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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.text.diff;

import java.util.ArrayList;
import java.util.List;

/**
 * This class handles sequences of replacements resulting from a comparison.
 * 

* The comparison of two objects sequences leads to the identification of common * parts and parts which only belong to the first or to the second sequence. The * common parts appear in the edit script in the form of keep commands, * they can be considered as synchronization objects between the two sequences. * These synchronization objects split the two sequences in synchronized * sub-sequences. The first sequence can be transformed into the second one by * replacing each synchronized sub-sequence of the first sequence by the * corresponding sub-sequence of the second sequence. This is a synthetic way to * see an {@link EditScript edit script}, replacing individual * {@link DeleteCommand delete}, {@link KeepCommand keep} and * {@link InsertCommand insert} commands by fewer replacements acting on * complete sub-sequences. *

*

* This class is devoted to perform this interpretation. It visits an * {@link EditScript edit script} (because it implements the * {@link CommandVisitor CommandVisitor} interface) and calls a user-supplied * handler implementing the {@link ReplacementsHandler ReplacementsHandler} * interface to process the sub-sequences. *

* * @see ReplacementsHandler * @see EditScript * @see StringsComparator * @param object type * @since 1.0 */ public class ReplacementsFinder implements CommandVisitor { /** * List of pending insertions. */ private final List pendingInsertions; /** * List of pending deletions. */ private final List pendingDeletions; /** * Count of elements skipped. */ private int skipped; /** Handler to call when synchronized sequences are found. */ private final ReplacementsHandler handler; /** * Constructs a new instance of {@link ReplacementsFinder}. * * @param handler handler to call when synchronized sequences are found */ public ReplacementsFinder(final ReplacementsHandler handler) { pendingInsertions = new ArrayList<>(); pendingDeletions = new ArrayList<>(); skipped = 0; this.handler = handler; } /** * Add an object to the pending deletions set. * * @param object object to delete */ @Override public void visitDeleteCommand(final T object) { pendingDeletions.add(object); } /** * Add an object to the pending insertions set. * * @param object object to insert */ @Override public void visitInsertCommand(final T object) { pendingInsertions.add(object); } /** * Handle a synchronization object. *

* When a synchronization object is identified, the pending insertions and * pending deletions sets are provided to the user handler as subsequences. *

* * @param object synchronization object detected */ @Override public void visitKeepCommand(final T object) { if (pendingDeletions.isEmpty() && pendingInsertions.isEmpty()) { ++skipped; } else { handler.handleReplacement(skipped, pendingDeletions, pendingInsertions); pendingDeletions.clear(); pendingInsertions.clear(); skipped = 1; } } }




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