de.flapdoodle.guava.Merger.java Source code

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Here is the source code for de.flapdoodle.guava.Merger.java

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/**
 * Copyright (C) 2013
 *   Michael Mosmann <michael@mosmann.de>
 *
 * 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 de.flapdoodle.guava;

import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

public abstract class Merger {

    private Merger() {
        // no instance
    }

    public static <T> ImmutableList<T> merge(Iterable<? extends T> left, Iterable<? extends T> right,
            Equivalence<? super T> matcher, Foldleft<? super T, T> fold) {
        ImmutableList.Builder<T> builder = ImmutableList.builder();
        Iterable<? extends T> notMerged = right;
        for (T l : left) {
            Iterable<? extends T> matching = Iterables.filter(notMerged, matcher.equivalentTo(l));
            notMerged = Iterables.filter(notMerged, Predicates.not(matcher.equivalentTo(l)));

            boolean noMatching = true;
            for (T r : matching) {
                builder.add(fold.apply(l, r));
                noMatching = false;
            }
            if (noMatching) {
                builder.add(l);
            }
        }
        builder.addAll(notMerged);
        return builder.build();
    }

    public static <T> ImmutableList<T> remove(Iterable<? extends T> src, Predicate<? super T> matcher,
            Function<T, Optional<T>> transformation) {
        ImmutableList.Builder<T> builder = ImmutableList.builder();
        for (T s : src) {
            if (matcher.apply(s)) {
                builder.addAll(transformation.apply(s).asSet());
            } else {
                builder.add(s);
            }
        }
        return builder.build();
    }
}