Java tutorial
/* * ==================================================================== * * The Apache Software License, Version 1.1 * * Copyright (c) 1999-2003 The Apache Software Foundation. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. 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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.commons.jrcs.diff; import java.util.List; /** * Holds a "delta" difference between to revisions of a text. * * @version $Revision$ $Date: 2006-04-12 18:30:19 +0100 (Wed, 12 Apr * 2006) $ * @author <a href="mailto:juanco@suigeneris.org">Juanco Anez</a> * @author <a href="mailto:bwm@hplb.hpl.hp.com">Brian McBride</a> * @see Diff * @see Chunk * @see Revision modifications 27 Apr 2003 bwm Added getOriginal() and * getRevised() accessor methods Added visitor pattern accept() method */ public abstract class Delta extends org.apache.commons.jrcs.util.ToString { protected Chunk original; protected Chunk revised; static Class[][] DeltaClass; static { DeltaClass = new Class[2][2]; DeltaClass[0][0] = org.apache.commons.jrcs.diff.ChangeDelta.class; DeltaClass[0][1] = org.apache.commons.jrcs.diff.AddDelta.class; DeltaClass[1][0] = org.apache.commons.jrcs.diff.DeleteDelta.class; DeltaClass[1][1] = org.apache.commons.jrcs.diff.ChangeDelta.class; } /** * Returns a Delta that corresponds to the given chunks in the original and * revised text respectively. * * @param orig * the chunk in the original text. * @param rev * the chunk in the revised text. */ public static Delta newDelta(Chunk orig, Chunk rev) { Class c = DeltaClass[orig.size() > 0 ? 1 : 0][rev.size() > 0 ? 1 : 0]; Delta result; try { result = (Delta) c.newInstance(); } catch (InstantiationException e) { return null; } catch (IllegalAccessException e) { return null; } result.init(orig, rev); return result; } /** * Creates an uninitialized delta. */ protected Delta() { // default constructor } /** * Creates a delta object with the given chunks from the original and * revised texts. */ protected Delta(Chunk orig, Chunk rev) { init(orig, rev); } /** * Initializaes the delta with the given chunks from the original and * revised texts. */ protected void init(Chunk orig, Chunk rev) { original = orig; revised = rev; } /** * Verifies that this delta can be used to patch the given text. * * @param target * the text to patch. * @throws PatchFailedException * if the patch cannot be applied. */ public abstract void verify(List target) throws PatchFailedException; /** * Applies this delta as a patch to the given text. * * @param target * the text to patch. * @throws PatchFailedException * if the patch cannot be applied. */ public final void patch(List target) throws PatchFailedException { verify(target); try { applyTo(target); } catch (Exception e) { throw new PatchFailedException(e.getMessage(), e); } } /** * Applies this delta as a patch to the given text. * * @param target * the text to patch. * @throws PatchFailedException * if the patch cannot be applied. */ public abstract void applyTo(List target); /** * Converts this delta into its Unix diff style string representation. * * @param s * a {@link StringBuffer StringBuffer} to which the string * representation will be appended. */ public void toString(StringBuffer s) { original.rangeString(s); s.append("x"); revised.rangeString(s); s.append(Diff.NL); original.toString(s, "> ", "\n"); s.append("---"); s.append(Diff.NL); revised.toString(s, "< ", "\n"); } /** * Converts this delta into its RCS style string representation. * * @param s * a {@link StringBuffer StringBuffer} to which the string * representation will be appended. * @param EOL * the string to use as line separator. */ public abstract void toRCSString(StringBuffer s, String EOL); /** * Converts this delta into its RCS style string representation. * * @param EOL * the string to use as line separator. */ public String toRCSString(String EOL) { StringBuffer s = new StringBuffer(); toRCSString(s, EOL); return s.toString(); } /** * Accessor method to return the chunk representing the original sequence of * items * * @return the original sequence */ public Chunk getOriginal() { return original; } /** * Accessor method to return the chunk representing the updated sequence of * items. * * @return the updated sequence */ public Chunk getRevised() { return revised; } /** * Accepts a visitor. * <p> * See the Visitor pattern in "Design Patterns" by the GOF4. * * @param visitor * The visitor. */ public abstract void accept(RevisionVisitor visitor); }