org.n52.janmayen.function

Class Functions

java.lang.Object

org.n52.janmayen.function.Functions

public final class Functions
extends Object

Utility functions for Function.

Method Summary

Modifier and Type	Method and Description
static <T,U extends T> Function<T,U>	cast(Class<? extends U> clazz) Returns a Function that casts it's input argument to any type.
static <T,U extends T> U	cast(T t) Casts it's input argument to any type.
static <T,U extends T> Function<T,Optional<U>>	castIfInstanceOf(Class<? extends U> clazz) Returns a Function that casts it'S input argument to the specified type if it's the right type.
static <T,U> Function<T,U>	constant(U u) Creates a function returning the same result for each invocation.
static <T,R> Supplier<R>	curry(Function<? super T,? extends R> function, T t) Curries the parameter of the Function and creates a Consumer.
static <T1,T2,R> Function<T2,R>	curryFirst(BiFunction<T1,T2,R> bifunction, T1 t1) Curries the first parameter of the BiFunction and creates a Function.
static <T1,T2,R> Function<T1,R>	currySecond(BiFunction<T1,T2,R> bifunction, T2 t2) Curries the second parameter of the BiFunction and creates a Function.
static <S,T,X extends Exception> Function<S,T>	errorWrapper(ThrowingFunction<S,T,X> fun) Wraps an ThrowingFunction into an Function that throws an Error if the function throws an Exception.
static <T,U> Function<T,U>	forSupplier(Supplier<U> supplier) Create a function for the the supplier, ignoring any supplied input.
static <K,V> Function<Map<K,V>,Set<K>>	keySetWhereValues(Predicate<? super V> predicate)
static <K,V> Function<Map<K,V>,Stream<K>>	keyStreamWhereValues(Predicate<? super V> predicate)
static <T> BinaryOperator<T>	mergeLeft(BiConsumer<T,T> merger)
static <T> BinaryOperator<T>	mergeRight(BiConsumer<T,T> merger)
static <K,V> BinaryOperator<Map<K,V>>	mergeToLeftMap(BinaryOperator<V> valueMerger)
static <K,V> BinaryOperator<Map<K,V>>	mergeToRightMap(BinaryOperator<V> valueMerger)
static <T> Function<T,T>	mutate(Consumer<? super T> action) Wrapps a Consumer into a Function that returns it's input argument.

Methods inherited from class java.lang.Object

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

Method Detail

cast

public static <T,U extends T> U cast(T t)
                              throws ClassCastException

Casts it's input argument to any type.

Type Parameters:

T - The input type.

U - The output type.

Parameters:

t - The object to be casted.

Returns:

The casted object.

Throws:

ClassCastException - if the object can not be casted.

cast

public static <T,U extends T> Function<T,U> cast(@Nonnull
                                                 Class<? extends U> clazz)

Returns a Function that casts it's input argument to any type.

Type Parameters:

T - The input type.

U - The output type.

Parameters:

clazz - The class the input should be casted to.

Returns:

The casting function.

See Also:

cast(java.lang.Object)

castIfInstanceOf

public static <T,U extends T> Function<T,Optional<U>> castIfInstanceOf(@Nonnull
                                                                       Class<? extends U> clazz)

Returns a Function that casts it'S input argument to the specified type if it's the right type. The returned Optional either contains the casted input arguemnt or is empty.

Type Parameters:

T - The input type.

U - The output type.

Parameters:

clazz - The class to

Returns:

An Optional containing the input

forSupplier

public static <T,U> Function<T,U> forSupplier(@Nonnull
                                              Supplier<U> supplier)

Create a function for the the supplier, ignoring any supplied input.

Type Parameters:

T - the type of the input to the function

U - the type of the result to the function

Parameters:

supplier - the supplier

Returns:

the function wrapping the supplier

constant

public static <T,U> Function<T,U> constant(@Nullable
                                           U u)

Creates a function returning the same result for each invocation.

Type Parameters:

T - the type of the input to the function

U - the type of the result to the function

Parameters:

u - the constant result

Returns:

the function

curry

public static <T,R> Supplier<R> curry(@Nonnull
                                      Function<? super T,? extends R> function,
                                      T t)

Curries the parameter of the Function and creates a Consumer.

Type Parameters:

T - the parameter type

R - the return type

Parameters:

function - the function

t - the curried parameter

Returns:

the curried function

curryFirst

public static <T1,T2,R> Function<T2,R> curryFirst(@Nonnull
                                                  BiFunction<T1,T2,R> bifunction,
                                                  T1 t1)

Curries the first parameter of the BiFunction and creates a Function.

Type Parameters:

T1 - the first parameter type

T2 - the second parameter type

R - the return type

Parameters:

bifunction - the function

t1 - the curried parameter

Returns:

the curried function

currySecond

public static <T1,T2,R> Function<T1,R> currySecond(@Nonnull
                                                   BiFunction<T1,T2,R> bifunction,
                                                   T2 t2)

Curries the second parameter of the BiFunction and creates a Function.

Type Parameters:

T1 - the first parameter type

T2 - the second parameter type

R - the return type

Parameters:

bifunction - the function

t2 - the curried parameter

Returns:

the curried function

mergeLeft

public static <T> BinaryOperator<T> mergeLeft(@Nonnull
                                              BiConsumer<T,T> merger)

mergeRight

public static <T> BinaryOperator<T> mergeRight(@Nonnull
                                               BiConsumer<T,T> merger)

mergeToLeftMap

public static <K,V> BinaryOperator<Map<K,V>> mergeToLeftMap(@Nonnull
                                                            BinaryOperator<V> valueMerger)

mergeToRightMap

public static <K,V> BinaryOperator<Map<K,V>> mergeToRightMap(@Nonnull
                                                             BinaryOperator<V> valueMerger)

keySetWhereValues

public static <K,V> Function<Map<K,V>,Set<K>> keySetWhereValues(Predicate<? super V> predicate)

keyStreamWhereValues

public static <K,V> Function<Map<K,V>,Stream<K>> keyStreamWhereValues(Predicate<? super V> predicate)

mutate

public static <T> Function<T,T> mutate(@Nonnull
                                       Consumer<? super T> action)

Wrapps a Consumer into a Function that returns it's input argument.

Type Parameters:

T - The consumed element's type.

Parameters:

action - The consumer.

Returns:

A function that applies the consumer and returns it's input.

errorWrapper

public static <S,T,X extends Exception> Function<S,T> errorWrapper(@Nonnull
                                                                   ThrowingFunction<S,T,X> fun)

Wraps an ThrowingFunction into an Function that throws an Error if the function throws an Exception.

Type Parameters:

S - the function's input type.

T - the function's output type.

X - the type of the the exception that might be thrown.

Parameters:

fun - the function.

Returns:

the wrapped function.