Class MapUtils

    • Method Summary

      All Methods Static Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      static void debugPrint​(PrintStream out, Object label, Map<?,​?> map)
      Prints the given map with nice line breaks.
      static <K,​V>
      Map<K,​V>
      emptyIfNull​(Map<K,​V> map)
      Returns an immutable empty map if the argument is null, or the argument itself otherwise.
      static <K,​V>
      IterableMap<K,​V>
      fixedSizeMap​(Map<K,​V> map)
      Returns a fixed-sized map backed by the given map.
      static <K,​V>
      SortedMap<K,​V>
      fixedSizeSortedMap​(SortedMap<K,​V> map)
      Returns a fixed-sized sorted map backed by the given sorted map.
      static <K> Boolean getBoolean​(Map<? super K,​?> map, K key)
      Gets a Boolean from a Map in a null-safe manner.
      static <K> Boolean getBoolean​(Map<? super K,​?> map, K key, Boolean defaultValue)
      Looks up the given key in the given map, converting the result into a boolean, using the default value if the conversion fails.
      static <K> boolean getBooleanValue​(Map<? super K,​?> map, K key)
      Gets a boolean from a Map in a null-safe manner.
      static <K> boolean getBooleanValue​(Map<? super K,​?> map, K key, boolean defaultValue)
      Gets a boolean from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Byte getByte​(Map<? super K,​?> map, K key)
      Gets a Byte from a Map in a null-safe manner.
      static <K> Byte getByte​(Map<? super K,​?> map, K key, Byte defaultValue)
      Looks up the given key in the given map, converting the result into a byte, using the default value if the conversion fails.
      static <K> byte getByteValue​(Map<? super K,​?> map, K key)
      Gets a byte from a Map in a null-safe manner.
      static <K> byte getByteValue​(Map<? super K,​?> map, K key, byte defaultValue)
      Gets a byte from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Double getDouble​(Map<? super K,​?> map, K key)
      Gets a Double from a Map in a null-safe manner.
      static <K> Double getDouble​(Map<? super K,​?> map, K key, Double defaultValue)
      Looks up the given key in the given map, converting the result into a double, using the default value if the conversion fails.
      static <K> double getDoubleValue​(Map<? super K,​?> map, K key)
      Gets a double from a Map in a null-safe manner.
      static <K> double getDoubleValue​(Map<? super K,​?> map, K key, double defaultValue)
      Gets a double from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Float getFloat​(Map<? super K,​?> map, K key)
      Gets a Float from a Map in a null-safe manner.
      static <K> Float getFloat​(Map<? super K,​?> map, K key, Float defaultValue)
      Looks up the given key in the given map, converting the result into a float, using the default value if the conversion fails.
      static <K> float getFloatValue​(Map<? super K,​?> map, K key)
      Gets a float from a Map in a null-safe manner.
      static <K> float getFloatValue​(Map<? super K,​?> map, K key, float defaultValue)
      Gets a float from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Integer getInteger​(Map<? super K,​?> map, K key)
      Gets a Integer from a Map in a null-safe manner.
      static <K> Integer getInteger​(Map<? super K,​?> map, K key, Integer defaultValue)
      Looks up the given key in the given map, converting the result into an integer, using the default value if the conversion fails.
      static <K> int getIntValue​(Map<? super K,​?> map, K key)
      Gets an int from a Map in a null-safe manner.
      static <K> int getIntValue​(Map<? super K,​?> map, K key, int defaultValue)
      Gets an int from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Long getLong​(Map<? super K,​?> map, K key)
      Gets a Long from a Map in a null-safe manner.
      static <K> Long getLong​(Map<? super K,​?> map, K key, Long defaultValue)
      Looks up the given key in the given map, converting the result into a long, using the default value if the conversion fails.
      static <K> long getLongValue​(Map<? super K,​?> map, K key)
      Gets a long from a Map in a null-safe manner.
      static <K> long getLongValue​(Map<? super K,​?> map, K key, long defaultValue)
      Gets a long from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> Map<?,​?> getMap​(Map<? super K,​?> map, K key)
      Gets a Map from a Map in a null-safe manner.
      static <K> Map<?,​?> getMap​(Map<? super K,​?> map, K key, Map<?,​?> defaultValue)
      Looks up the given key in the given map, converting the result into a map, using the default value if the conversion fails.
      static <K> Number getNumber​(Map<? super K,​?> map, K key)
      Gets a Number from a Map in a null-safe manner.
      static <K> Number getNumber​(Map<? super K,​?> map, K key, Number defaultValue)
      Looks up the given key in the given map, converting the result into a number, using the default value if the conversion fails.
      static <K,​V>
      V
      getObject​(Map<? super K,​V> map, K key)
      Gets from a Map in a null-safe manner.
      static <K,​V>
      V
      getObject​(Map<K,​V> map, K key, V defaultValue)
      Looks up the given key in the given map, converting null into the given default value.
      static <K> Short getShort​(Map<? super K,​?> map, K key)
      Gets a Short from a Map in a null-safe manner.
      static <K> Short getShort​(Map<? super K,​?> map, K key, Short defaultValue)
      Looks up the given key in the given map, converting the result into a short, using the default value if the conversion fails.
      static <K> short getShortValue​(Map<? super K,​?> map, K key)
      Gets a short from a Map in a null-safe manner.
      static <K> short getShortValue​(Map<? super K,​?> map, K key, short defaultValue)
      Gets a short from a Map in a null-safe manner, using the default value if the conversion fails.
      static <K> String getString​(Map<? super K,​?> map, K key)
      Gets a String from a Map in a null-safe manner.
      static <K> String getString​(Map<? super K,​?> map, K key, String defaultValue)
      Looks up the given key in the given map, converting the result into a string, using the default value if the conversion fails.
      static <K,​V>
      Map<V,​K>
      invertMap​(Map<K,​V> map)
      Inverts the supplied map returning a new HashMap such that the keys of the input are swapped with the values.
      static boolean isEmpty​(Map<?,​?> map)
      Null-safe check if the specified map is empty.
      static boolean isNotEmpty​(Map<?,​?> map)
      Null-safe check if the specified map is not empty.
      static <K,​V>
      IterableMap<K,​V>
      iterableMap​(Map<K,​V> map)
      Get the specified Map as an IterableMap.
      static <K,​V>
      IterableSortedMap<K,​V>
      iterableSortedMap​(SortedMap<K,​V> sortedMap)
      Get the specified SortedMap as an IterableSortedMap.
      static <K,​V>
      IterableMap<K,​V>
      lazyMap​(Map<K,​V> map, Factory<? extends V> factory)
      Returns a "lazy" map whose values will be created on demand.
      static <K,​V>
      IterableMap<K,​V>
      lazyMap​(Map<K,​V> map, Transformer<? super K,​? extends V> transformerFactory)
      Returns a "lazy" map whose values will be created on demand.
      static <K,​V>
      SortedMap<K,​V>
      lazySortedMap​(SortedMap<K,​V> map, Factory<? extends V> factory)
      Returns a "lazy" sorted map whose values will be created on demand.
      static <K,​V>
      SortedMap<K,​V>
      lazySortedMap​(SortedMap<K,​V> map, Transformer<? super K,​? extends V> transformerFactory)
      Returns a "lazy" sorted map whose values will be created on demand.
      static <K,​V>
      MultiValueMap<K,​V>
      multiValueMap​(Map<K,​? super Collection<V>> map)
      Deprecated.
      since 4.1, use MultiValuedMap instead
      static <K,​V,​C extends Collection<V>>
      MultiValueMap<K,​V>
      multiValueMap​(Map<K,​C> map, Class<C> collectionClass)
      Deprecated.
      since 4.1, use MultiValuedMap instead
      static <K,​V,​C extends Collection<V>>
      MultiValueMap<K,​V>
      multiValueMap​(Map<K,​C> map, Factory<C> collectionFactory)
      Deprecated.
      since 4.1, use MultiValuedMap instead
      static <K,​V>
      OrderedMap<K,​V>
      orderedMap​(Map<K,​V> map)
      Returns a map that maintains the order of keys that are added backed by the given map.
      static <K,​V,​E>
      void
      populateMap​(Map<K,​V> map, Iterable<? extends E> elements, Transformer<E,​K> keyTransformer, Transformer<E,​V> valueTransformer)
      Populates a Map using the supplied Transformers to transform the elements into keys and values.
      static <K,​V>
      void
      populateMap​(Map<K,​V> map, Iterable<? extends V> elements, Transformer<V,​K> keyTransformer)
      Populates a Map using the supplied Transformer to transform the elements into keys, using the unaltered element as the value in the Map.
      static <K,​V,​E>
      void
      populateMap​(MultiMap<K,​V> map, Iterable<? extends E> elements, Transformer<E,​K> keyTransformer, Transformer<E,​V> valueTransformer)
      Populates a MultiMap using the supplied Transformers to transform the elements into keys and values.
      static <K,​V>
      void
      populateMap​(MultiMap<K,​V> map, Iterable<? extends V> elements, Transformer<V,​K> keyTransformer)
      Populates a MultiMap using the supplied Transformer to transform the elements into keys, using the unaltered element as the value in the MultiMap.
      static <K,​V>
      IterableMap<K,​V>
      predicatedMap​(Map<K,​V> map, Predicate<? super K> keyPred, Predicate<? super V> valuePred)
      Returns a predicated (validating) map backed by the given map.
      static <K,​V>
      SortedMap<K,​V>
      predicatedSortedMap​(SortedMap<K,​V> map, Predicate<? super K> keyPred, Predicate<? super V> valuePred)
      Returns a predicated (validating) sorted map backed by the given map.
      static <K,​V>
      Map<K,​V>
      putAll​(Map<K,​V> map, Object[] array)
      Puts all the keys and values from the specified array into the map.
      static <K> void safeAddToMap​(Map<? super K,​Object> map, K key, Object value)
      Protects against adding null values to a map.
      static int size​(Map<?,​?> map)
      Gets the given map size or 0 if the map is null
      static <K,​V>
      Map<K,​V>
      synchronizedMap​(Map<K,​V> map)
      Returns a synchronized map backed by the given map.
      static <K,​V>
      SortedMap<K,​V>
      synchronizedSortedMap​(SortedMap<K,​V> map)
      Returns a synchronized sorted map backed by the given sorted map.
      static Map<String,​Object> toMap​(ResourceBundle resourceBundle)
      Creates a new HashMap using data copied from a ResourceBundle.
      static <K,​V>
      Properties
      toProperties​(Map<K,​V> map)
      Gets a new Properties object initialised with the values from a Map.
      static <K,​V>
      IterableMap<K,​V>
      transformedMap​(Map<K,​V> map, Transformer<? super K,​? extends K> keyTransformer, Transformer<? super V,​? extends V> valueTransformer)
      Returns a transformed map backed by the given map.
      static <K,​V>
      SortedMap<K,​V>
      transformedSortedMap​(SortedMap<K,​V> map, Transformer<? super K,​? extends K> keyTransformer, Transformer<? super V,​? extends V> valueTransformer)
      Returns a transformed sorted map backed by the given map.
      static <K,​V>
      Map<K,​V>
      unmodifiableMap​(Map<? extends K,​? extends V> map)
      Returns an unmodifiable map backed by the given map.
      static <K,​V>
      SortedMap<K,​V>
      unmodifiableSortedMap​(SortedMap<K,​? extends V> map)
      Returns an unmodifiable sorted map backed by the given sorted map.
      static void verbosePrint​(PrintStream out, Object label, Map<?,​?> map)
      Prints the given map with nice line breaks.
    • Field Detail

      • EMPTY_SORTED_MAP

        public static final SortedMap EMPTY_SORTED_MAP
        An empty unmodifiable sorted map. This is not provided in the JDK.
    • Method Detail

      • getObject

        public static <K,​V> V getObject​(Map<? super K,​V> map,
                                              K key)
        Gets from a Map in a null-safe manner.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map, null if null map input
      • getString

        public static <K> String getString​(Map<? super K,​?> map,
                                           K key)
        Gets a String from a Map in a null-safe manner.

        The String is obtained via toString.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a String, null if null map input
      • getBoolean

        public static <K> Boolean getBoolean​(Map<? super K,​?> map,
                                             K key)
        Gets a Boolean from a Map in a null-safe manner.

        If the value is a Boolean it is returned directly. If the value is a String and it equals 'true' ignoring case then true is returned, otherwise false. If the value is a Number an integer zero value returns false and non-zero returns true. Otherwise, null is returned.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Boolean, null if null map input
      • getNumber

        public static <K> Number getNumber​(Map<? super K,​?> map,
                                           K key)
        Gets a Number from a Map in a null-safe manner.

        If the value is a Number it is returned directly. If the value is a String it is converted using NumberFormat.parse(String) on the system default formatter returning null if the conversion fails. Otherwise, null is returned.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Number, null if null map input
      • getByte

        public static <K> Byte getByte​(Map<? super K,​?> map,
                                       K key)
        Gets a Byte from a Map in a null-safe manner.

        The Byte is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Byte, null if null map input
      • getShort

        public static <K> Short getShort​(Map<? super K,​?> map,
                                         K key)
        Gets a Short from a Map in a null-safe manner.

        The Short is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Short, null if null map input
      • getInteger

        public static <K> Integer getInteger​(Map<? super K,​?> map,
                                             K key)
        Gets a Integer from a Map in a null-safe manner.

        The Integer is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Integer, null if null map input
      • getLong

        public static <K> Long getLong​(Map<? super K,​?> map,
                                       K key)
        Gets a Long from a Map in a null-safe manner.

        The Long is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Long, null if null map input
      • getFloat

        public static <K> Float getFloat​(Map<? super K,​?> map,
                                         K key)
        Gets a Float from a Map in a null-safe manner.

        The Float is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Float, null if null map input
      • getDouble

        public static <K> Double getDouble​(Map<? super K,​?> map,
                                           K key)
        Gets a Double from a Map in a null-safe manner.

        The Double is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Double, null if null map input
      • getMap

        public static <K> Map<?,​?> getMap​(Map<? super K,​?> map,
                                                K key)
        Gets a Map from a Map in a null-safe manner.

        If the value returned from the specified map is not a Map then null is returned.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Map, null if null map input
      • getObject

        public static <K,​V> V getObject​(Map<K,​V> map,
                                              K key,
                                              V defaultValue)
        Looks up the given key in the given map, converting null into the given default value.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null
        Returns:
        the value in the map, or defaultValue if the original value is null or the map is null
      • getString

        public static <K> String getString​(Map<? super K,​?> map,
                                           K key,
                                           String defaultValue)
        Looks up the given key in the given map, converting the result into a string, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a string, or defaultValue if the original value is null, the map is null or the string conversion fails
      • getBoolean

        public static <K> Boolean getBoolean​(Map<? super K,​?> map,
                                             K key,
                                             Boolean defaultValue)
        Looks up the given key in the given map, converting the result into a boolean, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a boolean, or defaultValue if the original value is null, the map is null or the boolean conversion fails
      • getNumber

        public static <K> Number getNumber​(Map<? super K,​?> map,
                                           K key,
                                           Number defaultValue)
        Looks up the given key in the given map, converting the result into a number, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getByte

        public static <K> Byte getByte​(Map<? super K,​?> map,
                                       K key,
                                       Byte defaultValue)
        Looks up the given key in the given map, converting the result into a byte, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getShort

        public static <K> Short getShort​(Map<? super K,​?> map,
                                         K key,
                                         Short defaultValue)
        Looks up the given key in the given map, converting the result into a short, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getInteger

        public static <K> Integer getInteger​(Map<? super K,​?> map,
                                             K key,
                                             Integer defaultValue)
        Looks up the given key in the given map, converting the result into an integer, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getLong

        public static <K> Long getLong​(Map<? super K,​?> map,
                                       K key,
                                       Long defaultValue)
        Looks up the given key in the given map, converting the result into a long, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getFloat

        public static <K> Float getFloat​(Map<? super K,​?> map,
                                         K key,
                                         Float defaultValue)
        Looks up the given key in the given map, converting the result into a float, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getDouble

        public static <K> Double getDouble​(Map<? super K,​?> map,
                                           K key,
                                           Double defaultValue)
        Looks up the given key in the given map, converting the result into a double, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails
      • getMap

        public static <K> Map<?,​?> getMap​(Map<? super K,​?> map,
                                                K key,
                                                Map<?,​?> defaultValue)
        Looks up the given key in the given map, converting the result into a map, using the default value if the conversion fails.
        Type Parameters:
        K - the key type
        Parameters:
        map - the map whose value to look up
        key - the key of the value to look up in that map
        defaultValue - what to return if the value is null or if the conversion fails
        Returns:
        the value in the map as a number, or defaultValue if the original value is null, the map is null or the map conversion fails
      • getBooleanValue

        public static <K> boolean getBooleanValue​(Map<? super K,​?> map,
                                                  K key)
        Gets a boolean from a Map in a null-safe manner.

        If the value is a Boolean its value is returned. If the value is a String and it equals 'true' ignoring case then true is returned, otherwise false. If the value is a Number an integer zero value returns false and non-zero returns true. Otherwise, false is returned.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a Boolean, false if null map input
      • getByteValue

        public static <K> byte getByteValue​(Map<? super K,​?> map,
                                            K key)
        Gets a byte from a Map in a null-safe manner.

        The byte is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a byte, 0 if null map input
      • getShortValue

        public static <K> short getShortValue​(Map<? super K,​?> map,
                                              K key)
        Gets a short from a Map in a null-safe manner.

        The short is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a short, 0 if null map input
      • getIntValue

        public static <K> int getIntValue​(Map<? super K,​?> map,
                                          K key)
        Gets an int from a Map in a null-safe manner.

        The int is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as an int, 0 if null map input
      • getLongValue

        public static <K> long getLongValue​(Map<? super K,​?> map,
                                            K key)
        Gets a long from a Map in a null-safe manner.

        The long is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a long, 0L if null map input
      • getFloatValue

        public static <K> float getFloatValue​(Map<? super K,​?> map,
                                              K key)
        Gets a float from a Map in a null-safe manner.

        The float is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a float, 0.0F if null map input
      • getDoubleValue

        public static <K> double getDoubleValue​(Map<? super K,​?> map,
                                                K key)
        Gets a double from a Map in a null-safe manner.

        The double is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        Returns:
        the value in the Map as a double, 0.0 if null map input
      • getBooleanValue

        public static <K> boolean getBooleanValue​(Map<? super K,​?> map,
                                                  K key,
                                                  boolean defaultValue)
        Gets a boolean from a Map in a null-safe manner, using the default value if the conversion fails.

        If the value is a Boolean its value is returned. If the value is a String and it equals 'true' ignoring case then true is returned, otherwise false. If the value is a Number an integer zero value returns false and non-zero returns true. Otherwise, defaultValue is returned.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a Boolean, defaultValue if null map input
      • getByteValue

        public static <K> byte getByteValue​(Map<? super K,​?> map,
                                            K key,
                                            byte defaultValue)
        Gets a byte from a Map in a null-safe manner, using the default value if the conversion fails.

        The byte is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a byte, defaultValue if null map input
      • getShortValue

        public static <K> short getShortValue​(Map<? super K,​?> map,
                                              K key,
                                              short defaultValue)
        Gets a short from a Map in a null-safe manner, using the default value if the conversion fails.

        The short is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a short, defaultValue if null map input
      • getIntValue

        public static <K> int getIntValue​(Map<? super K,​?> map,
                                          K key,
                                          int defaultValue)
        Gets an int from a Map in a null-safe manner, using the default value if the conversion fails.

        The int is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as an int, defaultValue if null map input
      • getLongValue

        public static <K> long getLongValue​(Map<? super K,​?> map,
                                            K key,
                                            long defaultValue)
        Gets a long from a Map in a null-safe manner, using the default value if the conversion fails.

        The long is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a long, defaultValue if null map input
      • getFloatValue

        public static <K> float getFloatValue​(Map<? super K,​?> map,
                                              K key,
                                              float defaultValue)
        Gets a float from a Map in a null-safe manner, using the default value if the conversion fails.

        The float is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a float, defaultValue if null map input
      • getDoubleValue

        public static <K> double getDoubleValue​(Map<? super K,​?> map,
                                                K key,
                                                double defaultValue)
        Gets a double from a Map in a null-safe manner, using the default value if the conversion fails.

        The double is obtained from the results of getNumber(Map,Object).

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to use
        key - the key to look up
        defaultValue - return if the value is null or if the conversion fails
        Returns:
        the value in the Map as a double, defaultValue if null map input
      • toProperties

        public static <K,​V> Properties toProperties​(Map<K,​V> map)
        Gets a new Properties object initialised with the values from a Map. A null input will return an empty properties object.

        A Properties object may only store non-null keys and values, thus if the provided map contains either a key or value which is null, a NullPointerException will be thrown.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to convert to a Properties object
        Returns:
        the properties object
        Throws:
        NullPointerException - if a key or value in the provided map is null
      • toMap

        public static Map<String,​Object> toMap​(ResourceBundle resourceBundle)
        Creates a new HashMap using data copied from a ResourceBundle.
        Parameters:
        resourceBundle - the resource bundle to convert, may not be null
        Returns:
        the hashmap containing the data
        Throws:
        NullPointerException - if the bundle is null
      • verbosePrint

        public static void verbosePrint​(PrintStream out,
                                        Object label,
                                        Map<?,​?> map)
        Prints the given map with nice line breaks.

        This method prints a nicely formatted String describing the Map. Each map entry will be printed with key and value. When the value is a Map, recursive behaviour occurs.

        This method is NOT thread-safe in any special way. You must manually synchronize on either this class or the stream as required.

        Parameters:
        out - the stream to print to, must not be null
        label - The label to be used, may be null. If null, the label is not output. It typically represents the name of the property in a bean or similar.
        map - The map to print, may be null. If null, the text 'null' is output.
        Throws:
        NullPointerException - if the stream is null
      • debugPrint

        public static void debugPrint​(PrintStream out,
                                      Object label,
                                      Map<?,​?> map)
        Prints the given map with nice line breaks.

        This method prints a nicely formatted String describing the Map. Each map entry will be printed with key, value and value classname. When the value is a Map, recursive behaviour occurs.

        This method is NOT thread-safe in any special way. You must manually synchronize on either this class or the stream as required.

        Parameters:
        out - the stream to print to, must not be null
        label - The label to be used, may be null. If null, the label is not output. It typically represents the name of the property in a bean or similar.
        map - The map to print, may be null. If null, the text 'null' is output.
        Throws:
        NullPointerException - if the stream is null
      • invertMap

        public static <K,​V> Map<V,​K> invertMap​(Map<K,​V> map)
        Inverts the supplied map returning a new HashMap such that the keys of the input are swapped with the values.

        This operation assumes that the inverse mapping is well defined. If the input map had multiple entries with the same value mapped to different keys, the returned map will map one of those keys to the value, but the exact key which will be mapped is undefined.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to invert, may not be null
        Returns:
        a new HashMap containing the inverted data
        Throws:
        NullPointerException - if the map is null
      • safeAddToMap

        public static <K> void safeAddToMap​(Map<? super K,​Object> map,
                                            K key,
                                            Object value)
                                     throws NullPointerException
        Protects against adding null values to a map.

        This method checks the value being added to the map, and if it is null it is replaced by an empty string.

        This could be useful if the map does not accept null values, or for receiving data from a source that may provide null or empty string which should be held in the same way in the map.

        Keys are not validated. Note that this method can be used to circumvent the map's value type at runtime.

        Type Parameters:
        K - the key type
        Parameters:
        map - the map to add to, may not be null
        key - the key
        value - the value, null converted to ""
        Throws:
        NullPointerException - if the map is null
      • putAll

        public static <K,​V> Map<K,​V> putAll​(Map<K,​V> map,
                                                        Object[] array)
        Puts all the keys and values from the specified array into the map.

        This method is an alternative to the Map.putAll(java.util.Map) method and constructors. It allows you to build a map from an object array of various possible styles.

        If the first entry in the object array implements Map.Entry or KeyValue then the key and value are added from that object. If the first entry in the object array is an object array itself, then it is assumed that index 0 in the sub-array is the key and index 1 is the value. Otherwise, the array is treated as keys and values in alternate indices.

        For example, to create a color map:

         Map colorMap = MapUtils.putAll(new HashMap(), new String[][] {
             {"RED", "#FF0000"},
             {"GREEN", "#00FF00"},
             {"BLUE", "#0000FF"}
         });
         
        or:
         Map colorMap = MapUtils.putAll(new HashMap(), new String[] {
             "RED", "#FF0000",
             "GREEN", "#00FF00",
             "BLUE", "#0000FF"
         });
         
        or:
         Map colorMap = MapUtils.putAll(new HashMap(), new Map.Entry[] {
             new DefaultMapEntry("RED", "#FF0000"),
             new DefaultMapEntry("GREEN", "#00FF00"),
             new DefaultMapEntry("BLUE", "#0000FF")
         });
         
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to populate, must not be null
        array - an array to populate from, null ignored
        Returns:
        the input map
        Throws:
        NullPointerException - if map is null
        IllegalArgumentException - if sub-array or entry matching used and an entry is invalid
        ClassCastException - if the array contents is mixed
        Since:
        3.2
      • emptyIfNull

        public static <K,​V> Map<K,​V> emptyIfNull​(Map<K,​V> map)
        Returns an immutable empty map if the argument is null, or the argument itself otherwise.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map, possibly null
        Returns:
        an empty map if the argument is null
      • isEmpty

        public static boolean isEmpty​(Map<?,​?> map)
        Null-safe check if the specified map is empty.

        Null returns true.

        Parameters:
        map - the map to check, may be null
        Returns:
        true if empty or null
        Since:
        3.2
      • isNotEmpty

        public static boolean isNotEmpty​(Map<?,​?> map)
        Null-safe check if the specified map is not empty.

        Null returns false.

        Parameters:
        map - the map to check, may be null
        Returns:
        true if non-null and non-empty
        Since:
        3.2
      • synchronizedMap

        public static <K,​V> Map<K,​V> synchronizedMap​(Map<K,​V> map)
        Returns a synchronized map backed by the given map.

        You must manually synchronize on the returned buffer's iterator to avoid non-deterministic behavior:

         Map m = MapUtils.synchronizedMap(myMap);
         Set s = m.keySet();  // outside synchronized block
         synchronized (m) {  // synchronized on MAP!
             Iterator i = s.iterator();
             while (i.hasNext()) {
                 process (i.next());
             }
         }
         
        This method uses the implementation in Collections.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to synchronize, must not be null
        Returns:
        a synchronized map backed by the given map
      • unmodifiableMap

        public static <K,​V> Map<K,​V> unmodifiableMap​(Map<? extends K,​? extends V> map)
        Returns an unmodifiable map backed by the given map.

        This method uses the implementation in the decorators subpackage.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to make unmodifiable, must not be null
        Returns:
        an unmodifiable map backed by the given map
        Throws:
        NullPointerException - if the map is null
      • predicatedMap

        public static <K,​V> IterableMap<K,​V> predicatedMap​(Map<K,​V> map,
                                                                       Predicate<? super K> keyPred,
                                                                       Predicate<? super V> valuePred)
        Returns a predicated (validating) map backed by the given map.

        Only objects that pass the tests in the given predicates can be added to the map. Trying to add an invalid object results in an IllegalArgumentException. Keys must pass the key predicate, values must pass the value predicate. It is important not to use the original map after invoking this method, as it is a backdoor for adding invalid objects.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to predicate, must not be null
        keyPred - the predicate for keys, null means no check
        valuePred - the predicate for values, null means no check
        Returns:
        a predicated map backed by the given map
        Throws:
        NullPointerException - if the Map is null
      • transformedMap

        public static <K,​V> IterableMap<K,​V> transformedMap​(Map<K,​V> map,
                                                                        Transformer<? super K,​? extends K> keyTransformer,
                                                                        Transformer<? super V,​? extends V> valueTransformer)
        Returns a transformed map backed by the given map.

        This method returns a new map (decorating the specified map) that will transform any new entries added to it. Existing entries in the specified map will not be transformed. If you want that behaviour, see TransformedMap.transformedMap(java.util.Map<K, V>, org.apache.commons.collections4.Transformer<? super K, ? extends K>, org.apache.commons.collections4.Transformer<? super V, ? extends V>).

        Each object is passed through the transformers as it is added to the Map. It is important not to use the original map after invoking this method, as it is a backdoor for adding untransformed objects.

        If there are any elements already in the map being decorated, they are NOT transformed.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to transform, must not be null, typically empty
        keyTransformer - the transformer for the map keys, null means no transformation
        valueTransformer - the transformer for the map values, null means no transformation
        Returns:
        a transformed map backed by the given map
        Throws:
        NullPointerException - if the Map is null
      • fixedSizeMap

        public static <K,​V> IterableMap<K,​V> fixedSizeMap​(Map<K,​V> map)
        Returns a fixed-sized map backed by the given map. Elements may not be added or removed from the returned map, but existing elements can be changed (for instance, via the Map.put(Object,Object) method).
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map whose size to fix, must not be null
        Returns:
        a fixed-size map backed by that map
        Throws:
        NullPointerException - if the Map is null
      • lazyMap

        public static <K,​V> IterableMap<K,​V> lazyMap​(Map<K,​V> map,
                                                                 Factory<? extends V> factory)
        Returns a "lazy" map whose values will be created on demand.

        When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key.

        For instance:

         Factory factory = new Factory() {
             public Object create() {
                 return new Date();
             }
         }
         Map lazyMap = MapUtils.lazyMap(new HashMap(), factory);
         Object obj = lazyMap.get("test");
         
        After the above code is executed, obj will contain a new Date instance. Furthermore, that Date instance is the value for the "test" key in the map.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to make lazy, must not be null
        factory - the factory for creating new objects, must not be null
        Returns:
        a lazy map backed by the given map
        Throws:
        NullPointerException - if the Map or Factory is null
      • lazyMap

        public static <K,​V> IterableMap<K,​V> lazyMap​(Map<K,​V> map,
                                                                 Transformer<? super K,​? extends V> transformerFactory)
        Returns a "lazy" map whose values will be created on demand.

        When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key. The factory is a Transformer that will be passed the key which it must transform into the value.

        For instance:

         Transformer factory = new Transformer() {
             public Object transform(Object mapKey) {
                 return new File(mapKey);
             }
         }
         Map lazyMap = MapUtils.lazyMap(new HashMap(), factory);
         Object obj = lazyMap.get("C:/dev");
         
        After the above code is executed, obj will contain a new File instance for the C drive dev directory. Furthermore, that File instance is the value for the "C:/dev" key in the map.

        If a lazy map is wrapped by a synchronized map, the result is a simple synchronized cache. When an object is not is the cache, the cache itself calls back to the factory Transformer to populate itself, all within the same synchronized block.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to make lazy, must not be null
        transformerFactory - the factory for creating new objects, must not be null
        Returns:
        a lazy map backed by the given map
        Throws:
        NullPointerException - if the Map or Transformer is null
      • orderedMap

        public static <K,​V> OrderedMap<K,​V> orderedMap​(Map<K,​V> map)
        Returns a map that maintains the order of keys that are added backed by the given map.

        If a key is added twice, the order is determined by the first add. The order is observed through the keySet, values and entrySet.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to order, must not be null
        Returns:
        an ordered map backed by the given map
        Throws:
        NullPointerException - if the Map is null
      • multiValueMap

        @Deprecated
        public static <K,​V> MultiValueMap<K,​V> multiValueMap​(Map<K,​? super Collection<V>> map)
        Deprecated.
        since 4.1, use MultiValuedMap instead
        Creates a mult-value map backed by the given map which returns collections of type ArrayList.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to decorate
        Returns:
        a multi-value map backed by the given map which returns ArrayLists of values.
        Since:
        3.2
        See Also:
        MultiValueMap
      • multiValueMap

        @Deprecated
        public static <K,​V,​C extends Collection<V>> MultiValueMap<K,​V> multiValueMap​(Map<K,​C> map,
                                                                                                       Class<C> collectionClass)
        Deprecated.
        since 4.1, use MultiValuedMap instead
        Creates a multi-value map backed by the given map which returns collections of the specified type.
        Type Parameters:
        K - the key type
        V - the value type
        C - the collection class type
        Parameters:
        map - the map to decorate
        collectionClass - the type of collections to return from the map (must contain public no-arg constructor and extend Collection)
        Returns:
        a multi-value map backed by the given map which returns collections of the specified type
        Since:
        3.2
        See Also:
        MultiValueMap
      • multiValueMap

        @Deprecated
        public static <K,​V,​C extends Collection<V>> MultiValueMap<K,​V> multiValueMap​(Map<K,​C> map,
                                                                                                       Factory<C> collectionFactory)
        Deprecated.
        since 4.1, use MultiValuedMap instead
        Creates a multi-value map backed by the given map which returns collections created by the specified collection factory.
        Type Parameters:
        K - the key type
        V - the value type
        C - the collection class type
        Parameters:
        map - the map to decorate
        collectionFactory - a factor which creates collection objects
        Returns:
        a multi-value map backed by the given map which returns collections created by the specified collection factory
        Since:
        3.2
        See Also:
        MultiValueMap
      • synchronizedSortedMap

        public static <K,​V> SortedMap<K,​V> synchronizedSortedMap​(SortedMap<K,​V> map)
        Returns a synchronized sorted map backed by the given sorted map.

        You must manually synchronize on the returned buffer's iterator to avoid non-deterministic behavior:

         Map m = MapUtils.synchronizedSortedMap(myMap);
         Set s = m.keySet();  // outside synchronized block
         synchronized (m) {  // synchronized on MAP!
             Iterator i = s.iterator();
             while (i.hasNext()) {
                 process (i.next());
             }
         }
         
        This method uses the implementation in Collections.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to synchronize, must not be null
        Returns:
        a synchronized map backed by the given map
        Throws:
        NullPointerException - if the map is null
      • unmodifiableSortedMap

        public static <K,​V> SortedMap<K,​V> unmodifiableSortedMap​(SortedMap<K,​? extends V> map)
        Returns an unmodifiable sorted map backed by the given sorted map.

        This method uses the implementation in the decorators subpackage.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the sorted map to make unmodifiable, must not be null
        Returns:
        an unmodifiable map backed by the given map
        Throws:
        NullPointerException - if the map is null
      • predicatedSortedMap

        public static <K,​V> SortedMap<K,​V> predicatedSortedMap​(SortedMap<K,​V> map,
                                                                           Predicate<? super K> keyPred,
                                                                           Predicate<? super V> valuePred)
        Returns a predicated (validating) sorted map backed by the given map.

        Only objects that pass the tests in the given predicates can be added to the map. Trying to add an invalid object results in an IllegalArgumentException. Keys must pass the key predicate, values must pass the value predicate. It is important not to use the original map after invoking this method, as it is a backdoor for adding invalid objects.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to predicate, must not be null
        keyPred - the predicate for keys, null means no check
        valuePred - the predicate for values, null means no check
        Returns:
        a predicated map backed by the given map
        Throws:
        NullPointerException - if the SortedMap is null
      • transformedSortedMap

        public static <K,​V> SortedMap<K,​V> transformedSortedMap​(SortedMap<K,​V> map,
                                                                            Transformer<? super K,​? extends K> keyTransformer,
                                                                            Transformer<? super V,​? extends V> valueTransformer)
        Returns a transformed sorted map backed by the given map.

        This method returns a new sorted map (decorating the specified map) that will transform any new entries added to it. Existing entries in the specified map will not be transformed. If you want that behaviour, see TransformedSortedMap.transformedSortedMap(java.util.SortedMap<K, V>, org.apache.commons.collections4.Transformer<? super K, ? extends K>, org.apache.commons.collections4.Transformer<? super V, ? extends V>).

        Each object is passed through the transformers as it is added to the Map. It is important not to use the original map after invoking this method, as it is a backdoor for adding untransformed objects.

        If there are any elements already in the map being decorated, they are NOT transformed.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to transform, must not be null, typically empty
        keyTransformer - the transformer for the map keys, null means no transformation
        valueTransformer - the transformer for the map values, null means no transformation
        Returns:
        a transformed map backed by the given map
        Throws:
        NullPointerException - if the SortedMap is null
      • fixedSizeSortedMap

        public static <K,​V> SortedMap<K,​V> fixedSizeSortedMap​(SortedMap<K,​V> map)
        Returns a fixed-sized sorted map backed by the given sorted map. Elements may not be added or removed from the returned map, but existing elements can be changed (for instance, via the Map.put(Object,Object) method).
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map whose size to fix, must not be null
        Returns:
        a fixed-size map backed by that map
        Throws:
        NullPointerException - if the SortedMap is null
      • lazySortedMap

        public static <K,​V> SortedMap<K,​V> lazySortedMap​(SortedMap<K,​V> map,
                                                                     Factory<? extends V> factory)
        Returns a "lazy" sorted map whose values will be created on demand.

        When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key.

        For instance:

         Factory factory = new Factory() {
             public Object create() {
                 return new Date();
             }
         }
         SortedMap lazy = MapUtils.lazySortedMap(new TreeMap(), factory);
         Object obj = lazy.get("test");
         
        After the above code is executed, obj will contain a new Date instance. Furthermore, that Date instance is the value for the "test" key.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to make lazy, must not be null
        factory - the factory for creating new objects, must not be null
        Returns:
        a lazy map backed by the given map
        Throws:
        NullPointerException - if the SortedMap or Factory is null
      • lazySortedMap

        public static <K,​V> SortedMap<K,​V> lazySortedMap​(SortedMap<K,​V> map,
                                                                     Transformer<? super K,​? extends V> transformerFactory)
        Returns a "lazy" sorted map whose values will be created on demand.

        When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key. The factory is a Transformer that will be passed the key which it must transform into the value.

        For instance:

         Transformer factory = new Transformer() {
             public Object transform(Object mapKey) {
                 return new File(mapKey);
             }
         }
         SortedMap lazy = MapUtils.lazySortedMap(new TreeMap(), factory);
         Object obj = lazy.get("C:/dev");
         
        After the above code is executed, obj will contain a new File instance for the C drive dev directory. Furthermore, that File instance is the value for the "C:/dev" key in the map.

        If a lazy map is wrapped by a synchronized map, the result is a simple synchronized cache. When an object is not is the cache, the cache itself calls back to the factory Transformer to populate itself, all within the same synchronized block.

        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the map to make lazy, must not be null
        transformerFactory - the factory for creating new objects, must not be null
        Returns:
        a lazy map backed by the given map
        Throws:
        NullPointerException - if the Map or Transformer is null
      • populateMap

        public static <K,​V> void populateMap​(Map<K,​V> map,
                                                   Iterable<? extends V> elements,
                                                   Transformer<V,​K> keyTransformer)
        Populates a Map using the supplied Transformer to transform the elements into keys, using the unaltered element as the value in the Map.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the Map to populate.
        elements - the Iterable containing the input values for the map.
        keyTransformer - the Transformer used to transform the element into a key value
        Throws:
        NullPointerException - if the map, elements or transformer are null
      • populateMap

        public static <K,​V,​E> void populateMap​(Map<K,​V> map,
                                                           Iterable<? extends E> elements,
                                                           Transformer<E,​K> keyTransformer,
                                                           Transformer<E,​V> valueTransformer)
        Populates a Map using the supplied Transformers to transform the elements into keys and values.
        Type Parameters:
        K - the key type
        V - the value type
        E - the type of object contained in the Iterable
        Parameters:
        map - the Map to populate.
        elements - the Iterable containing the input values for the map.
        keyTransformer - the Transformer used to transform the element into a key value
        valueTransformer - the Transformer used to transform the element into a value
        Throws:
        NullPointerException - if the map, elements or transformers are null
      • populateMap

        public static <K,​V> void populateMap​(MultiMap<K,​V> map,
                                                   Iterable<? extends V> elements,
                                                   Transformer<V,​K> keyTransformer)
        Populates a MultiMap using the supplied Transformer to transform the elements into keys, using the unaltered element as the value in the MultiMap.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - the MultiMap to populate.
        elements - the Iterable to use as input values for the map.
        keyTransformer - the Transformer used to transform the element into a key value
        Throws:
        NullPointerException - if the map, elements or transformer are null
      • populateMap

        public static <K,​V,​E> void populateMap​(MultiMap<K,​V> map,
                                                           Iterable<? extends E> elements,
                                                           Transformer<E,​K> keyTransformer,
                                                           Transformer<E,​V> valueTransformer)
        Populates a MultiMap using the supplied Transformers to transform the elements into keys and values.
        Type Parameters:
        K - the key type
        V - the value type
        E - the type of object contained in the Iterable
        Parameters:
        map - the MultiMap to populate.
        elements - the Iterable containing the input values for the map.
        keyTransformer - the Transformer used to transform the element into a key value
        valueTransformer - the Transformer used to transform the element into a value
        Throws:
        NullPointerException - if the map, collection or transformers are null
      • iterableMap

        public static <K,​V> IterableMap<K,​V> iterableMap​(Map<K,​V> map)
        Get the specified Map as an IterableMap.
        Type Parameters:
        K - the key type
        V - the value type
        Parameters:
        map - to wrap if necessary.
        Returns:
        IterableMap<K, V>
        Throws:
        NullPointerException - if map is null
        Since:
        4.0
      • size

        public static int size​(Map<?,​?> map)
        Gets the given map size or 0 if the map is null
        Parameters:
        map - a Map or null
        Returns:
        the given map size or 0 if the map is null