Package no.mnemonic.commons.utilities.collections

Class MapUtils

java.lang.Object
no.mnemonic.commons.utilities.collections.MapUtils
public class MapUtils extends Object

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static final class 
    MapUtils.Pair<A,B>
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static <K, V> Map<K,V>
    addToMap(Map<K,V> map, K key, V value)
    Adds a key-value pair to a map unless the key or the value are null.
    static <K, V> Map<K,V>
    concatenate(Map<K,V>... maps)
    Concatenates multiple maps into one new map.
    static <K, V> Map<K,V>
    filterMap(Map<K,V> originMap, Collection<K> retainKeys)
    Creates a subset of the given map based on a collection of keys.
    static <K, V> boolean
    isEmpty(Map<K,V> map)
    Null-safe operation to test if a map is empty.
    static <K, V> Map<K,V>
    map(Collection<MapUtils.Pair<K,V>> collection)
    Creates a map from a collection containing key-value pairs.
    static <K, V, T> Map<K,V>
    map(Collection<T> collection, Function<T,MapUtils.Pair<K,V>> mapping)
    Creates a map from a collection using a mapping function to extract key-value pairs.
    static <K, V, T> Map<K,V>
    map(Function<T,MapUtils.Pair<K,V>> mapping, T... values)
    Creates a map from its arguments using a mapping function to extract key-value pairs.
    static <K, V> Map<K,V>
    map(Iterator<MapUtils.Pair<K,V>> iterator)
    Creates a map from an iterator supplying key-value pairs.
    static <K, V, T> Map<K,V>
    map(Iterator<T> iterator, Function<T,MapUtils.Pair<K,V>> mapping)
    Creates a map from an iterator using a mapping function to extract key-value pairs.
    static <K, V> Map<K,V>
    map(Map<K,V> map)
    Creates a map from a map
    static <K, V> Map<K,V>
    map(MapUtils.Pair<K,V>... pairs)
    Creates a map from key-value pairs.
    static <K, V> Map<K,V>
    modifyMap(Map<K,V> originMap, Map<K,V> addMap, Collection<K> removeKeys)
    Applies add/remove modifications to a map.
    static <K, V> MapUtils.Pair<K,V>
    pair(K key, V val)
    Convenience method to create a key/value MapUtils.Pair.
    static <K, V> int
    size(Map<K,V> map)
    Null-safe operation to determine the size of a map.

    Methods inherited from class java.lang.Object

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

  • Method Details

    • map

      public static <K, V> Map<K,V> map(Map<K,V> map)
      Creates a map from a map
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      map - Map to create new map from
      Returns:
      A new map containing the entries of the provided map, or an empty map if the provided argument was null

    • map

      @SafeVarargs public static <K, V> Map<K,V> map(MapUtils.Pair<K,V>... pairs)
      Creates a map from key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      pairs - Pairs converted to key-value entries in the map.
      Returns:
      A map containing the key-value pairs.

    • map

      public static <K, V> Map<K,V> map(Iterator<MapUtils.Pair<K,V>> iterator)
      Creates a map from an iterator supplying key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      iterator - An iterator supplying key-value pairs which are added to the map.
      Returns:
      A map containing all key-value pairs supplied by the given iterator.

    • map

      public static <K, V> Map<K,V> map(Collection<MapUtils.Pair<K,V>> collection)
      Creates a map from a collection containing key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      collection - A collection containing key-value pairs which are added to the map.
      Returns:
      A map containing all key-value pairs contained in the given collection.

    • map

      @SafeVarargs public static <K, V, T> Map<K,V> map(Function<T,MapUtils.Pair<K,V>> mapping, T... values)
      Creates a map from its arguments using a mapping function to extract key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      T - Type of argument values.
      Parameters:
      mapping - A mapping function applied to all values to extract key-value pairs.
      values - Values which are added to the map.
      Returns:
      A map containing all key-value pairs extracted from the values.

    • map

      public static <K, V, T> Map<K,V> map(Iterator<T> iterator, Function<T,MapUtils.Pair<K,V>> mapping)
      Creates a map from an iterator using a mapping function to extract key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      T - Type of elements supplied by 'iterator'.
      Parameters:
      iterator - An iterator which values are added to the map.
      mapping - A mapping function applied to all values supplied by 'iterator' to extract key-value pairs.
      Returns:
      A map containing all key-value pairs extracted from the given iterator.

    • map

      public static <K, V, T> Map<K,V> map(Collection<T> collection, Function<T,MapUtils.Pair<K,V>> mapping)
      Creates a map from a collection using a mapping function to extract key-value pairs.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      T - Type of elements in 'collection'.
      Parameters:
      collection - A collection which values are added to the map.
      mapping - A mapping function applied to all values contained in 'collection' to extract key-value pairs.
      Returns:
      A map containing all key-value pairs extracted from the given collection.

    • addToMap

      public static <K, V> Map<K,V> addToMap(Map<K,V> map, K key, V value)
      Adds a key-value pair to a map unless the key or the value are null.

      A new map is created if the provided map is null.

      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      map - Map to which the key-value pair will be added.
      key - Key in the map.
      value - Value added for the given key.
      Returns:
      Map including added key-value pair.

    • concatenate

      @SafeVarargs public static <K, V> Map<K,V> concatenate(Map<K,V>... maps)
      Concatenates multiple maps into one new map.

      If the same key exists in multiple maps the value stored in the last map will be used.

      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      maps - Multiple maps which will be concatenated.
      Returns:
      A map containing all key-value pairs from the given maps.

    • modifyMap

      public static <K, V> Map<K,V> modifyMap(Map<K,V> originMap, Map<K,V> addMap, Collection<K> removeKeys)
      Applies add/remove modifications to a map.

      This operation permits adding to and removing from one map in a single operation.

      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      originMap - Map to be modified.
      addMap - Map containing key-value pairs to be added.
      removeKeys - Collection containing keys to be removed.
      Returns:
      Same instance of 'originMap' passed in after modification.

    • filterMap

      public static <K, V> Map<K,V> filterMap(Map<K,V> originMap, Collection<K> retainKeys)
      Creates a subset of the given map based on a collection of keys. The original map is not altered.
      Type Parameters:
      K - Type of keys.
      V - Type of values.
      Parameters:
      originMap - Map to be filtered.
      retainKeys - Keys to retain in subset map.
      Returns:
      A new map containing only the keys listed in 'retainKeys'.

    • isEmpty

      public static <K, V> boolean isEmpty(Map<K,V> map)
      Null-safe operation to test if a map is empty.
      Type Parameters:
      K - Type of keys in map.
      V - Type of values in map.
      Parameters:
      map - Map to be tested.
      Returns:
      Returns true if the map is null or contains no elements.

    • size

      public static <K, V> int size(Map<K,V> map)
      Null-safe operation to determine the size of a map.
      Type Parameters:
      K - Type of keys in map.
      V - Type of values in map.
      Parameters:
      map - Map to compute size for.
      Returns:
      Returns 0 if the map is null, otherwise the number of elements in the map.

    • pair

      public static <K, V> MapUtils.Pair<K,V> pair(K key, V val)
      Convenience method to create a key/value MapUtils.Pair.
      Type Parameters:
      K - Type of key
      V - Type of value
      Parameters:
      key - Key
      val - Value
      Returns:
      A key/value pair