com.google.common.base
Class Suppliers

java.lang.Object
  com.google.common.base.Suppliers

public final class Suppliers
extends Object

Useful suppliers.

All methods return serializable suppliers as long as they're given serializable parameters.

Since:

2010.01.04 stable (imported from Google Collections Library)

Author:

Laurence Gonsalves, Harry Heymann

Method Summary

static <F,T> Supplier<T>	compose(Function<? super F,T> function, Supplier<F> first) Returns a new supplier which is the composition of the provided function and supplier.
static <T> Supplier<T>	memoize(Supplier<T> delegate) Returns a supplier which caches the instance retrieved during the first call to get() and returns that value on subsequent calls to get().
static <T> Supplier<T>	memoizeWithExpiration(Supplier<T> delegate, long duration, TimeUnit unit) Returns a supplier that caches the instance supplied by the delegate and removes the cached value after the specified time has passed.
static <T> Supplier<T>	ofInstance(T instance) Returns a supplier that always supplies instance.
static <T> Supplier<T>	synchronizedSupplier(Supplier<T> delegate) Returns a supplier whose get() method synchronizes on delegate before calling it, making it thread-safe.

Methods inherited from class java.lang.Object

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

Method Detail

compose

public static <F,T> Supplier<T> compose(Function<? super F,T> function,
                                        Supplier<F> first)

Returns a new supplier which is the composition of the provided function and supplier. In other words, the new supplier's value will be computed by retrieving the value from first, and then applying function to that value. Note that the resulting supplier will not call first or invoke function until it is called.

memoize

public static <T> Supplier<T> memoize(Supplier<T> delegate)

Returns a supplier which caches the instance retrieved during the first call to get() and returns that value on subsequent calls to get(). See: memoization

The returned supplier is thread-safe. The supplier's serialized form does not contain the cached value, which will be recalculated when get() is called on the reserialized instance.

memoizeWithExpiration

public static <T> Supplier<T> memoizeWithExpiration(Supplier<T> delegate,
                                                    long duration,
                                                    TimeUnit unit)

Returns a supplier that caches the instance supplied by the delegate and removes the cached value after the specified time has passed. Subsequent calls to get() return the cached value if the expiration time has not passed. After the expiration time, a new value is retrieved, cached, and returned. See: memoization

The returned supplier is thread-safe. The supplier's serialized form does not contain the cached value, which will be recalculated when get() is called on the reserialized instance.

Parameters:

duration - the length of time after a value is created that it should stop being returned by subsequent get() calls

unit - the unit that duration is expressed in

Throws:

IllegalArgumentException - if duration is not positive

Since:

2010.01.04 tentative

ofInstance

public static <T> Supplier<T> ofInstance(@Nullable
                                         T instance)

Returns a supplier that always supplies instance.

synchronizedSupplier

public static <T> Supplier<T> synchronizedSupplier(Supplier<T> delegate)

Returns a supplier whose get() method synchronizes on delegate before calling it, making it thread-safe.