# Class RowSorter<M>

java.lang.Object
javax.swing.RowSorter<M>

Type Parameters:
  `M` - the type of the underlying model

Direct Known Subclasses:
  `DefaultRowSorter`

public abstract class RowSorter<M> extends Object
`RowSorter` provides the basis for sorting and filtering. Beyond creating and installing a `RowSorter`, you very rarely need to interact with one directly. Refer to `TableRowSorter` for a concrete implementation of `RowSorter` for `JTable`.

`RowSorter`'s primary role is to provide a mapping between two coordinate systems: that of the view (for example a `JTable`) and that of the underlying data source, typically a model.

The view invokes the following methods on the `RowSorter`:

- `toggleSortOrder` — The view invokes this when the appropriate user gesture has occurred to trigger a sort. For example, the user clicked a column header in a table.
- One of the model change methods — The view invokes a model change method when the underlying model has changed. There may be order dependencies in how the events are delivered, so a `RowSorter` should not update its mapping until one of these methods is invoked.

Because the view makes extensive use of the `convertRowIndexToModel`, `convertRowIndexToView` and `getViewRowCount` methods, these methods need to be fast.

`RowSorter` provides notification of changes by way of `RowSorterListener`. Two types of notification are sent:

- `RowSorterEvent.Type.SORT_ORDER_CHANGED` — notifies listeners that the sort order has changed. This is typically followed by a notification that the sort has changed.
- `RowSorterEvent.Type.SORTED` — notifies listeners that the mapping maintained by the `RowSorter` has changed in some way.

`RowSorter` implementations typically don't have a one-to-one mapping with the underlying model, but they can. For example, if a database does the sorting, `toggleSortOrder` might call through to the database (on a background thread), and override the mapping methods to return the argument that is passed in.

Concrete implementations of `RowSorter` need to reference a model such as `TableModel` or `ListModel`. The view classes, such as `JTable` and `JList`, will also have a reference to the model. To avoid ordering dependencies, `RowSorter` implementations should not install a listener on the model. Instead the view class will call into the `RowSorter` when the model changes. For example, if a row is updated in a `TableModel` `JTable` invokes `rowsUpdated`. When the model changes, the view may call into any of the following methods: `modelStructureChanged`, `allRowsChanged`, `rowsInserted`, `rowsDeleted` and `rowsUpdated`.

Since:
  1.6
See Also:
  - `TableRowSorter`

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `RowSorter.SortKey`
  SortKey describes the sort order for a particular column.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `RowSorter()`
  Creates a `RowSorter`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addRowSorterListener(RowSorterListener l)`
  Adds a `RowSorterListener` to receive notification about this `RowSorter`.
  `abstract void`
  `allRowsChanged()`
  Invoked when the contents of the underlying model have completely changed.
  `abstract int`
  `convertRowIndexToModel(int index)`
  Returns the location of `index` in terms of the underlying model.
  `abstract int`
  `convertRowIndexToView(int index)`
  Returns the location of `index` in terms of the view.
  `protected void`
  `fireRowSorterChanged(int[] lastRowIndexToModel)`
  Notifies listener that the mapping has changed.
  `protected void`
  `fireSortOrderChanged()`
  Notifies listener that the sort order has changed.
  `abstract M`
  `getModel()`
  Returns the underlying model.
  `abstract int`
  `getModelRowCount()`
  Returns the number of rows in the underlying model.
  `abstract List<? extends RowSorter.SortKey>`
  `getSortKeys()`
  Returns the current sort keys.
  `abstract int`
  `getViewRowCount()`
  Returns the number of rows in the view.
  `abstract void`
  `modelStructureChanged()`
  Invoked when the underlying model structure has completely changed.
  `void`
  `removeRowSorterListener(RowSorterListener l)`
  Removes a `RowSorterListener`.
  `abstract void`
  `rowsDeleted(int firstRow, int endRow)`
  Invoked when rows have been deleted from the underlying model in the specified range (inclusive).
  `abstract void`
  `rowsInserted(int firstRow, int endRow)`
  Invoked when rows have been inserted into the underlying model in the specified range (inclusive).
  `abstract void`
  `rowsUpdated(int firstRow, int endRow)`
  Invoked when rows have been changed in the underlying model between the specified range (inclusive).
  `abstract void`
  `rowsUpdated(int firstRow, int endRow, int column)`
  Invoked when the column in the rows have been updated in the underlying model between the specified range.
  `abstract void`
  `setSortKeys(List<? extends RowSorter.SortKey> keys)`
  Sets the current sort keys.
  `abstract void`
  `toggleSortOrder(int column)`
  Reverses the sort order of the specified column.

  ### Methods declared in class Object

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

- ## Constructor Details

  - ### RowSorter

    public RowSorter()
    Creates a `RowSorter`.

- ## Method Details

  - ### getModel

    public abstract M getModel()
    Returns the underlying model.
    Returns:
      the underlying model

  - ### toggleSortOrder

    public abstract void toggleSortOrder(int column)
    Reverses the sort order of the specified column. It is up to subclasses to provide the exact behavior when invoked. Typically this will reverse the sort order from ascending to descending (or descending to ascending) if the specified column is already the primary sorted column; otherwise, makes the specified column the primary sorted column, with an ascending sort order. If the specified column is not sortable, this method has no effect.

    If this results in changing the sort order and sorting, the appropriate `RowSorterListener` notification will be sent.

    Parameters:
      `column` - the column to toggle the sort ordering of, in terms of the underlying model
    Throws:
      `IndexOutOfBoundsException` - if column is outside the range of the underlying model

  - ### convertRowIndexToModel

    public abstract int convertRowIndexToModel(int index)
    Returns the location of `index` in terms of the underlying model. That is, for the row `index` in the coordinates of the view this returns the row index in terms of the underlying model.
    Parameters:
      `index` - the row index in terms of the underlying view
    Returns:
      row index in terms of the view
    Throws:
      `IndexOutOfBoundsException` - if `index` is outside the range of the view

  - ### convertRowIndexToView

    public abstract int convertRowIndexToView(int index)
    Returns the location of `index` in terms of the view. That is, for the row `index` in the coordinates of the underlying model this returns the row index in terms of the view.
    Parameters:
      `index` - the row index in terms of the underlying model
    Returns:
      row index in terms of the view, or -1 if index has been filtered out of the view
    Throws:
      `IndexOutOfBoundsException` - if `index` is outside the range of the model

  - ### setSortKeys

    public abstract void setSortKeys(List<? extends RowSorter.SortKey> keys)
    Sets the current sort keys.
    Parameters:
      `keys` - the new `SortKeys`; `null` is a shorthand for specifying an empty list, indicating that the view should be unsorted

  - ### getSortKeys

    public abstract List<? extends RowSorter.SortKey> getSortKeys()
    Returns the current sort keys. This must return a `non-null List` and may return an unmodifiable `List`. If you need to change the sort keys, make a copy of the returned `List`, mutate the copy and invoke `setSortKeys` with the new list.
    Returns:
      the current sort order

  - ### getViewRowCount

    public abstract int getViewRowCount()
    Returns the number of rows in the view. If the contents have been filtered this might differ from the row count of the underlying model.
    Returns:
      number of rows in the view
    See Also:
      - `getModelRowCount()`

  - ### getModelRowCount

    public abstract int getModelRowCount()
    Returns the number of rows in the underlying model.
    Returns:
      number of rows in the underlying model
    See Also:
      - `getViewRowCount()`

  - ### modelStructureChanged

    public abstract void modelStructureChanged()
    Invoked when the underlying model structure has completely changed. For example, if the number of columns in a `TableModel` changed, this method would be invoked.

    You normally do not call this method. This method is public to allow view classes to call it.

  - ### allRowsChanged

    public abstract void allRowsChanged()
    Invoked when the contents of the underlying model have completely changed. The structure of the table is the same, only the contents have changed. This is typically sent when it is too expensive to characterize the change in terms of the other methods.

    You normally do not call this method. This method is public to allow view classes to call it.

  - ### rowsInserted

    public abstract void rowsInserted(int firstRow, int endRow)
    Invoked when rows have been inserted into the underlying model in the specified range (inclusive).

    The arguments give the indices of the effected range. The first argument is in terms of the model before the change, and must be less than or equal to the size of the model before the change. The second argument is in terms of the model after the change and must be less than the size of the model after the change. For example, if you have a 5-row model and add 3 items to the end of the model the indices are 5, 7.

    You normally do not call this method. This method is public to allow view classes to call it.

    Parameters:
      `firstRow` - the first row
      `endRow` - the last row
    Throws:
      `IndexOutOfBoundsException` - if either argument is invalid, or `firstRow` > `endRow`

  - ### rowsDeleted

    public abstract void rowsDeleted(int firstRow, int endRow)
    Invoked when rows have been deleted from the underlying model in the specified range (inclusive).

    The arguments give the indices of the effected range and are in terms of the model before the change. For example, if you have a 5-row model and delete 3 items from the end of the model the indices are 2, 4.

    You normally do not call this method. This method is public to allow view classes to call it.

    Parameters:
      `firstRow` - the first row
      `endRow` - the last row
    Throws:
      `IndexOutOfBoundsException` - if either argument is outside the range of the model before the change, or `firstRow` > `endRow`

  - ### rowsUpdated

    public abstract void rowsUpdated(int firstRow, int endRow)
    Invoked when rows have been changed in the underlying model between the specified range (inclusive).

    You normally do not call this method. This method is public to allow view classes to call it.

    Parameters:
      `firstRow` - the first row, in terms of the underlying model
      `endRow` - the last row, in terms of the underlying model
    Throws:
      `IndexOutOfBoundsException` - if either argument is outside the range of the underlying model, or `firstRow` > `endRow`

  - ### rowsUpdated

    public abstract void rowsUpdated(int firstRow, int endRow, int column)
    Invoked when the column in the rows have been updated in the underlying model between the specified range.

    You normally do not call this method. This method is public to allow view classes to call it.

    Parameters:
      `firstRow` - the first row, in terms of the underlying model
      `endRow` - the last row, in terms of the underlying model
      `column` - the column that has changed, in terms of the underlying model
    Throws:
      `IndexOutOfBoundsException` - if either argument is outside the range of the underlying model after the change, `firstRow` > `endRow`, or `column` is outside the range of the underlying model

  - ### addRowSorterListener

    public void addRowSorterListener(RowSorterListener l)
    Adds a `RowSorterListener` to receive notification about this `RowSorter`. If the same listener is added more than once it will receive multiple notifications. If `l` is `null` nothing is done.
    Parameters:
      `l` - the `RowSorterListener`

  - ### removeRowSorterListener

    public void removeRowSorterListener(RowSorterListener l)
    Removes a `RowSorterListener`. If `l` is `null` nothing is done.
    Parameters:
      `l` - the `RowSorterListener`

  - ### fireSortOrderChanged

    protected void fireSortOrderChanged()
    Notifies listener that the sort order has changed.

  - ### fireRowSorterChanged

    protected void fireRowSorterChanged(int[] lastRowIndexToModel)
    Notifies listener that the mapping has changed.
    Parameters:
      `lastRowIndexToModel` - the mapping from model indices to view indices prior to the sort, may be `null`