Package com.google.common.base

Class Suppliers

  • @GwtCompatible(emulated=true)
public final class Suppliers
extends java.lang.Object
    Useful suppliers.

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

    Since:
    2.0
    Author:
    Laurence Gonsalves, Harry Heymann

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static <F extends @Nullable java.lang.Object,​T extends @Nullable java.lang.Object>
      Supplier<T>      		 compose​(Function<? super F,​T> function, Supplier<F> supplier)
      Returns a new supplier which is the composition of the provided function and supplier.
      static <T extends @Nullable java.lang.Object>
      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 extends @Nullable java.lang.Object>
      Supplier<T>      		 memoizeWithExpiration​(Supplier<T> delegate, long duration, java.util.concurrent.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 extends @Nullable java.lang.Object>
      Supplier<T>      		 memoizeWithExpiration​(Supplier<T> delegate, java.time.Duration duration)
      Returns a supplier that caches the instance supplied by the delegate and removes the cached value after the specified time has passed.
      static <T extends @Nullable java.lang.Object>
      Supplier<T>      		 ofInstance​(T instance)
      Returns a supplier that always supplies instance.
      static <T extends @Nullable java.lang.Object>
      Function<Supplier<T>,​T>      		 supplierFunction()
      Returns a function that accepts a supplier and returns the result of invoking Supplier.get() on that supplier.
      static <T extends @Nullable java.lang.Object>
      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 extends @Nullable java.lang.Object,​T extends @Nullable java.lang.Object> Supplier<T> compose​(Function<? super F,​T> function,
                                                                                                                    Supplier<F> supplier)
        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 supplier, and then applying function to that value. Note that the resulting supplier will not call supplier or invoke function until it is called.

      • memoize

        public static <T extends @Nullable java.lang.Object> 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 delegate's get() method will be invoked at most once unless the underlying get() throws an exception. The supplier's serialized form does not contain the cached value, which will be recalculated when get() is called on the deserialized instance.

        When the underlying delegate throws an exception then this memoizing supplier will keep delegating calls until it returns valid data.

        If delegate is an instance created by an earlier call to memoize, it is returned directly.

      • memoizeWithExpiration

        public static <T extends @Nullable java.lang.Object> Supplier<T> memoizeWithExpiration​(Supplier<T> delegate,
                                                                                       long duration,
                                                                                       java.util.concurrent.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. The actual memoization does not happen when the underlying delegate throws an exception.

        When the underlying delegate throws an exception then this memoizing supplier will keep delegating calls until it returns valid data.

        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:
        java.lang.IllegalArgumentException - if duration is not positive
        Since:
        2.0

      • memoizeWithExpiration

        @Beta
@GwtIncompatible
public static <T extends @Nullable java.lang.Object> Supplier<T> memoizeWithExpiration​(Supplier<T> delegate,
                                                                                       java.time.Duration duration)
        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. The actual memoization does not happen when the underlying delegate throws an exception.

        When the underlying delegate throws an exception then this memoizing supplier will keep delegating calls until it returns valid data.

        Parameters:
        duration - the length of time after a value is created that it should stop being returned by subsequent get() calls
        Throws:
        java.lang.IllegalArgumentException - if duration is not positive
        Since:
        33.1.0

      • ofInstance

        public static <T extends @Nullable java.lang.Object> Supplier<T> ofInstance​(T instance)
        Returns a supplier that always supplies instance.

      • synchronizedSupplier

        public static <T extends @Nullable java.lang.Object> Supplier<T> synchronizedSupplier​(Supplier<T> delegate)
        Returns a supplier whose get() method synchronizes on delegate before calling it, making it thread-safe.

      • supplierFunction

        public static <T extends @Nullable java.lang.Object> Function<Supplier<T>,​T> supplierFunction()
        Returns a function that accepts a supplier and returns the result of invoking Supplier.get() on that supplier.

        Java 8+ users: use the method reference Supplier::get instead.

        Since:
        8.0