de.larssh.utils.collection

Class Maps

java.lang.Object

de.larssh.utils.collection.Maps

public final class Maps
extends Object

This class contains helper methods for Map.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Maps.Builder<K,V> Wraps around map to allow its fluent creation and modification.

Method Summary

Modifier and Type	Method and Description
static <K,V> Maps.Builder<K,V>	builder() Wraps a builder around an HashMap to allow fluent creation and modification of a Map.
static <K,V> Maps.Builder<K,V>	builder(Map<K,V> map) Wraps a builder around map to allow its fluent creation and modification.
static <K,V> Map.Entry<K,V>	entry(K key, V value) Creates an Map.Entry representing a mapping from the specified key to the specified value.
static <K,V> Map<K,V>	sort(Map<K,V> unsorted, Comparator<Map.Entry<K,V>> comparator) Sorts a Map based on a given Map.Entry Comparator.

Methods inherited from class java.lang.Object

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

Method Detail

builder

public static <K,V> Maps.Builder<K,V> builder()

Wraps a builder around an HashMap to allow fluent creation and modification of a Map.

To use strict typing Java compilers might need some hint about your maps key and value types in front of this method call. Check out the below example.

Usage example: The following shows how to create an unmodifiable map containing three entries.

 Map<String, Integer> map = Maps.<String, Integer>builder()
         .put("France", 33)
         .put("Germany", 49)
         .put("Italy", 39)
         .unmodifiable();
 

Type Parameters:

K - type of the maps key

V - type of the maps value

Returns:

a map builder

builder

public static <K,V> Maps.Builder<K,V> builder(Map<K,V> map)

Wraps a builder around map to allow its fluent creation and modification.

Usage example 1: The following shows how to create an unmodifiable LinkedHashMap containing three entries.

 Map<String, Integer> map = Maps.builder(new LinkedHashMap<String, Integer>())
         .put("France", 33)
         .put("Germany", 49)
         .put("Italy", 39)
         .unmodifiable();
 

Usage example 2: The following shows how to create a NavigableMap based on a TreeMap.

 NavigableMap<String, Integer> map = Maps.builder(new TreeMap<String, Integer>())
         .put("France", 33)
         .put("Germany", 49)
         .put("Italy", 39)
         .get();
 

Type Parameters:

K - type of the maps key

V - type of the maps value

Parameters:

map - the map to be wrapped

Returns:

a map builder wrapping map

entry

public static <K,V> Map.Entry<K,V> entry(@Nullable
                                         K key,
                                         @Nullable
                                         V value)

Creates an Map.Entry representing a mapping from the specified key to the specified value.

This entry is immutable. It does not support the method Map.Entry.setValue(Object).

Type Parameters:

K - the type of the key

V - the type of the value

Parameters:

key - the key represented by this entry

value - the value represented by this entry

Returns:

the immutable entry

sort

public static <K,V> Map<K,V> sort(Map<K,V> unsorted,
                                  Comparator<Map.Entry<K,V>> comparator)

Sorts a Map based on a given Map.Entry Comparator.

Currently returned map is implemented as LinkedHashMap though that might change.

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

Parameters:

unsorted - probably unsorted map

comparator - entry based comparator

Returns:

sorted map based on the given comparator