net.derquinse.common.collect.EmptyImmutableHierarchyMap.java Source code

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Here is the source code for net.derquinse.common.collect.EmptyImmutableHierarchyMap.java

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/*
 * Copyright 2008-2010 the original author or 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 net.derquinse.common.collect;

import java.util.Map;

import com.google.common.collect.ImmutableMap;

/**
 * An empty immutable hierarchy map.
 * @author Andres Rodriguez
 * @param <K> Type of the keys.
 * @param <V> Type of the values.
 */
final class EmptyImmutableHierarchyMap extends ImmutableHierarchyMap<Object, Object> {
    static final EmptyImmutableHierarchyMap INSTANCE = new EmptyImmutableHierarchyMap();

    private EmptyImmutableHierarchyMap() {
    }

    @Override
    protected Map<Object, Object> delegate() {
        return ImmutableMap.of();
    }

    /*
     * (non-Javadoc)
     * @see net.derquinse.common.collect.HierarchyMap#keyHierarchy()
     */
    public Hierarchy<Object> keyHierarchy() {
        return ImmutableHierarchy.of();
    }

}