Interface ClassToInstanceMap<B>

  • Type Parameters:
    B - the common supertype that all entries must share; often this is simply Object
    All Superinterfaces:
    Map<Class<? extends B>,​B>
    All Known Implementing Classes:
    ImmutableClassToInstanceMap, MutableClassToInstanceMap

    @DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
    public interface ClassToInstanceMap<B>
    extends Map<Class<? extends B>,​B>
    A map, each entry of which maps a Java raw type to an instance of that type. In addition to implementing Map, the additional type-safe operations putInstance(java.lang.Class<T>, T) and getInstance(java.lang.Class<T>) are available.

    Like any other Map<Class, Object>, this map may contain entries for primitive types, and a primitive type and its corresponding wrapper type may map to different values.

    This class's support for null requires some explanation: From release 31.0 onward, Guava specifies the nullness of its types through annotations. In the case of ClassToInstanceMap, it specifies that both the key and value types are restricted to non-nullable types. This specification is reasonable for keys, which must be non-null classes. This is in contrast to the specification for values: Null values are supported by the implementation MutableClassToInstanceMap, even though that implementation and this interface specify otherwise. Thus, if you use a nullness checker, you can safely suppress any warnings it produces when you write null values into a MutableClassToInstanceMap. Just be sure to be prepared for null values when reading from it, since nullness checkers will assume that vaules are non-null then, too.

    See the Guava User Guide article on ClassToInstanceMap.

    To map a generic type to an instance of that type, use TypeToInstanceMap instead.

    Kevin Bourrillion
    • Method Detail

      • getInstance

        <T extends B> T getInstance​(Class<T> type)
        Returns the value the specified class is mapped to, or null if no entry for this class is present. This will only return a value that was bound to this specific class, not a value that may have been bound to a subtype.
      • putInstance

        <T extends B> T putInstance​(Class<T> type,
                                    T value)
        Maps the specified class to the specified value. Does not associate this value with any of the class's supertypes.
        the value previously associated with this class (possibly null), or null if there was no previous entry.