Package org.apache.commons.text.diff
Interface CommandVisitor<T>
- Type Parameters:
T
- object type
- All Known Implementing Classes:
ReplacementsFinder
public interface CommandVisitor<T>
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.text.diff.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.text.diff.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:
- 1.0
-
Method Summary
Modifier and TypeMethodDescriptionvoid
visitDeleteCommand
(T object) Method called when a delete command is encountered.void
visitInsertCommand
(T object) Method called when an insert command is encountered.void
visitKeepCommand
(T object) Method called when a keep command is encountered.
-
Method Details
-
visitDeleteCommand
Method called when a delete command is encountered.- Parameters:
object
- object to delete (this object comes from the first sequence)
-
visitInsertCommand
Method called when an insert command is encountered.- Parameters:
object
- object to insert (this object comes from the second sequence)
-
visitKeepCommand
Method called when a keep command is encountered.- Parameters:
object
- object to keep (this object comes from the first sequence)
-