prefuse.data.column
Class ExpressionColumn

java.lang.Object
  prefuse.data.column.AbstractColumn
      prefuse.data.column.ExpressionColumn

All Implemented Interfaces:

Column

public class ExpressionColumn
extends AbstractColumn

Column instance that stores values provided by an Expression instance. These expressions can reference other column values within the same table. Values are evaluated when first requested and then cached to increase performance. This column maintains listeners for all referenced columns discovered in the expression and for the expression itself, invalidating all cached entries when an update to either occurs.

WARNING: Infinite recursion, eventually resulting in a StackOverflowError, could occur if an expression refers to its own column, or if two ExpressionColumns have expressions referring to each other. The responsibility for avoiding such situations is left with client programmers. Note that it is fine for one ExpressionColumn to reference another; however, the graph induced by such references must not contain any cycles.

Author:

jeffrey heer

See Also:

prefuse.data.expression

Field Summary

Fields inherited from class prefuse.data.column.AbstractColumn

m_columnType, m_defaultValue, m_listeners, m_parser, m_readOnly

Constructor Summary

ExpressionColumn(Table table, Expression expr)
Create a new ExpressionColumn.

Method Summary

boolean	canSet(java.lang.Class type) Indicates if the set method can be called without an exception being thrown for the given type.
java.lang.Object	get(int row) Get the data value at the specified row
boolean	getBoolean(int row) Get the data value at the specified row as a boolean
double	getDouble(int row) Get the data value at the specified row as a double
float	getFloat(int row) Get the data value at the specified row as a float
int	getInt(int row) Get the data value at the specified row as an integer
long	getLong(int row) Get the data value at the specified row as a long
int	getRowCount() Returns the number of rows in this data column
protected void	init()
void	invalidateCache(int start, int end) Invalidate a range of the cache.
boolean	isCacheValid(int row) Check if this ExpressionColumn has a valid cached value at the given row.
void	revertToDefault(int row) Has no effect, as all values in this column are derived.
void	set(java.lang.Object val, int row) Set the data value at the specified row
void	setMaximumRow(int nrows) Sets the number of rows in this data column

Methods inherited from class prefuse.data.column.AbstractColumn

addColumnListener, canGet, canGetBoolean, canGetDate, canGetDouble, canGetFloat, canGetInt, canGetLong, canGetString, canSetBoolean, canSetDate, canSetDouble, canSetFloat, canSetInt, canSetLong, canSetString, fireColumnEvent, fireColumnEvent, fireColumnEvent, fireColumnEvent, fireColumnEvent, fireColumnEvent, fireColumnEvent, getColumnType, getDate, getDefaultValue, getParser, getString, isCellEditable, isReadOnly, removeColumnListener, setBoolean, setDate, setDefaultValue, setDouble, setFloat, setInt, setLong, setParser, setReadOnly, setString

Methods inherited from class java.lang.Object

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

Constructor Detail

ExpressionColumn

public ExpressionColumn(Table table,
                        Expression expr)

Create a new ExpressionColumn.

Parameters:

table - the table this column is a member of

expr - the expression used to provide the column values

Method Detail

init

protected void init()

getRowCount

public int getRowCount()

Description copied from interface: Column

Returns the number of rows in this data column

Returns:

the number of rows

See Also:

Column.getRowCount()

setMaximumRow

public void setMaximumRow(int nrows)

Description copied from interface: Column

Sets the number of rows in this data column

Parameters:

nrows - the number of rows

See Also:

Column.setMaximumRow(int)

isCacheValid

public boolean isCacheValid(int row)

Check if this ExpressionColumn has a valid cached value at the given row.

Parameters:

row - the row to check for a valid cache entry

Returns:

true if the cache row is valid, false otherwise

invalidateCache

public void invalidateCache(int start,
                            int end)

Invalidate a range of the cache.

Parameters:

start - the start of the range to invalidate

end - the end of the range to invalidate, inclusive

revertToDefault

public void revertToDefault(int row)

Has no effect, as all values in this column are derived.

Specified by:

revertToDefault in interface Column

Overrides:

revertToDefault in class AbstractColumn

Parameters:

row - the row to revert

canSet

public boolean canSet(java.lang.Class type)

Description copied from class: AbstractColumn

Indicates if the set method can be called without an exception being thrown for the given type.

Specified by:

canSet in interface Column

Overrides:

canSet in class AbstractColumn

Parameters:

type - the Class of the data type to check

Returns:

true if the type is supported by this column, false otherwise

See Also:

AbstractColumn.canSet(java.lang.Class)

get

public java.lang.Object get(int row)

Description copied from interface: Column

Get the data value at the specified row

Parameters:

row - the row from which to retrieve the value

Returns:

the data value

See Also:

Column.get(int)

set

public void set(java.lang.Object val,
                int row)
         throws DataTypeException

Description copied from interface: Column

Set the data value at the specified row

Parameters:

val - the value to set

row - the row at which to set the value

Throws:

DataTypeException

See Also:

Column.set(java.lang.Object, int)

getBoolean

public boolean getBoolean(int row)
                   throws DataTypeException

Description copied from class: AbstractColumn

Get the data value at the specified row as a boolean

Specified by:

getBoolean in interface Column

Overrides:

getBoolean in class AbstractColumn

Parameters:

row - the row from which to retrieve the value

Returns:

the data value as a boolean

Throws:

DataTypeException - if this column does not support the boolean type

See Also:

Column.getBoolean(int)

getInt

public int getInt(int row)
           throws DataTypeException

Description copied from class: AbstractColumn

Get the data value at the specified row as an integer

Specified by:

getInt in interface Column

Overrides:

getInt in class AbstractColumn

Parameters:

row - the row from which to retrieve the value

Returns:

the data value as an integer

Throws:

DataTypeException - if this column does not support the integer type

See Also:

Column.getInt(int)

getDouble

public double getDouble(int row)
                 throws DataTypeException

Description copied from class: AbstractColumn

Get the data value at the specified row as a double

Specified by:

getDouble in interface Column

Overrides:

getDouble in class AbstractColumn

Parameters:

row - the row from which to retrieve the value

Returns:

the data value as a double

Throws:

DataTypeException - if this column does not support the double type

See Also:

Column.getDouble(int)

getFloat

public float getFloat(int row)
               throws DataTypeException

Description copied from class: AbstractColumn

Get the data value at the specified row as a float

Specified by:

getFloat in interface Column

Overrides:

getFloat in class AbstractColumn

Parameters:

row - the row from which to retrieve the value

Returns:

the data value as a float

Throws:

DataTypeException - if this column does not support the float type

See Also:

Column.getFloat(int)

getLong

public long getLong(int row)
             throws DataTypeException

Description copied from class: AbstractColumn

Get the data value at the specified row as a long

Specified by:

getLong in interface Column

Overrides:

getLong in class AbstractColumn

Parameters:

row - the row from which to retrieve the value

Returns:

the data value as a long

Throws:

DataTypeException - if this column does not support the long type

See Also:

Column.getLong(int)