io.atlassian.fugue

Class Suppliers

java.lang.Object

io.atlassian.fugue.Suppliers

public class Suppliers
extends Object

Provide utility functions for the class of functions that supply a return value when invoked.

Since:

1.0

Constructor Summary

Constructors

Constructor and Description
Suppliers()

Method Summary

Modifier and Type	Method and Description
static Supplier<Boolean>	alwaysFalse() Supplies false.
static <A> Supplier<A>	alwaysNull() Always returns null.
static Supplier<Boolean>	alwaysTrue() Supplies true.
static <A,B> Supplier<B>	ap(Supplier<A> sa, Supplier<Function<A,B>> sf) Performs function application within a supplier (applicative functor pattern).
static <A,B> Supplier<B>	compose(Function<? super A,B> transform, Supplier<A> first) Create a new Supplier by transforming the result calling the first Supplier
static <A,B> Supplier<B>	fromFunction(Function<? super A,? extends B> f, A a) Constantly applies the input value to the supplied function, and returns the result.
static <A> Supplier<A>	fromOption(Option<A> option) Turns an Option into a supplier, but throws an exception if undefined.
static <A> Supplier<A>	memoize(Supplier<A> supplier) A supplier that memoize the value return by another Supplier, whose Supplier.get() method is guaranteed to be call at most once.
static <A> Supplier<A>	ofInstance(A a) Creates a Supplier of a constant value.
static <A> Supplier<A>	weakMemoize(Supplier<A> supplier) A supplier that weakly memoize the value return by another Supplier , The returned Supplier is thread-safe

Methods inherited from class java.lang.Object

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

Constructor Detail

Suppliers

public Suppliers()

Method Detail

ofInstance

public static <A> Supplier<A> ofInstance(A a)

Creates a Supplier of a constant value.

Type Parameters:

A - the type

Parameters:

a - the constant value to supply

Returns:

a supplier that always supplies instance.

compose

public static <A,B> Supplier<B> compose(Function<? super A,B> transform,
                                        Supplier<A> first)

Create a new Supplier by transforming the result calling the first Supplier

Type Parameters:

A - return type of the Supplier to transform

B - return type of the new Supplier

Parameters:

transform - function to transform the result of a Supplier of A's to B's

first - a Supplier of A's

Returns:

a new Supplier returning B's

ap

public static <A,B> Supplier<B> ap(Supplier<A> sa,
                                   Supplier<Function<A,B>> sf)

Performs function application within a supplier (applicative functor pattern).

Parameters:

sa - supplier

sf - The Supplier function to apply.

Returns:

A new Supplier after applying the given Supplier function to the first argument.

Since:

4.0

alwaysTrue

public static Supplier<Boolean> alwaysTrue()

Supplies true.

Returns:

a supplier that always supplies true.

alwaysFalse

public static Supplier<Boolean> alwaysFalse()

Supplies false.

Returns:

a supplier that always supplies false.

alwaysNull

public static <A> Supplier<A> alwaysNull()

Always returns null. Not a very good idea.

Type Parameters:

A - the type

Returns:

a supplier that always supplies null.

fromOption

public static <A> Supplier<A> fromOption(Option<A> option)

Turns an Option into a supplier, but throws an exception if undefined. Not a very good idea.

Type Parameters:

A - the type

Parameters:

option - the option to attempt to get values from

Returns:

a Supplier that always calls Maybe.get(), which throws an Exception if the option is None

Since:

2.0

fromFunction

public static <A,B> Supplier<B> fromFunction(Function<? super A,? extends B> f,
                                             A a)

Constantly applies the input value to the supplied function, and returns the result.

Type Parameters:

A - the input type

B - the result type

Parameters:

f - the function

a - the value

Returns:

a Supplier that always calls Function.apply(Object)

Since:

2.2

memoize

public static <A> Supplier<A> memoize(Supplier<A> supplier)

A supplier that memoize the value return by another Supplier, whose Supplier.get() method is guaranteed to be call at most once. The returned Supplier is thread-safe

Type Parameters:

A - the type

Parameters:

supplier - the supplier to memoize

Returns:

the memoizing supplier

weakMemoize

public static <A> Supplier<A> weakMemoize(Supplier<A> supplier)

A supplier that weakly memoize the value return by another Supplier , The returned Supplier is thread-safe

Type Parameters:

A - the type

Parameters:

supplier - the supplier to memoize

Returns:

the weakly memoizing supplier