
com.cinchapi.common.collect.MergeStrategies Maven / Gradle / Ivy
/*
* Copyright (c) 2013-2018 Cinchapi Inc.
*
* 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 com.cinchapi.common.collect;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
/**
* A collection of strategies for
* {@link Association#merge(java.util.Map, java.util.function.BiFunction)} and
* {@link java.util.Map#merge(Object, Object, java.util.function.BiFunction)}.
*
* @author Jeff Nelson
*/
public final class MergeStrategies {
private MergeStrategies() {/* no-init */}
/**
* Return a merge strategy that uses the incoming value if there is a
* conflict with an existing value in the into {@link Map}.
*
* @return the result of applying the strategy
*/
public static Object theirs(Object ours, Object theirs) {
return theirs;
}
/**
* Return a merge strategy that uses the existing value if there is a
* conflict with an incoming value in the from {@link Map}.
*
* @return the result of applying the strategy
*/
public static Object ours(Object ours, Object theirs) {
return ours;
}
/**
* Return a merge strategy that will concatenate the stored and incoming
* values if there is a conflict between the into and from
* {@link Map maps}.
*
* This strategy will map the conflicting key to a collection that contains
* the value from the into map (or values if the value is a
* collection) followed by the value (or values) from the from map.
*
*
* @return the result of applying the strategy
*/
@SuppressWarnings("unchecked")
public static Object concat(Object ours, Object theirs) {
if(ours instanceof Collection && theirs instanceof Collection) {
((Collection
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