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.

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

Constructors
Constructor and Description

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

Constructors
Constructor and Description
`ExpressionColumn(Table table, Expression expr)` Create a new ExpressionColumn.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`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)

Class ExpressionColumn

Field Summary

Fields inherited from class prefuse.data.column.AbstractColumn

Constructor Summary

Method Summary

Methods inherited from class prefuse.data.column.AbstractColumn

Methods inherited from class java.lang.Object

Constructor Detail

ExpressionColumn

Method Detail

init

getRowCount

setMaximumRow

isCacheValid

invalidateCache

revertToDefault

canSet

get

set

getBoolean

getInt

getDouble

getFloat

getLong