com.google.common.collect
Class ImmutableMap<K,V>

java.lang.Object
  extended by com.google.common.collect.ImmutableMap<K,V>
All Implemented Interfaces:
Serializable, Map<K,V>
Direct Known Subclasses:
ImmutableBiMap, ImmutableSortedMap

public abstract class ImmutableMap<K,V>
extends Object
implements Map<K,V>, Serializable

An immutable, hash-based Map with reliable user-specified iteration order. Does not permit null keys or values.

Unlike Collections.unmodifiableMap(java.util.Map), which is a view of a separate map which can still change, an instance of ImmutableMap contains its own data and will never change. ImmutableMap is convenient for public static final maps ("constant maps") and also lets you easily make a "defensive copy" of a map provided to your class by a caller.

Note: Although this class is not final, it cannot be subclassed as it has no public or protected constructors. Thus, instances of this class are guaranteed to be immutable.

Author:
Jesse Wilson, Kevin Bourrillion
See Also:
ImmutableList, ImmutableSet, Serialized Form

Nested Class Summary
static class ImmutableMap.Builder<K,V>
          A builder for creating immutable map instances, especially public static final maps ("constant maps").
 
Nested classes/interfaces inherited from interface java.util.Map
Map.Entry<K,V>
 
Method Summary
static
<K,V> ImmutableMap.Builder<K,V>
builder()
          Returns a new builder.
 void clear()
          Guaranteed to throw an exception and leave the map unmodified.
 boolean containsKey(Object key)
          Returns true if this map contains a mapping for the specified key.
abstract  boolean containsValue(Object value)
          Returns true if this map maps one or more keys to the specified value.
static
<K,V> ImmutableMap<K,V>
copyOf(Map<? extends K,? extends V> map)
          Returns an immutable map containing the same entries as map.
abstract  ImmutableSet<Map.Entry<K,V>> entrySet()
          Returns an immutable set of the mappings in this map.
 boolean equals(Object object)
          Indicates whether some other object is "equal to" this one.
abstract  V get(Object key)
          Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
 int hashCode()
          Returns a hash code value for the object.
 boolean isEmpty()
          Returns true if this map contains no key-value mappings.
abstract  ImmutableSet<K> keySet()
          Returns an immutable set of the keys in this map.
static
<K,V> ImmutableMap<K,V>
of()
          Returns the empty map.
static
<K,V> ImmutableMap<K,V>
of(K k1, V v1)
          Returns an immutable map containing a single entry.
static
<K,V> ImmutableMap<K,V>
of(K k1, V v1, K k2, V v2)
          Returns an immutable map containing the given entries, in order.
static
<K,V> ImmutableMap<K,V>
of(K k1, V v1, K k2, V v2, K k3, V v3)
          Returns an immutable map containing the given entries, in order.
static
<K,V> ImmutableMap<K,V>
of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4)
          Returns an immutable map containing the given entries, in order.
static
<K,V> ImmutableMap<K,V>
of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5)
          Returns an immutable map containing the given entries, in order.
 V put(K k, V v)
          Guaranteed to throw an exception and leave the map unmodified.
 void putAll(Map<? extends K,? extends V> map)
          Guaranteed to throw an exception and leave the map unmodified.
 V remove(Object o)
          Guaranteed to throw an exception and leave the map unmodified.
 String toString()
          Returns a string representation of the object.
abstract  ImmutableCollection<V> values()
          Returns an immutable collection of the values in this map.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Map
size
 

Method Detail

of

public static <K,V> ImmutableMap<K,V> of()
Returns the empty map. This map behaves and performs comparably to Collections.emptyMap(), and is preferable mainly for consistency and maintainability of your code.


of

public static <K,V> ImmutableMap<K,V> of(K k1,
                                         V v1)
Returns an immutable map containing a single entry. This map behaves and performs comparably to Collections.singletonMap(K, V) but will not accept a null key or value. It is preferable mainly for consistency and maintainability of your code.


of

public static <K,V> ImmutableMap<K,V> of(K k1,
                                         V v1,
                                         K k2,
                                         V v2)
Returns an immutable map containing the given entries, in order.

Throws:
IllegalArgumentException - if duplicate keys are provided

of

public static <K,V> ImmutableMap<K,V> of(K k1,
                                         V v1,
                                         K k2,
                                         V v2,
                                         K k3,
                                         V v3)
Returns an immutable map containing the given entries, in order.

Throws:
IllegalArgumentException - if duplicate keys are provided

of

public static <K,V> ImmutableMap<K,V> of(K k1,
                                         V v1,
                                         K k2,
                                         V v2,
                                         K k3,
                                         V v3,
                                         K k4,
                                         V v4)
Returns an immutable map containing the given entries, in order.

Throws:
IllegalArgumentException - if duplicate keys are provided

of

public static <K,V> ImmutableMap<K,V> of(K k1,
                                         V v1,
                                         K k2,
                                         V v2,
                                         K k3,
                                         V v3,
                                         K k4,
                                         V v4,
                                         K k5,
                                         V v5)
Returns an immutable map containing the given entries, in order.

Throws:
IllegalArgumentException - if duplicate keys are provided

builder

public static <K,V> ImmutableMap.Builder<K,V> builder()
Returns a new builder. The generated builder is equivalent to the builder created by the ImmutableMap.Builder constructor.


copyOf

public static <K,V> ImmutableMap<K,V> copyOf(Map<? extends K,? extends V> map)
Returns an immutable map containing the same entries as map. If map somehow contains entries with duplicate keys (for example, if it is a SortedMap whose comparator is not consistent with equals), the results of this method are undefined.

Note: Despite what the method name suggests, if map is an ImmutableMap, no copy will actually be performed, and the given map itself will be returned.

Throws:
NullPointerException - if any key or value in map is null

put

public final V put(K k,
                   V v)
Guaranteed to throw an exception and leave the map unmodified.

Specified by:
put in interface Map<K,V>
Parameters:
k - key with which the specified value is to be associated
v - value to be associated with the specified key
Returns:
the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)
Throws:
UnsupportedOperationException - always

remove

public final V remove(Object o)
Guaranteed to throw an exception and leave the map unmodified.

Specified by:
remove in interface Map<K,V>
Parameters:
o - key whose mapping is to be removed from the map
Returns:
the previous value associated with key, or null if there was no mapping for key.
Throws:
UnsupportedOperationException - always

putAll

public final void putAll(Map<? extends K,? extends V> map)
Guaranteed to throw an exception and leave the map unmodified.

Specified by:
putAll in interface Map<K,V>
Parameters:
map - mappings to be stored in this map
Throws:
UnsupportedOperationException - always

clear

public final void clear()
Guaranteed to throw an exception and leave the map unmodified.

Specified by:
clear in interface Map<K,V>
Throws:
UnsupportedOperationException - always

isEmpty

public boolean isEmpty()
Description copied from interface: java.util.Map
Returns true if this map contains no key-value mappings.

Specified by:
isEmpty in interface Map<K,V>
Returns:
true if this map contains no key-value mappings

containsKey

public boolean containsKey(@Nullable
                           Object key)
Description copied from interface: java.util.Map
Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.)

Specified by:
containsKey in interface Map<K,V>
Parameters:
key - key whose presence in this map is to be tested
Returns:
true if this map contains a mapping for the specified key

containsValue

public abstract boolean containsValue(@Nullable
                                      Object value)
Description copied from interface: java.util.Map
Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations of the Map interface.

Specified by:
containsValue in interface Map<K,V>
Parameters:
value - value whose presence in this map is to be tested
Returns:
true if this map maps one or more keys to the specified value

get

public abstract V get(@Nullable
                      Object key)
Description copied from interface: java.util.Map
Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that (key==null ? k==null : key.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Specified by:
get in interface Map<K,V>
Parameters:
key - the key whose associated value is to be returned
Returns:
the value to which the specified key is mapped, or null if this map contains no mapping for the key

entrySet

public abstract ImmutableSet<Map.Entry<K,V>> entrySet()
Returns an immutable set of the mappings in this map. The entries are in the same order as the parameters used to build this map.

Specified by:
entrySet in interface Map<K,V>
Returns:
a set view of the mappings contained in this map

keySet

public abstract ImmutableSet<K> keySet()
Returns an immutable set of the keys in this map. These keys are in the same order as the parameters used to build this map.

Specified by:
keySet in interface Map<K,V>
Returns:
a set view of the keys contained in this map

values

public abstract ImmutableCollection<V> values()
Returns an immutable collection of the values in this map. The values are in the same order as the parameters used to build this map.

Specified by:
values in interface Map<K,V>
Returns:
a collection view of the values contained in this map

equals

public boolean equals(@Nullable
                      Object object)
Description copied from class: java.lang.Object
Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specified by:
equals in interface Map<K,V>
Overrides:
equals in class Object
Parameters:
object - the reference object with which to compare.
Returns:
true if this object is the same as the obj argument; false otherwise.
See Also:
Object.hashCode(), Hashtable

hashCode

public int hashCode()
Description copied from class: java.lang.Object
Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)

Specified by:
hashCode in interface Map<K,V>
Overrides:
hashCode in class Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), Hashtable

toString

public String toString()
Description copied from class: java.lang.Object
Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:
toString in class Object
Returns:
a string representation of the object.