io.atlassian.fugue.extras

Class ImmutableMaps

java.lang.Object

io.atlassian.fugue.extras.ImmutableMaps

public class ImmutableMaps
extends Object

Provides some utility methods to convert Iterables to ImmutableMap, and to transform Maps.

Since:

2.0

Method Summary

Modifier and Type	Method and Description
static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2>	collect(Map<K1,V1> from, Function<? super K1,Option<K2>> keyPartial, Function<? super V1,Option<V2>> valuePartial) Filters and maps (aka transforms) the source map.
static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2>	collect(Map<K1,V1> from, Function<Map.Entry<K1,V1>,Option<Map.Entry<K2,V2>>> partial) Filters and maps (aka transforms) the source map.
static <K1,K2,V> com.google.common.collect.ImmutableMap<K2,V>	collectByKey(Map<K1,V> from, Function<? super K1,Option<K2>> keyPartial) Filters and maps (aka transforms) the source map.
static <K,V1,V2> com.google.common.collect.ImmutableMap<K,V2>	collectByValue(Map<K,V1> from, Function<? super V1,Option<V2>> valuePartial) Filters and maps (aka transforms) the source map.
static <K,V> com.google.common.collect.ImmutableMap<K,V>	mapBy(Iterable<V> from, Function<? super V,? extends K> keyTransformer) Builds an immutable map that is keyed by the result of applying keyTransformer to each element of the given iterable of values.
static <K,V> BiFunction<K,V,Map.Entry<K,V>>	mapEntry() Returns a function that takes a key of type K and a value of type V and returns a Map entry.
static <K,V> com.google.common.collect.ImmutableMap<K,V>	mapTo(Iterable<K> from, Function<? super K,? extends V> valueTransformer) Builds an immutable map from the given iterable and compute the value by applying the valueTransformer.
static <K,V> com.google.common.collect.ImmutableMap<K,V>	toMap(Iterable<Map.Entry<K,V>> from) Builds an immutable map from the given iterable of Map.Entry.
static <T,K,V> com.google.common.collect.ImmutableMap<K,V>	toMap(Iterable<T> from, Function<? super T,? extends K> keyTransformer, Function<? super T,? extends V> valueTransformer) Builds an immutable map from the given iterable, with key derived from the application of the iterable to the keyTransformer, and value derived from the application of the iterable to the valueTransformer.
static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2>	transform(Map<K1,V1> from, Function<? super K1,? extends K2> keyTransformer, Function<? super V1,? extends V2> valueTransformer) Returns an immutable map that applies the keyTransformer and valueTransformer functions to each entry of fromMap.
static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2>	transform(Map<K1,V1> from, Function<Map.Entry<K1,V1>,Map.Entry<K2,V2>> function) Returns an immutable map that applies function to each entry of fromMap.
static <K1,K2,V> com.google.common.collect.ImmutableMap<K2,V>	transformKey(Map<K1,V> from, Function<? super K1,? extends K2> keyTransformer) Returns an immutable map that applies keyTransformer to the key of each entry of the source map.
static <K,V1,V2> com.google.common.collect.ImmutableMap<K,V2>	transformValue(Map<K,V1> from, Function<? super V1,? extends V2> valueTransformer) Returns an immutable map that applies valueTransformer to the value of each entry of the source map.

Methods inherited from class java.lang.Object

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

Method Detail

mapEntry

public static <K,V> BiFunction<K,V,Map.Entry<K,V>> mapEntry()

Returns a function that takes a key of type K and a value of type V and returns a Map entry.

Type Parameters:

K - the key type

V - the value type

Returns:

a function that takes a K and a V and return the corresponding Map entry

toMap

public static <K,V> com.google.common.collect.ImmutableMap<K,V> toMap(Iterable<Map.Entry<K,V>> from)

Builds an immutable map from the given iterable of Map.Entry.

Any null entries will be filtered out. Additionally, any entries containing null key or value will also be filtered out. If multiple entries return the same key, IllegalArgumentException will be thrown.

Type Parameters:

K - the key type

V - the value type

Parameters:

from - the iterable we use as the source

Returns:

the transformed map

toMap

public static <T,K,V> com.google.common.collect.ImmutableMap<K,V> toMap(Iterable<T> from,
                                                                        Function<? super T,? extends K> keyTransformer,
                                                                        Function<? super T,? extends V> valueTransformer)

Builds an immutable map from the given iterable, with key derived from the application of the iterable to the keyTransformer, and value derived from the application of the iterable to the valueTransformer.

null value is allowed and will be passed to the keyTransformer and valueTransformer. However, if either the keyTransformer or the valueTransformer returns null for an entry, the entry is ignored. If keyTransformer returns the same key for multiple entries, IllegalArgumentException will be thrown.

Type Parameters:

T - the input type

K - the key type

V - the value type

Parameters:

from - the iterable we use as the source

keyTransformer - transform keys

valueTransformer - transform values

Returns:

the transformed map

mapBy

public static <K,V> com.google.common.collect.ImmutableMap<K,V> mapBy(Iterable<V> from,
                                                                      Function<? super V,? extends K> keyTransformer)

Builds an immutable map that is keyed by the result of applying keyTransformer to each element of the given iterable of values.

null value is allowed but will be ignored. If keyTransformer returns the same key for multiple entries, IllegalArgumentException will be thrown.

Type Parameters:

K - the key type

V - the value type

Parameters:

from - the iterable we use as the source

keyTransformer - transform keys

Returns:

the transformed map

mapTo

public static <K,V> com.google.common.collect.ImmutableMap<K,V> mapTo(Iterable<K> from,
                                                                      Function<? super K,? extends V> valueTransformer)

Builds an immutable map from the given iterable and compute the value by applying the valueTransformer.

null value is allowed but will be ignored. If there are duplicate entries in the iterable, IllegalArgumentException will be thrown.

Type Parameters:

K - the key type

V - the value type

Parameters:

from - the iterable we use as the source

valueTransformer - transform values

Returns:

the transformed map

transform

public static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2> transform(Map<K1,V1> from,
                                                                                    Function<Map.Entry<K1,V1>,Map.Entry<K2,V2>> function)

Returns an immutable map that applies function to each entry of fromMap. If null is returned by the function for any entry, or if an entry returned by the function contains a null key or value, that entry is discarded in the result. If the function returns entries with the same key for multiple entries, IllegalArgumentException will be thrown.

Type Parameters:

K1 - the input key type

K2 - the output key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the map we use as the source

function - transform keys and values

Returns:

the transformed map

transform

public static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2> transform(Map<K1,V1> from,
                                                                                    Function<? super K1,? extends K2> keyTransformer,
                                                                                    Function<? super V1,? extends V2> valueTransformer)

Returns an immutable map that applies the keyTransformer and valueTransformer functions to each entry of fromMap. If for any entry, a null key or value is returned, that entry is discarded in the result. If the keyTransformer function returns the same key for multiple entries, IllegalArgumentException will be thrown.

Type Parameters:

K1 - the input key type

K2 - the output key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the map we use as the source

keyTransformer - transform keys

valueTransformer - transform values

Returns:

the transformed map

transformKey

public static <K1,K2,V> com.google.common.collect.ImmutableMap<K2,V> transformKey(Map<K1,V> from,
                                                                                  Function<? super K1,? extends K2> keyTransformer)

Returns an immutable map that applies keyTransformer to the key of each entry of the source map. If null is returned by the keyTransformer for any entry, that entry is discarded in the result. If an entry contains a null value, it will also be discarded in the result. If the function returns the same result key for multiple keys, IllegalArgumentException will be thrown.

Type Parameters:

K1 - the input key type

K2 - the output key type

V - the value type

Parameters:

from - the map we use as the source

keyTransformer - transform keys

Returns:

the transformed map

transformValue

public static <K,V1,V2> com.google.common.collect.ImmutableMap<K,V2> transformValue(Map<K,V1> from,
                                                                                    Function<? super V1,? extends V2> valueTransformer)

Returns an immutable map that applies valueTransformer to the value of each entry of the source map. If null is returned by the valueTransformer for any entry, that entry is discarded in the result. If an entry contains a null key, it will also be discarded in the result.

Type Parameters:

K - the key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the iterable we use as the source

valueTransformer - transform values

Returns:

the transformed map

collect

public static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2> collect(Map<K1,V1> from,
                                                                                  Function<Map.Entry<K1,V1>,Option<Map.Entry<K2,V2>>> partial)

Filters and maps (aka transforms) the source map. Applies the given partial function to each entry of the unfiltered map. If the application returns none, the entry will be left out; otherwise, the transformed entry contained in the Option will be added to the result map.

Type Parameters:

K1 - the input key type

K2 - the output key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the iterable we use as the source

partial - transform and select entries

Returns:

the transformed map

collect

public static <K1,K2,V1,V2> com.google.common.collect.ImmutableMap<K2,V2> collect(Map<K1,V1> from,
                                                                                  Function<? super K1,Option<K2>> keyPartial,
                                                                                  Function<? super V1,Option<V2>> valuePartial)

Filters and maps (aka transforms) the source map. Applies the given partial key function and partial value function to the key and value of each entry of the unfiltered map. If either of the application returns none, the entry will be left out; otherwise, an entry of transformed key and transformed value contained in the options will be added to the result map.

Type Parameters:

K1 - the input key type

K2 - the output key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the iterable we use as the source

keyPartial - transform and collect keys

valuePartial - transform and collect values

Returns:

the transformed map

collectByKey

public static <K1,K2,V> com.google.common.collect.ImmutableMap<K2,V> collectByKey(Map<K1,V> from,
                                                                                  Function<? super K1,Option<K2>> keyPartial)

Filters and maps (aka transforms) the source map. Applies the given partial key function to the key of each entry of the unfiltered map. If the application returns none, the entry will be left out; otherwise, an entry of transformed key contained in the option and the original value will be added to the result map.

Type Parameters:

K1 - the input key type

K2 - the output key type

V - the value type

Parameters:

from - the iterable we use as the source

keyPartial - transform and collect keys

Returns:

the transformed map

collectByValue

public static <K,V1,V2> com.google.common.collect.ImmutableMap<K,V2> collectByValue(Map<K,V1> from,
                                                                                    Function<? super V1,Option<V2>> valuePartial)

Filters and maps (aka transforms) the source map. Applies the given partial value function to the value of each entry of the unfiltered map. If the application returns none, the entry will be left out; otherwise, an entry of the original key and the transformed key contained in the option will be added to the result map.

Type Parameters:

K - the key type

V1 - the input value type

V2 - the output value type

Parameters:

from - the iterable we use as the source

valuePartial - transform and collect values

Returns:

the transformed map