org.trancecode.collection.TcMaps.java Source code

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Here is the source code for org.trancecode.collection.TcMaps.java

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/*
 * Copyright (C) 2008 Herve Quiroz
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 
 *
 * $Id$
 */
package org.trancecode.collection;

import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMap.Builder;
import com.google.common.collect.Maps;

import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.trancecode.function.TcPredicates;
import org.trancecode.lang.TcObjects;

/**
 * Utility methods related to {@link Map}.
 * 
 * @author Herve Quiroz
 */
public final class TcMaps {
    private TcMaps() {
        // No instantiation
    }

    public static <K, V> Map<K, V> merge(final Map<K, V> map1, final Map<? extends K, ? extends V> map2) {
        final Builder<K, V> builder = ImmutableMap.builder();
        @SuppressWarnings("unchecked")
        final Set<K> map2keys = (Set<K>) map2.keySet();
        final Predicate<K> keyFilter = Predicates.not(TcPredicates.isContainedBy(map2keys));
        final Map<K, V> map1WithoutKeysFromMap2 = Maps.filterKeys(map1, keyFilter);
        return builder.putAll(map1WithoutKeysFromMap2).putAll(map2).build();
    }

    public static <K, V> Map<K, V> copyAndPut(final Map<K, V> map, final K key, final V value) {
        Preconditions.checkNotNull(map);
        Preconditions.checkNotNull(key);
        if (map instanceof ImmutableMap && TcObjects.equals(map.get(key), value)) {
            return map;
        }

        final Builder<K, V> builder = ImmutableMap.builder();
        final Map<K, V> mapWithoutKey = Maps.filterKeys(map, Predicates.not(Predicates.equalTo(key)));
        return builder.putAll(mapWithoutKey).put(key, value).build();
    }

    public static <K, V> V get(final Map<K, V> map, final K key, final V defaultValue) {
        if (map.containsKey(key)) {
            return map.get(key);
        }

        return defaultValue;
    }

    public static <K, V> Map<K, V> fromEntries(final Iterable<Entry<K, V>> entries) {
        final Function<Entry<K, V>, K> keyFunction = MapFunctions.getKey();
        final Function<Entry<K, V>, V> valueFunction = MapFunctions.getValue();
        final Map<K, Entry<K, V>> intermediate = Maps.uniqueIndex(entries, keyFunction);
        return Maps.transformValues(intermediate, valueFunction);
    }
}