Package org.deltava.util

Class CollectionUtils

java.lang.Object

org.deltava.util.CollectionUtils

public class CollectionUtils
extends Object

A utility class for dealing with Collections.

Since:

1.0

Version:

10.2

Author:

Luke

Method Summary

Modifier and Type	Method	Description
static <K, V> void	addMapCollection(Map<K,Collection<V>> m, K key, V entry)	Adds an entry to a Collection contained as a Map value.
static <K, V> void	addMapCollection(Map<K,Collection<V>> m, K key, V entry, Supplier<Collection<V>> cf)	Adds an entry to a Collection contained as a Map value, allowing a specific Collection constructor.
static <K, V> Map<K,V>	createMap(Collection<K> keys, Collection<V> values)	Converts two Collections into a Map.
static <K, V> Map<K,V>	createMap(Collection<V> values, Function<V,K> f)	Converts a Collection into a Map.
static <T> Collection<T>	getDelta(Collection<T> c1, Collection<T> c2)	Determines which elements are contained within only one Collection.
static <T> boolean	hasDelta(Collection<T> c1, Collection<T> c2)	Compares two Collections to see if there are any differences between them.
static boolean	isEmpty(Collection<?> c)	A null-safe mechanism to determine if a collection has no data.
static <T> Collection<T>	join(Collection<T>... data)	Joins multiple Collections into a single Collection without duplicates.
static <T> Collection<T>	nonNull(Supplier<Collection<T>> cf, T... values)	Creates a Collection of non-null values.
static <T> Collection<T>	nonNull(T... values)	Creates a Collection of non-null values.
static <T> List<T>	sort(Collection<T> c, Comparator<T> cmp)	Clones and sorts a Collection using a particular Comparator.
static <T> Collection<T>	union(Collection<T> c1, Collection<T> c2)	Examines two Collections and returns the items present in both.

Methods inherited from class java.lang.Object

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

Method Details

isEmpty

public static boolean isEmpty(Collection<?> c)

A null-safe mechanism to determine if a collection has no data.

Parameters:

c - the Collection to check

Returns:

TRUE if c is null or has no elements, otherwise FALSE

getDelta

public static <T> Collection<T> getDelta(Collection<T> c1,
 Collection<T> c2)

Determines which elements are contained within only one Collection.

Parameters:

c1 - the Collection to examine

c2 - the entries to check

Returns:

a List of entries contained within c1, but not c2

Throws:

NullPointerException - if c1 or c2 are null

hasDelta

public static <T> boolean hasDelta(Collection<T> c1,
 Collection<T> c2)

Compares two Collections to see if there are any differences between them. This is done by comparing their sizes, and then calling c1.containsAll(c2) to ensure that all of c2 is contained within c1.

Parameters:

c1 - the first Collection of entries

c2 - the second Collection of entries

Returns:

TRUE if c1.size() != c2.size() or !c1.containsAll(c2), otherwise FALSE

join

@SafeVarargs
public static <T> Collection<T> join(Collection<T>... data)

Joins multiple Collections into a single Collection without duplicates.

Parameters:

data - the Collections to join

Returns:

a Collection of unique results

createMap

public static <K,
V> Map<K,V> createMap(Collection<V> values,
 Function<V,K> f)

Converts a Collection into a Map.

Parameters:

values - the values to use

f - the function to call on each value to get the key value

Returns:

a Map of the values, indexed by their key

createMap

public static <K,
V> Map<K,V> createMap(Collection<K> keys,
 Collection<V> values)

Converts two Collections into a Map. The resulting Map will be the same size as the smallest of the two supplied Collections, and the key/value pairs will be assigned in the normal iteration order of each Collection.

Parameters:

keys - a Collection of key objects

values - a Collection of value objects

Returns:

a Map of key/value pairs.

sort

public static <T> List<T> sort(Collection<T> c,
 Comparator<T> cmp)

Clones and sorts a Collection using a particular Comparator.

Parameters:

c - the Collection to sort

cmp - the Comparator

Returns:

a sorted Collection

union

public static <T> Collection<T> union(Collection<T> c1,
 Collection<T> c2)

Examines two Collections and returns the items present in both.

Parameters:

c1 - the first Collection

c2 - the second Collection

Returns:

a Collection of items present in both c1 and c2

addMapCollection

public static <K,
V> void addMapCollection(Map<K,Collection<V>> m,
 K key,
 V entry)

Adds an entry to a Collection contained as a Map value.

Parameters:

m - the Map

key - the key

entry - the value

addMapCollection

public static <K,
V> void addMapCollection(Map<K,Collection<V>> m,
 K key,
 V entry,
 Supplier<Collection<V>> cf)

Adds an entry to a Collection contained as a Map value, allowing a specific Collection constructor.

Parameters:

m - the Map

key - the key

entry - the value

cf - the Collection Supplier

nonNull

@SafeVarargs
public static <T> Collection<T> nonNull(T... values)

Creates a Collection of non-null values.

Parameters:

values - the values to add

Returns:

a Collection of non-null values

nonNull

@SafeVarargs
public static <T> Collection<T> nonNull(Supplier<Collection<T>> cf,
 T... values)

Creates a Collection of non-null values.

Parameters:

cf - the Collection factory function

values - the values to add

Returns:

a Collection of non-null values