Class HashBasedTable<R,C,V>
- java.lang.Object
-
- com.google.common.collect.HashBasedTable<R,C,V>
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- All Implemented Interfaces:
Table<R,C,V>
,Serializable
@GwtCompatible(serializable=true) public class HashBasedTable<R,C,V> extends Object
Implementation ofTable
using linked hash tables. This guarantees predictable iteration order of the various views.The views returned by
Table.column(C)
,columnKeySet()
, andTable.columnMap()
have iterators that don't supportremove()
. 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 likecolumn(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.
See the Guava User Guide article on
Table
.- Since:
- 7.0
- Author:
- Jared Levy
- See Also:
- Serialized Form
-
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description 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)
Returnstrue
if the table contains a mapping with the specified row and column keys.boolean
containsColumn(Object columnKey)
Returnstrue
if the table contains a mapping with the specified column.boolean
containsRow(Object rowKey)
Returnstrue
if the table contains a mapping with the specified row key.boolean
containsValue(Object value)
Returnstrue
if the table contains a mapping with the specified value.static <R,C,V>
HashBasedTable<R,C,V>create()
Creates an emptyHashBasedTable
.static <R,C,V>
HashBasedTable<R,C,V>create(int expectedRows, int expectedCellsPerRow)
Creates an emptyHashBasedTable
with the specified map sizes.static <R,C,V>
HashBasedTable<R,C,V>create(Table<? extends R,? extends C,? extends V> table)
Creates aHashBasedTable
with the same mappings as the specified table.boolean
equals(Object obj)
Indicates whether some other object is "equal to" this one.V
get(Object rowKey, Object columnKey)
Returns the value corresponding to the given row and column keys, ornull
if no such mapping exists.int
hashCode()
Returns a hash code value for the object.boolean
isEmpty()
Returnstrue
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 representationrowMap().toString()
.Collection<V>
values()
Returns a collection of all values, which may contain duplicates.
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-
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Method Detail
-
create
public static <R,C,V> HashBasedTable<R,C,V> create()
Creates an emptyHashBasedTable
.
-
create
public static <R,C,V> HashBasedTable<R,C,V> create(int expectedRows, int expectedCellsPerRow)
Creates an emptyHashBasedTable
with the specified map sizes.- Parameters:
expectedRows
- the expected number of distinct row keysexpectedCellsPerRow
- the expected number of column key / value mappings in each row- Throws:
IllegalArgumentException
- ifexpectedRows
orexpectedCellsPerRow
is negative
-
create
public static <R,C,V> HashBasedTable<R,C,V> create(Table<? extends R,? extends C,? extends V> table)
Creates aHashBasedTable
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 intable
is null
-
contains
public boolean contains(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
Description copied from interface:Table
Returnstrue
if the table contains a mapping with the specified row and column keys.
-
containsColumn
public boolean containsColumn(@CheckForNull Object columnKey)
Description copied from interface:Table
Returnstrue
if the table contains a mapping with the specified column.- Specified by:
containsColumn
in interfaceTable<R,C,V>
- Parameters:
columnKey
- key of column to search for
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containsRow
public boolean containsRow(@CheckForNull Object rowKey)
Description copied from interface:Table
Returnstrue
if the table contains a mapping with the specified row key.- Specified by:
containsRow
in interfaceTable<R,C,V>
- Parameters:
rowKey
- key of row to search for
-
containsValue
public boolean containsValue(@CheckForNull Object value)
Description copied from interface:Table
Returnstrue
if the table contains a mapping with the specified value.- Specified by:
containsValue
in interfaceTable<R,C,V>
- Parameters:
value
- value to search for
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get
@CheckForNull public V get(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
Description copied from interface:Table
Returns the value corresponding to the given row and column keys, ornull
if no such mapping exists.
-
isEmpty
public boolean isEmpty()
Description copied from interface:Table
Returnstrue
if the table contains no mappings.
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size
public int size()
Description copied from interface:Table
Returns the number of row key / column key / value mappings in the table.
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clear
public void clear()
Description copied from interface:Table
Removes all mappings from the table.
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put
@CanIgnoreReturnValue @CheckForNull 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 interfaceTable<R,C,V>
- Parameters:
rowKey
- row key that the value should be associated withcolumnKey
- column key that the value should be associated withvalue
- 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
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remove
@CanIgnoreReturnValue @CheckForNull public V remove(@CheckForNull Object rowKey, @CheckForNull Object columnKey)
Description copied from interface:Table
Removes the mapping, if any, associated with the given keys.
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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 theadd
oraddAll
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.
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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.
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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()
.
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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.
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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 interfaceTable<R,C,V>
- Returns:
- set of column keys
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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.
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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 supportput()
orputAll()
, orsetValue()
on its entries.In contrast, the maps returned by
rowMap().get()
have the same behavior as those returned byTable.row(R)
. Those maps may supportsetValue()
,put()
, andputAll()
.
-
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 supportput()
orputAll()
, orsetValue()
on its entries.In contrast, the maps returned by
columnMap().get()
have the same behavior as those returned byTable.column(C)
. Those maps may supportsetValue()
,put()
, andputAll()
.
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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 callingTable.put(R, C, V)
with each row key / column key / value mapping intable
.
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equals
public boolean equals(@CheckForNull Object obj)
Description copied from class:java.lang.Object
Indicates whether some other object is "equal to" this one.The
equals
method implements an equivalence relation on non-null object references:- It is reflexive: for any non-null reference value
x
,x.equals(x)
should returntrue
. - It is symmetric: for any non-null reference values
x
andy
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any non-null reference values
x
,y
, andz
, ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
. - It is consistent: for any non-null reference values
x
andy
, multiple invocations ofx.equals(y)
consistently returntrue
or consistently returnfalse
, provided no information used inequals
comparisons on the objects is modified. - For any non-null reference value
x
,x.equals(null)
should returnfalse
.
The
equals
method for classObject
implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference valuesx
andy
, this method returnstrue
if and only ifx
andy
refer to the same object (x == y
has the valuetrue
).Note that it is generally necessary to override the
hashCode
method whenever this method is overridden, so as to maintain the general contract for thehashCode
method, which states that equal objects must have equal hash codes.- Specified by:
equals
in interfaceTable<R extends @Nullable Object,C extends @Nullable Object,V extends @Nullable Object>
- Overrides:
equals
in classObject
- Parameters:
obj
- the reference object with which to compare.- Returns:
true
if this object is the same as the obj argument;false
otherwise.- See Also:
Object.hashCode()
,HashMap
- It is reflexive: for any non-null reference value
-
hashCode
public int hashCode()
Description copied from class:java.lang.Object
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided byHashMap
.The general contract of
hashCode
is:- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
hashCode
method must consistently return the same integer, provided no information used inequals
comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. - If two objects are equal according to the
equals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. - It is not required that if two objects are unequal
according to the
Object.equals(java.lang.Object)
method, then calling thehashCode
method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by class
Object
does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.) - Whenever it is invoked on the same object more than once during
an execution of a Java application, the
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