org.grouplens.lenskit.util

Class TypeUtils

java.lang.Object

org.grouplens.lenskit.util.TypeUtils

public class TypeUtils
extends Object

Various type utilities used in LensKit.

Constructor Summary

Constructors

Constructor and Description
TypeUtils()

Method Summary

Modifier and Type	Method and Description
static <T> Function<Class<?>,Class<? extends T>>	asSubclass(Class<T> supertype) Function that casts classes to specified types.
static Function<Object,Class<?>>	extractClass() Function that gets the class for its argument.
static Function<Object,Class<?>>	extractClass(boolean acceptNull) Function that gets the class for its argument.
static <T> Function<T,Class<? extends T>>	extractClass(Class<T> supertype) Function that gets the class for its argument.
static <T> Function<T,Class<? extends T>>	extractClass(Class<T> supertype, boolean acceptNull) Function that gets the class for its argument.
static <T> Set<Class<? extends T>>	findTypes(Iterable<? extends T> objects, Class<T> parent) Build the set of types implemented by the objects' classes.
static Predicate<Class<?>>	isSubclass(Class<?> cls)
static Predicate<Class<?>>	subtypePredicate(Class<?> parent) A predicate that accepts classes which are subtypes of (assignable to) the parent class.
static Set<Class<?>>	typeClosure(Class<?> type) Return the supertype closure of a type (the type and all its transitive supertypes).

Methods inherited from class java.lang.Object

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

Constructor Detail

TypeUtils

public TypeUtils()

Method Detail

findTypes

public static <T> Set<Class<? extends T>> findTypes(Iterable<? extends T> objects,
                                                    Class<T> parent)

Build the set of types implemented by the objects' classes. This includes all supertypes which are themselves subclasses of parent. The resulting set is the set of all subclasses of parent such that there exists some object in objects assignable to one of them.

Parameters:

objects - A collection of objects. This iterable may be fast (returning a modified version of the same object).

parent - The parent type of interest.

Returns:

The set of types applicable to objects in objects.

typeClosure

public static Set<Class<?>> typeClosure(Class<?> type)

Return the supertype closure of a type (the type and all its transitive supertypes).

Parameters:

type - The type.

Returns:

All supertypes of the type, including the type itself.

isSubclass

public static Predicate<Class<?>> isSubclass(Class<?> cls)

asSubclass

public static <T> Function<Class<?>,Class<? extends T>> asSubclass(Class<T> supertype)

Function that casts classes to specified types. This function does not accept nulls.

Parameters:

supertype - A class known to be a valid supertype for any argument.

extractClass

public static <T> Function<T,Class<? extends T>> extractClass(Class<T> supertype,
                                                              boolean acceptNull)

Function that gets the class for its argument.

Parameters:

supertype - A class known to be a valid supertype for any argument.

acceptNull - Whether nulls are accepted & passed through. If false, the function will never return null.

extractClass

public static <T> Function<T,Class<? extends T>> extractClass(Class<T> supertype)

Function that gets the class for its argument. This function does not accept nulls.

Parameters:

supertype - A class known to be a valid supertype for any argument.

extractClass

public static Function<Object,Class<?>> extractClass()

Function that gets the class for its argument.

extractClass

public static Function<Object,Class<?>> extractClass(boolean acceptNull)

Function that gets the class for its argument.

subtypePredicate

public static Predicate<Class<?>> subtypePredicate(Class<?> parent)

A predicate that accepts classes which are subtypes of (assignable to) the parent class.

Parameters:

parent - The parent class.

Returns:

A predicate that returns true when applied to a subtype of parent. That is, it implements paret.isAssignableFrom(type).