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/* * Copyright 2002-2018 the original author or authors. * * 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 * * https://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.springframework.util.comparator; import java.io.Serializable; import java.util.ArrayList; import java.util.Comparator; import java.util.List; import org.springframework.lang.Nullable; import org.springframework.util.Assert; /** * A comparator that chains a sequence of one or more Comparators. * * <p>A compound comparator calls each Comparator in sequence until a single * Comparator returns a non-zero result, or the comparators are exhausted and * zero is returned. * * <p>This facilitates in-memory sorting similar to multi-column sorting in SQL. * The order of any single Comparator in the list can also be reversed. * * @author Keith Donald * @author Juergen Hoeller * @since 1.2.2 * @param <T> the type of objects that may be compared by this comparator * @deprecated as of Spring Framework 5.0, in favor of the standard JDK 8 * {@link Comparator#thenComparing(Comparator)} */ @Deprecated @SuppressWarnings({ "serial", "rawtypes" }) public class CompoundComparator<T> implements Comparator<T>, Serializable { private final List<InvertibleComparator> comparators; /** * Construct a CompoundComparator with initially no Comparators. Clients * must add at least one Comparator before calling the compare method or an * IllegalStateException is thrown. */ public CompoundComparator() { this.comparators = new ArrayList<>(); } /** * Construct a CompoundComparator from the Comparators in the provided array. * <p>All Comparators will default to ascending sort order, * unless they are InvertibleComparators. * @param comparators the comparators to build into a compound comparator * @see InvertibleComparator */ @SuppressWarnings("unchecked") public CompoundComparator(Comparator... comparators) { Assert.notNull(comparators, "Comparators must not be null"); this.comparators = new ArrayList<>(comparators.length); for (Comparator comparator : comparators) { addComparator(comparator); } } /** * Add a Comparator to the end of the chain. * <p>The Comparator will default to ascending sort order, * unless it is a InvertibleComparator. * @param comparator the Comparator to add to the end of the chain * @see InvertibleComparator */ @SuppressWarnings("unchecked") public void addComparator(Comparator<? extends T> comparator) { if (comparator instanceof InvertibleComparator) { this.comparators.add((InvertibleComparator) comparator); } else { this.comparators.add(new InvertibleComparator(comparator)); } } /** * Add a Comparator to the end of the chain using the provided sort order. * @param comparator the Comparator to add to the end of the chain * @param ascending the sort order: ascending (true) or descending (false) */ @SuppressWarnings("unchecked") public void addComparator(Comparator<? extends T> comparator, boolean ascending) { this.comparators.add(new InvertibleComparator(comparator, ascending)); } /** * Replace the Comparator at the given index. * <p>The Comparator will default to ascending sort order, * unless it is a InvertibleComparator. * @param index the index of the Comparator to replace * @param comparator the Comparator to place at the given index * @see InvertibleComparator */ @SuppressWarnings("unchecked") public void setComparator(int index, Comparator<? extends T> comparator) { if (comparator instanceof InvertibleComparator) { this.comparators.set(index, (InvertibleComparator) comparator); } else { this.comparators.set(index, new InvertibleComparator(comparator)); } } /** * Replace the Comparator at the given index using the given sort order. * @param index the index of the Comparator to replace * @param comparator the Comparator to place at the given index * @param ascending the sort order: ascending (true) or descending (false) */ public void setComparator(int index, Comparator<T> comparator, boolean ascending) { this.comparators.set(index, new InvertibleComparator<>(comparator, ascending)); } /** * Invert the sort order of each sort definition contained by this compound * comparator. */ public void invertOrder() { for (InvertibleComparator comparator : this.comparators) { comparator.invertOrder(); } } /** * Invert the sort order of the sort definition at the specified index. * @param index the index of the comparator to invert */ public void invertOrder(int index) { this.comparators.get(index).invertOrder(); } /** * Change the sort order at the given index to ascending. * @param index the index of the comparator to change */ public void setAscendingOrder(int index) { this.comparators.get(index).setAscending(true); } /** * Change the sort order at the given index to descending sort. * @param index the index of the comparator to change */ public void setDescendingOrder(int index) { this.comparators.get(index).setAscending(false); } /** * Returns the number of aggregated comparators. */ public int getComparatorCount() { return this.comparators.size(); } @Override @SuppressWarnings("unchecked") public int compare(T o1, T o2) { Assert.state(!this.comparators.isEmpty(), "No sort definitions have been added to this CompoundComparator to compare"); for (InvertibleComparator comparator : this.comparators) { int result = comparator.compare(o1, o2); if (result != 0) { return result; } } return 0; } @Override @SuppressWarnings("unchecked") public boolean equals(@Nullable Object other) { return (this == other || (other instanceof CompoundComparator && this.comparators.equals(((CompoundComparator<T>) other).comparators))); } @Override public int hashCode() { return this.comparators.hashCode(); } @Override public String toString() { return "CompoundComparator: " + this.comparators; } }