Module com.github.benmanes.caffeine
Package com.github.benmanes.caffeine.cache

Interface Interner<E>

  • Type Parameters:
    E - the type of elements
    Functional Interface:
    This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
    @FunctionalInterface
public interface Interner<E>
    Provides similar behavior to String.intern() for any immutable type.

    Note that String.intern() has some well-known performance limitations and should generally be avoided. Prefer newWeakInterner() or another Interner implementation even for String interning.

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      E intern​(E sample)
      Chooses and returns the representative instance for any collection of instances that are equal to each other.
      static <E> Interner<E> newStrongInterner()
      Returns a new thread-safe interner that retains a strong reference to each instance it has interned, thus preventing these instances from being garbage-collected.
      static <E> Interner<E> newWeakInterner()
      Returns a new thread-safe interner that retains a weak reference to each instance it has interned, and so does not prevent these instances from being garbage-collected.

    • Method Detail

      • intern

        E intern​(E sample)
        Chooses and returns the representative instance for any collection of instances that are equal to each other. If two equal inputs are given to this method, both calls will return the same instance. That is, intern(a).equals(a) always holds, and intern(a) == intern(b) if and only if a.equals(b). Note that intern(a) is permitted to return one instance now and a different instance later if the original interned instance was garbage-collected.

        Warning: Do not use with mutable objects.

        Parameters:
        sample - the element to add if absent
        Returns:
        the representative instance, possibly the sample if absent
        Throws:
        NullPointerException - if sample is null

      • newStrongInterner

        static <E> Interner<E> newStrongInterner()
        Returns a new thread-safe interner that retains a strong reference to each instance it has interned, thus preventing these instances from being garbage-collected.
        Type Parameters:
        E - the type of elements
        Returns:
        an interner for retrieving the canonical instance

      • newWeakInterner

        static <E> Interner<E> newWeakInterner()
        Returns a new thread-safe interner that retains a weak reference to each instance it has interned, and so does not prevent these instances from being garbage-collected.
        Type Parameters:
        E - the type of elements
        Returns:
        an interner for retrieving the canonical instance