org.grouplens.grapht.util

Class Types

java.lang.Object

org.grouplens.grapht.util.Types

public final class Types
extends Object

Static helper methods for working with types.

Author:

GroupLens Research, GroupLens Research

Method Summary

Modifier and Type	Method and Description
static Class<?>	box(Class<?> type) Return the boxed version of the given type if the type is primitive.
static Type	box(Type type) Return the boxed version of the given type if the type is primitive.
static Class<?>	erase(Type type) Compute the erasure of a type.
static ClassLoader	getDefaultClassLoader() Deprecated. Use ClassLoaders.inferDefault() instead.
static Class<?>	getProvidedType(Class<? extends javax.inject.Provider<?>> providerClass) Get the type that is provided by a given implementation of Provider.
static Class<?>	getProvidedType(javax.inject.Provider<?> provider) Get the type that is provided by the Provider instance.
static int	getTypeDistance(Class<?> child, Class<?> parent) Return the type distance between the child and parent types.
static boolean	hasNullableAnnotation(Annotation[] annotations) Return true if the array of Annotations contains an Annotation with a simple name of 'Nullable'.
static boolean	isInstantiable(Class<?> type) Return true if the type is not abstract and not an interface, and has a constructor annotated with Inject or its only constructor is the default constructor.
static Type	parameterizedType(Class<?> type, Type... arguments) Create a parameterized type wrapping the given class and type arguments.
static boolean	shouldBeInstantiable(Class<?> type) Return true if the type is not abstract and not an interface.

Methods inherited from class java.lang.Object

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

Method Detail

parameterizedType

public static Type parameterizedType(Class<?> type,
                                     Type... arguments)

Create a parameterized type wrapping the given class and type arguments.

Parameters:

type -

arguments -

Returns:

box

public static Type box(Type type)

Return the boxed version of the given type if the type is primitive. Otherwise, if the type is not a primitive the original type is returned. As an example, int.class is converted to Integer.class, but List.class is unchanged. This version of box preserves generics.

Parameters:

type - The possibly unboxed type

Returns:

The boxed type

box

public static Class<?> box(Class<?> type)

Return the boxed version of the given type if the type is primitive. Otherwise, if the type is not primitive the original class is returned.

Parameters:

type - The possibly unboxed type

Returns:

The boxed type

erase

public static Class<?> erase(Type type)

Compute the erasure of a type.

Parameters:

type - The type to erase.

Returns:

The class representing the erasure of the type.

Throws:

IllegalArgumentException - if type is unerasable (e.g. it is a type variable or a wildcard).

getTypeDistance

public static int getTypeDistance(@Nonnull
                                  Class<?> child,
                                  @Nonnull
                                  Class<?> parent)

Return the type distance between the child and parent types. The child type must be a subtype of the parent. The type distance between a class and itself is 0; the distance from a class to one of its immediate supertypes (superclass or a directly implemented interface) is 1; deeper distances are computed recursively.

Parameters:

child - The child type

parent - The parent type

Returns:

The type distance

Throws:

IllegalArgumentException - if child is not a subtype of parent.

getProvidedType

public static Class<?> getProvidedType(Class<? extends javax.inject.Provider<?>> providerClass)

Get the type that is provided by a given implementation of Provider.

Parameters:

providerClass - The provider's class

Returns:

The provided class type

Throws:

IllegalArgumentException - if the class doesn't actually implement Provider

getProvidedType

public static Class<?> getProvidedType(javax.inject.Provider<?> provider)

Get the type that is provided by the Provider instance.

Parameters:

provider - The provider instance queried

Returns:

The provided class type

See Also:

getProvidedType(Class)

isInstantiable

public static boolean isInstantiable(Class<?> type)

Return true if the type is not abstract and not an interface, and has a constructor annotated with Inject or its only constructor is the default constructor.

Parameters:

type - A class type

Returns:

True if the class type is instantiable

shouldBeInstantiable

public static boolean shouldBeInstantiable(Class<?> type)

Return true if the type is not abstract and not an interface. This will return true essentially when the class "should" have a default constructor or a constructor annotated with @Inject to be used properly.

As another special rule, if the input type is Void, false is returned because for most intents and purposes, it is not instantiable.

Parameters:

type - The type to test

Returns:

True if it should be instantiable

hasNullableAnnotation

public static boolean hasNullableAnnotation(Annotation[] annotations)

Return true if the array of Annotations contains an Annotation with a simple name of 'Nullable'. It does not matter which actual Nullable annotation is present.

Parameters:

annotations - Array of annotations, e.g. from a setter or constructor

Returns:

True if there exists a Nullable annotation in the array

getDefaultClassLoader

@Deprecated
public static ClassLoader getDefaultClassLoader()

Deprecated. Use ClassLoaders.inferDefault() instead.

Infer a default class loader.

Returns:

A reasonable default class loader.