MultiMap (pdevs 3.0 API)

java.lang.Object
- util.MultiMap<K,V>

Type Parameters:

K - the class of keys

V - the class of values

All Implemented Interfaces:

Iterable<V>
```
public class MultiMap<K,V>
extends Object
implements Iterable<V>
```
Implements a simple version of a multi-value map, based on a HashMap for the map part and a HashSet for the multiple values part. Using this map any key can map to any number of values. null values and keys are permitted by implementation.
This class is actually a decorator of a HashMap instance, for the Map interface forces the entrySet() method to return a set of entries (Key, Set(Value)), while a set of entries (Key, Value) was preferred in this implementation. Same issue for the iterator.

Author:

cmascart

Field Summary

Fields
Modifier and Type Field and Description

private HashMap<K,HashSet<V>> _map
The decorated HashMap.

Fields
Modifier and Type	Field and Description
`private HashMap<K,HashSet<V>>`	`_map` The decorated `HashMap`.

Constructor Summary

Constructors
Constructor and Description
`MultiMap()` Basic constructor, instantiates the decorated map with an empty instance of `HashMap`.
`MultiMap(Map<? extends K,? extends V> m)` Copy constructor, instantiates the decorated map and then copy the parameter entries into the new instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Clears the map, removing from index all keys and their associated values.
`boolean`	`containsKey(K key)` Returns whether the map contains the key given in parameter.
`boolean`	`containsValue(V value)` Returns whether the map contains the given value is present in the map.
`Set<Map.Entry<K,V>>`	`entrySet()` Generate a `Set` of `Map.Entry` of Key/Value.
`boolean`	`equals(Object o)` Compare the `MultiMap` to another object to determine if the decorated `Map` contains the same entries of (key, value) than the parameter.
`Set<V>`	`get(K key)` Getter on the set of values associated with a given key.
`boolean`	`isEmpty()` Returns whether the map contains no key at all.
`Iterator<V>`	`iterator()` Generate an iterator on a generated `Set` of `Map.Entry` of key/value.
`Set<K>`	`keySet()` Generate a `Set` that contains all keys that are in this `MultiMap`.
`V`	`put(K key, V value)` Add a given value to a given key in the `MultiMap`.
`void`	`putAll(Map<? extends K,? extends Set<V>> m)` Add all key/value from a given `Map` into the `MultiMap`.
`Set<V>`	`remove(K key)` Remove a key and its values from the MultiMap.
`V`	`remove(K key, V value)` Remove a given value from the set associated to a given key.
`int`	`size()` Computes the size of the decorated map.
`int`	`totalSize()` Computes the total size of the decorated map.
`Collection<V>`	`values()` generate a `HashSet` containing all values stored in the MultiMap.

Methods inherited from class java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Field Detail
  - _map
```
private HashMap<K,HashSet<V>> _map
```
    The decorated HashMap.
- Constructor Detail
  - MultiMap
```
public MultiMap()
```
    Basic constructor, instantiates the decorated map with an empty instance of HashMap.
  - MultiMap
```
public MultiMap(Map<? extends K,? extends V> m)
```
    Copy constructor, instantiates the decorated map and then copy the parameter entries into the new instance.
    
    Parameters:
    
    m - The map to copy.
- Method Detail
  - size
```
public int size()
```
    Computes the size of the decorated map.
    
    Returns:
    
    the number of keys (= size) of this map.
  - totalSize
```
public int totalSize()
```
    Computes the total size of the decorated map.
    
    Returns:
    
    the number of values (= total size) in the map.
  - isEmpty
```
public boolean isEmpty()
```
    Returns whether the map contains no key at all.
    
    Returns:
    
    true if the map contains no key, false otherwise.
  - containsKey
```
public boolean containsKey(K key)
```
    Returns whether the map contains the key given in parameter.
    
    Parameters:
    
    key - The key to be tested.
    
    Returns:
    
    true if the key is present in the map, false else.
  - containsValue
```
public boolean containsValue(V value)
```
    Returns whether the map contains the given value is present in the map.
    
    Parameters:
    
    value - The value to be tested.
    
    Returns:
    
    true if the value is present in the map, false otherwise.
  - clear
```
public void clear()
```
    Clears the map, removing from index all keys and their associated values.
  - keySet
```
public Set<K> keySet()
```
    Generate a Set that contains all keys that are in this MultiMap.
    
    Returns:
    
    The set of keys of the decorated map.
  - get
```
public Set<V> get(K key)
```
    Getter on the set of values associated with a given key.
    
    Parameters:
    
    key - The given key.
    
    Returns:
    
    The set of values associated with the key.
  - remove
```
public Set<V> remove(K key)
```
    Remove a key and its values from the MultiMap.
    
    Parameters:
    
    key - The key to remove.
    
    Returns:
    
    The removed Set of value if it exist, and null otherwise.
  - remove
```
public V remove(K key,
                V value)
```
    Remove a given value from the set associated to a given key.
    
    Parameters:
    
    key - The key from which remove the value.
    
    value - The value to remove.
    
    Returns:
    
    The removed value if the key and it exist, and null otherwise.
  - putAll
```
public void putAll(Map<? extends K,? extends Set<V>> m)
```
    Add all key/value from a given Map into the MultiMap.
    
    Parameters:
    
    m - The map from which extract keys and values.
  - values
```
public Collection<V> values()
```
    generate a HashSet containing all values stored in the MultiMap.
    
    Returns:
    
    All values stored in the MultiMap.
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    Generate a Set of Map.Entry of Key/Value. Each entry contain a value and its key.
    
    Returns:
    
    The set of entries (key, value).
  - put
```
public V put(K key,
             V value)
```
    Add a given value to a given key in the MultiMap.
    
    Parameters:
    
    key - The given key.
    
    value - The given value to add.
    
    Returns:
    
    The value.
  - iterator
```
public Iterator<V> iterator()
```
    Generate an iterator on a generated Set of Map.Entry of key/value.
    
    Specified by:
    
    iterator in interface Iterable<V>
    
    Returns:
    
    An iterator on a generated set of entries (key, value).
  - equals
```
public boolean equals(Object o)
```
    Compare the MultiMap to another object to determine if the decorated Map contains the same entries of (key, value) than the parameter.
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    o - The object to be compared to.
    
    Returns:
    
    true if they are equals, false otherwise.

Class MultiMap<K,V>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Field Detail

_map

Constructor Detail

MultiMap

MultiMap

Method Detail

size

totalSize

isEmpty

containsKey

containsValue

clear

keySet

get

remove

remove

putAll

values

entrySet

put

iterator

equals