org.apache.commons.collections4

## Class MapUtils

- java.lang.Object
- - org.apache.commons.collections4.MapUtils

-     public class MapUtils
      extends Object

  Provides utility methods and decorators for `Map` and `SortedMap` instances.

  It contains various type safe methods as well as other useful features like deep copying.

  It also provides the following decorators:

  - `fixedSizeMap(Map)`
  - `fixedSizeSortedMap(SortedMap)`
  - `lazyMap(Map,Factory)`
  - `lazyMap(Map,Transformer)`
  - `lazySortedMap(SortedMap,Factory)`
  - `lazySortedMap(SortedMap,Transformer)`
  - `predicatedMap(Map,Predicate,Predicate)`
  - `predicatedSortedMap(SortedMap,Predicate,Predicate)`
  - `transformedMap(Map, Transformer, Transformer)`
  - `transformedSortedMap(SortedMap, Transformer, Transformer)`
  - `multiValueMap( Map )`
  - `multiValueMap( Map, Class )`
  - `multiValueMap( Map, Factory )`
  Since:
    1.0
  Version:
    $Id: MapUtils.java 1686921 2015-06-22 19:48:47Z tn $

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static SortedMap` | `EMPTY_SORTED_MAP` An empty unmodifiable sorted map.

  - ### Method Summary

    Methods
    Modifier and Type | Method and 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 `Transformer`s 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 `Transformer`s 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 <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.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 `Transformer`s 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 `Transformer`s 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
      Throws:
        `NullPointerException` - if map is null
      Since:
        4.0

    - #### iterableSortedMap

          public static <K,V> IterableSortedMap<K,V> iterableSortedMap(SortedMap<K,V> sortedMap)

      Get the specified `SortedMap` as an `IterableSortedMap`.
      Type Parameters:
        `K` - the key type
        `V` - the value type
      Parameters:
        `sortedMap` - to wrap if necessary
      Returns:
        `IterableSortedMap`
      Throws:
        `NullPointerException` - if sortedMap is null
      Since:
        4.0

Copyright © 2001–2015 The Apache Software Foundation. All rights reserved.