org.opencypher.tools

Class Functions

java.lang.Object

org.opencypher.tools.Functions

public class Functions
extends Object

Utilities for working with Java functions.

Constructor Summary

Constructors

Constructor and Description
Functions()

Method Summary

Modifier and Type	Method and Description
static <T> Collector<Optional<T>,List<T>,List<T>>	flatList() A Collector that collects optional values to a list.
static <T> T	identity(T value) A method that is useful as a method reference to implement an identity function.
static <K,V> Map<K,V>	map(Collection<V> values, Function<V,K> key) Create a Map by applying a function that extracts the key from a collection of values.
static <K,V> Map<K,V>	map(Function<V,K> key, V... values) Create a Map by applying a function that extracts the key from an array of values.
static <I,O> Supplier<O>	map(Supplier<I> source, Function<I,O> map) Convert the value supplied by a Supplier by passing it through a Function.
static <T> T	requireNonNull(Class<T> type, T value) Require an instance not to be null, using the (simple) name of the required type as an error message if it is.

Methods inherited from class java.lang.Object

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

Constructor Detail

Functions

public Functions()

Method Detail

requireNonNull

public static <T> T requireNonNull(Class<T> type,
                                   T value)

Require an instance not to be null, using the (simple) name of the required type as an error message if it is.

Type Parameters:

T - the type.

Parameters:

type - the required type.

value - the value that must not be null.

Returns:

the value, that is guaranteed not to be null.

See Also:

Objects.requireNonNull(Object, Supplier)

map

public static <I,O> Supplier<O> map(Supplier<I> source,
                                    Function<I,O> map)

Convert the value supplied by a Supplier by passing it through a Function.

Type Parameters:

I - the type of the value supplied by the original supplier.

O - the type of the value supplied by the resulting supplier.

Parameters:

source - the source supplier that supplies the original value.

map - the function that converts the value of the original supplier.

Returns:

a converting supplier.

map

@SafeVarargs
public static <K,V> Map<K,V> map(Function<V,K> key,
                                              V... values)

Create a Map by applying a function that extracts the key from an array of values.

Type Parameters:

K - the type of the keys.

V - the type of the values.

Parameters:

key - the key extraction function.

values - the values of the map (from which the keys are extracted).

Returns:

a Map from the keys of the values to the values.

identity

public static <T> T identity(T value)

A method that is useful as a method reference to implement an identity function.

Type Parameters:

T - the type of the value.

Parameters:

value - the input (and output) value of the function.

Returns:

the value that was passed in.

map

public static <K,V> Map<K,V> map(Collection<V> values,
                                 Function<V,K> key)

Create a Map by applying a function that extracts the key from a collection of values.

Type Parameters:

K - the type of the keys.

V - the type of the values.

Parameters:

values - the values of the map (from which the keys are extracted).

key - the key extraction function.

Returns:

a Map from the keys of the values to the values.

flatList

public static <T> Collector<Optional<T>,List<T>,List<T>> flatList()

A Collector that collects optional values to a list. The collector only collects values that are present.

Type Parameters:

T - the type of values to collect.

Returns:

a collector that collects optional values to a list.