Package com.google.common.collect

Class HashBasedTable<R,​C,​V>

  • All Implemented Interfaces:
    Table<R,​C,​V>, Serializable
    @GwtCompatible(serializable=true)
public class HashBasedTable<R,​C,​V>
extends Object
    Implementation of Table using linked hash tables. This guarantees predictable iteration order of the various views.

    The views returned by Table.column(C), 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.

    See the Guava User Guide article on Table.

    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

      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)
      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)
      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, or null if no such mapping exists.
      int hashCode()
      Returns a hash code value for the object.
      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.

    • 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​(@NullableDecl
                        Object rowKey,
                        @NullableDecl
                        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​(@NullableDecl
                              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​(@NullableDecl
                           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​(@NullableDecl
                             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​(@NullableDecl
             Object rowKey,
             @NullableDecl
             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​(@NullableDecl
                      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 return true.
        • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
        • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
        • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
        • For any non-null reference value x, x.equals(null) should return false.

        The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

        Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

        Specified by:
        equals in interface Table<R,​C,​V>
        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

      • remove

        @CanIgnoreReturnValue
public V remove​(@NullableDecl
                Object rowKey,
                @NullableDecl
                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>

      • 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

        @CanIgnoreReturnValue
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

      • 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

      • 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

      • 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 by HashMap.

        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 in equals 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 the hashCode 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 the hashCode 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.)

        Specified by:
        hashCode in interface Table<R,​C,​V>
        Overrides:
        hashCode in class Object
        Returns:
        a hash code value for this object.
        See Also:
        Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

      • toString

        public String toString()
        Returns the string representation rowMap().toString().
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.