com.groupbyinc.common.apache.commons.collections4.sequence.CommandVisitor Maven / Gradle / Ivy
/*
* 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.collections4.sequence;
/**
* This interface should be implemented by user object to walk
* through {@link EditScript EditScript} objects.
*
* Users should implement this interface in order to walk through
* the {@link EditScript EditScript} object created by the comparison
* of two sequences. This is a direct application of the visitor
* design pattern. The {@link EditScript#visit EditScript.visit}
* method takes an object implementing this interface as an argument,
* it will perform the loop over all commands in the script and the
* proper methods of the user class will be called as the commands are
* encountered.
*
* The implementation of the user visitor class will depend on the
* need. Here are two examples.
*
* The first example is a visitor that build the longest common
* subsequence:
*
* import org.apache.commons.collections4.comparators.sequence.CommandVisitor;
*
* import java.util.ArrayList;
*
* public class LongestCommonSubSequence implements CommandVisitor {
*
* public LongestCommonSubSequence() {
* a = new ArrayList();
* }
*
* public void visitInsertCommand(Object object) {
* }
*
* public void visitKeepCommand(Object object) {
* a.add(object);
* }
*
* public void visitDeleteCommand(Object object) {
* }
*
* public Object[] getSubSequence() {
* return a.toArray();
* }
*
* private ArrayList a;
*
* }
*
*
* The second example is a visitor that shows the commands and the way
* they transform the first sequence into the second one:
*
* import org.apache.commons.collections4.comparators.sequence.CommandVisitor;
*
* import java.util.Arrays;
* import java.util.ArrayList;
* import java.util.Iterator;
*
* public class ShowVisitor implements CommandVisitor {
*
* public ShowVisitor(Object[] sequence1) {
* v = new ArrayList();
* v.addAll(Arrays.asList(sequence1));
* index = 0;
* }
*
* public void visitInsertCommand(Object object) {
* v.insertElementAt(object, index++);
* display("insert", object);
* }
*
* public void visitKeepCommand(Object object) {
* ++index;
* display("keep ", object);
* }
*
* public void visitDeleteCommand(Object object) {
* v.remove(index);
* display("delete", object);
* }
*
* private void display(String commandName, Object object) {
* System.out.println(commandName + " " + object + " ->" + this);
* }
*
* public String toString() {
* StringBuffer buffer = new StringBuffer();
* for (Iterator iter = v.iterator(); iter.hasNext();) {
* buffer.append(' ').append(iter.next());
* }
* return buffer.toString();
* }
*
* private ArrayList v;
* private int index;
*
* }
*
*
* @since 4.0
* @version $Id: CommandVisitor.java 1477760 2013-04-30 18:34:03Z tn $
*/
public interface CommandVisitor {
/**
* Method called when an insert command is encountered.
*
* @param object object to insert (this object comes from the second sequence)
*/
void visitInsertCommand(T object);
/**
* Method called when a keep command is encountered.
*
* @param object object to keep (this object comes from the first sequence)
*/
void visitKeepCommand(T object);
/**
* Method called when a delete command is encountered.
*
* @param object object to delete (this object comes from the first sequence)
*/
void visitDeleteCommand(T object);
}