/*
* 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 EditScript objects. Users should implement this interface in order to walk through the EditScript object created by the comparison of two sequences. This is a direct application of the visitor design pattern. The 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
/**
* This interface should be implemented by user object to walk
* through {@link EditScript EditScript} objects.
* <p>
* 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.
* </p>
* <p>
* The implementation of the user visitor class will depend on the
* need. Here are two examples.
* </p>
* <p>
* The first example is a visitor that build the longest common
* subsequence:
* </p>
* <pre>
* 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;
*
* }
* </pre>
* <p>
* The second example is a visitor that shows the commands and the way
* they transform the first sequence into the second one:
* </p>
* <pre>
* 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;
*
* }
* </pre>
*
* @since 4.0
*/
public interface CommandVisitor<T> {
Method called when an insert command is encountered.
Params: - object – object to insert (this object comes from the second sequence)
/**
* 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.
Params: - object – object to keep (this object comes from the first sequence)
/**
* 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.
Params: - object – object to delete (this object comes from the first sequence)
/**
* Method called when a delete command is encountered.
*
* @param object object to delete (this object comes from the first sequence)
*/
void visitDeleteCommand(T object);
}