TypeToken.java
/*
* Copyright (C) 2006 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.reflect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ForwardingSet;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;
import com.google.common.collect.Ordering;
import com.google.common.primitives.Primitives;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;
/**
* A {@link Type} with generics.
*
* <p>Operations that are otherwise only available in {@link Class} are implemented to support
* {@code Type}, for example {@link #isSubtypeOf}, {@link #isArray} and {@link #getComponentType}.
* It also provides additional utilities such as {@link #getTypes}, {@link #resolveType}, etc.
*
* <p>There are three ways to get a {@code TypeToken} instance:
*
* <ul>
* <li>Wrap a {@code Type} obtained via reflection. For example: {@code
* TypeToken.of(method.getGenericReturnType())}.
* <li>Capture a generic type with a (usually anonymous) subclass. For example:
* <pre>{@code
* new TypeToken<List<String>>() {}
* }</pre>
* <p>Note that it's critical that the actual type argument is carried by a subclass. The
* following code is wrong because it only captures the {@code <T>} type variable of the
* {@code listType()} method signature; while {@code <String>} is lost in erasure:
* <pre>{@code
* class Util {
* static <T> TypeToken<List<T>> listType() {
* return new TypeToken<List<T>>() {};
* }
* }
*
* TypeToken<List<String>> stringListType = Util.<String>listType();
* }</pre>
* <li>Capture a generic type with a (usually anonymous) subclass and resolve it against a context
* class that knows what the type parameters are. For example:
* <pre>{@code
* abstract class IKnowMyType<T> {
* TypeToken<T> type = new TypeToken<T>(getClass()) {};
* }
* new IKnowMyType<String>() {}.type => String
* }</pre>
* </ul>
*
* <p>{@code TypeToken} is serializable when no type variable is contained in the type.
*
* <p>Note to Guice users: {@code} TypeToken is similar to Guice's {@code TypeLiteral} class except
* that it is serializable and offers numerous additional utility methods.
*
* @author Bob Lee
* @author Sven Mawson
* @author Ben Yu
* @since 12.0
*/
@Beta
@SuppressWarnings("serial") // SimpleTypeToken is the serialized form.
@ElementTypesAreNonnullByDefault
public abstract class TypeToken<T> extends TypeCapture<T> implements Serializable {
private final Type runtimeType;
/** Resolver for resolving parameter and field types with {@link #runtimeType} as context. */
@CheckForNull private transient TypeResolver invariantTypeResolver;
/** Resolver for resolving covariant types with {@link #runtimeType} as context. */
@CheckForNull private transient TypeResolver covariantTypeResolver;
/**
* Constructs a new type token of {@code T}.
*
* <p>Clients create an empty anonymous subclass. Doing so embeds the type parameter in the
* anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.
*
* <p>For example:
*
* <pre>{@code
* TypeToken<List<String>> t = new TypeToken<List<String>>() {};
* }</pre>
*/
protected TypeToken() {
this.runtimeType = capture();
checkState(
!(runtimeType instanceof TypeVariable),
"Cannot construct a TypeToken for a type variable.\n"
+ "You probably meant to call new TypeToken<%s>(getClass()) "
+ "that can resolve the type variable for you.\n"
+ "If you do need to create a TypeToken of a type variable, "
+ "please use TypeToken.of() instead.",
runtimeType);
}
/**
* Constructs a new type token of {@code T} while resolving free type variables in the context of
* {@code declaringClass}.
*
* <p>Clients create an empty anonymous subclass. Doing so embeds the type parameter in the
* anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.
*
* <p>For example:
*
* <pre>{@code
* abstract class IKnowMyType<T> {
* TypeToken<T> getMyType() {
* return new TypeToken<T>(getClass()) {};
* }
* }
*
* new IKnowMyType<String>() {}.getMyType() => String
* }</pre>
*/
protected TypeToken(Class<?> declaringClass) {
Type captured = super.capture();
if (captured instanceof Class) {
this.runtimeType = captured;
} else {
this.runtimeType = TypeResolver.covariantly(declaringClass).resolveType(captured);
}
}
private TypeToken(Type type) {
this.runtimeType = checkNotNull(type);
}
/** Returns an instance of type token that wraps {@code type}. */
public static <T> TypeToken<T> of(Class<T> type) {
return new SimpleTypeToken<T>(type);
}
/** Returns an instance of type token that wraps {@code type}. */
public static TypeToken<?> of(Type type) {
return new SimpleTypeToken<>(type);
}
/**
* Returns the raw type of {@code T}. Formally speaking, if {@code T} is returned by {@link
* java.lang.reflect.Method#getGenericReturnType}, the raw type is what's returned by {@link
* java.lang.reflect.Method#getReturnType} of the same method object. Specifically:
*
* <ul>
* <li>If {@code T} is a {@code Class} itself, {@code T} itself is returned.
* <li>If {@code T} is a {@link ParameterizedType}, the raw type of the parameterized type is
* returned.
* <li>If {@code T} is a {@link GenericArrayType}, the returned type is the corresponding array
* class. For example: {@code List<Integer>[] => List[]}.
* <li>If {@code T} is a type variable or a wildcard type, the raw type of the first upper bound
* is returned. For example: {@code <X extends Foo> => Foo}.
* </ul>
*/
public final Class<? super T> getRawType() {
// For wildcard or type variable, the first bound determines the runtime type.
Class<?> rawType = getRawTypes().iterator().next();
@SuppressWarnings("unchecked") // raw type is |T|
Class<? super T> result = (Class<? super T>) rawType;
return result;
}
/** Returns the represented type. */
public final Type getType() {
return runtimeType;
}
/**
* Returns a new {@code TypeToken} where type variables represented by {@code typeParam} are
* substituted by {@code typeArg}. For example, it can be used to construct {@code Map<K, V>} for
* any {@code K} and {@code V} type:
*
* <pre>{@code
* static <K, V> TypeToken<Map<K, V>> mapOf(
* TypeToken<K> keyType, TypeToken<V> valueType) {
* return new TypeToken<Map<K, V>>() {}
* .where(new TypeParameter<K>() {}, keyType)
* .where(new TypeParameter<V>() {}, valueType);
* }
* }</pre>
*
* @param <X> The parameter type
* @param typeParam the parameter type variable
* @param typeArg the actual type to substitute
*/
/*
* TODO(cpovirk): Is there any way for us to support TypeParameter instances for type parameters
* that have nullable bounds? Unfortunately, if we change the parameter to TypeParameter<? extends
* @Nullable X>, then users might pass a TypeParameter<Y>, where Y is a subtype of X, while still
* passing a TypeToken<X>. This would be invalid. Maybe we could accept a TypeParameter<@PolyNull
* X> if we support such a thing? It would be weird or misleading for users to be able to pass
* `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but
* hopefully no one would do that, anyway. See also the comment on TypeParameter itself.
*
* TODO(cpovirk): Elaborate on this / merge with other comment?
*/
public final <X> TypeToken<T> where(TypeParameter<X> typeParam, TypeToken<X> typeArg) {
TypeResolver resolver =
new TypeResolver()
.where(
ImmutableMap.of(
new TypeResolver.TypeVariableKey(typeParam.typeVariable), typeArg.runtimeType));
// If there's any type error, we'd report now rather than later.
return new SimpleTypeToken<T>(resolver.resolveType(runtimeType));
}
/**
* Returns a new {@code TypeToken} where type variables represented by {@code typeParam} are
* substituted by {@code typeArg}. For example, it can be used to construct {@code Map<K, V>} for
* any {@code K} and {@code V} type:
*
* <pre>{@code
* static <K, V> TypeToken<Map<K, V>> mapOf(
* Class<K> keyType, Class<V> valueType) {
* return new TypeToken<Map<K, V>>() {}
* .where(new TypeParameter<K>() {}, keyType)
* .where(new TypeParameter<V>() {}, valueType);
* }
* }</pre>
*
* @param <X> The parameter type
* @param typeParam the parameter type variable
* @param typeArg the actual type to substitute
*/
/*
* TODO(cpovirk): Is there any way for us to support TypeParameter instances for type parameters
* that have nullable bounds? See discussion on the other overload of this method.
*/
public final <X> TypeToken<T> where(TypeParameter<X> typeParam, Class<X> typeArg) {
return where(typeParam, of(typeArg));
}
/**
* Resolves the given {@code type} against the type context represented by this type. For example:
*
* <pre>{@code
* new TypeToken<List<String>>() {}.resolveType(
* List.class.getMethod("get", int.class).getGenericReturnType())
* => String.class
* }</pre>
*/
public final TypeToken<?> resolveType(Type type) {
checkNotNull(type);
// Being conservative here because the user could use resolveType() to resolve a type in an
// invariant context.
return of(getInvariantTypeResolver().resolveType(type));
}
private TypeToken<?> resolveSupertype(Type type) {
TypeToken<?> supertype = of(getCovariantTypeResolver().resolveType(type));
// super types' type mapping is a subset of type mapping of this type.
supertype.covariantTypeResolver = covariantTypeResolver;
supertype.invariantTypeResolver = invariantTypeResolver;
return supertype;
}
/**
* Returns the generic superclass of this type or {@code null} if the type represents {@link
* Object} or an interface. This method is similar but different from {@link
* Class#getGenericSuperclass}. For example, {@code new TypeToken<StringArrayList>()
* {}.getGenericSuperclass()} will return {@code new TypeToken<ArrayList<String>>() {}}; while
* {@code StringArrayList.class.getGenericSuperclass()} will return {@code ArrayList<E>}, where
* {@code E} is the type variable declared by class {@code ArrayList}.
*
* <p>If this type is a type variable or wildcard, its first upper bound is examined and returned
* if the bound is a class or extends from a class. This means that the returned type could be a
* type variable too.
*/
@CheckForNull
final TypeToken<? super T> getGenericSuperclass() {
if (runtimeType instanceof TypeVariable) {
// First bound is always the super class, if one exists.
return boundAsSuperclass(((TypeVariable<?>) runtimeType).getBounds()[0]);
}
if (runtimeType instanceof WildcardType) {
// wildcard has one and only one upper bound.
return boundAsSuperclass(((WildcardType) runtimeType).getUpperBounds()[0]);
}
Type superclass = getRawType().getGenericSuperclass();
if (superclass == null) {
return null;
}
@SuppressWarnings("unchecked") // super class of T
TypeToken<? super T> superToken = (TypeToken<? super T>) resolveSupertype(superclass);
return superToken;
}
@CheckForNull
private TypeToken<? super T> boundAsSuperclass(Type bound) {
TypeToken<?> token = of(bound);
if (token.getRawType().isInterface()) {
return null;
}
@SuppressWarnings("unchecked") // only upper bound of T is passed in.
TypeToken<? super T> superclass = (TypeToken<? super T>) token;
return superclass;
}
/**
* Returns the generic interfaces that this type directly {@code implements}. This method is
* similar but different from {@link Class#getGenericInterfaces()}. For example, {@code new
* TypeToken<List<String>>() {}.getGenericInterfaces()} will return a list that contains {@code
* new TypeToken<Iterable<String>>() {}}; while {@code List.class.getGenericInterfaces()} will
* return an array that contains {@code Iterable<T>}, where the {@code T} is the type variable
* declared by interface {@code Iterable}.
*
* <p>If this type is a type variable or wildcard, its upper bounds are examined and those that
* are either an interface or upper-bounded only by interfaces are returned. This means that the
* returned types could include type variables too.
*/
final ImmutableList<TypeToken<? super T>> getGenericInterfaces() {
if (runtimeType instanceof TypeVariable) {
return boundsAsInterfaces(((TypeVariable<?>) runtimeType).getBounds());
}
if (runtimeType instanceof WildcardType) {
return boundsAsInterfaces(((WildcardType) runtimeType).getUpperBounds());
}
ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
for (Type interfaceType : getRawType().getGenericInterfaces()) {
@SuppressWarnings("unchecked") // interface of T
TypeToken<? super T> resolvedInterface =
(TypeToken<? super T>) resolveSupertype(interfaceType);
builder.add(resolvedInterface);
}
return builder.build();
}
private ImmutableList<TypeToken<? super T>> boundsAsInterfaces(Type[] bounds) {
ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
for (Type bound : bounds) {
@SuppressWarnings("unchecked") // upper bound of T
TypeToken<? super T> boundType = (TypeToken<? super T>) of(bound);
if (boundType.getRawType().isInterface()) {
builder.add(boundType);
}
}
return builder.build();
}
/**
* Returns the set of interfaces and classes that this type is or is a subtype of. The returned
* types are parameterized with proper type arguments.
*
* <p>Subtypes are always listed before supertypes. But the reverse is not true. A type isn't
* necessarily a subtype of all the types following. Order between types without subtype
* relationship is arbitrary and not guaranteed.
*
* <p>If this type is a type variable or wildcard, upper bounds that are themselves type variables
* aren't included (their super interfaces and superclasses are).
*/
public final TypeSet getTypes() {
return new TypeSet();
}
/**
* Returns the generic form of {@code superclass}. For example, if this is {@code
* ArrayList<String>}, {@code Iterable<String>} is returned given the input {@code
* Iterable.class}.
*/
public final TypeToken<? super T> getSupertype(Class<? super T> superclass) {
checkArgument(
this.someRawTypeIsSubclassOf(superclass),
"%s is not a super class of %s",
superclass,
this);
if (runtimeType instanceof TypeVariable) {
return getSupertypeFromUpperBounds(superclass, ((TypeVariable<?>) runtimeType).getBounds());
}
if (runtimeType instanceof WildcardType) {
return getSupertypeFromUpperBounds(superclass, ((WildcardType) runtimeType).getUpperBounds());
}
if (superclass.isArray()) {
return getArraySupertype(superclass);
}
@SuppressWarnings("unchecked") // resolved supertype
TypeToken<? super T> supertype =
(TypeToken<? super T>) resolveSupertype(toGenericType(superclass).runtimeType);
return supertype;
}
/**
* Returns subtype of {@code this} with {@code subclass} as the raw class. For example, if this is
* {@code Iterable<String>} and {@code subclass} is {@code List}, {@code List<String>} is
* returned.
*/
public final TypeToken<? extends T> getSubtype(Class<?> subclass) {
checkArgument(
!(runtimeType instanceof TypeVariable), "Cannot get subtype of type variable <%s>", this);
if (runtimeType instanceof WildcardType) {
return getSubtypeFromLowerBounds(subclass, ((WildcardType) runtimeType).getLowerBounds());
}
// unwrap array type if necessary
if (isArray()) {
return getArraySubtype(subclass);
}
// At this point, it's either a raw class or parameterized type.
checkArgument(
getRawType().isAssignableFrom(subclass), "%s isn't a subclass of %s", subclass, this);
Type resolvedTypeArgs = resolveTypeArgsForSubclass(subclass);
@SuppressWarnings("unchecked") // guarded by the isAssignableFrom() statement above
TypeToken<? extends T> subtype = (TypeToken<? extends T>) of(resolvedTypeArgs);
checkArgument(
subtype.isSubtypeOf(this), "%s does not appear to be a subtype of %s", subtype, this);
return subtype;
}
/**
* Returns true if this type is a supertype of the given {@code type}. "Supertype" is defined
* according to <a
* href="http://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.5.1">the rules for type
* arguments</a> introduced with Java generics.
*
* @since 19.0
*/
public final boolean isSupertypeOf(TypeToken<?> type) {
return type.isSubtypeOf(getType());
}
/**
* Returns true if this type is a supertype of the given {@code type}. "Supertype" is defined
* according to <a
* href="http://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.5.1">the rules for type
* arguments</a> introduced with Java generics.
*
* @since 19.0
*/
public final boolean isSupertypeOf(Type type) {
return of(type).isSubtypeOf(getType());
}
/**
* Returns true if this type is a subtype of the given {@code type}. "Subtype" is defined
* according to <a
* href="http://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.5.1">the rules for type
* arguments</a> introduced with Java generics.
*
* @since 19.0
*/
public final boolean isSubtypeOf(TypeToken<?> type) {
return isSubtypeOf(type.getType());
}
/**
* Returns true if this type is a subtype of the given {@code type}. "Subtype" is defined
* according to <a
* href="http://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.5.1">the rules for type
* arguments</a> introduced with Java generics.
*
* @since 19.0
*/
public final boolean isSubtypeOf(Type supertype) {
checkNotNull(supertype);
if (supertype instanceof WildcardType) {
// if 'supertype' is <? super Foo>, 'this' can be:
// Foo, SubFoo, <? extends Foo>.
// if 'supertype' is <? extends Foo>, nothing is a subtype.
return any(((WildcardType) supertype).getLowerBounds()).isSupertypeOf(runtimeType);
}
// if 'this' is wildcard, it's a suptype of to 'supertype' if any of its "extends"
// bounds is a subtype of 'supertype'.
if (runtimeType instanceof WildcardType) {
// <? super Base> is of no use in checking 'from' being a subtype of 'to'.
return any(((WildcardType) runtimeType).getUpperBounds()).isSubtypeOf(supertype);
}
// if 'this' is type variable, it's a subtype if any of its "extends"
// bounds is a subtype of 'supertype'.
if (runtimeType instanceof TypeVariable) {
return runtimeType.equals(supertype)
|| any(((TypeVariable<?>) runtimeType).getBounds()).isSubtypeOf(supertype);
}
if (runtimeType instanceof GenericArrayType) {
return of(supertype).isSupertypeOfArray((GenericArrayType) runtimeType);
}
// Proceed to regular Type subtype check
if (supertype instanceof Class) {
return this.someRawTypeIsSubclassOf((Class<?>) supertype);
} else if (supertype instanceof ParameterizedType) {
return this.isSubtypeOfParameterizedType((ParameterizedType) supertype);
} else if (supertype instanceof GenericArrayType) {
return this.isSubtypeOfArrayType((GenericArrayType) supertype);
} else { // to instanceof TypeVariable
return false;
}
}
/**
* Returns true if this type is known to be an array type, such as {@code int[]}, {@code T[]},
* {@code <? extends Map<String, Integer>[]>} etc.
*/
public final boolean isArray() {
return getComponentType() != null;
}
/**
* Returns true if this type is one of the nine primitive types (including {@code void}).
*
* @since 15.0
*/
public final boolean isPrimitive() {
return (runtimeType instanceof Class) && ((Class<?>) runtimeType).isPrimitive();
}
/**
* Returns the corresponding wrapper type if this is a primitive type; otherwise returns {@code
* this} itself. Idempotent.
*
* @since 15.0
*/
public final TypeToken<T> wrap() {
if (isPrimitive()) {
@SuppressWarnings("unchecked") // this is a primitive class
Class<T> type = (Class<T>) runtimeType;
return of(Primitives.wrap(type));
}
return this;
}
private boolean isWrapper() {
return Primitives.allWrapperTypes().contains(runtimeType);
}
/**
* Returns the corresponding primitive type if this is a wrapper type; otherwise returns {@code
* this} itself. Idempotent.
*
* @since 15.0
*/
public final TypeToken<T> unwrap() {
if (isWrapper()) {
@SuppressWarnings("unchecked") // this is a wrapper class
Class<T> type = (Class<T>) runtimeType;
return of(Primitives.unwrap(type));
}
return this;
}
/**
* Returns the array component type if this type represents an array ({@code int[]}, {@code T[]},
* {@code <? extends Map<String, Integer>[]>} etc.), or else {@code null} is returned.
*/
@CheckForNull
public final TypeToken<?> getComponentType() {
Type componentType = Types.getComponentType(runtimeType);
if (componentType == null) {
return null;
}
return of(componentType);
}
/**
* Returns the {@link Invokable} for {@code method}, which must be a member of {@code T}.
*
* @since 14.0
*/
public final Invokable<T, Object> method(Method method) {
checkArgument(
this.someRawTypeIsSubclassOf(method.getDeclaringClass()),
"%s not declared by %s",
method,
this);
return new Invokable.MethodInvokable<T>(method) {
@Override
Type getGenericReturnType() {
return getCovariantTypeResolver().resolveType(super.getGenericReturnType());
}
@Override
Type[] getGenericParameterTypes() {
return getInvariantTypeResolver().resolveTypesInPlace(super.getGenericParameterTypes());
}
@Override
Type[] getGenericExceptionTypes() {
return getCovariantTypeResolver().resolveTypesInPlace(super.getGenericExceptionTypes());
}
@Override
public TypeToken<T> getOwnerType() {
return TypeToken.this;
}
@Override
public String toString() {
return getOwnerType() + "." + super.toString();
}
};
}
/**
* Returns the {@link Invokable} for {@code constructor}, which must be a member of {@code T}.
*
* @since 14.0
*/
public final Invokable<T, T> constructor(Constructor<?> constructor) {
checkArgument(
constructor.getDeclaringClass() == getRawType(),
"%s not declared by %s",
constructor,
getRawType());
return new Invokable.ConstructorInvokable<T>(constructor) {
@Override
Type getGenericReturnType() {
return getCovariantTypeResolver().resolveType(super.getGenericReturnType());
}
@Override
Type[] getGenericParameterTypes() {
return getInvariantTypeResolver().resolveTypesInPlace(super.getGenericParameterTypes());
}
@Override
Type[] getGenericExceptionTypes() {
return getCovariantTypeResolver().resolveTypesInPlace(super.getGenericExceptionTypes());
}
@Override
public TypeToken<T> getOwnerType() {
return TypeToken.this;
}
@Override
public String toString() {
return getOwnerType() + "(" + Joiner.on(", ").join(getGenericParameterTypes()) + ")";
}
};
}
/**
* The set of interfaces and classes that {@code T} is or is a subtype of. {@link Object} is not
* included in the set if this type is an interface.
*
* @since 13.0
*/
public class TypeSet extends ForwardingSet<TypeToken<? super T>> implements Serializable {
@CheckForNull private transient ImmutableSet<TypeToken<? super T>> types;
TypeSet() {}
/** Returns the types that are interfaces implemented by this type. */
public TypeSet interfaces() {
return new InterfaceSet(this);
}
/** Returns the types that are classes. */
public TypeSet classes() {
return new ClassSet();
}
@Override
protected Set<TypeToken<? super T>> delegate() {
ImmutableSet<TypeToken<? super T>> filteredTypes = types;
if (filteredTypes == null) {
// Java has no way to express ? super T when we parameterize TypeToken vs. Class.
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableList<TypeToken<? super T>> collectedTypes =
(ImmutableList) TypeCollector.FOR_GENERIC_TYPE.collectTypes(TypeToken.this);
return (types =
FluentIterable.from(collectedTypes)
.filter(TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD)
.toSet());
} else {
return filteredTypes;
}
}
/** Returns the raw types of the types in this set, in the same order. */
public Set<Class<? super T>> rawTypes() {
// Java has no way to express ? super T when we parameterize TypeToken vs. Class.
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableList<Class<? super T>> collectedTypes =
(ImmutableList) TypeCollector.FOR_RAW_TYPE.collectTypes(getRawTypes());
return ImmutableSet.copyOf(collectedTypes);
}
private static final long serialVersionUID = 0;
}
private final class InterfaceSet extends TypeSet {
private final transient TypeSet allTypes;
@CheckForNull private transient ImmutableSet<TypeToken<? super T>> interfaces;
InterfaceSet(TypeSet allTypes) {
this.allTypes = allTypes;
}
@Override
protected Set<TypeToken<? super T>> delegate() {
ImmutableSet<TypeToken<? super T>> result = interfaces;
if (result == null) {
return (interfaces =
FluentIterable.from(allTypes).filter(TypeFilter.INTERFACE_ONLY).toSet());
} else {
return result;
}
}
@Override
public TypeSet interfaces() {
return this;
}
@Override
public Set<Class<? super T>> rawTypes() {
// Java has no way to express ? super T when we parameterize TypeToken vs. Class.
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableList<Class<? super T>> collectedTypes =
(ImmutableList) TypeCollector.FOR_RAW_TYPE.collectTypes(getRawTypes());
return FluentIterable.from(collectedTypes)
.filter(
new Predicate<Class<?>>() {
@Override
public boolean apply(Class<?> type) {
return type.isInterface();
}
})
.toSet();
}
@Override
public TypeSet classes() {
throw new UnsupportedOperationException("interfaces().classes() not supported.");
}
private Object readResolve() {
return getTypes().interfaces();
}
private static final long serialVersionUID = 0;
}
private final class ClassSet extends TypeSet {
@CheckForNull private transient ImmutableSet<TypeToken<? super T>> classes;
@Override
protected Set<TypeToken<? super T>> delegate() {
ImmutableSet<TypeToken<? super T>> result = classes;
if (result == null) {
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableList<TypeToken<? super T>> collectedTypes =
(ImmutableList)
TypeCollector.FOR_GENERIC_TYPE.classesOnly().collectTypes(TypeToken.this);
return (classes =
FluentIterable.from(collectedTypes)
.filter(TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD)
.toSet());
} else {
return result;
}
}
@Override
public TypeSet classes() {
return this;
}
@Override
public Set<Class<? super T>> rawTypes() {
// Java has no way to express ? super T when we parameterize TypeToken vs. Class.
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableList<Class<? super T>> collectedTypes =
(ImmutableList) TypeCollector.FOR_RAW_TYPE.classesOnly().collectTypes(getRawTypes());
return ImmutableSet.copyOf(collectedTypes);
}
@Override
public TypeSet interfaces() {
throw new UnsupportedOperationException("classes().interfaces() not supported.");
}
private Object readResolve() {
return getTypes().classes();
}
private static final long serialVersionUID = 0;
}
private enum TypeFilter implements Predicate<TypeToken<?>> {
IGNORE_TYPE_VARIABLE_OR_WILDCARD {
@Override
public boolean apply(TypeToken<?> type) {
return !(type.runtimeType instanceof TypeVariable
|| type.runtimeType instanceof WildcardType);
}
},
INTERFACE_ONLY {
@Override
public boolean apply(TypeToken<?> type) {
return type.getRawType().isInterface();
}
}
}
/**
* Returns true if {@code o} is another {@code TypeToken} that represents the same {@link Type}.
*/
@Override
public boolean equals(@CheckForNull Object o) {
if (o instanceof TypeToken) {
TypeToken<?> that = (TypeToken<?>) o;
return runtimeType.equals(that.runtimeType);
}
return false;
}
@Override
public int hashCode() {
return runtimeType.hashCode();
}
@Override
public String toString() {
return Types.toString(runtimeType);
}
/** Implemented to support serialization of subclasses. */
protected Object writeReplace() {
// TypeResolver just transforms the type to our own impls that are Serializable
// except TypeVariable.
return of(new TypeResolver().resolveType(runtimeType));
}
/**
* Ensures that this type token doesn't contain type variables, which can cause unchecked type
* errors for callers like {@link TypeToInstanceMap}.
*/
@CanIgnoreReturnValue
final TypeToken<T> rejectTypeVariables() {
new TypeVisitor() {
@Override
void visitTypeVariable(TypeVariable<?> type) {
throw new IllegalArgumentException(
runtimeType + "contains a type variable and is not safe for the operation");
}
@Override
void visitWildcardType(WildcardType type) {
visit(type.getLowerBounds());
visit(type.getUpperBounds());
}
@Override
void visitParameterizedType(ParameterizedType type) {
visit(type.getActualTypeArguments());
visit(type.getOwnerType());
}
@Override
void visitGenericArrayType(GenericArrayType type) {
visit(type.getGenericComponentType());
}
}.visit(runtimeType);
return this;
}
private boolean someRawTypeIsSubclassOf(Class<?> superclass) {
for (Class<?> rawType : getRawTypes()) {
if (superclass.isAssignableFrom(rawType)) {
return true;
}
}
return false;
}
private boolean isSubtypeOfParameterizedType(ParameterizedType supertype) {
Class<?> matchedClass = of(supertype).getRawType();
if (!someRawTypeIsSubclassOf(matchedClass)) {
return false;
}
TypeVariable<?>[] typeVars = matchedClass.getTypeParameters();
Type[] supertypeArgs = supertype.getActualTypeArguments();
for (int i = 0; i < typeVars.length; i++) {
Type subtypeParam = getCovariantTypeResolver().resolveType(typeVars[i]);
// If 'supertype' is "List<? extends CharSequence>"
// and 'this' is StringArrayList,
// First step is to figure out StringArrayList "is-a" List<E> where <E> = String.
// String is then matched against <? extends CharSequence>, the supertypeArgs[0].
if (!of(subtypeParam).is(supertypeArgs[i], typeVars[i])) {
return false;
}
}
// We only care about the case when the supertype is a non-static inner class
// in which case we need to make sure the subclass's owner type is a subtype of the
// supertype's owner.
return Modifier.isStatic(((Class<?>) supertype.getRawType()).getModifiers())
|| supertype.getOwnerType() == null
|| isOwnedBySubtypeOf(supertype.getOwnerType());
}
private boolean isSubtypeOfArrayType(GenericArrayType supertype) {
if (runtimeType instanceof Class) {
Class<?> fromClass = (Class<?>) runtimeType;
if (!fromClass.isArray()) {
return false;
}
return of(fromClass.getComponentType()).isSubtypeOf(supertype.getGenericComponentType());
} else if (runtimeType instanceof GenericArrayType) {
GenericArrayType fromArrayType = (GenericArrayType) runtimeType;
return of(fromArrayType.getGenericComponentType())
.isSubtypeOf(supertype.getGenericComponentType());
} else {
return false;
}
}
private boolean isSupertypeOfArray(GenericArrayType subtype) {
if (runtimeType instanceof Class) {
Class<?> thisClass = (Class<?>) runtimeType;
if (!thisClass.isArray()) {
return thisClass.isAssignableFrom(Object[].class);
}
return of(subtype.getGenericComponentType()).isSubtypeOf(thisClass.getComponentType());
} else if (runtimeType instanceof GenericArrayType) {
return of(subtype.getGenericComponentType())
.isSubtypeOf(((GenericArrayType) runtimeType).getGenericComponentType());
} else {
return false;
}
}
/**
* {@code A.is(B)} is defined as {@code Foo<A>.isSubtypeOf(Foo<B>)}.
*
* <p>Specifically, returns true if any of the following conditions is met:
*
* <ol>
* <li>'this' and {@code formalType} are equal.
* <li>'this' and {@code formalType} have equal canonical form.
* <li>{@code formalType} is {@code <? extends Foo>} and 'this' is a subtype of {@code Foo}.
* <li>{@code formalType} is {@code <? super Foo>} and 'this' is a supertype of {@code Foo}.
* </ol>
*
* Note that condition 2 isn't technically accurate under the context of a recursively bounded
* type variables. For example, {@code Enum<? extends Enum<E>>} canonicalizes to {@code Enum<?>}
* where {@code E} is the type variable declared on the {@code Enum} class declaration. It's
* technically <em>not</em> true that {@code Foo<Enum<? extends Enum<E>>>} is a subtype of {@code
* Foo<Enum<?>>} according to JLS. See testRecursiveWildcardSubtypeBug() for a real example.
*
* <p>It appears that properly handling recursive type bounds in the presence of implicit type
* bounds is not easy. For now we punt, hoping that this defect should rarely cause issues in real
* code.
*
* @param formalType is {@code Foo<formalType>} a supertype of {@code Foo<T>}?
* @param declaration The type variable in the context of a parameterized type. Used to infer type
* bound when {@code formalType} is a wildcard with implicit upper bound.
*/
private boolean is(Type formalType, TypeVariable<?> declaration) {
if (runtimeType.equals(formalType)) {
return true;
}
if (formalType instanceof WildcardType) {
WildcardType your = canonicalizeWildcardType(declaration, (WildcardType) formalType);
// if "formalType" is <? extends Foo>, "this" can be:
// Foo, SubFoo, <? extends Foo>, <? extends SubFoo>, <T extends Foo> or
// <T extends SubFoo>.
// if "formalType" is <? super Foo>, "this" can be:
// Foo, SuperFoo, <? super Foo> or <? super SuperFoo>.
return every(your.getUpperBounds()).isSupertypeOf(runtimeType)
&& every(your.getLowerBounds()).isSubtypeOf(runtimeType);
}
return canonicalizeWildcardsInType(runtimeType).equals(canonicalizeWildcardsInType(formalType));
}
/**
* In reflection, {@code Foo<?>.getUpperBounds()[0]} is always {@code Object.class}, even when Foo
* is defined as {@code Foo<T extends String>}. Thus directly calling {@code <?>.is(String.class)}
* will return false. To mitigate, we canonicalize wildcards by enforcing the following
* invariants:
*
* <ol>
* <li>{@code canonicalize(t)} always produces the equal result for equivalent types. For
* example both {@code Enum<?>} and {@code Enum<? extends Enum<?>>} canonicalize to {@code
* Enum<? extends Enum<E>}.
* <li>{@code canonicalize(t)} produces a "literal" supertype of t. For example: {@code Enum<?
* extends Enum<?>>} canonicalizes to {@code Enum<?>}, which is a supertype (if we disregard
* the upper bound is implicitly an Enum too).
* <li>If {@code canonicalize(A) == canonicalize(B)}, then {@code Foo<A>.isSubtypeOf(Foo<B>)}
* and vice versa. i.e. {@code A.is(B)} and {@code B.is(A)}.
* <li>{@code canonicalize(canonicalize(A)) == canonicalize(A)}.
* </ol>
*/
private static Type canonicalizeTypeArg(TypeVariable<?> declaration, Type typeArg) {
return typeArg instanceof WildcardType
? canonicalizeWildcardType(declaration, ((WildcardType) typeArg))
: canonicalizeWildcardsInType(typeArg);
}
private static Type canonicalizeWildcardsInType(Type type) {
if (type instanceof ParameterizedType) {
return canonicalizeWildcardsInParameterizedType((ParameterizedType) type);
}
if (type instanceof GenericArrayType) {
return Types.newArrayType(
canonicalizeWildcardsInType(((GenericArrayType) type).getGenericComponentType()));
}
return type;
}
// WARNING: the returned type may have empty upper bounds, which may violate common expectations
// by user code or even some of our own code. It's fine for the purpose of checking subtypes.
// Just don't ever let the user access it.
private static WildcardType canonicalizeWildcardType(
TypeVariable<?> declaration, WildcardType type) {
Type[] declared = declaration.getBounds();
List<Type> upperBounds = new ArrayList<>();
for (Type bound : type.getUpperBounds()) {
if (!any(declared).isSubtypeOf(bound)) {
upperBounds.add(canonicalizeWildcardsInType(bound));
}
}
return new Types.WildcardTypeImpl(type.getLowerBounds(), upperBounds.toArray(new Type[0]));
}
private static ParameterizedType canonicalizeWildcardsInParameterizedType(
ParameterizedType type) {
Class<?> rawType = (Class<?>) type.getRawType();
TypeVariable<?>[] typeVars = rawType.getTypeParameters();
Type[] typeArgs = type.getActualTypeArguments();
for (int i = 0; i < typeArgs.length; i++) {
typeArgs[i] = canonicalizeTypeArg(typeVars[i], typeArgs[i]);
}
return Types.newParameterizedTypeWithOwner(type.getOwnerType(), rawType, typeArgs);
}
private static Bounds every(Type[] bounds) {
// Every bound must match. On any false, result is false.
return new Bounds(bounds, false);
}
private static Bounds any(Type[] bounds) {
// Any bound matches. On any true, result is true.
return new Bounds(bounds, true);
}
private static class Bounds {
private final Type[] bounds;
private final boolean target;
Bounds(Type[] bounds, boolean target) {
this.bounds = bounds;
this.target = target;
}
boolean isSubtypeOf(Type supertype) {
for (Type bound : bounds) {
if (of(bound).isSubtypeOf(supertype) == target) {
return target;
}
}
return !target;
}
boolean isSupertypeOf(Type subtype) {
TypeToken<?> type = of(subtype);
for (Type bound : bounds) {
if (type.isSubtypeOf(bound) == target) {
return target;
}
}
return !target;
}
}
private ImmutableSet<Class<? super T>> getRawTypes() {
final ImmutableSet.Builder<Class<?>> builder = ImmutableSet.builder();
new TypeVisitor() {
@Override
void visitTypeVariable(TypeVariable<?> t) {
visit(t.getBounds());
}
@Override
void visitWildcardType(WildcardType t) {
visit(t.getUpperBounds());
}
@Override
void visitParameterizedType(ParameterizedType t) {
builder.add((Class<?>) t.getRawType());
}
@Override
void visitClass(Class<?> t) {
builder.add(t);
}
@Override
void visitGenericArrayType(GenericArrayType t) {
builder.add(Types.getArrayClass(of(t.getGenericComponentType()).getRawType()));
}
}.visit(runtimeType);
// Cast from ImmutableSet<Class<?>> to ImmutableSet<Class<? super T>>
@SuppressWarnings({"unchecked", "rawtypes"})
ImmutableSet<Class<? super T>> result = (ImmutableSet) builder.build();
return result;
}
private boolean isOwnedBySubtypeOf(Type supertype) {
for (TypeToken<?> type : getTypes()) {
Type ownerType = type.getOwnerTypeIfPresent();
if (ownerType != null && of(ownerType).isSubtypeOf(supertype)) {
return true;
}
}
return false;
}
/**
* Returns the owner type of a {@link ParameterizedType} or enclosing class of a {@link Class}, or
* null otherwise.
*/
@CheckForNull
private Type getOwnerTypeIfPresent() {
if (runtimeType instanceof ParameterizedType) {
return ((ParameterizedType) runtimeType).getOwnerType();
} else if (runtimeType instanceof Class<?>) {
return ((Class<?>) runtimeType).getEnclosingClass();
} else {
return null;
}
}
/**
* Returns the type token representing the generic type declaration of {@code cls}. For example:
* {@code TypeToken.getGenericType(Iterable.class)} returns {@code Iterable<T>}.
*
* <p>If {@code cls} isn't parameterized and isn't a generic array, the type token of the class is
* returned.
*/
@VisibleForTesting
static <T> TypeToken<? extends T> toGenericType(Class<T> cls) {
if (cls.isArray()) {
Type arrayOfGenericType =
Types.newArrayType(
// If we are passed with int[].class, don't turn it to GenericArrayType
toGenericType(cls.getComponentType()).runtimeType);
@SuppressWarnings("unchecked") // array is covariant
TypeToken<? extends T> result = (TypeToken<? extends T>) of(arrayOfGenericType);
return result;
}
TypeVariable<Class<T>>[] typeParams = cls.getTypeParameters();
Type ownerType =
cls.isMemberClass() && !Modifier.isStatic(cls.getModifiers())
? toGenericType(cls.getEnclosingClass()).runtimeType
: null;
if ((typeParams.length > 0) || ((ownerType != null) && ownerType != cls.getEnclosingClass())) {
@SuppressWarnings("unchecked") // Like, it's Iterable<T> for Iterable.class
TypeToken<? extends T> type =
(TypeToken<? extends T>)
of(Types.newParameterizedTypeWithOwner(ownerType, cls, typeParams));
return type;
} else {
return of(cls);
}
}
private TypeResolver getCovariantTypeResolver() {
TypeResolver resolver = covariantTypeResolver;
if (resolver == null) {
resolver = (covariantTypeResolver = TypeResolver.covariantly(runtimeType));
}
return resolver;
}
private TypeResolver getInvariantTypeResolver() {
TypeResolver resolver = invariantTypeResolver;
if (resolver == null) {
resolver = (invariantTypeResolver = TypeResolver.invariantly(runtimeType));
}
return resolver;
}
private TypeToken<? super T> getSupertypeFromUpperBounds(
Class<? super T> supertype, Type[] upperBounds) {
for (Type upperBound : upperBounds) {
@SuppressWarnings("unchecked") // T's upperbound is <? super T>.
TypeToken<? super T> bound = (TypeToken<? super T>) of(upperBound);
if (bound.isSubtypeOf(supertype)) {
@SuppressWarnings({"rawtypes", "unchecked"}) // guarded by the isSubtypeOf check.
TypeToken<? super T> result = bound.getSupertype((Class) supertype);
return result;
}
}
throw new IllegalArgumentException(supertype + " isn't a super type of " + this);
}
private TypeToken<? extends T> getSubtypeFromLowerBounds(Class<?> subclass, Type[] lowerBounds) {
if (lowerBounds.length > 0) {
@SuppressWarnings("unchecked") // T's lower bound is <? extends T>
TypeToken<? extends T> bound = (TypeToken<? extends T>) of(lowerBounds[0]);
// Java supports only one lowerbound anyway.
return bound.getSubtype(subclass);
}
throw new IllegalArgumentException(subclass + " isn't a subclass of " + this);
}
private TypeToken<? super T> getArraySupertype(Class<? super T> supertype) {
// with component type, we have lost generic type information
// Use raw type so that compiler allows us to call getSupertype()
@SuppressWarnings("rawtypes")
TypeToken componentType = getComponentType();
// TODO(cpovirk): checkArgument?
if (componentType == null) {
throw new IllegalArgumentException(supertype + " isn't a super type of " + this);
}
// array is covariant. component type is super type, so is the array type.
@SuppressWarnings("unchecked") // going from raw type back to generics
/*
* requireNonNull is safe because we call getArraySupertype only after checking
* supertype.isArray().
*/
TypeToken<?> componentSupertype =
componentType.getSupertype(requireNonNull(supertype.getComponentType()));
@SuppressWarnings("unchecked") // component type is super type, so is array type.
TypeToken<? super T> result =
(TypeToken<? super T>)
// If we are passed with int[].class, don't turn it to GenericArrayType
of(newArrayClassOrGenericArrayType(componentSupertype.runtimeType));
return result;
}
private TypeToken<? extends T> getArraySubtype(Class<?> subclass) {
Class<?> subclassComponentType = subclass.getComponentType();
if (subclassComponentType == null) {
throw new IllegalArgumentException(subclass + " does not appear to be a subtype of " + this);
}
// array is covariant. component type is subtype, so is the array type.
// requireNonNull is safe because we call getArraySubtype only when isArray().
TypeToken<?> componentSubtype =
requireNonNull(getComponentType()).getSubtype(subclassComponentType);
@SuppressWarnings("unchecked") // component type is subtype, so is array type.
TypeToken<? extends T> result =
(TypeToken<? extends T>)
// If we are passed with int[].class, don't turn it to GenericArrayType
of(newArrayClassOrGenericArrayType(componentSubtype.runtimeType));
return result;
}
private Type resolveTypeArgsForSubclass(Class<?> subclass) {
// If both runtimeType and subclass are not parameterized, return subclass
// If runtimeType is not parameterized but subclass is, process subclass as a parameterized type
// If runtimeType is a raw type (i.e. is a parameterized type specified as a Class<?>), we
// return subclass as a raw type
if (runtimeType instanceof Class
&& ((subclass.getTypeParameters().length == 0)
|| (getRawType().getTypeParameters().length != 0))) {
// no resolution needed
return subclass;
}
// class Base<A, B> {}
// class Sub<X, Y> extends Base<X, Y> {}
// Base<String, Integer>.subtype(Sub.class):
// Sub<X, Y>.getSupertype(Base.class) => Base<X, Y>
// => X=String, Y=Integer
// => Sub<X, Y>=Sub<String, Integer>
TypeToken<?> genericSubtype = toGenericType(subclass);
@SuppressWarnings({"rawtypes", "unchecked"}) // subclass isn't <? extends T>
Type supertypeWithArgsFromSubtype =
genericSubtype.getSupertype((Class) getRawType()).runtimeType;
return new TypeResolver()
.where(supertypeWithArgsFromSubtype, runtimeType)
.resolveType(genericSubtype.runtimeType);
}
/**
* Creates an array class if {@code componentType} is a class, or else, a {@link
* GenericArrayType}. This is what Java7 does for generic array type parameters.
*/
private static Type newArrayClassOrGenericArrayType(Type componentType) {
return Types.JavaVersion.JAVA7.newArrayType(componentType);
}
private static final class SimpleTypeToken<T> extends TypeToken<T> {
SimpleTypeToken(Type type) {
super(type);
}
private static final long serialVersionUID = 0;
}
/**
* Collects parent types from a sub type.
*
* @param <K> The type "kind". Either a TypeToken, or Class.
*/
private abstract static class TypeCollector<K> {
static final TypeCollector<TypeToken<?>> FOR_GENERIC_TYPE =
new TypeCollector<TypeToken<?>>() {
@Override
Class<?> getRawType(TypeToken<?> type) {
return type.getRawType();
}
@Override
Iterable<? extends TypeToken<?>> getInterfaces(TypeToken<?> type) {
return type.getGenericInterfaces();
}
@Override
@CheckForNull
TypeToken<?> getSuperclass(TypeToken<?> type) {
return type.getGenericSuperclass();
}
};
static final TypeCollector<Class<?>> FOR_RAW_TYPE =
new TypeCollector<Class<?>>() {
@Override
Class<?> getRawType(Class<?> type) {
return type;
}
@Override
Iterable<? extends Class<?>> getInterfaces(Class<?> type) {
return Arrays.asList(type.getInterfaces());
}
@Override
@CheckForNull
Class<?> getSuperclass(Class<?> type) {
return type.getSuperclass();
}
};
/** For just classes, we don't have to traverse interfaces. */
final TypeCollector<K> classesOnly() {
return new ForwardingTypeCollector<K>(this) {
@Override
Iterable<? extends K> getInterfaces(K type) {
return ImmutableSet.of();
}
@Override
ImmutableList<K> collectTypes(Iterable<? extends K> types) {
ImmutableList.Builder<K> builder = ImmutableList.builder();
for (K type : types) {
if (!getRawType(type).isInterface()) {
builder.add(type);
}
}
return super.collectTypes(builder.build());
}
};
}
final ImmutableList<K> collectTypes(K type) {
return collectTypes(ImmutableList.of(type));
}
ImmutableList<K> collectTypes(Iterable<? extends K> types) {
// type -> order number. 1 for Object, 2 for anything directly below, so on so forth.
Map<K, Integer> map = Maps.newHashMap();
for (K type : types) {
collectTypes(type, map);
}
return sortKeysByValue(map, Ordering.natural().reverse());
}
/** Collects all types to map, and returns the total depth from T up to Object. */
@CanIgnoreReturnValue
private int collectTypes(K type, Map<? super K, Integer> map) {
Integer existing = map.get(type);
if (existing != null) {
// short circuit: if set contains type it already contains its supertypes
return existing;
}
// Interfaces should be listed before Object.
int aboveMe = getRawType(type).isInterface() ? 1 : 0;
for (K interfaceType : getInterfaces(type)) {
aboveMe = Math.max(aboveMe, collectTypes(interfaceType, map));
}
K superclass = getSuperclass(type);
if (superclass != null) {
aboveMe = Math.max(aboveMe, collectTypes(superclass, map));
}
/*
* TODO(benyu): should we include Object for interface? Also, CharSequence[] and Object[] for
* String[]?
*
*/
map.put(type, aboveMe + 1);
return aboveMe + 1;
}
private static <K, V> ImmutableList<K> sortKeysByValue(
final Map<K, V> map, final Comparator<? super V> valueComparator) {
Ordering<K> keyOrdering =
new Ordering<K>() {
@Override
public int compare(K left, K right) {
// requireNonNull is safe because we are passing keys in the map.
return valueComparator.compare(
requireNonNull(map.get(left)), requireNonNull(map.get(right)));
}
};
return keyOrdering.immutableSortedCopy(map.keySet());
}
abstract Class<?> getRawType(K type);
abstract Iterable<? extends K> getInterfaces(K type);
@CheckForNull
abstract K getSuperclass(K type);
private static class ForwardingTypeCollector<K> extends TypeCollector<K> {
private final TypeCollector<K> delegate;
ForwardingTypeCollector(TypeCollector<K> delegate) {
this.delegate = delegate;
}
@Override
Class<?> getRawType(K type) {
return delegate.getRawType(type);
}
@Override
Iterable<? extends K> getInterfaces(K type) {
return delegate.getInterfaces(type);
}
@Override
@CheckForNull
K getSuperclass(K type) {
return delegate.getSuperclass(type);
}
}
}
// This happens to be the hash of the class as of now. So setting it makes a backward compatible
// change. Going forward, if any incompatible change is added, we can change the UID back to 1.
private static final long serialVersionUID = 3637540370352322684L;
}