uk.ac.starlink.votable

Interface TabularData

All Superinterfaces:

AutoCloseable, Closeable

public interface TabularData
extends Closeable

Contains the actual cell contents of a VOTable TABLE element.

The cell data may always be retrieved sequentially from the table by acquiring a RowSequence object (method getRowSequence()) - this allows you to read all the data from the first row to the last. Multiple RowSequences may be simultaneously active. In some cases random access may also be available; if isRandom() returns true, then the getRowAccess(), getRow(long) and getCell(long, int) methods can be used to retrieve cell values in any order.

The objects retrieved from cells in a given column are of course determined by the corresponding FIELD element (FieldElement object), in particular its arraysize and datatype attributes. What object is returned from each column is described by the following rules:

• If the element is a scalar or (fixed-dimension) 1-element array, a primitive wrapper object (Integer, Float etc) will be normally be returned
• If the element is an array, a java array of primitives (int[], float[] etc) will normally be returned. This is stored in column-major order, where that makes a difference (for arrays with more than one dimension).
• Complex types types are treated by adding an extra dimension to the shape of the data, the most rapidly varying, of size 2.
• Character (char and unicodeChar) arrays are automatically turned into Strings or String arrays, with dimensionality one less than that suggested by the arraysize attribute
• The element may be null

In any case the class of returned objects in a given column may be determined by calling the getContentClass(int) method.

Author:

Mark Taylor

Method Summary

Modifier and Type	Method and Description
Object	getCell(long irow, int icol) Returns the contents of a given table cell (optional).
int	getColumnCount() Returns the number of columns in the table data.
Class<?>	getContentClass(int icol) Returns a class to which all elements in a given column can be cast.
Object[]	getRow(long irow) Returns the contents of a given table row (optional).
RowAccess	getRowAccess() Returns an object which can provide random access for the table data.
long	getRowCount() Returns the number of rows in the table data.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table data sequentially.
boolean	isRandom() Indicates whether random access is provided by this table.

Methods inherited from interface java.io.Closeable

close

Method Detail

getColumnCount

int getColumnCount()

Returns the number of columns in the table data.

Returns:

number of cells in each row

getRowCount

long getRowCount()

Returns the number of rows in the table data. If this cannot be determined (easily), the value -1 may be returned. The result will always be positive if isRandom() returns true.

Returns:

number of rows, or -1 if unknown

getContentClass

Class<?> getContentClass(int icol)

Returns a class to which all elements in a given column can be cast.

Parameters:

icol - the column (0-based)

Returns:

a class to which any non-null element returned by this object in column icol will belong

getRowSequence

RowSequence getRowSequence()
                    throws IOException

Returns an object which can iterate over all the rows in the table data sequentially. In general the returned object is only safe for use within a single thread.

Returns:

an object providing sequential access to the data

Throws:

IOException

isRandom

boolean isRandom()

Indicates whether random access is provided by this table. Only if the result is true may the getRow(long) and getCell(long, int) methods be used.

Returns:

true iff random access methods are available

getRowAccess

RowAccess getRowAccess()
                throws IOException

Returns an object which can provide random access for the table data. In general the returned object is only safe for use within a single thread.

Returns:

an object providing random access to the data

Throws:

IOException - if there is I/O trouble

UnsupportedOperationException - if isRandom returns false

getCell

Object getCell(long irow,
               int icol)
        throws IOException

Returns the contents of a given table cell (optional). The class of the returned object will be compatible with that returned by getContentClass(icol). Only provided if getRandom returns true.

Parameters:

irow - row index

icol - column index

Returns:

contents of the cell at irow, icol

Throws:

IOException - if there is I/O trouble

UnsupportedOperationException - if isRandom returns false

getRow

Object[] getRow(long irow)
         throws IOException

Returns the contents of a given table row (optional). Only provided if getRandom returns true.

Parameters:

irow - row index

Returns:

array of objects giving the cells in row irow (one cell per column)

Throws:

IOException - if there is I/O trouble

UnsupportedOperationException - if isRandom returns false