uk.ac.starlink.table

Class CountCheckRowSequence

java.lang.Object

uk.ac.starlink.table.CountCheckRowSequence

All Implemented Interfaces:

Closeable, AutoCloseable, RowData, RowSequence, Sequence

public class CountCheckRowSequence
extends Object
implements RowSequence

RowSequence wrapper class that guarantees a given number of rows. The expectation is that the underlying row sequence has the declared row count, but if it has a different number the output of this sequence is forced to the declared value by adding dummy rows or discarding extra rows as required. If such adjustments are required, suitable messages are written through the logging system.

Since:

10 Nov 2022

Author:

Mark Taylor

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.
static RowSequence	getSafeRowSequence(RowSequence rseq, int ncol, long nrow) Returns a row sequence guaranteed to give the required number of rows.
boolean	next() Attempts to advance the current row to the next one.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

next

public boolean next()
             throws IOException

Description copied from interface: RowSequence

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 RowSequence.getCell(int) or RowSequence.getRow() methods.

Specified by:

next in interface RowSequence

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

public Object getCell(int icol)
               throws IOException

Description copied from interface: RowSequence

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

Specified by:

getCell in interface RowSequence

Parameters:

icol - column index

Returns:

the contents of cell icol in the current row

Throws:

IOException - if there is an error reading the data

getRow

public Object[] getRow()
                throws IOException

Description copied from interface: RowSequence

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

Specified by:

getRow in interface RowSequence

Returns:

an array of the objects in each cell in row irow

Throws:

IOException - if there is an error reading the data

close

public void close()
           throws IOException

Description copied from interface: RowSequence

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 Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface RowSequence

Throws:

IOException

getSafeRowSequence

public static RowSequence getSafeRowSequence(RowSequence rseq,
                                             int ncol,
                                             long nrow)

Returns a row sequence guaranteed to give the required number of rows.

Parameters:

rseq - row sequence on which the returned one is based

ncol - number of columns (required for constructing dummy rows)

nrow - required number of rows, or -1 for no requirement

Returns:

safe row sequence; if nrow<0 the input sequence will be returned