org.apache.calcite.util.CompositeMap.java Source code

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Here is the source code for org.apache.calcite.util.CompositeMap.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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 org.apache.calcite.util;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;

import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

/** Unmodifiable view onto multiple backing maps. An element occurs in the map
 * if it occurs in any of the backing maps; the value is the value that occurs
 * in the first map that contains the key.
 *
 * @param <K> Key type
 * @param <V> Value type
 */
public class CompositeMap<K, V> implements Map<K, V> {
    private final ImmutableList<Map<K, V>> maps;

    public CompositeMap(ImmutableList<Map<K, V>> maps) {
        this.maps = maps;
    }

    /** Creates a CompositeMap. */
    // Would like to use '@SafeVarargs' but JDK 1.6 doesn't support it.
    @SuppressWarnings("varargs")
    public static <K, V> CompositeMap<K, V> of(Map<K, V> map0, Map<K, V>... maps) {
        return new CompositeMap<K, V>(list(map0, maps));
    }

    private static <E> ImmutableList<E> list(E e, E[] es) {
        ImmutableList.Builder<E> builder = ImmutableList.builder();
        builder.add(e);
        for (E map : es) {
            builder.add(map);
        }
        return builder.build();
    }

    public int size() {
        return keySet().size();
    }

    public boolean isEmpty() {
        // Empty iff all maps are empty.
        for (Map<K, V> map : maps) {
            if (!map.isEmpty()) {
                return false;
            }
        }
        return true;
    }

    public boolean containsKey(Object key) {
        for (Map<K, V> map : maps) {
            if (map.containsKey(key)) {
                return true;
            }
        }
        return false;
    }

    public boolean containsValue(Object value) {
        for (Map<K, V> map : maps) {
            if (map.containsValue(value)) {
                return true;
            }
        }
        return false;
    }

    public V get(Object key) {
        for (Map<K, V> map : maps) {
            //noinspection SuspiciousMethodCalls
            if (map.containsKey(key)) {
                return map.get(key);
            }
        }
        return null;
    }

    public V put(K key, V value) {
        // we are an unmodifiable view on the maps
        throw new UnsupportedOperationException();
    }

    public V remove(Object key) {
        // we are an unmodifiable view on the maps
        throw new UnsupportedOperationException();
    }

    public void putAll(Map<? extends K, ? extends V> m) {
        // we are an unmodifiable view on the maps
        throw new UnsupportedOperationException();
    }

    public void clear() {
        // we are an unmodifiable view on the maps
        throw new UnsupportedOperationException();
    }

    public Set<K> keySet() {
        final Set<K> keys = new LinkedHashSet<K>();
        for (Map<K, V> map : maps) {
            keys.addAll(map.keySet());
        }
        return keys;
    }

    private Map<K, V> combinedMap() {
        ImmutableMap.Builder<K, V> builder = ImmutableMap.builder();
        final Set<K> keys = new LinkedHashSet<K>();
        for (Map<K, V> map : maps) {
            for (Entry<K, V> entry : map.entrySet()) {
                if (keys.add(entry.getKey())) {
                    builder.put(entry);
                }
            }
        }
        return builder.build();
    }

    public Collection<V> values() {
        return combinedMap().values();
    }

    public Set<Entry<K, V>> entrySet() {
        return combinedMap().entrySet();
    }
}

// End CompositeMap.java