com.google.common.collect
Class HashBasedTable<R,C,V>

java.lang.Object
  com.google.common.collect.HashBasedTable<R,C,V>

All Implemented Interfaces:

Table<R,C,V>, Serializable

@GwtCompatible(serializable=true)
@Beta
public class HashBasedTable<R,C,V>
extends Object

Implementation of Table using hash tables.

The views returned by column(C), columnKeySet(), and columnMap() have iterators that don't support remove(). Otherwise, all optional operations are supported. Null row keys, columns keys, and values are not supported.

Lookups by row key are often faster than lookups by column key, because the data is stored in a Map<R, Map<C, V>>. A method call like column(columnKey).get(rowKey) still runs quickly, since the row key is provided. However, column(columnKey).size() takes longer, since an iteration across all row keys occurs.

Note that this implementation is not synchronized. If multiple threads access this table concurrently and one of the threads modifies the table, it must be synchronized externally.

Since:

7.0

Author:

Jared Levy

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface com.google.common.collect.Table

Table.Cell<R,C,V>

Method Summary

Set<Table.Cell<R,C,V>>	cellSet() Returns a set of all row key / column key / value triplets.
void	clear() Removes all mappings from the table.
Map<R,V>	column(C columnKey) Returns a view of all mappings that have the given column key.
Set<C>	columnKeySet() Returns a set of column keys that have one or more values in the table.
Map<C,Map<R,V>>	columnMap() Returns a view that associates each column key with the corresponding map from row keys to values.
boolean	contains(Object rowKey, Object columnKey) Returns true if the table contains a mapping with the specified row and column keys.
boolean	containsColumn(Object columnKey) Returns true if the table contains a mapping with the specified column.
boolean	containsRow(Object rowKey) Returns true if the table contains a mapping with the specified row key.
boolean	containsValue(Object value) Returns true if the table contains a mapping with the specified value.
static <R,C,V> HashBasedTable<R,C,V>	create() Creates an empty HashBasedTable.
static <R,C,V> HashBasedTable<R,C,V>	create(int expectedRows, int expectedCellsPerRow) Creates an empty HashBasedTable with the specified map sizes.
static <R,C,V> HashBasedTable<R,C,V>	create(Table<? extends R,? extends C,? extends V> table) Creates a HashBasedTable with the same mappings as the specified table.
boolean	equals(Object obj) Compares the specified object with this table for equality.
V	get(Object rowKey, Object columnKey) Returns the value corresponding to the given row and column keys, or null if no such mapping exists.
int	hashCode() Returns the hash code for this table.
boolean	isEmpty() Returns true if the table contains no mappings.
V	put(R rowKey, C columnKey, V value) Associates the specified value with the specified keys.
void	putAll(Table<? extends R,? extends C,? extends V> table) Copies all mappings from the specified table to this table.
V	remove(Object rowKey, Object columnKey) Removes the mapping, if any, associated with the given keys.
Map<C,V>	row(R rowKey) Returns a view of all mappings that have the given row key.
Set<R>	rowKeySet() Returns a set of row keys that have one or more values in the table.
Map<R,Map<C,V>>	rowMap() Returns a view that associates each row key with the corresponding map from column keys to values.
int	size() Returns the number of row key / column key / value mappings in the table.
String	toString() Returns the string representation rowMap().toString().
Collection<V>	values() Returns a collection of all values, which may contain duplicates.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

create

public static <R,C,V> HashBasedTable<R,C,V> create()

Creates an empty HashBasedTable.

create

public static <R,C,V> HashBasedTable<R,C,V> create(int expectedRows,
                                                   int expectedCellsPerRow)

Creates an empty HashBasedTable with the specified map sizes.

Parameters:

expectedRows - the expected number of distinct row keys

expectedCellsPerRow - the expected number of column key / value mappings in each row

Throws:

IllegalArgumentException - if expectedRows or expectedCellsPerRow is negative

create

public static <R,C,V> HashBasedTable<R,C,V> create(Table<? extends R,? extends C,? extends V> table)

Creates a HashBasedTable with the same mappings as the specified table.

Parameters:

table - the table to copy

Throws:

NullPointerException - if any of the row keys, column keys, or values in table is null

contains

public boolean contains(@Nullable
                        Object rowKey,
                        @Nullable
                        Object columnKey)

Description copied from interface: Table

Returns true if the table contains a mapping with the specified row and column keys.

Specified by:

contains in interface Table<R,C,V>

Parameters:

rowKey - key of row to search for

columnKey - key of column to search for

containsColumn

public boolean containsColumn(@Nullable
                              Object columnKey)

Description copied from interface: Table

Returns true if the table contains a mapping with the specified column.

Specified by:

containsColumn in interface Table<R,C,V>

Parameters:

columnKey - key of column to search for

containsRow

public boolean containsRow(@Nullable
                           Object rowKey)

Description copied from interface: Table

Returns true if the table contains a mapping with the specified row key.

Specified by:

containsRow in interface Table<R,C,V>

Parameters:

rowKey - key of row to search for

containsValue

public boolean containsValue(@Nullable
                             Object value)

Description copied from interface: Table

Returns true if the table contains a mapping with the specified value.

Specified by:

containsValue in interface Table<R,C,V>

Parameters:

value - value to search for

get

public V get(@Nullable
             Object rowKey,
             @Nullable
             Object columnKey)

Description copied from interface: Table

Returns the value corresponding to the given row and column keys, or null if no such mapping exists.

Specified by:

get in interface Table<R,C,V>

Parameters:

rowKey - key of row to search for

columnKey - key of column to search for

equals

public boolean equals(@Nullable
                      Object obj)

Description copied from interface: Table

Compares the specified object with this table for equality. Two tables are equal when their cell views, as returned by Table.cellSet(), are equal.

Specified by:

equals in interface Table<R,C,V>

remove

public V remove(@Nullable
                Object rowKey,
                @Nullable
                Object columnKey)

Description copied from interface: Table

Removes the mapping, if any, associated with the given keys.

Specified by:

remove in interface Table<R,C,V>

Parameters:

rowKey - row key of mapping to be removed

columnKey - column key of mapping to be removed

Returns:

the value previously associated with the keys, or null if no such value existed

isEmpty

public boolean isEmpty()

Description copied from interface: Table

Returns true if the table contains no mappings.

Specified by:

isEmpty in interface Table<R,C,V>

size

public int size()

Description copied from interface: Table

Returns the number of row key / column key / value mappings in the table.

Specified by:

size in interface Table<R,C,V>

hashCode

public int hashCode()

Description copied from interface: Table

Returns the hash code for this table. The hash code of a table is defined as the hash code of its cell view, as returned by Table.cellSet().

Specified by:

hashCode in interface Table<R,C,V>

Overrides:

hashCode in class Object

toString

public String toString()

Returns the string representation rowMap().toString().

Overrides:

toString in class Object

clear

public void clear()

Description copied from interface: Table

Removes all mappings from the table.

Specified by:

clear in interface Table<R,C,V>

put

public V put(R rowKey,
             C columnKey,
             V value)

Description copied from interface: Table

Associates the specified value with the specified keys. If the table already contained a mapping for those keys, the old value is replaced with the specified value.

Specified by:

put in interface Table<R,C,V>

Parameters:

rowKey - row key that the value should be associated with

columnKey - column key that the value should be associated with

value - value to be associated with the specified keys

Returns:

the value previously associated with the keys, or null if no mapping existed for the keys

putAll

public void putAll(Table<? extends R,? extends C,? extends V> table)

Description copied from interface: Table

Copies all mappings from the specified table to this table. The effect is equivalent to calling Table.put(R, C, V) with each row key / column key / value mapping in table.

Specified by:

putAll in interface Table<R,C,V>

Parameters:

table - the table to add to this table

cellSet

public Set<Table.Cell<R,C,V>> cellSet()

Returns a set of all row key / column key / value triplets. Changes to the returned set will update the underlying table, and vice versa. The cell set does not support the add or addAll methods.

The set's iterator traverses the mappings for the first row, the mappings for the second row, and so on.

Each cell is an immutable snapshot of a row key / column key / value mapping, taken at the time the cell is returned by a method call to the set or its iterator.

Specified by:

cellSet in interface Table<R,C,V>

Returns:

set of table cells consisting of row key / column key / value triplets

row

public Map<C,V> row(R rowKey)

Description copied from interface: Table

Returns a view of all mappings that have the given row key. For each row key / column key / value mapping in the table with that row key, the returned map associates the column key with the value. If no mappings in the table have the provided row key, an empty map is returned.

Changes to the returned map will update the underlying table, and vice versa.

Specified by:

row in interface Table<R,C,V>

Parameters:

rowKey - key of row to search for in the table

Returns:

the corresponding map from column keys to values

column

public Map<R,V> column(C columnKey)

Returns a view of all mappings that have the given column key. For each row key / column key / value mapping in the table with that column key, the returned map associates the row key with the value. If no mappings in the table have the provided column key, an empty map is returned.

Changes to the returned map will update the underlying table, and vice versa.

The returned map's views have iterators that don't support remove().

Specified by:

column in interface Table<R,C,V>

Parameters:

columnKey - key of column to search for in the table

Returns:

the corresponding map from row keys to values

rowKeySet

public Set<R> rowKeySet()

Description copied from interface: Table

Returns a set of row keys that have one or more values in the table. Changes to the set will update the underlying table, and vice versa.

Specified by:

rowKeySet in interface Table<R,C,V>

Returns:

set of row keys

columnKeySet

public Set<C> columnKeySet()

Returns a set of column keys that have one or more values in the table. Changes to the set will update the underlying table, and vice versa.

The returned set has an iterator that does not support remove().

The set's iterator traverses the columns of the first row, the columns of the second row, etc., skipping any columns that have appeared previously.

Specified by:

columnKeySet in interface Table<R,C,V>

Returns:

set of column keys

values

public Collection<V> values()

Returns a collection of all values, which may contain duplicates. Changes to the returned collection will update the underlying table, and vice versa.

The collection's iterator traverses the values for the first row, the values for the second row, and so on.

Specified by:

values in interface Table<R,C,V>

Returns:

collection of values

rowMap

public Map<R,Map<C,V>> rowMap()

Description copied from interface: Table

Returns a view that associates each row key with the corresponding map from column keys to values. Changes to the returned map will update this table. The returned map does not support put() or putAll(), or setValue() on its entries.

In contrast, the maps returned by rowMap().get() have the same behavior as those returned by Table.row(R). Those maps may support setValue(), put(), and putAll().

Specified by:

rowMap in interface Table<R,C,V>

Returns:

a map view from each row key to a secondary map from column keys to values

columnMap

public Map<C,Map<R,V>> columnMap()

Description copied from interface: Table

Returns a view that associates each column key with the corresponding map from row keys to values. Changes to the returned map will update this table. The returned map does not support put() or putAll(), or setValue() on its entries.

In contrast, the maps returned by columnMap().get() have the same behavior as those returned by Table.column(C). Those maps may support setValue(), put(), and putAll().

Specified by:

columnMap in interface Table<R,C,V>

Returns:

a map view from each column key to a secondary map from row keys to values