</CODE>
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Used to set whether the enumeration will be keep its internal index up to date with the record store record additions/deletions/changes.</TD>
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<CODE> byte[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#nextRecord()">nextRecord</A></B>()</CODE>
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Returns a copy of the <em>next</em> record in this enumeration, where <em>next</em> is defined by the comparator and/or filter supplied in the constructor of this enumerator.</TD>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#nextRecordId()">nextRecordId</A></B>()</CODE>
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Returns the recordId of the <em>next</em> record in this enumeration, where <em>next</em> is defined by the comparator and/or filter supplied in the constructor of this enumerator.</TD>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#numRecords()">numRecords</A></B>()</CODE>
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Returns the number of records available in this enumeration's set.</TD>
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<CODE> byte[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#previousRecord()">previousRecord</A></B>()</CODE>
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Returns a copy of the <em>previous</em> record in this enumeration, where <em>previous</em> is defined by the comparator and/or filter supplied in the constructor of this enumerator.</TD>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#previousRecordId()">previousRecordId</A></B>()</CODE>
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Returns the recordId of the <em>previous</em> record in this enumeration, where <em>previous</em> is defined by the comparator and/or filter supplied in the constructor of this enumerator.</TD>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#rebuild()">rebuild</A></B>()</CODE>
<BR>
Request that the enumeration be updated to reflect the current record set.</TD>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../javax/microedition/rms/RecordEnumeration.html#reset()">reset</A></B>()</CODE>
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Returns the enumeration index to the same state as right after the enumeration was created.</TD>
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