@GwtCompatible public final class Tables extends Object
Table
.
See the Guava User Guide article on Tables
.
Modifier and Type | Method and Description |
---|---|
static <R,C,V> Table.Cell<R,C,V> |
immutableCell(R rowKey,
C columnKey,
V value)
Returns an immutable cell with the specified row key, column key, and value.
|
static <R,C,V> Table<R,C,V> |
newCustomTable(Map<R,Map<C,V>> backingMap,
Supplier<? extends Map<C,V>> factory)
Creates a table that uses the specified backing map and factory.
|
static <R,C,V> Table<R,C,V> |
synchronizedTable(Table<R,C,V> table)
Returns a synchronized (thread-safe) table backed by the specified table.
|
static <T,R,C,V,I extends Table<R,C,V>> |
toTable(Function<? super T,? extends R> rowFunction,
Function<? super T,? extends C> columnFunction,
Function<? super T,? extends V> valueFunction,
BinaryOperator<V> mergeFunction,
Supplier<I> tableSupplier)
Returns a
Collector that accumulates elements into a Table created using the
specified supplier, whose cells are generated by applying the provided mapping functions to the
input elements. |
static <T,R,C,V,I extends Table<R,C,V>> |
toTable(Function<? super T,? extends R> rowFunction,
Function<? super T,? extends C> columnFunction,
Function<? super T,? extends V> valueFunction,
Supplier<I> tableSupplier)
Returns a
Collector that accumulates elements into a Table created using the
specified supplier, whose cells are generated by applying the provided mapping functions to the
input elements. |
static <R,C,V1,V2> |
transformValues(Table<R,C,V1> fromTable,
Function<? super V1,V2> function)
Returns a view of a table where each value is transformed by a function.
|
static <R,C,V> Table<C,R,V> |
transpose(Table<R,C,V> table)
Creates a transposed view of a given table that flips its row and column keys.
|
static <R,C,V> RowSortedTable<R,C,V> |
unmodifiableRowSortedTable(RowSortedTable<R,? extends C,? extends V> table)
Returns an unmodifiable view of the specified row-sorted table.
|
static <R,C,V> Table<R,C,V> |
unmodifiableTable(Table<? extends R,? extends C,? extends V> table)
Returns an unmodifiable view of the specified table.
|
@Beta public static <T,R,C,V,I extends Table<R,C,V>> Collector<T,?,I> toTable(Function<? super T,? extends R> rowFunction, Function<? super T,? extends C> columnFunction, Function<? super T,? extends V> valueFunction, Supplier<I> tableSupplier)
Collector
that accumulates elements into a Table
created using the
specified supplier, whose cells are generated by applying the provided mapping functions to the
input elements. Cells are inserted into the generated Table
in encounter order.
If multiple input elements map to the same row and column, an IllegalStateException
is thrown when the collection operation is performed.
public static <T,R,C,V,I extends Table<R,C,V>> Collector<T,?,I> toTable(Function<? super T,? extends R> rowFunction, Function<? super T,? extends C> columnFunction, Function<? super T,? extends V> valueFunction, BinaryOperator<V> mergeFunction, Supplier<I> tableSupplier)
Collector
that accumulates elements into a Table
created using the
specified supplier, whose cells are generated by applying the provided mapping functions to the
input elements. Cells are inserted into the generated Table
in encounter order.
If multiple input elements map to the same row and column, the specified merging function is
used to combine the values. Like Collectors.toMap(java.util.function.Function, java.util.function.Function,
BinaryOperator, java.util.function.Supplier)
, this Collector throws a NullPointerException
on null values returned from valueFunction
, and treats nulls
returned from mergeFunction
as removals of that row/column pair.
public static <R,C,V> Table.Cell<R,C,V> immutableCell(R rowKey, C columnKey, V value)
The returned cell is serializable.
rowKey
- the row key to be associated with the returned cellcolumnKey
- the column key to be associated with the returned cellvalue
- the value to be associated with the returned cellpublic static <R,C,V> Table<C,R,V> transpose(Table<R,C,V> table)
get(columnKey, rowKey)
on the generated table always returns the same value as
calling get(rowKey, columnKey)
on the original table. Updating the original table
changes the contents of the transposed table and vice versa.
The returned table supports update operations as long as the input table supports the
analogous operation with swapped rows and columns. For example, in a HashBasedTable
instance, rowKeySet().iterator()
supports remove()
but columnKeySet().iterator()
doesn't. With a transposed HashBasedTable
, it's the other
way around.
@Beta public static <R,C,V> Table<R,C,V> newCustomTable(Map<R,Map<C,V>> backingMap, Supplier<? extends Map<C,V>> factory)
Map
classes.
The factory
-generated and backingMap
classes determine the table iteration
order. However, the table's row()
method returns instances of a different class than
factory.get()
does.
Call this method only when the simpler factory methods in classes like HashBasedTable
and TreeBasedTable
won't suffice.
The views returned by the Table
methods Table.column(C)
, Table.columnKeySet()
, and Table.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.
The table is serializable if backingMap
, factory
, the maps generated by
factory
, and the table contents are all serializable.
Note: the table assumes complete ownership over of backingMap
and the maps returned
by factory
. Those objects should not be manually updated and they should not use soft,
weak, or phantom references.
backingMap
- place to store the mapping from each row key to its corresponding column key
/ value mapfactory
- supplier of new, empty maps that will each hold all column key / value mappings
for a given row keyIllegalArgumentException
- if backingMap
is not empty@Beta public static <R,C,V1,V2> Table<R,C,V2> transformValues(Table<R,C,V1> fromTable, Function<? super V1,V2> function)
Changes in the underlying table are reflected in this view. Conversely, this view supports removal operations, and these are reflected in the underlying table.
It's acceptable for the underlying table to contain null keys, and even null values provided that the function is capable of accepting null input. The transformed table might contain null values, if the function sometimes gives a null result.
The returned table is not thread-safe or serializable, even if the underlying table is.
The function is applied lazily, invoked when needed. This is necessary for the returned
table to be a view, but it means that the function will be applied many times for bulk
operations like Table.containsValue(java.lang.Object)
and Table.toString()
. For this to perform
well, function
should be fast. To avoid lazy evaluation when the returned table doesn't
need to be a view, copy the returned table into a new table of your choosing.
public static <R,C,V> Table<R,C,V> unmodifiableTable(Table<? extends R,? extends C,? extends V> table)
UnsupportedOperationException
.
The returned table will be serializable if the specified table is serializable.
Consider using an ImmutableTable
, which is guaranteed never to change.
@Beta public static <R,C,V> RowSortedTable<R,C,V> unmodifiableRowSortedTable(RowSortedTable<R,? extends C,? extends V> table)
UnsupportedOperationException
.
The returned table will be serializable if the specified table is serializable.
table
- the row-sorted table for which an unmodifiable view is to be returnedpublic static <R,C,V> Table<R,C,V> synchronizedTable(Table<R,C,V> table)
It is imperative that the user manually synchronize on the returned table when accessing any of its collection views:
Table<R, C, V> table = Tables.synchronizedTable(HashBasedTable.<R, C, V>create());
...
Map<C, V> row = table.row(rowKey); // Needn't be in synchronized block
...
synchronized (table) { // Synchronizing on table, not row!
Iterator<Entry<C, V>> i = row.entrySet().iterator(); // Must be in synchronized block
while (i.hasNext()) {
foo(i.next());
}
}
Failure to follow this advice may result in non-deterministic behavior.
The returned table will be serializable if the specified table is serializable.
table
- the table to be wrapped in a synchronized viewCopyright © 2010–2019. All rights reserved.