uk.ac.starlink.table

Class CalcStarTable<C>

java.lang.Object

uk.ac.starlink.table.AbstractStarTable

uk.ac.starlink.table.CalcStarTable<C>

Type Parameters:

C - type of object that is calculated from each row of the input table, and supplies values to the corresponding row of this table

All Implemented Interfaces:

Closeable, AutoCloseable, StarTable

public abstract class CalcStarTable<C>
extends AbstractStarTable

StarTable implementation whose column values are derived from some single calculation on the column values of another table. The idea is that the cell values in a given row of an instance of this table are cheaply-obtained members of an object which is obtained by a potentially expensive calculation on the cell values of the corresponding row in the other table.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	CalcStarTable.Col<C,T> Defines a column for use with this table implementation.

Constructor Summary

Constructors

Constructor and Description
CalcStarTable(StarTable base, CalcStarTable.Col<C,?>[] columns) Constructor.

Method Summary

Modifier and Type	Method and Description
abstract C	createCalculation(long irow) Creates the calculation object for the given row of the input table.
abstract C	createCalculation(RowData baseRow) Creates the calculation object for the current row of the input table.
StarTable	getBaseTable() Returns the input table on which this table is based.
Object	getCell(long irow, int icol) The AbstractStarTable implementation of this method throws an UnsupportedOperationException, since unless otherwise provided there is no random access.
int	getColumnCount() Returns the number of columns in this table.
ColumnInfo	getColumnInfo(int icol) Returns the object describing the data in a given column.
Object[]	getRow(long irow) The AbstractStarTable implementation of this method constructs a row by repeated invocation of AbstractStarTable.getCell(long, int).
RowAccess	getRowAccess() Returns an object which can provide random access to this table's data, if random access is implemented.
long	getRowCount() Returns the number of rows in this table, if known.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table sequentially.
RowSplittable	getRowSplittable() Returns a default splittable which relies on table random access if available, or otherwise provides only sequential access (no splits).
boolean	isRandom() The AbstractStarTable implementation of this method returns false.

Methods inherited from class uk.ac.starlink.table.AbstractStarTable

checkedLongToInt, close, getColumnAuxDataInfos, getName, getParameters, getURL, setName, setParameters, setURL

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.starlink.table.StarTable

getParameterByName, setParameter

Constructor Detail

CalcStarTable

public CalcStarTable(StarTable base,
                     CalcStarTable.Col<C,?>[] columns)

Constructor.

Parameters:

base - input table

columns - array defining the columns of this table

Method Detail

createCalculation

public abstract C createCalculation(RowData baseRow)
                             throws IOException

Creates the calculation object for the current row of the input table.

Parameters:

baseRow - row from base table

Returns:

calculation object corresponding to baseRow

Throws:

IOException

createCalculation

public abstract C createCalculation(long irow)
                             throws IOException

Creates the calculation object for the given row of the input table. Only works for random-access tables.

Parameters:

irow - row index for which calculation is required

Returns:

calculation object for input table row irow

Throws:

IOException

getBaseTable

public StarTable getBaseTable()

Returns the input table on which this table is based.

Returns:

base table

getColumnInfo

public ColumnInfo getColumnInfo(int icol)

Description copied from interface: StarTable

Returns the object describing the data in a given column.

Specified by:

getColumnInfo in interface StarTable

Specified by:

getColumnInfo in class AbstractStarTable

Parameters:

icol - the column for which header information is required

Returns:

a ValueInfo object for column icol

getColumnCount

public int getColumnCount()

Description copied from interface: StarTable

Returns the number of columns in this table.

Specified by:

getColumnCount in interface StarTable

Specified by:

getColumnCount in class AbstractStarTable

Returns:

the number of columns

getRowCount

public long getRowCount()

Description copied from interface: StarTable

Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.

Specified by:

getRowCount in interface StarTable

Specified by:

getRowCount in class AbstractStarTable

Returns:

the number of rows, or -1

isRandom

public boolean isRandom()

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method returns false.

Specified by:

isRandom in interface StarTable

Overrides:

isRandom in class AbstractStarTable

Returns:

true if table random access methods are available

getRowSequence

public RowSequence getRowSequence()
                           throws IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowSequence in interface StarTable

Specified by:

getRowSequence in class AbstractStarTable

Returns:

new RowSequence

Throws:

IOException - if there is an error providing access

getRowSplittable

public RowSplittable getRowSplittable()
                               throws IOException

Description copied from class: AbstractStarTable

Returns a default splittable which relies on table random access if available, or otherwise provides only sequential access (no splits).

It is often possible to provide a better implementation than this.

Specified by:

getRowSplittable in interface StarTable

Overrides:

getRowSplittable in class AbstractStarTable

Returns:

Tables.getDefaultRowSplittable(this)

Throws:

IOException

See Also:

RowRunner

getRowAccess

public RowAccess getRowAccess()
                       throws IOException

Description copied from interface: StarTable

Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowAccess in interface StarTable

Overrides:

getRowAccess in class AbstractStarTable

Returns:

new RowAccess

Throws:

IOException - if there is an error setting up access

getRow

public Object[] getRow(long irow)
                throws IOException

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method constructs a row by repeated invocation of AbstractStarTable.getCell(long, int).

Specified by:

getRow in interface StarTable

Overrides:

getRow in class AbstractStarTable

Parameters:

irow - the index of the row to retrieve

Returns:

an array of the objects in each cell in row irow

Throws:

IOException - if there is an error reading the data

getCell

public Object getCell(long irow,
                      int icol)
               throws IOException

Description copied from class: AbstractStarTable

The AbstractStarTable implementation of this method throws an UnsupportedOperationException, since unless otherwise provided there is no random access.

Specified by:

getCell in interface StarTable

Overrides:

getCell in class AbstractStarTable

Parameters:

irow - the index of the cell's row

icol - the index of the cell's column

Returns:

the contents of this cell

Throws:

IOException - if there is an error reading the data