uk.ac.starlink.table

Class ColumnData

java.lang.Object

uk.ac.starlink.table.ColumnData

Direct Known Subclasses:

ArrayColumn, BinResultColumnData, BlankColumn, ConstantColumn, WrapperColumn

public abstract class ColumnData
extends Object

A column which can supply and possibly store cells in array-like storage as well as supply column metadata. Note there is nothing in this class which describes the number of elements it contains (length of the column). Columns are intended to be managed by tables, and it is the table which should keep track of this information.

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
ColumnData() Constructs a new ColumnData with no metadata.
ColumnData(ColumnInfo colinfo) Constructs a new ColumnData with metadata supplied by a given ColumnInfo object.
ColumnData(ValueInfo base) Performs ColumnData initialisation based on template ValueInfo object.

Method Summary

Modifier and Type	Method and Description
ColumnInfo	getColumnInfo() Returns the ColumnInfo which provides the metadata for this column.
boolean	isWritable() Indicates whether this object can store values.
abstract Object	readValue(long irow) Returns the value stored at a given row in this column.
void	setColumnInfo(ColumnInfo colinfo) Sets the ColumnInfo which provides the metadata for this column.
void	storeValue(long irow, Object val) Stores a given value in a given row for this column.

Methods inherited from class java.lang.Object

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

Constructor Detail

ColumnData

public ColumnData()

Constructs a new ColumnData with no metadata.

ColumnData

public ColumnData(ColumnInfo colinfo)

Constructs a new ColumnData with metadata supplied by a given ColumnInfo object.

Parameters:

colinfo - the column metadata

ColumnData

public ColumnData(ValueInfo base)

Performs ColumnData initialisation based on template ValueInfo object.

Parameters:

base - template

Method Detail

getColumnInfo

public ColumnInfo getColumnInfo()

Returns the ColumnInfo which provides the metadata for this column.

Returns:

the column metadata

setColumnInfo

public void setColumnInfo(ColumnInfo colinfo)

Sets the ColumnInfo which provides the metadata for this column.

Parameters:

colinfo - the column metadata

readValue

public abstract Object readValue(long irow)
                          throws IOException

Returns the value stored at a given row in this column.

Parameters:

irow - the row from which to retrieve the value

Returns:

the value stored at irow

Throws:

IOException - if there is some problem reading

storeValue

public void storeValue(long irow,
                       Object val)
                throws IOException

Stores a given value in a given row for this column. Will only work if the isWritable method returns true. The implementation in the ColumnData class throws an UnsupportedOperationException.

Parameters:

val - the object to store

irow - the row to store it in

Throws:

UnsupportedOperationException - if !isWritable()

NullPointerException - if val==null and this column is not nullable

ArrayStoreException - if val is not compatible with the content class of this column

IOException - if there is some problem writing

isWritable

public boolean isWritable()

Indicates whether this object can store values. The implementation in the ColumnData class returns false

Returns:

true iff storeValue(long, java.lang.Object) can be used