uk.ac.starlink.table

Interface RowSequence

All Superinterfaces:

AutoCloseable, Closeable, RowData, Sequence

All Known Subinterfaces:

ConeQueryRowSequence, ConeResultRowSequence, RowSplittable

All Known Implementing Classes:

AccessRowSequence, ColumnQueryRowSequence, CountCheckRowSequence, EmptyRowSequence, IteratorRowSequence, MappingRowSplittable, OnceRowPipe, ParallelResultRowSequence, ProgressRowSequence, ProgressRowSplittable, RandomRowSplittable, ReaderRowSequence, SequentialJELRowReader, SequentialResultRowSequence, SequentialRowSplittable, WrapperQuerySequence, WrapperRowSequence

public interface RowSequence
extends Closeable, RowData, Sequence

Provides sequential access to the data in a table. The data is a sequence of rows which may be processed from the first to the last. A RowSequence iterates over the rows one at a time. It starts off positioned before the first row, so the next method must be invoked before the first row can be accessed.

Typical usage might look like this:

     RowSequence rseq = table.getRowSequence();
     try {
         while ( rseq.next() ) {
             Object[] row = rseq.getRow();
                ...
         }
     }
     finally {
         rseq.close();
     }
 

A RowSequence cannot in general be expected to be used safely from multiple threads.

Author:

Mark Taylor (Starlink)

Method Summary

Modifier and Type	Method and Description
void	close() Indicates that this sequence will not be required any more.
Object	getCell(int icol) Returns the contents of a cell in the current row.
Object[]	getRow() Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.
boolean	next() Attempts to advance the current row to the next one.

Method Detail

next

boolean next()
      throws IOException

Attempts to advance the current row to the next one. If true is returned the attempt has been successful, and if false is returned there are no more rows in this sequence. Since the initial position of a RowSequence is before the first row, this method must be called before current row data can be accessed using the getCell(int) or getRow() methods.

Specified by:

next in interface Sequence

Returns:

true iff this sequence has been advanced to the next row

Throws:

IOException - if there is some error

getCell

Object getCell(int icol)
        throws IOException

Returns the contents of a cell in the current row. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass(). An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getCell in interface RowData

Parameters:

icol - column index

Returns:

the contents of cell icol in the current row

Throws:

IOException - if there is an error reading the data

IllegalStateException - if there is no current row (before the start of the table)

getRow

Object[] getRow()
         throws IOException

Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table. An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getRow in interface RowData

Returns:

an array of the objects in each cell in row irow

Throws:

IOException - if there is an error reading the data

close

void close()
    throws IOException

Indicates that this sequence will not be required any more. This should release resources associated with this object. The effect of calling any of the other methods following a close is undefined.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException