com.google.common.collect.Tables Maven / Gradle / Ivy
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/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Objects;
import com.google.common.base.Supplier;
import com.google.common.collect.Table.Cell;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import javax.annotation.Nullable;
/**
* Provides static methods that involve a {@code Table}.
*
* See the Guava User Guide article on
* {@code Tables}.
*
* @author Jared Levy
* @author Louis Wasserman
* @since 7.0
*/
@GwtCompatible
public final class Tables {
private Tables() {}
/**
* Returns an immutable cell with the specified row key, column key, and
* value.
*
*
The returned cell is serializable.
*
* @param rowKey the row key to be associated with the returned cell
* @param columnKey the column key to be associated with the returned cell
* @param value the value to be associated with the returned cell
*/
public static Cell immutableCell(
@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
return new ImmutableCell<>(rowKey, columnKey, value);
}
static final class ImmutableCell extends AbstractCell implements Serializable {
private final R rowKey;
private final C columnKey;
private final V value;
ImmutableCell(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
this.rowKey = rowKey;
this.columnKey = columnKey;
this.value = value;
}
@Override
public R getRowKey() {
return rowKey;
}
@Override
public C getColumnKey() {
return columnKey;
}
@Override
public V getValue() {
return value;
}
private static final long serialVersionUID = 0;
}
abstract static class AbstractCell implements Cell {
// needed for serialization
AbstractCell() {}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Cell) {
Cell other = (Cell) obj;
return Objects.equal(getRowKey(), other.getRowKey())
&& Objects.equal(getColumnKey(), other.getColumnKey())
&& Objects.equal(getValue(), other.getValue());
}
return false;
}
@Override
public int hashCode() {
return Objects.hashCode(getRowKey(), getColumnKey(), getValue());
}
@Override
public String toString() {
return "(" + getRowKey() + "," + getColumnKey() + ")=" + getValue();
}
}
/**
* Creates a transposed view of a given table that flips its row and column
* keys. In other words, calling {@code get(columnKey, rowKey)} on the
* generated table always returns the same value as calling {@code
* 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 {@link HashBasedTable} instance, {@code
* rowKeySet().iterator()} supports {@code remove()} but {@code
* columnKeySet().iterator()} doesn't. With a transposed {@link
* HashBasedTable}, it's the other way around.
*/
public static Table transpose(Table table) {
return (table instanceof TransposeTable)
? ((TransposeTable) table).original
: new TransposeTable(table);
}
private static class TransposeTable extends AbstractTable {
final Table original;
TransposeTable(Table original) {
this.original = checkNotNull(original);
}
@Override
public void clear() {
original.clear();
}
@Override
public Map column(R columnKey) {
return original.row(columnKey);
}
@Override
public Set columnKeySet() {
return original.rowKeySet();
}
@Override
public Map> columnMap() {
return original.rowMap();
}
@Override
public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
return original.contains(columnKey, rowKey);
}
@Override
public boolean containsColumn(@Nullable Object columnKey) {
return original.containsRow(columnKey);
}
@Override
public boolean containsRow(@Nullable Object rowKey) {
return original.containsColumn(rowKey);
}
@Override
public boolean containsValue(@Nullable Object value) {
return original.containsValue(value);
}
@Override
public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
return original.get(columnKey, rowKey);
}
@Override
public V put(C rowKey, R columnKey, V value) {
return original.put(columnKey, rowKey, value);
}
@Override
public void putAll(Table table) {
original.putAll(transpose(table));
}
@Override
public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
return original.remove(columnKey, rowKey);
}
@Override
public Map row(C rowKey) {
return original.column(rowKey);
}
@Override
public Set rowKeySet() {
return original.columnKeySet();
}
@Override
public Map> rowMap() {
return original.columnMap();
}
@Override
public int size() {
return original.size();
}
@Override
public Collection values() {
return original.values();
}
// Will cast TRANSPOSE_CELL to a type that always succeeds
private static final Function, Cell> TRANSPOSE_CELL =
new Function, Cell>() {
@Override
public Cell apply(Cell cell) {
return immutableCell(cell.getColumnKey(), cell.getRowKey(), cell.getValue());
}
};
@SuppressWarnings("unchecked")
@Override
Iterator> cellIterator() {
return Iterators.transform(original.cellSet().iterator(), (Function) TRANSPOSE_CELL);
}
}
/**
* Creates a table that uses the specified backing map and factory. It can
* generate a table based on arbitrary {@link Map} classes.
*
* The {@code factory}-generated and {@code backingMap} classes determine
* the table iteration order. However, the table's {@code row()} method
* returns instances of a different class than {@code factory.get()} does.
*
*
Call this method only when the simpler factory methods in classes like
* {@link HashBasedTable} and {@link TreeBasedTable} won't suffice.
*
*
The views returned by the {@code Table} methods {@link Table#column},
* {@link Table#columnKeySet}, and {@link Table#columnMap} have iterators that
* don't support {@code 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 {@code Map>}. A method call like
* {@code column(columnKey).get(rowKey)} still runs quickly, since the row key
* is provided. However, {@code 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 {@code backingMap}, {@code factory}, the
* maps generated by {@code factory}, and the table contents are all
* serializable.
*
*
Note: the table assumes complete ownership over of {@code backingMap}
* and the maps returned by {@code factory}. Those objects should not be
* manually updated and they should not use soft, weak, or phantom references.
*
* @param backingMap place to store the mapping from each row key to its
* corresponding column key / value map
* @param factory supplier of new, empty maps that will each hold all column
* key / value mappings for a given row key
* @throws IllegalArgumentException if {@code backingMap} is not empty
* @since 10.0
*/
@Beta
public static Table newCustomTable(
Map> backingMap, Supplier> factory) {
checkArgument(backingMap.isEmpty());
checkNotNull(factory);
// TODO(jlevy): Wrap factory to validate that the supplied maps are empty?
return new StandardTable<>(backingMap, factory);
}
/**
* Returns a view of a table where each value is transformed by a function.
* All other properties of the table, such as iteration order, are left
* intact.
*
* 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 {@link Table#containsValue} and
* {@code Table.toString()}. For this to perform well, {@code 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.
*
* @since 10.0
*/
@Beta
public static Table transformValues(
Table fromTable, Function function) {
return new TransformedTable<>(fromTable, function);
}
private static class TransformedTable extends AbstractTable {
final Table fromTable;
final Function function;
TransformedTable(Table fromTable, Function function) {
this.fromTable = checkNotNull(fromTable);
this.function = checkNotNull(function);
}
@Override
public boolean contains(Object rowKey, Object columnKey) {
return fromTable.contains(rowKey, columnKey);
}
@Override
public V2 get(Object rowKey, Object columnKey) {
// The function is passed a null input only when the table contains a null
// value.
return contains(rowKey, columnKey) ? function.apply(fromTable.get(rowKey, columnKey)) : null;
}
@Override
public int size() {
return fromTable.size();
}
@Override
public void clear() {
fromTable.clear();
}
@Override
public V2 put(R rowKey, C columnKey, V2 value) {
throw new UnsupportedOperationException();
}
@Override
public void putAll(Table table) {
throw new UnsupportedOperationException();
}
@Override
public V2 remove(Object rowKey, Object columnKey) {
return contains(rowKey, columnKey)
? function.apply(fromTable.remove(rowKey, columnKey))
: null;
}
@Override
public Map row(R rowKey) {
return Maps.transformValues(fromTable.row(rowKey), function);
}
@Override
public Map column(C columnKey) {
return Maps.transformValues(fromTable.column(columnKey), function);
}
Function, Cell> cellFunction() {
return new Function, Cell>() {
@Override
public Cell apply(Cell cell) {
return immutableCell(
cell.getRowKey(), cell.getColumnKey(), function.apply(cell.getValue()));
}
};
}
@Override
Iterator> cellIterator() {
return Iterators.transform(fromTable.cellSet().iterator(), cellFunction());
}
@Override
public Set rowKeySet() {
return fromTable.rowKeySet();
}
@Override
public Set columnKeySet() {
return fromTable.columnKeySet();
}
@Override
Collection createValues() {
return Collections2.transform(fromTable.values(), function);
}
@Override
public Map> rowMap() {
Function, Map> rowFunction =
new Function, Map>() {
@Override
public Map apply(Map row) {
return Maps.transformValues(row, function);
}
};
return Maps.transformValues(fromTable.rowMap(), rowFunction);
}
@Override
public Map> columnMap() {
Function, Map> columnFunction =
new Function, Map>() {
@Override
public Map apply(Map column) {
return Maps.transformValues(column, function);
}
};
return Maps.transformValues(fromTable.columnMap(), columnFunction);
}
}
/**
* Returns an unmodifiable view of the specified table. This method allows modules to provide
* users with "read-only" access to internal tables. Query operations on the returned table
* "read through" to the specified table, and attempts to modify the returned table, whether
* direct or via its collection views, result in an {@code UnsupportedOperationException}.
*
* The returned table will be serializable if the specified table is serializable.
*
*
Consider using an {@link ImmutableTable}, which is guaranteed never to change.
*
* @since 11.0
*/
public static Table unmodifiableTable(
Table table) {
return new UnmodifiableTable<>(table);
}
private static class UnmodifiableTable extends ForwardingTable
implements Serializable {
final Table delegate;
UnmodifiableTable(Table delegate) {
this.delegate = checkNotNull(delegate);
}
@SuppressWarnings("unchecked") // safe, covariant cast
@Override
protected Table delegate() {
return (Table) delegate;
}
@Override
public Set> cellSet() {
return Collections.unmodifiableSet(super.cellSet());
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public Map column(@Nullable C columnKey) {
return Collections.unmodifiableMap(super.column(columnKey));
}
@Override
public Set columnKeySet() {
return Collections.unmodifiableSet(super.columnKeySet());
}
@Override
public Map> columnMap() {
Function, Map> wrapper = unmodifiableWrapper();
return Collections.unmodifiableMap(Maps.transformValues(super.columnMap(), wrapper));
}
@Override
public V put(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
throw new UnsupportedOperationException();
}
@Override
public void putAll(Table table) {
throw new UnsupportedOperationException();
}
@Override
public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
throw new UnsupportedOperationException();
}
@Override
public Map row(@Nullable R rowKey) {
return Collections.unmodifiableMap(super.row(rowKey));
}
@Override
public Set rowKeySet() {
return Collections.unmodifiableSet(super.rowKeySet());
}
@Override
public Map> rowMap() {
Function, Map> wrapper = unmodifiableWrapper();
return Collections.unmodifiableMap(Maps.transformValues(super.rowMap(), wrapper));
}
@Override
public Collection values() {
return Collections.unmodifiableCollection(super.values());
}
private static final long serialVersionUID = 0;
}
/**
* Returns an unmodifiable view of the specified row-sorted table. This method allows modules to
* provide users with "read-only" access to internal tables. Query operations on the returned
* table "read through" to the specified table, and attempts to modify the returned table, whether
* direct or via its collection views, result in an {@code UnsupportedOperationException}.
*
* The returned table will be serializable if the specified table is serializable.
*
* @param table the row-sorted table for which an unmodifiable view is to be returned
* @return an unmodifiable view of the specified table
* @since 11.0
*/
@Beta
public static RowSortedTable unmodifiableRowSortedTable(
RowSortedTable table) {
/*
* It's not ? extends R, because it's technically not covariant in R. Specifically,
* table.rowMap().comparator() could return a comparator that only works for the ? extends R.
* Collections.unmodifiableSortedMap makes the same distinction.
*/
return new UnmodifiableRowSortedMap<>(table);
}
static final class UnmodifiableRowSortedMap extends UnmodifiableTable
implements RowSortedTable {
public UnmodifiableRowSortedMap(RowSortedTable delegate) {
super(delegate);
}
@Override
protected RowSortedTable delegate() {
return (RowSortedTable) super.delegate();
}
@Override
public SortedMap> rowMap() {
Function, Map> wrapper = unmodifiableWrapper();
return Collections.unmodifiableSortedMap(Maps.transformValues(delegate().rowMap(), wrapper));
}
@Override
public SortedSet rowKeySet() {
return Collections.unmodifiableSortedSet(delegate().rowKeySet());
}
private static final long serialVersionUID = 0;
}
@SuppressWarnings("unchecked")
private static Function, Map> unmodifiableWrapper() {
return (Function) UNMODIFIABLE_WRAPPER;
}
private static final Function, ? extends Map> UNMODIFIABLE_WRAPPER =
new Function, Map>() {
@Override
public Map apply(Map input) {
return Collections.unmodifiableMap(input);
}
};
/**
* Returns a synchronized (thread-safe) table backed by the specified table. In order to guarantee
* serial access, it is critical that all access to the backing table is accomplished
* through the returned table.
*
* It is imperative that the user manually synchronize on the returned table when accessing any
* of its collection views:
*
*
{@code
* Table table = Tables.synchronizedTable(HashBasedTable.create());
* ...
* Map row = table.row(rowKey); // Needn't be in synchronized block
* ...
* synchronized (table) { // Synchronizing on table, not row!
* Iterator> 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.
*
* @param table the table to be wrapped in a synchronized view
* @return a synchronized view of the specified table
* @since 22.0
*/
public static Table synchronizedTable(Table table) {
return Synchronized.table(table, null);
}
static boolean equalsImpl(Table table, @Nullable Object obj) {
if (obj == table) {
return true;
} else if (obj instanceof Table) {
Table that = (Table) obj;
return table.cellSet().equals(that.cellSet());
} else {
return false;
}
}
}