Package 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

- ## Field Summary

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

- ## Method Summary

  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`
  `getBoolean(Map<? super K,?> map, K key, Function<K,Boolean> defaultFunction)`
  Looks up the given key in the given map, converting the result into a boolean, using the defaultFunction to produce 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> boolean`
  `getBooleanValue(Map<? super K,?> map, K key, Function<K,Boolean> defaultFunction)`
  Gets a boolean from a Map in a null-safe manner, using the default value produced by the defaultFunction 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`
  `getByte(Map<? super K,?> map, K key, Function<K,Byte> defaultFunction)`
  Looks up the given key in the given map, converting the result into a byte, using the defaultFunction to produce 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> byte`
  `getByteValue(Map<? super K,?> map, K key, Function<K,Byte> defaultFunction)`
  Gets a byte from a Map in a null-safe manner, using the default value produced by the defaultFunction 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`
  `getDouble(Map<? super K,?> map, K key, Function<K,Double> defaultFunction)`
  Looks up the given key in the given map, converting the result into a double, using the defaultFunction to produce 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> double`
  `getDoubleValue(Map<? super K,?> map, K key, Function<K,Double> defaultFunction)`
  Gets a double from a Map in a null-safe manner, using the default value produced by the defaultFunction 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`
  `getFloat(Map<? super K,?> map, K key, Function<K,Float> defaultFunction)`
  Looks up the given key in the given map, converting the result into a float, using the defaultFunction to produce 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> float`
  `getFloatValue(Map<? super K,?> map, K key, Function<K,Float> defaultFunction)`
  Gets a float from a Map in a null-safe manner, using the default value produced by the defaultFunction if the conversion fails.
  `static <K> Integer`
  `getInteger(Map<? super K,?> map, K key)`
  Gets an 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> Integer`
  `getInteger(Map<? super K,?> map, K key, Function<K,Integer> defaultFunction)`
  Looks up the given key in the given map, converting the result into an integer, using the defaultFunction to produce 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> int`
  `getIntValue(Map<? super K,?> map, K key, Function<K,Integer> defaultFunction)`
  Gets an int from a Map in a null-safe manner, using the default value produced by the defaultFunction 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`
  `getLong(Map<? super K,?> map, K key, Function<K,Long> defaultFunction)`
  Looks up the given key in the given map, converting the result into a Long, using the defaultFunction to produce 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> long`
  `getLongValue(Map<? super K,?> map, K key, Function<K,Long> defaultFunction)`
  Gets a long from a Map in a null-safe manner, using the default value produced by the defaultFunction 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, Function<K,Map<?,?>> defaultFunction)`
  Looks up the given key in the given map, converting the result into a map, using the defaultFunction to produce the default value if the conversion fails.
  `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> Number`
  `getNumber(Map<? super K,?> map, K key, Function<K,Number> defaultFunction)`
  Looks up the given key in the given map, converting the result into a number, using the defaultFunction to produce 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`
  `getShort(Map<? super K,?> map, K key, Function<K,Short> defaultFunction)`
  Looks up the given key in the given map, converting the result into a short, using the defaultFunction to produce 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> short`
  `getShortValue(Map<? super K,?> map, K key, Function<K,Short> defaultFunction)`
  Gets a short from a Map in a null-safe manner, using the default value produced by the defaultFunction 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> String`
  `getString(Map<? super K,?> map, K key, Function<K,String> defaultFunction)`
  Looks up the given key in the given map, converting the result into a string, using the defaultFunction to produce 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)`
  Gets the specified `Map` as an `IterableMap`.
  `static <K, V> IterableSortedMap<K,V>`
  `iterableSortedMap(SortedMap<K,V> sortedMap)`
  Gets 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 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 initialized 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 Details

  - ### EMPTY_SORTED_MAP

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

- ## Method Details

  - ### 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 class name. When the value is a Map, recursive behavior 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`

  - ### 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`

  - ### 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

  - ### 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

  - ### 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

  - ### 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

  - ### getBoolean

    public static <K> Boolean getBoolean(Map<? super K,?> map, K key, Function<K,Boolean> defaultFunction)
    Looks up the given key in the given map, converting the result into a boolean, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a boolean, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the boolean conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getBooleanValue

    public static <K> boolean getBooleanValue(Map<? super K,?> map, K key, Function<K,Boolean> defaultFunction)
    Gets a boolean from a Map in a null-safe manner, using the default value produced by the defaultFunction 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 produced by the `defaultFunction` is returned.

    Type Parameters:
      `K` - the key type
    Parameters:
      `map` - the map to use
      `key` - the key to look up
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a Boolean, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getByte

    public static <K> Byte getByte(Map<? super K,?> map, K key, Function<K,Byte> defaultFunction)
    Looks up the given key in the given map, converting the result into a byte, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getByteValue

    public static <K> byte getByteValue(Map<? super K,?> map, K key, Function<K,Byte> defaultFunction)
    Gets a byte from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a byte, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getDouble

    public static <K> Double getDouble(Map<? super K,?> map, K key, Function<K,Double> defaultFunction)
    Looks up the given key in the given map, converting the result into a double, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getDoubleValue

    public static <K> double getDoubleValue(Map<? super K,?> map, K key, Function<K,Double> defaultFunction)
    Gets a double from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a double, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getFloat

    public static <K> Float getFloat(Map<? super K,?> map, K key, Function<K,Float> defaultFunction)
    Looks up the given key in the given map, converting the result into a float, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getFloatValue

    public static <K> float getFloatValue(Map<? super K,?> map, K key, Function<K,Float> defaultFunction)
    Gets a float from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a float, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### getInteger

    public static <K> Integer getInteger(Map<? super K,?> map, K key)
    Gets an 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 an Integer, `null` if null map input

  - ### getInteger

    public static <K> Integer getInteger(Map<? super K,?> map, K key, Function<K,Integer> defaultFunction)
    Looks up the given key in the given map, converting the result into an integer, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getIntValue

    public static <K> int getIntValue(Map<? super K,?> map, K key, Function<K,Integer> defaultFunction)
    Gets an int from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as an int, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getLong

    public static <K> Long getLong(Map<? super K,?> map, K key, Function<K,Long> defaultFunction)
    Looks up the given key in the given map, converting the result into a Long, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getLongValue

    public static <K> long getLongValue(Map<? super K,?> map, K key, Function<K,Long> defaultFunction)
    Gets a long from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a long, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getMap

    public static <K> Map<?,?> getMap(Map<? super K,?> map, K key, Function<K,Map<?,?>> defaultFunction)
    Looks up the given key in the given map, converting the result into a map, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the map conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getNumber

    public static <K> Number getNumber(Map<? super K,?> map, K key, Function<K,Number> defaultFunction)
    Looks up the given key in the given map, converting the result into a number, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### 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

  - ### 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

  - ### getShort

    public static <K> Short getShort(Map<? super K,?> map, K key, Function<K,Short> defaultFunction)
    Looks up the given key in the given map, converting the result into a short, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a number, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the number conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getShortValue

    public static <K> short getShortValue(Map<? super K,?> map, K key, Function<K,Short> defaultFunction)
    Gets a short from a Map in a null-safe manner, using the default value produced by the defaultFunction 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
      `defaultFunction` - produce the default value to return if the value is null or if the conversion fails
    Returns:
      the value in the Map as a short, default value produced by the `defaultFunction` if null map input
    Since:
      4.5.0-M1

  - ### 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

  - ### 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

  - ### getString

    public static <K> String getString(Map<? super K,?> map, K key, Function<K,String> defaultFunction)
    Looks up the given key in the given map, converting the result into a string, using the defaultFunction to produce 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
      `defaultFunction` - what to produce the default value if the value is null or if the conversion fails
    Returns:
      the value in the map as a string, or defaultValue produced by the defaultFunction if the original value is null, the map is null or the string conversion fails
    Since:
      4.5.0-M1

  - ### 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

  - ### 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, must not be null
    Returns:
      a new HashMap containing the inverted data
    Throws:
      `NullPointerException` - if the map 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

  - ### iterableMap

    public static <K, V> IterableMap<K,V> iterableMap(Map<K,V> map)
    Gets 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

  - ### iterableSortedMap

    public static <K, V> IterableSortedMap<K,V> iterableSortedMap(SortedMap<K,V> sortedMap)
    Gets the specified `SortedMap` as an `IterableSortedMap`.
    Type Parameters:
      `K` - the key type
      `V` - the value type
    Parameters:
      `sortedMap` - to wrap if necessary
    Returns:
      `IterableSortedMap`<K, V>
    Throws:
      `NullPointerException` - if sortedMap is null
    Since:
      4.0

  - ### 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

  - ### 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

  - ### 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 multi-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`

  - ### 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

  - ### 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(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(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

  - ### 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

  - ### 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

  - ### 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

  - ### 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

  - ### 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, must not be null
      `key` - the key
      `value` - the value, null converted to ""
    Throws:
      `NullPointerException` - if the map is null

  - ### 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

  - ### 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);
         Sets 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

  - ### 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);
         Sets 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

  - ### 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, must not be null
    Returns:
      the HashMap containing the data
    Throws:
      `NullPointerException` - if the bundle is null

  - ### toProperties

    public static <K, V> Properties toProperties(Map<K,V> map)
    Gets a new Properties object initialized 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`

  - ### 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 behavior, 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

  - ### 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 behavior, 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

  - ### 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

  - ### 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

  - ### 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 behavior 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`