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/*
* Copyright (C) 2012 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 com.google.common.annotations.Beta;
import com.google.common.collect.ForwardingMap;
import com.google.common.collect.ImmutableMap;
import java.util.Map;
/**
* A type-to-instance map backed by an {@link ImmutableMap}. See also {@link
* MutableTypeToInstanceMap}.
*
* @author Ben Yu
* @since 13.0
*/
@Beta
public final class ImmutableTypeToInstanceMap<B> extends ForwardingMap<TypeToken<? extends B>, B>
implements TypeToInstanceMap<B> {
/** Returns an empty type to instance map. */
public static <B> ImmutableTypeToInstanceMap<B> of() {
return new ImmutableTypeToInstanceMap<B>(ImmutableMap.<TypeToken<? extends B>, B>of());
}
/** Returns a new builder. */
public static <B> Builder<B> builder() {
return new Builder<B>();
}
/**
* A builder for creating immutable type-to-instance maps. Example:
* <pre> {@code
*
* static final ImmutableTypeToInstanceMap<Handler<?>> HANDLERS =
* ImmutableTypeToInstanceMap.<Handler<?>>builder()
* .put(new TypeToken<Handler<Foo>>() {}, new FooHandler())
* .put(new TypeToken<Handler<Bar>>() {}, new SubBarHandler())
* .build();}</pre>
*
* 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 13.0
*/
@Beta
public static final class Builder<B> {
private final ImmutableMap.Builder<TypeToken<? extends B>, B> mapBuilder
= ImmutableMap.builder();
private Builder() {}
/**
* Associates {@code key} with {@code value} in the built map. Duplicate
* keys are not allowed, and will cause {@link #build} to fail.
*/
public <T extends B> Builder<B> put(Class<T> key, T value) {
mapBuilder.put(TypeToken.of(key), value);
return this;
}
/**
* Associates {@code key} with {@code value} in the built map. Duplicate
* keys are not allowed, and will cause {@link #build} to fail.
*/
public <T extends B> Builder<B> put(TypeToken<T> key, T value) {
mapBuilder.put(key.rejectTypeVariables(), value);
return this;
}
/**
* Returns a new immutable type-to-instance map containing the entries
* provided to this builder.
*
* @throws IllegalArgumentException if duplicate keys were added
*/
public ImmutableTypeToInstanceMap<B> build() {
return new ImmutableTypeToInstanceMap<B>(mapBuilder.build());
}
}
private final ImmutableMap<TypeToken<? extends B>, B> delegate;
private ImmutableTypeToInstanceMap(ImmutableMap<TypeToken<? extends B>, B> delegate) {
this.delegate = delegate;
}
@Override public <T extends B> T getInstance(TypeToken<T> type) {
return trustedGet(type.rejectTypeVariables());
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override public <T extends B> T putInstance(TypeToken<T> type, T value) {
throw new UnsupportedOperationException();
}
@Override public <T extends B> T getInstance(Class<T> type) {
return trustedGet(TypeToken.of(type));
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override public <T extends B> T putInstance(Class<T> type, T value) {
throw new UnsupportedOperationException();
}
@Override protected Map<TypeToken<? extends B>, B> delegate() {
return delegate;
}
@SuppressWarnings("unchecked") // value could not get in if not a T
private <T extends B> T trustedGet(TypeToken<T> type) {
return (T) delegate.get(type);
}
}
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