org.apache.commons.collections

## Class MapUtils

- java.lang.Object
- - org.apache.commons.collections.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)`
  - `typedMap(Map, Class, Class)`
  - `typedSortedMap(SortedMap, Class, Class)`
  - `multiValueMap( Map )`
  - `multiValueMap( Map, Class )`
  - `multiValueMap( Map, Factory )`
  Since:
    Commons Collections 1.0
  Version:
    $Revision: 1713178 $ $Date: 2015-11-07 21:59:09 +0100 (Sat, 07 Nov 2015) $
  Author:
    James Strachan, Nissim Karpenstein, Kasper Nielsen, Paul Jack, Stephen Colebourne, Matthew Hawthorne, Arun Mammen Thomas, Janek Bogucki, Max Rydahl Andersen, Ashwin S, James Carman, Neil O'Toole

- - ### Field Summary

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

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `MapUtils()` `MapUtils` should not normally be instantiated.

  - ### 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 Map` | `fixedSizeMap(Map map)` Returns a fixed-sized map backed by the given map.
    `static SortedMap` | `fixedSizeSortedMap(SortedMap map)` Returns a fixed-sized sorted map backed by the given sorted map.
    `static Boolean` | `getBoolean(Map map, Object key)` Gets a Boolean from a Map in a null-safe manner.
    `static Boolean` | `getBoolean(Map map, Object 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 boolean` | `getBooleanValue(Map map, Object key)` Gets a boolean from a Map in a null-safe manner.
    `static boolean` | `getBooleanValue(Map map, Object key, boolean defaultValue)` Gets a boolean from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Byte` | `getByte(Map map, Object key)` Gets a Byte from a Map in a null-safe manner.
    `static Byte` | `getByte(Map map, Object 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 byte` | `getByteValue(Map map, Object key)` Gets a byte from a Map in a null-safe manner.
    `static byte` | `getByteValue(Map map, Object key, byte defaultValue)` Gets a byte from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Double` | `getDouble(Map map, Object key)` Gets a Double from a Map in a null-safe manner.
    `static Double` | `getDouble(Map map, Object 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 double` | `getDoubleValue(Map map, Object key)` Gets a double from a Map in a null-safe manner.
    `static double` | `getDoubleValue(Map map, Object key, double defaultValue)` Gets a double from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Float` | `getFloat(Map map, Object key)` Gets a Float from a Map in a null-safe manner.
    `static Float` | `getFloat(Map map, Object 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 float` | `getFloatValue(Map map, Object key)` Gets a float from a Map in a null-safe manner.
    `static float` | `getFloatValue(Map map, Object key, float defaultValue)` Gets a float from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Integer` | `getInteger(Map map, Object key)` Gets a Integer from a Map in a null-safe manner.
    `static Integer` | `getInteger(Map map, Object 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 int` | `getIntValue(Map map, Object key)` Gets an int from a Map in a null-safe manner.
    `static int` | `getIntValue(Map map, Object key, int defaultValue)` Gets an int from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Long` | `getLong(Map map, Object key)` Gets a Long from a Map in a null-safe manner.
    `static Long` | `getLong(Map map, Object 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 long` | `getLongValue(Map map, Object key)` Gets a long from a Map in a null-safe manner.
    `static long` | `getLongValue(Map map, Object key, long defaultValue)` Gets a long from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static Map` | `getMap(Map map, Object key)` Gets a Map from a Map in a null-safe manner.
    `static Map` | `getMap(Map map, Object 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 Number` | `getNumber(Map map, Object key)` Gets a Number from a Map in a null-safe manner.
    `static Number` | `getNumber(Map map, Object 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 Object` | `getObject(Map map, Object key)` Gets from a Map in a null-safe manner.
    `static Object` | `getObject(Map map, Object key, Object defaultValue)` Looks up the given key in the given map, converting null into the given default value.
    `static Short` | `getShort(Map map, Object key)` Gets a Short from a Map in a null-safe manner.
    `static Short` | `getShort(Map map, Object 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 short` | `getShortValue(Map map, Object key)` Gets a short from a Map in a null-safe manner.
    `static short` | `getShortValue(Map map, Object key, short defaultValue)` Gets a short from a Map in a null-safe manner, using the default value if the the conversion fails.
    `static String` | `getString(Map map, Object key)` Gets a String from a Map in a null-safe manner.
    `static String` | `getString(Map map, Object 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 Map` | `invertMap(Map 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 Map` | `lazyMap(Map map, Factory factory)` Returns a "lazy" map whose values will be created on demand.
    `static Map` | `lazyMap(Map map, Transformer transformerFactory)` Returns a "lazy" map whose values will be created on demand.
    `static SortedMap` | `lazySortedMap(SortedMap map, Factory factory)` Returns a "lazy" sorted map whose values will be created on demand.
    `static SortedMap` | `lazySortedMap(SortedMap map, Transformer transformerFactory)` Returns a "lazy" sorted map whose values will be created on demand.
    `protected static void` | `logInfo(Exception ex)` Logs the given exception to `System.out`.
    `static Map` | `multiValueMap(Map map)` Creates a mult-value map backed by the given map which returns collections of type ArrayList.
    `static Map` | `multiValueMap(Map map, Class collectionClass)` Creates a multi-value map backed by the given map which returns collections of the specified type.
    `static Map` | `multiValueMap(Map map, Factory collectionFactory)` Creates a multi-value map backed by the given map which returns collections created by the specified collection factory.
    `static Map` | `orderedMap(Map map)` Returns a map that maintains the order of keys that are added backed by the given map.
    `static Map` | `predicatedMap(Map map, Predicate keyPred, Predicate valuePred)` Returns a predicated (validating) map backed by the given map.
    `static SortedMap` | `predicatedSortedMap(SortedMap map, Predicate keyPred, Predicate valuePred)` Returns a predicated (validating) sorted map backed by the given map.
    `static Map` | `putAll(Map map, Object[] array)` Puts all the keys and values from the specified array into the map.
    `static void` | `safeAddToMap(Map map, Object key, Object value)` Protects against adding null values to a map.
    `static Map` | `synchronizedMap(Map map)` Returns a synchronized map backed by the given map.
    `static Map` | `synchronizedSortedMap(SortedMap map)` Returns a synchronized sorted map backed by the given sorted map.
    `static Map` | `toMap(ResourceBundle resourceBundle)` Creates a new HashMap using data copied from a ResourceBundle.
    `static Properties` | `toProperties(Map map)` Gets a new Properties object initialised with the values from a Map.
    `static Map` | `transformedMap(Map map, Transformer keyTransformer, Transformer valueTransformer)` Returns a transformed map backed by the given map.
    `static SortedMap` | `transformedSortedMap(SortedMap map, Transformer keyTransformer, Transformer valueTransformer)` Returns a transformed sorted map backed by the given map.
    `static Map` | `typedMap(Map map, Class keyType, Class valueType)` Returns a typed map backed by the given map.
    `static SortedMap` | `typedSortedMap(SortedMap map, Class keyType, Class valueType)` Returns a typed sorted map backed by the given map.
    `static Map` | `unmodifiableMap(Map map)` Returns an unmodifiable map backed by the given map.
    `static Map` | `unmodifiableSortedMap(SortedMap 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_MAP

          public static final Map EMPTY_MAP

      An empty unmodifiable map. This was not provided in JDK1.2.

    - #### EMPTY_SORTED_MAP

          public static final SortedMap EMPTY_SORTED_MAP

      An empty unmodifiable sorted map. This is not provided in the JDK.

  - ### Constructor Detail

    - #### MapUtils

          public MapUtils()

      `MapUtils` should not normally be instantiated.

  - ### Method Detail

    - #### getObject

          public static Object getObject(Map map,
                         Object key)

      Gets from a Map in a null-safe manner.
      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 String getString(Map map,
                         Object key)

      Gets a String from a Map in a null-safe manner.

      The String is obtained via `toString`.

      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 Boolean getBoolean(Map map,
                           Object 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.

      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 Number getNumber(Map map,
                         Object 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.

      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 Byte getByte(Map map,
                     Object key)

      Gets a Byte from a Map in a null-safe manner.

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

      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 Short getShort(Map map,
                       Object key)

      Gets a Short from a Map in a null-safe manner.

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

      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 Integer getInteger(Map map,
                           Object key)

      Gets a Integer from a Map in a null-safe manner.

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

      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 Long getLong(Map map,
                     Object key)

      Gets a Long from a Map in a null-safe manner.

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

      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 Float getFloat(Map map,
                       Object key)

      Gets a Float from a Map in a null-safe manner.

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

      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 Double getDouble(Map map,
                         Object key)

      Gets a Double from a Map in a null-safe manner.

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

      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 Map getMap(Map map,
                   Object 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.

      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 Object getObject(Map map,
                         Object key,
                         Object defaultValue)

      Looks up the given key in the given map, converting null into the given default value.
      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 String getString(Map map,
                         Object 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.
      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 Boolean getBoolean(Map map,
                           Object 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.
      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 Number getNumber(Map map,
                         Object 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.
      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 Byte getByte(Map map,
                     Object 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.
      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 Short getShort(Map map,
                       Object 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.
      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 Integer getInteger(Map map,
                           Object 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.
      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 Long getLong(Map map,
                     Object 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.
      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 Float getFloat(Map map,
                       Object 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.
      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 Double getDouble(Map map,
                         Object 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.
      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 Map getMap(Map map,
                   Object 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.
      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 boolean getBooleanValue(Map map,
                                Object 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.

      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 byte getByteValue(Map map,
                          Object key)

      Gets a byte from a Map in a null-safe manner.

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

      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 short getShortValue(Map map,
                            Object key)

      Gets a short from a Map in a null-safe manner.

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

      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 int getIntValue(Map map,
                        Object key)

      Gets an int from a Map in a null-safe manner.

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

      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 long getLongValue(Map map,
                          Object key)

      Gets a long from a Map in a null-safe manner.

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

      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 float getFloatValue(Map map,
                            Object key)

      Gets a float from a Map in a null-safe manner.

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

      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 double getDoubleValue(Map map,
                              Object key)

      Gets a double from a Map in a null-safe manner.

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

      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 boolean getBooleanValue(Map map,
                                Object 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.

      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 byte getByteValue(Map map,
                          Object 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)`.

      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 short getShortValue(Map map,
                            Object 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)`.

      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 int getIntValue(Map map,
                        Object 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)`.

      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 long getLongValue(Map map,
                          Object 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)`.

      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 float getFloatValue(Map map,
                            Object 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)`.

      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 double getDoubleValue(Map map,
                              Object 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)`.

      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 Properties toProperties(Map map)

      Gets a new Properties object initialised with the values from a Map. A null input will return an empty properties object.
      Parameters:
        `map` - the map to convert to a Properties object, may not be null
      Returns:
        the properties object

    - #### toMap

          public static Map 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`

    - #### logInfo

          protected static void logInfo(Exception ex)

      Logs the given exception to `System.out`.

      This method exists as Jakarta Collections does not depend on logging.

      Parameters:
        `ex` - the exception to log

    - #### invertMap

          public static Map invertMap(Map 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.

      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 void safeAddToMap(Map map,
                          Object 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.

      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 Map putAll(Map 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")
           });

      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:
        Commons Collections 3.2

    - #### 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:
        Commons Collections 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:
        Commons Collections 3.2

    - #### synchronizedMap

          public static Map synchronizedMap(Map 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`.
      Parameters:
        `map` - the map to synchronize, must not be null
      Returns:
        a synchronized map backed by the given map
      Throws:
        `IllegalArgumentException` - if the map is null

    - #### unmodifiableMap

          public static Map unmodifiableMap(Map map)

      Returns an unmodifiable map backed by the given map.

      This method uses the implementation in the decorators subpackage.

      Parameters:
        `map` - the map to make unmodifiable, must not be null
      Returns:
        an unmodifiable map backed by the given map
      Throws:
        `IllegalArgumentException` - if the map is null

    - #### predicatedMap

          public static Map predicatedMap(Map map,
                          Predicate keyPred,
                          Predicate 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.

      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:
        `IllegalArgumentException` - if the Map is null

    - #### typedMap

          public static Map typedMap(Map map,
                     Class keyType,
                     Class valueType)

      Returns a typed map backed by the given map.

      Only keys and values of the specified types can be added to the map.

      Parameters:
        `map` - the map to limit to a specific type, must not be null
        `keyType` - the type of keys which may be added to the map, must not be null
        `valueType` - the type of values which may be added to the map, must not be null
      Returns:
        a typed map backed by the specified map
      Throws:
        `IllegalArgumentException` - if the Map or Class is null

    - #### transformedMap

          public static Map transformedMap(Map map,
                           Transformer keyTransformer,
                           Transformer 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.decorateTransform(java.util.Map, org.apache.commons.collections.Transformer, org.apache.commons.collections.Transformer)`.

      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.

      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:
        `IllegalArgumentException` - if the Map is null

    - #### fixedSizeMap

          public static Map fixedSizeMap(Map 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).
      Parameters:
        `map` - the map whose size to fix, must not be null
      Returns:
        a fixed-size map backed by that map
      Throws:
        `IllegalArgumentException` - if the Map is null

    - #### lazyMap

          public static Map lazyMap(Map map,
                    Factory 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.
      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:
        `IllegalArgumentException` - if the Map or Factory is null

    - #### lazyMap

          public static Map lazyMap(Map map,
                    Transformer 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.

      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:
        `IllegalArgumentException` - if the Map or Transformer is null

    - #### orderedMap

          public static Map orderedMap(Map 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.

      Parameters:
        `map` - the map to order, must not be null
      Returns:
        an ordered map backed by the given map
      Throws:
        `IllegalArgumentException` - if the Map is null

    - #### multiValueMap

          public static Map multiValueMap(Map map)

      Creates a mult-value map backed by the given map which returns collections of type ArrayList.
      Parameters:
        `map` - the map to decorate
      Returns:
        a multi-value map backed by the given map which returns ArrayLists of values.
      Since:
        Commons Collections 3.2
      See Also:
        `MultiValueMap`

    - #### multiValueMap

          public static Map multiValueMap(Map map,
                          Class collectionClass)

      Creates a multi-value map backed by the given map which returns collections of the specified 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:
        Commons Collections 3.2
      See Also:
        `MultiValueMap`

    - #### multiValueMap

          public static Map multiValueMap(Map map,
                          Factory collectionFactory)

      Creates a multi-value map backed by the given map which returns collections created by the specified collection factory.
      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:
        Commons Collections 3.2
      See Also:
        `MultiValueMap`

    - #### synchronizedSortedMap

          public static Map synchronizedSortedMap(SortedMap 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`.
      Parameters:
        `map` - the map to synchronize, must not be null
      Returns:
        a synchronized map backed by the given map
      Throws:
        `IllegalArgumentException` - if the map is null

    - #### unmodifiableSortedMap

          public static Map unmodifiableSortedMap(SortedMap map)

      Returns an unmodifiable sorted map backed by the given sorted map.

      This method uses the implementation in the decorators subpackage.

      Parameters:
        `map` - the sorted map to make unmodifiable, must not be null
      Returns:
        an unmodifiable map backed by the given map
      Throws:
        `IllegalArgumentException` - if the map is null

    - #### predicatedSortedMap

          public static SortedMap predicatedSortedMap(SortedMap map,
                                      Predicate keyPred,
                                      Predicate 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.

      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:
        `IllegalArgumentException` - if the SortedMap is null

    - #### typedSortedMap

          public static SortedMap typedSortedMap(SortedMap map,
                                 Class keyType,
                                 Class valueType)

      Returns a typed sorted map backed by the given map.

      Only keys and values of the specified types can be added to the map.

      Parameters:
        `map` - the map to limit to a specific type, must not be null
        `keyType` - the type of keys which may be added to the map, must not be null
        `valueType` - the type of values which may be added to the map, must not be null
      Returns:
        a typed map backed by the specified map

    - #### transformedSortedMap

          public static SortedMap transformedSortedMap(SortedMap map,
                                       Transformer keyTransformer,
                                       Transformer 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.decorateTransform(java.util.SortedMap, org.apache.commons.collections.Transformer, org.apache.commons.collections.Transformer)`.

      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.

      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:
        `IllegalArgumentException` - if the SortedMap is null

    - #### fixedSizeSortedMap

          public static SortedMap fixedSizeSortedMap(SortedMap 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).
      Parameters:
        `map` - the map whose size to fix, must not be null
      Returns:
        a fixed-size map backed by that map
      Throws:
        `IllegalArgumentException` - if the SortedMap is null

    - #### lazySortedMap

          public static SortedMap lazySortedMap(SortedMap map,
                                Factory 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.
      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:
        `IllegalArgumentException` - if the SortedMap or Factory is null

    - #### lazySortedMap

          public static SortedMap lazySortedMap(SortedMap map,
                                Transformer 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.

      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:
        `IllegalArgumentException` - if the Map or Transformer is null

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