ImmutableClassToInstanceMap.java
/*
* Copyright (C) 2009 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.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.primitives.Primitives;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.Immutable;
import java.io.Serializable;
import java.util.Map;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A {@link ClassToInstanceMap} whose contents will never change, with many other important
* properties detailed at {@link ImmutableCollection}.
*
* @author Kevin Bourrillion
* @since 2.0
*/
@Immutable(containerOf = "B")
@GwtIncompatible
public final class ImmutableClassToInstanceMap<B> extends ForwardingMap<Class<? extends B>, B>
implements ClassToInstanceMap<B>, Serializable {
private static final ImmutableClassToInstanceMap<Object> EMPTY =
new ImmutableClassToInstanceMap<>(ImmutableMap.<Class<?>, Object>of());
/**
* Returns an empty {@code ImmutableClassToInstanceMap}.
*
* <p><b>Performance note:</b> the instance returned is a singleton.
*
* @since 19.0
*/
@SuppressWarnings("unchecked")
public static <B> ImmutableClassToInstanceMap<B> of() {
return (ImmutableClassToInstanceMap<B>) EMPTY;
}
/**
* Returns an {@code ImmutableClassToInstanceMap} containing a single entry.
*
* @since 19.0
*/
public static <B, T extends B> ImmutableClassToInstanceMap<B> of(Class<T> type, T value) {
ImmutableMap<Class<? extends B>, B> map = ImmutableMap.<Class<? extends B>, B>of(type, value);
return new ImmutableClassToInstanceMap<B>(map);
}
/**
* Returns a new builder. The generated builder is equivalent to the builder created by the {@link
* Builder} constructor.
*/
public static <B> Builder<B> builder() {
return new Builder<B>();
}
/**
* A builder for creating immutable class-to-instance maps. Example:
*
* <pre>{@code
* static final ImmutableClassToInstanceMap<Handler> HANDLERS =
* new ImmutableClassToInstanceMap.Builder<Handler>()
* .put(FooHandler.class, new FooHandler())
* .put(BarHandler.class, new SubBarHandler())
* .put(Handler.class, new QuuxHandler())
* .build();
* }</pre>
*
* <p>After invoking {@link #build()} it is still possible to add more entries and build again.
* Thus each map generated by this builder will be a superset of any map generated before it.
*
* @since 2.0
*/
public static final class Builder<B> {
private final ImmutableMap.Builder<Class<? extends B>, B> mapBuilder = ImmutableMap.builder();
/**
* Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
* and will cause {@link #build} to fail.
*/
@CanIgnoreReturnValue
public <T extends B> Builder<B> put(Class<T> key, T value) {
mapBuilder.put(key, value);
return this;
}
/**
* Associates all of {@code map's} keys and values in the built map. Duplicate keys are not
* allowed, and will cause {@link #build} to fail.
*
* @throws NullPointerException if any key or value in {@code map} is null
* @throws ClassCastException if any value is not an instance of the type specified by its key
*/
@CanIgnoreReturnValue
public <T extends B> Builder<B> putAll(Map<? extends Class<? extends T>, ? extends T> map) {
for (Entry<? extends Class<? extends T>, ? extends T> entry : map.entrySet()) {
Class<? extends T> type = entry.getKey();
T value = entry.getValue();
mapBuilder.put(type, cast(type, value));
}
return this;
}
private static <B, T extends B> T cast(Class<T> type, B value) {
return Primitives.wrap(type).cast(value);
}
/**
* Returns a new immutable class-to-instance map containing the entries provided to this
* builder.
*
* @throws IllegalArgumentException if duplicate keys were added
*/
public ImmutableClassToInstanceMap<B> build() {
ImmutableMap<Class<? extends B>, B> map = mapBuilder.build();
if (map.isEmpty()) {
return of();
} else {
return new ImmutableClassToInstanceMap<B>(map);
}
}
}
/**
* Returns an immutable map containing the same entries as {@code map}. If {@code map} somehow
* contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
* comparator is not <i>consistent with equals</i>), the results of this method are undefined.
*
* <p><b>Note:</b> Despite what the method name suggests, if {@code map} is an {@code
* ImmutableClassToInstanceMap}, no copy will actually be performed.
*
* @throws NullPointerException if any key or value in {@code map} is null
* @throws ClassCastException if any value is not an instance of the type specified by its key
*/
public static <B, S extends B> ImmutableClassToInstanceMap<B> copyOf(
Map<? extends Class<? extends S>, ? extends S> map) {
if (map instanceof ImmutableClassToInstanceMap) {
@SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) map;
return cast;
}
return new Builder<B>().putAll(map).build();
}
private final ImmutableMap<Class<? extends B>, B> delegate;
private ImmutableClassToInstanceMap(ImmutableMap<Class<? extends B>, B> delegate) {
this.delegate = delegate;
}
@Override
protected Map<Class<? extends B>, B> delegate() {
return delegate;
}
@Override
@SuppressWarnings("unchecked") // value could not get in if not a T
public <T extends B> @Nullable T getInstance(Class<T> type) {
return (T) delegate.get(checkNotNull(type));
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public <T extends B> T putInstance(Class<T> type, T value) {
throw new UnsupportedOperationException();
}
Object readResolve() {
return isEmpty() ? of() : this;
}
}