org.eclipse.xtext.xbase.typesystem.util.Multimaps2.java Source code

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Here is the source code for org.eclipse.xtext.xbase.typesystem.util.Multimaps2.java

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/*******************************************************************************
 * Copyright (c) 2012 itemis AG (http://www.itemis.eu) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.xbase.typesystem.util;

import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;

import com.google.common.base.Supplier;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;

/**
 * Provides static creating a {@link #newLinkedHashListMultimap() LinkedHashListMultimap}.
 * 
 * @see Multimaps
 * @author Sebastian Zarnekow - Initial contribution and API
 */
public class Multimaps2 {

    /**
     * Creates a new, empty {@code ListMultimap} with the default initial capacities that uses a linked map internally.
     */
    public static <K, V> ListMultimap<K, V> newLinkedHashListMultimap() {
        return Multimaps.newListMultimap(Maps.<K, Collection<V>>newLinkedHashMap(), new Supplier<List<V>>() {
            @Override
            public List<V> get() {
                return Lists.newArrayList();
            }
        });
    }

    /**
     * Constructs an empty {@code ListMultimap} with enough capacity to hold the specified numbers of keys and values
     * without resizing. It uses a linked map internally.
     * 
     * @param expectedKeys
     *            the expected number of distinct keys
     * @param expectedValuesPerKey
     *            the expected average number of values per key
     * @throws IllegalArgumentException
     *             if {@code expectedKeys} or {@code expectedValuesPerKey} is negative
     */
    public static <K, V> ListMultimap<K, V> newLinkedHashListMultimap(int expectedKeys,
            final int expectedValuesPerKey) {
        return Multimaps.newListMultimap(new LinkedHashMap<K, Collection<V>>(expectedKeys),
                new Supplier<List<V>>() {
                    @Override
                    public List<V> get() {
                        return Lists.newArrayListWithCapacity(expectedValuesPerKey);
                    }
                });
    }

    /**
     * Constructs an {@code ArrayListMultimap} with the same mappings as the specified multimap. It uses a linked map
     * internally..
     * 
     * @param multimap
     *            the multimap whose contents are copied to this multimap
     */
    public static <K, V> ListMultimap<K, V> newLinkedHashListMultimap(Multimap<K, V> multimap) {
        int keySetSize = multimap.keySet().size();
        int expectedKeys = Math.max(keySetSize, 2);
        ListMultimap<K, V> result = newLinkedHashListMultimap(expectedKeys,
                Math.max(3, multimap.size() / expectedKeys));
        result.putAll(multimap);
        return result;
    }

}