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.
@NullMarked @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

    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 Details

    • 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