java 文本差异对比高亮工具（基于谷歌文本比对工具）

直接上代码：

package *.*.*.util;import com.zdww.cd.mrs.biz.internal.constants.DiffMatchPatch;
import com.zdww.cd.mrs.biz.internal.constants.DiffMatchPatch.Diff;
import org.junit.Test;import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;/*** 文本差异高亮算法** @Author : cron* @Date: 2020-01-15*/
@SuppressWarnings("all")
public class EventEditHistoryHighLightUtil {/*** 传入2个字符串进行相比高亮显示* eg:* 原数据一:王五张三* 原数据二:张三李四* <span style='color:red'>王五</span>张三* 张三<span style='color:red'>李四</span>*/public static String[] getHighLightDifferentOld(String a, String b) {String[] temp = getDiff(a, b);String[] result = {getHighLight(a, temp[0]), getHighLight(b, temp[1])};return result;}private static String getHighLight(String source, String temp) {StringBuffer sb = new StringBuffer();char[] sourceChars = source.toCharArray();char[] tempChars = temp.toCharArray();boolean flag = false;for (int i = 0; i < sourceChars.length; i++) {if (tempChars[i] != ' ') {if (i == 0) {sb.append("<span style='color:red'>").append(sourceChars[i]);} else if (flag) {sb.append(sourceChars[i]);} else {sb.append("<span style='color:red'>").append(sourceChars[i]);}flag = true;if (i == sourceChars.length - 1) {sb.append("</span>");}} else if (flag) {sb.append("</span>").append(sourceChars[i]);flag = false;} else {sb.append(sourceChars[i]);}}return sb.toString();}public static String[] getDiff(String a, String b) {String[] result = null;//选取长度较小的字符串用来穷举子串if (a.length() < b.length()) {result = getDiff(a, b, 0, a.length());} else {result = getDiff(b, a, 0, b.length());result = new String[]{result[1], result[0]};}return result;}/*** 将a的指定部分与b进行比较生成比对结果*/private static String[] getDiff(String a, String b, int start, int end) {String[] result = new String[]{a, b};int len = result[0].length();while (len > 0) {for (int i = start; i < end - len + 1; i++) {String sub = result[0].substring(i, i + len);int idx = -1;if ((idx = result[1].indexOf(sub)) != -1) {result[0] = setEmpty(result[0], i, i + len);result[1] = setEmpty(result[1], idx, idx + len);if (i > 0) {//递归获取空白区域左边差异result = getDiff(result[0], result[1], 0, i);}if (i + len < end) {//递归获取空白区域右边差异result = getDiff(result[0], result[1], i + len, end);}len = 0;//退出while循环break;}}len = len / 2;}return result;}/*** 将字符串s指定的区域设置成空格*/public static String setEmpty(String s, int start, int end) {char[] array = s.toCharArray();for (int i = start; i < end; i++) {array[i] = ' ';}return new String(array);}@Testpublic void getHighLightDifferentOld() {String a = "测试测试测试仅关注界面和功能，数据准确性在暂不测试";String b = "提交留言数据仅关注界面和功能，数据准确性在暂不测试";String[] anb = getHighLightDifferent(a, b);anb[1] = anb[1].replaceAll("red", "green");System.out.println(Arrays.toString(anb));}//--------------new -------------------------public static String[] getHighLightDifferent(String altbe, String altaf) {//字符串1  altbe  字符串2  altafList<Integer> beList = rememberSpacing(altbe);List<Integer> afList = rememberSpacing(altaf);altbe = altbe.replace(" ", "");altaf = altaf.replace(" ", "");LinkedList<Diff> t = new DiffMatchPatch().diff_main(altbe, altaf);StringBuffer s1 = new StringBuffer();StringBuffer s2 = new StringBuffer();Integer indexBe = 0;Integer indexAf = 0;for (Diff diff : t) {StringBuffer diffTextBe = new StringBuffer(diff.text);StringBuffer diffTextAf = new StringBuffer(diff.text);if ("EQUAL".equalsIgnoreCase(diff.operation.toString())) {addSpacing(beList, indexBe, diffTextBe);addSpacing(afList, indexAf, diffTextAf);s1.append(diffTextBe);s2.append(diffTextAf);indexBe += diffTextBe.length();indexAf += diffTextAf.length();}indexBe = appendString2("DELETE", diff, s1, s2, beList, indexBe);indexAf = appendString2("INSERT", diff, s2, s1, afList, indexAf);}String[] result = new String[2];result[0] = s1.toString();result[1] = s2.toString();return result;}//    public static void appendString(String type, Diff diff, StringBuffer sbOne, StringBuffer sbTwo) {
//        if (type.equals(diff.operation.toString())) {
//            if (" ".equals(diff.text)) {
//                sbOne.append(" ");
//                sbTwo.append(" ");
//            } else {
//                sbOne.append("<em class='f-required'>").append(diff.text).append("</em>");
//            }
//        }
//    }private static List<Integer> rememberSpacing(String str) {List<Integer> list = new ArrayList<>();for (int i = 0; i < str.length(); i++) {if (' ' == str.charAt(i)) {list.add(i);}}return list;}public static void addSpacing(List<Integer> list, Integer index, StringBuffer str) {for (Integer o : list) {if (o >= index && o < index + str.length()) {str.insert(o - index, ' ');}}}public static Integer appendString2(String type, Diff diff, StringBuffer sbOne,StringBuffer sbTwo, List<Integer> list, Integer i) {Integer result = i;if (type.equals(diff.operation.toString())) {StringBuffer sb = new StringBuffer(diff.text);for (Integer o : list) {if (o >= i && o < i + sb.length()) {sb.insert(o - i, ' ');}}sbOne.append("<span style='color:red'>").append(sb).append("</span>");result = i + sb.length();}return result;}@Testpublic void getHighLightDifferent() {String altbe = "提交留言数据仅关   注界面和  功能，数据准确性在暂不测试";String altaf = "提交留言数据仅关注   界面和功能，数据准确性在暂不测试提交     留言数据仅关注界面和功能，数据准确性在暂不测试";String[] highLightDifferentNew = getHighLightDifferent(altbe, altaf);System.out.println(Arrays.toString(highLightDifferentNew));}}

其中的old 方法是原来的方法存在一个小bug，所以这里推荐getHighLightDifferent这个方法；

谷歌比对工具类：

package com.zdww.cd.mrs.biz.internal.constants;
/** Diff Match and Patch** Copyright 2006 Google Inc.* http://code.google.com/p/google-diff-match-patch/** Licensed 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.*/import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/** Functions for diff, match and patch.* Computes the difference between two texts to create a patch.* Applies the patch onto another text, allowing for errors.** @author fraser@google.com (Neil Fraser)*//*** Class containing the diff, match and patch methods.* Also contains the behaviour settings.*/
@SuppressWarnings("all")
public class DiffMatchPatch {// Defaults.// Set these on your diff_match_patch instance to override the defaults./*** Number of seconds to map a diff before giving up (0 for infinity).*/public float Diff_Timeout = 1.0f;/*** Cost of an empty edit operation in terms of edit characters.*/public short Diff_EditCost = 4;/*** The size beyond which the double-ended diff activates.* Double-ending is twice as fast, but less accurate.*/public short Diff_DualThreshold = 32;/*** At what point is no match declared (0.0 = perfection, 1.0 = very loose).*/public float Match_Threshold = 0.5f;/*** How far to search for a match (0 = exact location, 1000+ = broad match).* A match this many characters away from the expected location will add* 1.0 to the score (0.0 is a perfect match).*/public int Match_Distance = 1000;/*** When deleting a large block of text (over ~64 characters), how close does* the contents have to match the expected contents. (0.0 = perfection,* 1.0 = very loose).  Note that Match_Threshold controls how closely the* end points of a delete need to match.*/public float Patch_DeleteThreshold = 0.5f;/*** Chunk size for context length.*/public short Patch_Margin = 4;/*** The number of bits in an int.*/private int Match_MaxBits = 32;/*** Internal class for returning results from diff_linesToChars().* Other less paranoid languages just use a three-element array.*/protected static class LinesToCharsResult {protected String chars1;protected String chars2;protected List<String> lineArray;protected LinesToCharsResult(String chars1, String chars2,List<String> lineArray) {this.chars1 = chars1;this.chars2 = chars2;this.lineArray = lineArray;}}//  DIFF FUNCTIONS/*** The data structure representing a diff is a Linked list of Diff objects:* {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"),*  Diff(Operation.EQUAL, " world.")}* which means: delete "Hello", add "Goodbye" and keep " world."*/public enum Operation {DELETE, INSERT, EQUAL}/*** Find the differences between two texts.* Run a faster slightly less optimal diff* This method allows the 'checklines' of diff_main() to be optional.* Most of the time checklines is wanted, so default to true.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @return Linked List of Diff objects.*/public LinkedList<Diff> diff_main(String text1, String text2) {return diff_main(text1, text2, true);}/*** Find the differences between two texts.  Simplifies the problem by* stripping any common prefix or suffix off the texts before diffing.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @param checklines Speedup flag.  If false, then don't run a*     line-level diff first to identify the changed areas.*     If true, then run a faster slightly less optimal diff* @return Linked List of Diff objects.*/public LinkedList<Diff> diff_main(String text1, String text2, boolean checklines) {// Check for equality (speedup)LinkedList<Diff> diffs;if (text1.equals(text2)) {diffs = new LinkedList<Diff>();diffs.add(new Diff(Operation.EQUAL, text1));return diffs;}// Trim off common prefix (speedup)int commonlength = diff_commonPrefix(text1, text2);String commonprefix = text1.substring(0, commonlength);text1 = text1.substring(commonlength);text2 = text2.substring(commonlength);// Trim off common suffix (speedup)commonlength = diff_commonSuffix(text1, text2);String commonsuffix = text1.substring(text1.length() - commonlength);text1 = text1.substring(0, text1.length() - commonlength);text2 = text2.substring(0, text2.length() - commonlength);// Compute the diff on the middle blockdiffs = diff_compute(text1, text2, checklines);// Restore the prefix and suffixif (commonprefix.length() != 0) {diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));}if (commonsuffix.length() != 0) {diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));}diff_cleanupMerge(diffs);return diffs;}/*** Find the differences between two texts.  Assumes that the texts do not* have any common prefix or suffix.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @param checklines Speedup flag.  If false, then don't run a*     line-level diff first to identify the changed areas.*     If true, then run a faster slightly less optimal diff* @return Linked List of Diff objects.*/protected LinkedList<Diff> diff_compute(String text1, String text2,boolean checklines) {LinkedList<Diff> diffs = new LinkedList<Diff>();if (text1.length() == 0) {// Just add some text (speedup)diffs.add(new Diff(Operation.INSERT, text2));return diffs;}if (text2.length() == 0) {// Just delete some text (speedup)diffs.add(new Diff(Operation.DELETE, text1));return diffs;}String longtext = text1.length() > text2.length() ? text1 : text2;String shorttext = text1.length() > text2.length() ? text2 : text1;int i = longtext.indexOf(shorttext);if (i != -1) {// Shorter text is inside the longer text (speedup)Operation op = (text1.length() > text2.length()) ?Operation.DELETE : Operation.INSERT;diffs.add(new Diff(op, longtext.substring(0, i)));diffs.add(new Diff(Operation.EQUAL, shorttext));diffs.add(new Diff(op, longtext.substring(i + shorttext.length())));return diffs;}longtext = shorttext = null;  // Garbage collect.// Check to see if the problem can be split in two.String[] hm = diff_halfMatch(text1, text2);if (hm != null) {// A half-match was found, sort out the return data.String text1_a = hm[0];String text1_b = hm[1];String text2_a = hm[2];String text2_b = hm[3];String mid_common = hm[4];// Send both pairs off for separate processing.LinkedList<Diff> diffs_a = diff_main(text1_a, text2_a, checklines);LinkedList<Diff> diffs_b = diff_main(text1_b, text2_b, checklines);// Merge the results.diffs = diffs_a;diffs.add(new Diff(Operation.EQUAL, mid_common));diffs.addAll(diffs_b);return diffs;}// Perform a real diff.if (checklines && (text1.length() < 100 || text2.length() < 100)) {checklines = false;  // Too trivial for the overhead.}List<String> linearray = null;if (checklines) {// Scan the text on a line-by-line basis first.LinesToCharsResult b = diff_linesToChars(text1, text2);text1 = b.chars1;text2 = b.chars2;linearray = b.lineArray;}diffs = diff_map(text1, text2);if (diffs == null) {// No acceptable result.diffs = new LinkedList<Diff>();diffs.add(new Diff(Operation.DELETE, text1));diffs.add(new Diff(Operation.INSERT, text2));}if (checklines) {// Convert the diff back to original text.diff_charsToLines(diffs, linearray);// Eliminate freak matches (e.g. blank lines)diff_cleanupSemantic(diffs);// Rediff any replacement blocks, this time character-by-character.// Add a dummy entry at the end.diffs.add(new Diff(Operation.EQUAL, ""));int count_delete = 0;int count_insert = 0;String text_delete = "";String text_insert = "";ListIterator<Diff> pointer = diffs.listIterator();Diff thisDiff = pointer.next();while (thisDiff != null) {switch (thisDiff.operation) {case INSERT:count_insert++;text_insert += thisDiff.text;break;case DELETE:count_delete++;text_delete += thisDiff.text;break;case EQUAL:// Upon reaching an equality, check for prior redundancies.if (count_delete >= 1 && count_insert >= 1) {// Delete the offending records and add the merged ones.pointer.previous();for (int j = 0; j < count_delete + count_insert; j++) {pointer.previous();pointer.remove();}for (Diff newDiff : diff_main(text_delete, text_insert, false)) {pointer.add(newDiff);}}count_insert = 0;count_delete = 0;text_delete = "";text_insert = "";break;}thisDiff = pointer.hasNext() ? pointer.next() : null;}diffs.removeLast();  // Remove the dummy entry at the end.}return diffs;}/*** Split two texts into a list of strings.  Reduce the texts to a string of* hashes where each Unicode character represents one line.* @param text1 First string.* @param text2 Second string.* @return An object containing the encoded text1, the encoded text2 and*     the List of unique strings.  The zeroth element of the List of*     unique strings is intentionally blank.*/protected LinesToCharsResult diff_linesToChars(String text1, String text2) {List<String> lineArray = new ArrayList<String>();Map<String, Integer> lineHash = new HashMap<String, Integer>();// e.g. linearray[4] == "Hello\n"// e.g. linehash.get("Hello\n") == 4// "\x00" is a valid character, but various debuggers don't like it.// So we'll insert a junk entry to avoid generating a null character.lineArray.add("");String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash);String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash);return new LinesToCharsResult(chars1, chars2, lineArray);}/*** Split a text into a list of strings.  Reduce the texts to a string of* hashes where each Unicode character represents one line.* @param text String to encode.* @param lineArray List of unique strings.* @param lineHash Map of strings to indices.* @return Encoded string.*/private String diff_linesToCharsMunge(String text, List<String> lineArray,Map<String, Integer> lineHash) {int lineStart = 0;int lineEnd = -1;String line;StringBuilder chars = new StringBuilder();// Walk the text, pulling out a substring for each line.// text.split('\n') would would temporarily double our memory footprint.// Modifying text would create many large strings to garbage collect.while (lineEnd < text.length() - 1) {lineEnd = text.indexOf('\n', lineStart);if (lineEnd == -1) {lineEnd = text.length() - 1;}line = text.substring(lineStart, lineEnd + 1);lineStart = lineEnd + 1;if (lineHash.containsKey(line)) {chars.append(String.valueOf((char) (int) lineHash.get(line)));} else {lineArray.add(line);lineHash.put(line, lineArray.size() - 1);chars.append(String.valueOf((char) (lineArray.size() - 1)));}}return chars.toString();}/*** Rehydrate the text in a diff from a string of line hashes to real lines of* text.* @param diffs LinkedList of Diff objects.* @param lineArray List of unique strings.*/protected void diff_charsToLines(LinkedList<Diff> diffs,List<String> lineArray) {StringBuilder text;for (Diff diff : diffs) {text = new StringBuilder();for (int y = 0; y < diff.text.length(); y++) {text.append(lineArray.get(diff.text.charAt(y)));}diff.text = text.toString();}}/*** Explore the intersection points between the two texts.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @return LinkedList of Diff objects or null if no diff available.*/protected LinkedList<Diff> diff_map(String text1, String text2) {long ms_end = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);// Cache the text lengths to prevent multiple calls.int text1_length = text1.length();int text2_length = text2.length();int max_d = text1_length + text2_length - 1;boolean doubleEnd = Diff_DualThreshold * 2 < max_d;List<Set<Long>> v_map1 = new ArrayList<Set<Long>>();List<Set<Long>> v_map2 = new ArrayList<Set<Long>>();Map<Integer, Integer> v1 = new HashMap<Integer, Integer>();Map<Integer, Integer> v2 = new HashMap<Integer, Integer>();v1.put(1, 0);v2.put(1, 0);int x, y;Long footstep = 0L;  // Used to track overlapping paths.Map<Long, Integer> footsteps = new HashMap<Long, Integer>();boolean done = false;// If the total number of characters is odd, then the front path will// collide with the reverse path.boolean front = ((text1_length + text2_length) % 2 == 1);for (int d = 0; d < max_d; d++) {// Bail out if timeout reached.if (Diff_Timeout > 0 && System.currentTimeMillis() > ms_end) {return null;}// Walk the front path one step.v_map1.add(new HashSet<Long>());  // Adds at index 'd'.for (int k = -d; k <= d; k += 2) {if (k == -d || k != d && v1.get(k - 1) < v1.get(k + 1)) {x = v1.get(k + 1);} else {x = v1.get(k - 1) + 1;}y = x - k;if (doubleEnd) {footstep = diff_footprint(x, y);if (front && (footsteps.containsKey(footstep))) {done = true;}if (!front) {footsteps.put(footstep, d);}}while (!done && x < text1_length && y < text2_length&& text1.charAt(x) == text2.charAt(y)) {x++;y++;if (doubleEnd) {footstep = diff_footprint(x, y);if (front && (footsteps.containsKey(footstep))) {done = true;}if (!front) {footsteps.put(footstep, d);}}}v1.put(k, x);v_map1.get(d).add(diff_footprint(x, y));if (x == text1_length && y == text2_length) {// Reached the end in single-path mode.return diff_path1(v_map1, text1, text2);} else if (done) {// Front path ran over reverse path.v_map2 = v_map2.subList(0, footsteps.get(footstep) + 1);LinkedList<Diff> a = diff_path1(v_map1, text1.substring(0, x),text2.substring(0, y));a.addAll(diff_path2(v_map2, text1.substring(x), text2.substring(y)));return a;}}if (doubleEnd) {// Walk the reverse path one step.v_map2.add(new HashSet<Long>());  // Adds at index 'd'.for (int k = -d; k <= d; k += 2) {if (k == -d || k != d && v2.get(k - 1) < v2.get(k + 1)) {x = v2.get(k + 1);} else {x = v2.get(k - 1) + 1;}y = x - k;footstep = diff_footprint(text1_length - x, text2_length - y);if (!front && (footsteps.containsKey(footstep))) {done = true;}if (front) {footsteps.put(footstep, d);}while (!done && x < text1_length && y < text2_length&& text1.charAt(text1_length - x - 1)== text2.charAt(text2_length - y - 1)) {x++;y++;footstep = diff_footprint(text1_length - x, text2_length - y);if (!front && (footsteps.containsKey(footstep))) {done = true;}if (front) {footsteps.put(footstep, d);}}v2.put(k, x);v_map2.get(d).add(diff_footprint(x, y));if (done) {// Reverse path ran over front path.v_map1 = v_map1.subList(0, footsteps.get(footstep) + 1);LinkedList<Diff> a= diff_path1(v_map1, text1.substring(0, text1_length - x),text2.substring(0, text2_length - y));a.addAll(diff_path2(v_map2, text1.substring(text1_length - x),text2.substring(text2_length - y)));return a;}}}}// Number of diffs equals number of characters, no commonality at all.return null;}/*** Work from the middle back to the start to determine the path.* @param v_map List of path sets.* @param text1 Old string fragment to be diffed.* @param text2 New string fragment to be diffed.* @return LinkedList of Diff objects.*/protected LinkedList<Diff> diff_path1(List<Set<Long>> v_map,String text1, String text2) {LinkedList<Diff> path = new LinkedList<Diff>();int x = text1.length();int y = text2.length();Operation last_op = null;for (int d = v_map.size() - 2; d >= 0; d--) {while (true) {if (v_map.get(d).contains(diff_footprint(x - 1, y))) {x--;if (last_op == Operation.DELETE) {path.getFirst().text = text1.charAt(x) + path.getFirst().text;} else {path.addFirst(new Diff(Operation.DELETE,text1.substring(x, x + 1)));}last_op = Operation.DELETE;break;} else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {y--;if (last_op == Operation.INSERT) {path.getFirst().text = text2.charAt(y) + path.getFirst().text;} else {path.addFirst(new Diff(Operation.INSERT,text2.substring(y, y + 1)));}last_op = Operation.INSERT;break;} else {x--;y--;assert (text1.charAt(x) == text2.charAt(y)): "No diagonal.  Can't happen. (diff_path1)";if (last_op == Operation.EQUAL) {path.getFirst().text = text1.charAt(x) + path.getFirst().text;} else {path.addFirst(new Diff(Operation.EQUAL, text1.substring(x, x + 1)));}last_op = Operation.EQUAL;}}}return path;}/*** Work from the middle back to the end to determine the path.* @param v_map List of path sets.* @param text1 Old string fragment to be diffed.* @param text2 New string fragment to be diffed.* @return LinkedList of Diff objects.*/protected LinkedList<Diff> diff_path2(List<Set<Long>> v_map,String text1, String text2) {LinkedList<Diff> path = new LinkedList<Diff>();int x = text1.length();int y = text2.length();Operation last_op = null;for (int d = v_map.size() - 2; d >= 0; d--) {while (true) {if (v_map.get(d).contains(diff_footprint(x - 1, y))) {x--;if (last_op == Operation.DELETE) {path.getLast().text += text1.charAt(text1.length() - x - 1);} else {path.addLast(new Diff(Operation.DELETE,text1.substring(text1.length() - x - 1, text1.length() - x)));}last_op = Operation.DELETE;break;} else if (v_map.get(d).contains(diff_footprint(x, y - 1))) {y--;if (last_op == Operation.INSERT) {path.getLast().text += text2.charAt(text2.length() - y - 1);} else {path.addLast(new Diff(Operation.INSERT,text2.substring(text2.length() - y - 1, text2.length() - y)));}last_op = Operation.INSERT;break;} else {x--;y--;assert (text1.charAt(text1.length() - x - 1)== text2.charAt(text2.length() - y - 1)): "No diagonal.  Can't happen. (diff_path2)";if (last_op == Operation.EQUAL) {path.getLast().text += text1.charAt(text1.length() - x - 1);} else {path.addLast(new Diff(Operation.EQUAL,text1.substring(text1.length() - x - 1, text1.length() - x)));}last_op = Operation.EQUAL;}}}return path;}/*** Compute a good hash of two integers.* @param x First int.* @param y Second int.* @return A long made up of both ints.*/protected long diff_footprint(int x, int y) {// The maximum size for a long is 9,223,372,036,854,775,807// The maximum size for an int is 2,147,483,647// Two ints fit nicely in one long.long result = x;result = result << 32;result += y;return result;}/*** Determine the common prefix of two strings* @param text1 First string.* @param text2 Second string.* @return The number of characters common to the start of each string.*/public int diff_commonPrefix(String text1, String text2) {// Performance analysis: http://neil.fraser.name/news/2007/10/09/int n = Math.min(text1.length(), text2.length());for (int i = 0; i < n; i++) {if (text1.charAt(i) != text2.charAt(i)) {return i;}}return n;}/*** Determine the common suffix of two strings* @param text1 First string.* @param text2 Second string.* @return The number of characters common to the end of each string.*/public int diff_commonSuffix(String text1, String text2) {// Performance analysis: http://neil.fraser.name/news/2007/10/09/int text1_length = text1.length();int text2_length = text2.length();int n = Math.min(text1_length, text2_length);for (int i = 1; i <= n; i++) {if (text1.charAt(text1_length - i) != text2.charAt(text2_length - i)) {return i - 1;}}return n;}/*** Do the two texts share a substring which is at least half the length of* the longer text?* @param text1 First string.* @param text2 Second string.* @return Five element String array, containing the prefix of text1, the*     suffix of text1, the prefix of text2, the suffix of text2 and the*     common middle.  Or null if there was no match.*/protected String[] diff_halfMatch(String text1, String text2) {String longtext = text1.length() > text2.length() ? text1 : text2;String shorttext = text1.length() > text2.length() ? text2 : text1;if (longtext.length() < 10 || shorttext.length() < 1) {return null;  // Pointless.}// First check if the second quarter is the seed for a half-match.String[] hm1 = diff_halfMatchI(longtext, shorttext,(longtext.length() + 3) / 4);// Check again based on the third quarter.String[] hm2 = diff_halfMatchI(longtext, shorttext,(longtext.length() + 1) / 2);String[] hm;if (hm1 == null && hm2 == null) {return null;} else if (hm2 == null) {hm = hm1;} else if (hm1 == null) {hm = hm2;} else {// Both matched.  Select the longest.hm = hm1[4].length() > hm2[4].length() ? hm1 : hm2;}// A half-match was found, sort out the return data.if (text1.length() > text2.length()) {return hm;//return new String[]{hm[0], hm[1], hm[2], hm[3], hm[4]};} else {return new String[]{hm[2], hm[3], hm[0], hm[1], hm[4]};}}/*** Does a substring of shorttext exist within longtext such that the* substring is at least half the length of longtext?* @param longtext Longer string.* @param shorttext Shorter string.* @param i Start index of quarter length substring within longtext.* @return Five element String array, containing the prefix of longtext, the*     suffix of longtext, the prefix of shorttext, the suffix of shorttext*     and the common middle.  Or null if there was no match.*/private String[] diff_halfMatchI(String longtext, String shorttext, int i) {// Start with a 1/4 length substring at position i as a seed.String seed = longtext.substring(i, i + longtext.length() / 4);int j = -1;String best_common = "";String best_longtext_a = "", best_longtext_b = "";String best_shorttext_a = "", best_shorttext_b = "";while ((j = shorttext.indexOf(seed, j + 1)) != -1) {int prefixLength = diff_commonPrefix(longtext.substring(i),  shorttext.substring(j));int suffixLength = diff_commonSuffix(longtext.substring(0, i),shorttext.substring(0, j));if (best_common.length() < suffixLength + prefixLength) {best_common = shorttext.substring(j - suffixLength, j)+ shorttext.substring(j, j + prefixLength);best_longtext_a = longtext.substring(0, i - suffixLength);best_longtext_b = longtext.substring(i + prefixLength);best_shorttext_a = shorttext.substring(0, j - suffixLength);best_shorttext_b = shorttext.substring(j + prefixLength);}}if (best_common.length() >= longtext.length() / 2) {return new String[]{best_longtext_a, best_longtext_b,best_shorttext_a, best_shorttext_b, best_common};} else {return null;}}/*** Reduce the number of edits by eliminating semantically trivial equalities.* @param diffs LinkedList of Diff objects.*/public void diff_cleanupSemantic(LinkedList<Diff> diffs) {if (diffs.isEmpty()) {return;}boolean changes = false;Stack<Diff> equalities = new Stack<Diff>();  // Stack of qualities.String lastequality = null; // Always equal to equalities.lastElement().textListIterator<Diff> pointer = diffs.listIterator();// Number of characters that changed prior to the equality.int length_changes1 = 0;// Number of characters that changed after the equality.int length_changes2 = 0;Diff thisDiff = pointer.next();while (thisDiff != null) {if (thisDiff.operation == Operation.EQUAL) {// equality foundequalities.push(thisDiff);length_changes1 = length_changes2;length_changes2 = 0;lastequality = thisDiff.text;} else {// an insertion or deletionlength_changes2 += thisDiff.text.length();if (lastequality != null && (lastequality.length() <= length_changes1)&& (lastequality.length() <= length_changes2)) {//System.out.println("Splitting: '" + lastequality + "'");// Walk back to offending equality.while (thisDiff != equalities.lastElement()) {thisDiff = pointer.previous();}pointer.next();// Replace equality with a delete.pointer.set(new Diff(Operation.DELETE, lastequality));// Insert a corresponding an insert.pointer.add(new Diff(Operation.INSERT, lastequality));equalities.pop();  // Throw away the equality we just deleted.if (!equalities.empty()) {// Throw away the previous equality (it needs to be reevaluated).equalities.pop();}if (equalities.empty()) {// There are no previous equalities, walk back to the start.while (pointer.hasPrevious()) {pointer.previous();}} else {// There is a safe equality we can fall back to.thisDiff = equalities.lastElement();while (thisDiff != pointer.previous()) {// Intentionally empty loop.}}length_changes1 = 0;  // Reset the counters.length_changes2 = 0;lastequality = null;changes = true;}}thisDiff = pointer.hasNext() ? pointer.next() : null;}if (changes) {diff_cleanupMerge(diffs);}diff_cleanupSemanticLossless(diffs);}/*** Look for single edits surrounded on both sides by equalities* which can be shifted sideways to align the edit to a word boundary.* e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.* @param diffs LinkedList of Diff objects.*/public void diff_cleanupSemanticLossless(LinkedList<Diff> diffs) {String equality1, edit, equality2;String commonString;int commonOffset;int score, bestScore;String bestEquality1, bestEdit, bestEquality2;// Create a new iterator at the start.ListIterator<Diff> pointer = diffs.listIterator();Diff prevDiff = pointer.hasNext() ? pointer.next() : null;Diff thisDiff = pointer.hasNext() ? pointer.next() : null;Diff nextDiff = pointer.hasNext() ? pointer.next() : null;// Intentionally ignore the first and last element (don't need checking).while (nextDiff != null) {if (prevDiff.operation == Operation.EQUAL &&nextDiff.operation == Operation.EQUAL) {// This is a single edit surrounded by equalities.equality1 = prevDiff.text;edit = thisDiff.text;equality2 = nextDiff.text;// First, shift the edit as far left as possible.commonOffset = diff_commonSuffix(equality1, edit);if (commonOffset != 0) {commonString = edit.substring(edit.length() - commonOffset);equality1 = equality1.substring(0, equality1.length() - commonOffset);edit = commonString + edit.substring(0, edit.length() - commonOffset);equality2 = commonString + equality2;}// Second, step character by character right, looking for the best fit.bestEquality1 = equality1;bestEdit = edit;bestEquality2 = equality2;bestScore = diff_cleanupSemanticScore(equality1, edit)+ diff_cleanupSemanticScore(edit, equality2);while (edit.length() != 0 && equality2.length() != 0&& edit.charAt(0) == equality2.charAt(0)) {equality1 += edit.charAt(0);edit = edit.substring(1) + equality2.charAt(0);equality2 = equality2.substring(1);score = diff_cleanupSemanticScore(equality1, edit)+ diff_cleanupSemanticScore(edit, equality2);// The >= encourages trailing rather than leading whitespace on edits.if (score >= bestScore) {bestScore = score;bestEquality1 = equality1;bestEdit = edit;bestEquality2 = equality2;}}if (!prevDiff.text.equals(bestEquality1)) {// We have an improvement, save it back to the diff.if (bestEquality1.length() != 0) {prevDiff.text = bestEquality1;} else {pointer.previous(); // Walk past nextDiff.pointer.previous(); // Walk past thisDiff.pointer.previous(); // Walk past prevDiff.pointer.remove(); // Delete prevDiff.pointer.next(); // Walk past thisDiff.pointer.next(); // Walk past nextDiff.}thisDiff.text = bestEdit;if (bestEquality2.length() != 0) {nextDiff.text = bestEquality2;} else {pointer.remove(); // Delete nextDiff.nextDiff = thisDiff;thisDiff = prevDiff;}}}prevDiff = thisDiff;thisDiff = nextDiff;nextDiff = pointer.hasNext() ? pointer.next() : null;}}/*** Given two strings, compute a score representing whether the internal* boundary falls on logical boundaries.* Scores range from 5 (best) to 0 (worst).* @param one First string.* @param two Second string.* @return The score.*/private int diff_cleanupSemanticScore(String one, String two) {if (one.length() == 0 || two.length() == 0) {// Edges are the best.return 5;}// Each port of this function behaves slightly differently due to// subtle differences in each language's definition of things like// 'whitespace'.  Since this function's purpose is largely cosmetic,// the choice has been made to use each language's native features// rather than force total conformity.int score = 0;// One point for non-alphanumeric.if (!Character.isLetterOrDigit(one.charAt(one.length() - 1))|| !Character.isLetterOrDigit(two.charAt(0))) {score++;// Two points for whitespace.if (Character.isWhitespace(one.charAt(one.length() - 1))|| Character.isWhitespace(two.charAt(0))) {score++;// Three points for line breaks.if (Character.getType(one.charAt(one.length() - 1)) == Character.CONTROL|| Character.getType(two.charAt(0)) == Character.CONTROL) {score++;// Four points for blank lines.if (BLANKLINEEND.matcher(one).find()|| BLANKLINESTART.matcher(two).find()) {score++;}}}}return score;}private Pattern BLANKLINEEND= Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);private Pattern BLANKLINESTART= Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);/*** Reduce the number of edits by eliminating operationally trivial equalities.* @param diffs LinkedList of Diff objects.*/public void diff_cleanupEfficiency(LinkedList<Diff> diffs) {if (diffs.isEmpty()) {return;}boolean changes = false;Stack<Diff> equalities = new Stack<Diff>();  // Stack of equalities.String lastequality = null; // Always equal to equalities.lastElement().textListIterator<Diff> pointer = diffs.listIterator();// Is there an insertion operation before the last equality.boolean pre_ins = false;// Is there a deletion operation before the last equality.boolean pre_del = false;// Is there an insertion operation after the last equality.boolean post_ins = false;// Is there a deletion operation after the last equality.boolean post_del = false;Diff thisDiff = pointer.next();Diff safeDiff = thisDiff;  // The last Diff that is known to be unsplitable.while (thisDiff != null) {if (thisDiff.operation == Operation.EQUAL) {// equality foundif (thisDiff.text.length() < Diff_EditCost && (post_ins || post_del)) {// Candidate found.equalities.push(thisDiff);pre_ins = post_ins;pre_del = post_del;lastequality = thisDiff.text;} else {// Not a candidate, and can never become one.equalities.clear();lastequality = null;safeDiff = thisDiff;}post_ins = post_del = false;} else {// an insertion or deletionif (thisDiff.operation == Operation.DELETE) {post_del = true;} else {post_ins = true;}/** Five types to be split:* <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>* <ins>A</ins>X<ins>C</ins><del>D</del>* <ins>A</ins><del>B</del>X<ins>C</ins>* <ins>A</del>X<ins>C</ins><del>D</del>* <ins>A</ins><del>B</del>X<del>C</del>*/if (lastequality != null&& ((pre_ins && pre_del && post_ins && post_del)|| ((lastequality.length() < Diff_EditCost / 2)&& ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0)+ (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3))) {//System.out.println("Splitting: '" + lastequality + "'");// Walk back to offending equality.while (thisDiff != equalities.lastElement()) {thisDiff = pointer.previous();}pointer.next();// Replace equality with a delete.pointer.set(new Diff(Operation.DELETE, lastequality));// Insert a corresponding an insert.pointer.add(thisDiff = new Diff(Operation.INSERT, lastequality));equalities.pop();  // Throw away the equality we just deleted.lastequality = null;if (pre_ins && pre_del) {// No changes made which could affect previous entry, keep going.post_ins = post_del = true;equalities.clear();safeDiff = thisDiff;} else {if (!equalities.empty()) {// Throw away the previous equality (it needs to be reevaluated).equalities.pop();}if (equalities.empty()) {// There are no previous questionable equalities,// walk back to the last known safe diff.thisDiff = safeDiff;} else {// There is an equality we can fall back to.thisDiff = equalities.lastElement();}while (thisDiff != pointer.previous()) {// Intentionally empty loop.}post_ins = post_del = false;}changes = true;}}thisDiff = pointer.hasNext() ? pointer.next() : null;}if (changes) {diff_cleanupMerge(diffs);}}/*** Reorder and merge like edit sections.  Merge equalities.* Any edit section can move as long as it doesn't cross an equality.* @param diffs LinkedList of Diff objects.*/public void diff_cleanupMerge(LinkedList<Diff> diffs) {diffs.add(new Diff(Operation.EQUAL, ""));  // Add a dummy entry at the end.ListIterator<Diff> pointer = diffs.listIterator();int count_delete = 0;int count_insert = 0;String text_delete = "";String text_insert = "";Diff thisDiff = pointer.next();Diff prevEqual = null;int commonlength;while (thisDiff != null) {switch (thisDiff.operation) {case INSERT:count_insert++;text_insert += thisDiff.text;prevEqual = null;break;case DELETE:count_delete++;text_delete += thisDiff.text;prevEqual = null;break;case EQUAL:if (count_delete != 0 || count_insert != 0) {// Delete the offending records.pointer.previous();  // Reverse direction.while (count_delete-- > 0) {pointer.previous();pointer.remove();}while (count_insert-- > 0) {pointer.previous();pointer.remove();}if (count_delete != 0 && count_insert != 0) {// Factor out any common prefixies.commonlength = diff_commonPrefix(text_insert, text_delete);if (commonlength != 0) {if (pointer.hasPrevious()) {thisDiff = pointer.previous();assert thisDiff.operation == Operation.EQUAL: "Previous diff should have been an equality.";thisDiff.text += text_insert.substring(0, commonlength);pointer.next();} else {pointer.add(new Diff(Operation.EQUAL,text_insert.substring(0, commonlength)));}text_insert = text_insert.substring(commonlength);text_delete = text_delete.substring(commonlength);}// Factor out any common suffixies.commonlength = diff_commonSuffix(text_insert, text_delete);if (commonlength != 0) {thisDiff = pointer.next();thisDiff.text = text_insert.substring(text_insert.length()- commonlength) + thisDiff.text;text_insert = text_insert.substring(0, text_insert.length()- commonlength);text_delete = text_delete.substring(0, text_delete.length()- commonlength);pointer.previous();}}// Insert the merged records.if (text_delete.length() != 0) {pointer.add(new Diff(Operation.DELETE, text_delete));}if (text_insert.length() != 0) {pointer.add(new Diff(Operation.INSERT, text_insert));}// Step forward to the equality.thisDiff = pointer.hasNext() ? pointer.next() : null;} else if (prevEqual != null) {// Merge this equality with the previous one.prevEqual.text += thisDiff.text;pointer.remove();thisDiff = pointer.previous();pointer.next();  // Forward direction}count_insert = 0;count_delete = 0;text_delete = "";text_insert = "";prevEqual = thisDiff;break;}thisDiff = pointer.hasNext() ? pointer.next() : null;}// System.out.println(diff);if (diffs.getLast().text.length() == 0) {diffs.removeLast();  // Remove the dummy entry at the end.}/** Second pass: look for single edits surrounded on both sides by equalities* which can be shifted sideways to eliminate an equality.* e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC*/boolean changes = false;// Create a new iterator at the start.// (As opposed to walking the current one back.)pointer = diffs.listIterator();Diff prevDiff = pointer.hasNext() ? pointer.next() : null;thisDiff = pointer.hasNext() ? pointer.next() : null;Diff nextDiff = pointer.hasNext() ? pointer.next() : null;// Intentionally ignore the first and last element (don't need checking).while (nextDiff != null) {if (prevDiff.operation == Operation.EQUAL &&nextDiff.operation == Operation.EQUAL) {// This is a single edit surrounded by equalities.if (thisDiff.text.endsWith(prevDiff.text)) {// Shift the edit over the previous equality.thisDiff.text = prevDiff.text + thisDiff.text.substring(0, thisDiff.text.length() - prevDiff.text.length());nextDiff.text = prevDiff.text + nextDiff.text;pointer.previous(); // Walk past nextDiff.pointer.previous(); // Walk past thisDiff.pointer.previous(); // Walk past prevDiff.pointer.remove(); // Delete prevDiff.pointer.next(); // Walk past thisDiff.thisDiff = pointer.next(); // Walk past nextDiff.nextDiff = pointer.hasNext() ? pointer.next() : null;changes = true;} else if (thisDiff.text.startsWith(nextDiff.text)) {// Shift the edit over the next equality.prevDiff.text += nextDiff.text;thisDiff.text = thisDiff.text.substring(nextDiff.text.length())+ nextDiff.text;pointer.remove(); // Delete nextDiff.nextDiff = pointer.hasNext() ? pointer.next() : null;changes = true;}}prevDiff = thisDiff;thisDiff = nextDiff;nextDiff = pointer.hasNext() ? pointer.next() : null;}// If shifts were made, the diff needs reordering and another shift sweep.if (changes) {diff_cleanupMerge(diffs);}}/*** loc is a location in text1, compute and return the equivalent location in* text2.* e.g. "The cat" vs "The big cat", 1->1, 5->8* @param diffs LinkedList of Diff objects.* @param loc Location within text1.* @return Location within text2.*/public int diff_xIndex(LinkedList<Diff> diffs, int loc) {int chars1 = 0;int chars2 = 0;int last_chars1 = 0;int last_chars2 = 0;Diff lastDiff = null;for (Diff aDiff : diffs) {if (aDiff.operation != Operation.INSERT) {// Equality or deletion.chars1 += aDiff.text.length();}if (aDiff.operation != Operation.DELETE) {// Equality or insertion.chars2 += aDiff.text.length();}if (chars1 > loc) {// Overshot the location.lastDiff = aDiff;break;}last_chars1 = chars1;last_chars2 = chars2;}if (lastDiff != null && lastDiff.operation == Operation.DELETE) {// The location was deleted.return last_chars2;}// Add the remaining character length.return last_chars2 + (loc - last_chars1);}/*** Convert a Diff list into a pretty HTML report.* @param diffs LinkedList of Diff objects.* @return HTML representation.*/public String diff_prettyHtml(LinkedList<Diff> diffs) {StringBuilder html = new StringBuilder();int i = 0;for (Diff aDiff : diffs) {String text = aDiff.text.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;").replace("\n", "&para;<BR>");switch (aDiff.operation) {case INSERT:html.append("<INS STYLE=\"background:#E6FFE6;\" TITLE=\"i=").append(i).append("\">").append(text).append("</INS>");break;case DELETE:html.append("<DEL STYLE=\"background:#FFE6E6;\" TITLE=\"i=").append(i).append("\">").append(text).append("</DEL>");break;case EQUAL:html.append("<SPAN TITLE=\"i=").append(i).append("\">").append(text).append("</SPAN>");break;}if (aDiff.operation != Operation.DELETE) {i += aDiff.text.length();}}return html.toString();}/*** Compute and return the source text (all equalities and deletions).* @param diffs LinkedList of Diff objects.* @return Source text.*/public String diff_text1(LinkedList<Diff> diffs) {StringBuilder text = new StringBuilder();for (Diff aDiff : diffs) {if (aDiff.operation != Operation.INSERT) {text.append(aDiff.text);}}return text.toString();}/*** Compute and return the destination text (all equalities and insertions).* @param diffs LinkedList of Diff objects.* @return Destination text.*/public String diff_text2(LinkedList<Diff> diffs) {StringBuilder text = new StringBuilder();for (Diff aDiff : diffs) {if (aDiff.operation != Operation.DELETE) {text.append(aDiff.text);}}return text.toString();}/*** Compute the Levenshtein distance; the number of inserted, deleted or* substituted characters.* @param diffs LinkedList of Diff objects.* @return Number of changes.*/public int diff_levenshtein(LinkedList<Diff> diffs) {int levenshtein = 0;int insertions = 0;int deletions = 0;for (Diff aDiff : diffs) {switch (aDiff.operation) {case INSERT:insertions += aDiff.text.length();break;case DELETE:deletions += aDiff.text.length();break;case EQUAL:// A deletion and an insertion is one substitution.levenshtein += Math.max(insertions, deletions);insertions = 0;deletions = 0;break;}}levenshtein += Math.max(insertions, deletions);return levenshtein;}/*** Crush the diff into an encoded string which describes the operations* required to transform text1 into text2.* E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.* Operations are tab-separated.  Inserted text is escaped using %xx notation.* @param diffs Array of diff tuples.* @return Delta text.*/public String diff_toDelta(LinkedList<Diff> diffs) {StringBuilder text = new StringBuilder();for (Diff aDiff : diffs) {switch (aDiff.operation) {case INSERT:try {text.append("+").append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' ')).append("\t");} catch (UnsupportedEncodingException e) {// Not likely on modern system.throw new Error("This system does not support UTF-8.", e);}break;case DELETE:text.append("-").append(aDiff.text.length()).append("\t");break;case EQUAL:text.append("=").append(aDiff.text.length()).append("\t");break;}}String delta = text.toString();if (delta.length() != 0) {// Strip off trailing tab character.delta = delta.substring(0, delta.length() - 1);delta = unescapeForEncodeUriCompatability(delta);}return delta;}/*** Given the original text1, and an encoded string which describes the* operations required to transform text1 into text2, compute the full diff.* @param text1 Source string for the diff.* @param delta Delta text.* @return Array of diff tuples or null if invalid.* @throws IllegalArgumentException If invalid input.*/public LinkedList<Diff> diff_fromDelta(String text1, String delta)throws IllegalArgumentException {LinkedList<Diff> diffs = new LinkedList<Diff>();int pointer = 0;  // Cursor in text1String[] tokens = delta.split("\t");for (String token : tokens) {if (token.length() == 0) {// Blank tokens are ok (from a trailing \t).continue;}// Each token begins with a one character parameter which specifies the// operation of this token (delete, insert, equality).String param = token.substring(1);switch (token.charAt(0)) {case '+':// decode would change all "+" to " "param = param.replace("+", "%2B");try {param = URLDecoder.decode(param, "UTF-8");} catch (UnsupportedEncodingException e) {// Not likely on modern system.throw new Error("This system does not support UTF-8.", e);} catch (IllegalArgumentException e) {// Malformed URI sequence.throw new IllegalArgumentException("Illegal escape in diff_fromDelta: " + param, e);}diffs.add(new Diff(Operation.INSERT, param));break;case '-':// Fall through.case '=':int n;try {n = Integer.parseInt(param);} catch (NumberFormatException e) {throw new IllegalArgumentException("Invalid number in diff_fromDelta: " + param, e);}if (n < 0) {throw new IllegalArgumentException("Negative number in diff_fromDelta: " + param);}String text;try {text = text1.substring(pointer, pointer += n);} catch (StringIndexOutOfBoundsException e) {throw new IllegalArgumentException("Delta length (" + pointer+ ") larger than source text length (" + text1.length()+ ").", e);}if (token.charAt(0) == '=') {diffs.add(new Diff(Operation.EQUAL, text));} else {diffs.add(new Diff(Operation.DELETE, text));}break;default:// Anything else is an error.throw new IllegalArgumentException("Invalid diff operation in diff_fromDelta: " + token.charAt(0));}}if (pointer != text1.length()) {throw new IllegalArgumentException("Delta length (" + pointer+ ") smaller than source text length (" + text1.length() + ").");}return diffs;}//  MATCH FUNCTIONS/*** Locate the best instance of 'pattern' in 'text' near 'loc'.* Returns -1 if no match found.* @param text The text to search.* @param pattern The pattern to search for.* @param loc The location to search around.* @return Best match index or -1.*/public int match_main(String text, String pattern, int loc) {loc = Math.max(0, Math.min(loc, text.length()));if (text.equals(pattern)) {// Shortcut (potentially not guaranteed by the algorithm)return 0;} else if (text.length() == 0) {// Nothing to match.return -1;} else if (loc + pattern.length() <= text.length()&& text.substring(loc, loc + pattern.length()).equals(pattern)) {// Perfect match at the perfect spot!  (Includes case of null pattern)return loc;} else {// Do a fuzzy compare.return match_bitap(text, pattern, loc);}}/*** Locate the best instance of 'pattern' in 'text' near 'loc' using the* Bitap algorithm.  Returns -1 if no match found.* @param text The text to search.* @param pattern The pattern to search for.* @param loc The location to search around.* @return Best match index or -1.*/protected int match_bitap(String text, String pattern, int loc) {assert (Match_MaxBits == 0 || pattern.length() <= Match_MaxBits): "Pattern too long for this application.";// Initialise the alphabet.Map<Character, Integer> s = match_alphabet(pattern);// Highest score beyond which we give up.double score_threshold = Match_Threshold;// Is there a nearby exact match? (speedup)int best_loc = text.indexOf(pattern, loc);if (best_loc != -1) {score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),score_threshold);// What about in the other direction? (speedup)best_loc = text.lastIndexOf(pattern, loc + pattern.length());if (best_loc != -1) {score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),score_threshold);}}// Initialise the bit arrays.int matchmask = 1 << (pattern.length() - 1);best_loc = -1;int bin_min, bin_mid;int bin_max = pattern.length() + text.length();// Empty initialization added to appease Java compiler.int[] last_rd = new int[0];for (int d = 0; d < pattern.length(); d++) {// Scan for the best match; each iteration allows for one more error.// Run a binary search to determine how far from 'loc' we can stray at// this error level.bin_min = 0;bin_mid = bin_max;while (bin_min < bin_mid) {if (match_bitapScore(d, loc + bin_mid, loc, pattern)<= score_threshold) {bin_min = bin_mid;} else {bin_max = bin_mid;}bin_mid = (bin_max - bin_min) / 2 + bin_min;}// Use the result from this iteration as the maximum for the next.bin_max = bin_mid;int start = Math.max(1, loc - bin_mid + 1);int finish = Math.min(loc + bin_mid, text.length()) + pattern.length();int[] rd = new int[finish + 2];rd[finish + 1] = (1 << d) - 1;for (int j = finish; j >= start; j--) {int charMatch;if (text.length() <= j - 1 || !s.containsKey(text.charAt(j - 1))) {// Out of range.charMatch = 0;} else {charMatch = s.get(text.charAt(j - 1));}if (d == 0) {// First pass: exact match.rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;} else {// Subsequent passes: fuzzy match.rd[j] = ((rd[j + 1] << 1) | 1) & charMatch| (((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1];}if ((rd[j] & matchmask) != 0) {double score = match_bitapScore(d, j - 1, loc, pattern);// This match will almost certainly be better than any existing// match.  But check anyway.if (score <= score_threshold) {// Told you so.score_threshold = score;best_loc = j - 1;if (best_loc > loc) {// When passing loc, don't exceed our current distance from loc.start = Math.max(1, 2 * loc - best_loc);} else {// Already passed loc, downhill from here on in.break;}}}}if (match_bitapScore(d + 1, loc, loc, pattern) > score_threshold) {// No hope for a (better) match at greater error levels.break;}last_rd = rd;}return best_loc;}/*** Compute and return the score for a match with e errors and x location.* @param e Number of errors in match.* @param x Location of match.* @param loc Expected location of match.* @param pattern Pattern being sought.* @return Overall score for match (0.0 = good, 1.0 = bad).*/private double match_bitapScore(int e, int x, int loc, String pattern) {float accuracy = (float) e / pattern.length();int proximity = Math.abs(loc - x);if (Match_Distance == 0) {// Dodge divide by zero error.return proximity == 0 ? accuracy : 1.0;}return accuracy + (proximity / (float) Match_Distance);}/*** Initialise the alphabet for the Bitap algorithm.* @param pattern The text to encode.* @return Hash of character locations.*/protected Map<Character, Integer> match_alphabet(String pattern) {Map<Character, Integer> s = new HashMap<Character, Integer>();char[] char_pattern = pattern.toCharArray();for (char c : char_pattern) {s.put(c, 0);}int i = 0;for (char c : char_pattern) {s.put(c, s.get(c) | (1 << (pattern.length() - i - 1)));i++;}return s;}//  PATCH FUNCTIONS/*** Increase the context until it is unique,* but don't let the pattern expand beyond Match_MaxBits.* @param patch The patch to grow.* @param text Source text.*/protected void patch_addContext(Patch patch, String text) {if (text.length() == 0) {return;}String pattern = text.substring(patch.start2, patch.start2 + patch.length1);int padding = 0;// Look for the first and last matches of pattern in text.  If two different// matches are found, increase the pattern length.while (text.indexOf(pattern) != text.lastIndexOf(pattern)&& pattern.length() < Match_MaxBits - Patch_Margin - Patch_Margin) {padding += Patch_Margin;pattern = text.substring(Math.max(0, patch.start2 - padding),Math.min(text.length(), patch.start2 + patch.length1 + padding));}// Add one chunk for good luck.padding += Patch_Margin;// Add the prefix.String prefix = text.substring(Math.max(0, patch.start2 - padding),patch.start2);if (prefix.length() != 0) {patch.diffs.addFirst(new Diff(Operation.EQUAL, prefix));}// Add the suffix.String suffix = text.substring(patch.start2 + patch.length1,Math.min(text.length(), patch.start2 + patch.length1 + padding));if (suffix.length() != 0) {patch.diffs.addLast(new Diff(Operation.EQUAL, suffix));}// Roll back the start points.patch.start1 -= prefix.length();patch.start2 -= prefix.length();// Extend the lengths.patch.length1 += prefix.length() + suffix.length();patch.length2 += prefix.length() + suffix.length();}/*** Compute a list of patches to turn text1 into text2.* A set of diffs will be computed.* @param text1 Old text.* @param text2 New text.* @return LinkedList of Patch objects.*/public LinkedList<Patch> patch_make(String text1, String text2) {// No diffs provided, compute our own.LinkedList<Diff> diffs = diff_main(text1, text2, true);if (diffs.size() > 2) {diff_cleanupSemantic(diffs);diff_cleanupEfficiency(diffs);}return patch_make(text1, diffs);}/*** Compute a list of patches to turn text1 into text2.* text1 will be derived from the provided diffs.* @param diffs Array of diff tuples for text1 to text2.* @return LinkedList of Patch objects.*/public LinkedList<Patch> patch_make(LinkedList<Diff> diffs) {// No origin string provided, compute our own.String text1 = diff_text1(diffs);return patch_make(text1, diffs);}/*** Compute a list of patches to turn text1 into text2.* text2 is ignored, diffs are the delta between text1 and text2.* @param text1 Old text* @param text2 Ignored.* @param diffs Array of diff tuples for text1 to text2.* @return LinkedList of Patch objects.* @deprecated Prefer patch_make(String text1, LinkedList<Diff> diffs).*/public LinkedList<Patch> patch_make(String text1, String text2,LinkedList<Diff> diffs) {return patch_make(text1, diffs);}/*** Compute a list of patches to turn text1 into text2.* text2 is not provided, diffs are the delta between text1 and text2.* @param text1 Old text.* @param diffs Array of diff tuples for text1 to text2.* @return LinkedList of Patch objects.*/public LinkedList<Patch> patch_make(String text1, LinkedList<Diff> diffs) {LinkedList<Patch> patches = new LinkedList<Patch>();if (diffs.isEmpty()) {return patches;  // Get rid of the null case.}Patch patch = new Patch();int char_count1 = 0;  // Number of characters into the text1 string.int char_count2 = 0;  // Number of characters into the text2 string.// Start with text1 (prepatch_text) and apply the diffs until we arrive at// text2 (postpatch_text). We recreate the patches one by one to determine// context info.String prepatch_text = text1;String postpatch_text = text1;for (Diff aDiff : diffs) {if (patch.diffs.isEmpty() && aDiff.operation != Operation.EQUAL) {// A new patch starts here.patch.start1 = char_count1;patch.start2 = char_count2;}switch (aDiff.operation) {case INSERT:patch.diffs.add(aDiff);patch.length2 += aDiff.text.length();postpatch_text = postpatch_text.substring(0, char_count2)+ aDiff.text + postpatch_text.substring(char_count2);break;case DELETE:patch.length1 += aDiff.text.length();patch.diffs.add(aDiff);postpatch_text = postpatch_text.substring(0, char_count2)+ postpatch_text.substring(char_count2 + aDiff.text.length());break;case EQUAL:if (aDiff.text.length() <= 2 * Patch_Margin&& !patch.diffs.isEmpty() && aDiff != diffs.getLast()) {// Small equality inside a patch.patch.diffs.add(aDiff);patch.length1 += aDiff.text.length();patch.length2 += aDiff.text.length();}if (aDiff.text.length() >= 2 * Patch_Margin) {// Time for a new patch.if (!patch.diffs.isEmpty()) {patch_addContext(patch, prepatch_text);patches.add(patch);patch = new Patch();// Unlike Unidiff, our patch lists have a rolling context.// http://code.google.com/p/google-diff-match-patch/wiki/Unidiff// Update prepatch text & pos to reflect the application of the// just completed patch.prepatch_text = postpatch_text;char_count1 = char_count2;}}break;}// Update the current character count.if (aDiff.operation != Operation.INSERT) {char_count1 += aDiff.text.length();}if (aDiff.operation != Operation.DELETE) {char_count2 += aDiff.text.length();}}// Pick up the leftover patch if not empty.if (!patch.diffs.isEmpty()) {patch_addContext(patch, prepatch_text);patches.add(patch);}return patches;}/*** Given an array of patches, return another array that is identical.* @param patches Array of patch objects.* @return Array of patch objects.*/public LinkedList<Patch> patch_deepCopy(LinkedList<Patch> patches) {LinkedList<Patch> patchesCopy = new LinkedList<Patch>();for (Patch aPatch : patches) {Patch patchCopy = new Patch();for (Diff aDiff : aPatch.diffs) {Diff diffCopy = new Diff(aDiff.operation, aDiff.text);patchCopy.diffs.add(diffCopy);}patchCopy.start1 = aPatch.start1;patchCopy.start2 = aPatch.start2;patchCopy.length1 = aPatch.length1;patchCopy.length2 = aPatch.length2;patchesCopy.add(patchCopy);}return patchesCopy;}/*** Merge a set of patches onto the text.  Return a patched text, as well* as an array of true/false values indicating which patches were applied.* @param patches Array of patch objects* @param text Old text.* @return Two element Object array, containing the new text and an array of*      boolean values.*/public Object[] patch_apply(LinkedList<Patch> patches, String text) {if (patches.isEmpty()) {return new Object[]{text, new boolean[0]};}// Deep copy the patches so that no changes are made to originals.patches = patch_deepCopy(patches);String nullPadding = patch_addPadding(patches);text = nullPadding + text + nullPadding;patch_splitMax(patches);int x = 0;// delta keeps track of the offset between the expected and actual location// of the previous patch.  If there are patches expected at positions 10 and// 20, but the first patch was found at 12, delta is 2 and the second patch// has an effective expected position of 22.int delta = 0;boolean[] results = new boolean[patches.size()];for (Patch aPatch : patches) {int expected_loc = aPatch.start2 + delta;String text1 = diff_text1(aPatch.diffs);int start_loc;int end_loc = -1;if (text1.length() > this.Match_MaxBits) {// patch_splitMax will only provide an oversized pattern in the case of// a monster delete.start_loc = match_main(text,text1.substring(0, this.Match_MaxBits), expected_loc);if (start_loc != -1) {end_loc = match_main(text,text1.substring(text1.length() - this.Match_MaxBits),expected_loc + text1.length() - this.Match_MaxBits);if (end_loc == -1 || start_loc >= end_loc) {// Can't find valid trailing context.  Drop this patch.start_loc = -1;}}} else {start_loc = match_main(text, text1, expected_loc);}if (start_loc == -1) {// No match found.  :(results[x] = false;// Subtract the delta for this failed patch from subsequent patches.delta -= aPatch.length2 - aPatch.length1;} else {// Found a match.  :)results[x] = true;delta = start_loc - expected_loc;String text2;if (end_loc == -1) {text2 = text.substring(start_loc,Math.min(start_loc + text1.length(), text.length()));} else {text2 = text.substring(start_loc,Math.min(end_loc + this.Match_MaxBits, text.length()));}if (text1.equals(text2)) {// Perfect match, just shove the replacement text in.text = text.substring(0, start_loc) + diff_text2(aPatch.diffs)+ text.substring(start_loc + text1.length());} else {// Imperfect match.  Run a diff to get a framework of equivalent// indices.LinkedList<Diff> diffs = diff_main(text1, text2, false);if (text1.length() > this.Match_MaxBits&& diff_levenshtein(diffs) / (float) text1.length()> this.Patch_DeleteThreshold) {// The end points match, but the content is unacceptably bad.results[x] = false;} else {diff_cleanupSemanticLossless(diffs);int index1 = 0;for (Diff aDiff : aPatch.diffs) {if (aDiff.operation != Operation.EQUAL) {int index2 = diff_xIndex(diffs, index1);if (aDiff.operation == Operation.INSERT) {// Insertiontext = text.substring(0, start_loc + index2) + aDiff.text+ text.substring(start_loc + index2);} else if (aDiff.operation == Operation.DELETE) {// Deletiontext = text.substring(0, start_loc + index2)+ text.substring(start_loc + diff_xIndex(diffs,index1 + aDiff.text.length()));}}if (aDiff.operation != Operation.DELETE) {index1 += aDiff.text.length();}}}}}x++;}// Strip the padding off.text = text.substring(nullPadding.length(), text.length()- nullPadding.length());return new Object[]{text, results};}/*** Add some padding on text start and end so that edges can match something.* Intended to be called only from within patch_apply.* @param patches Array of patch objects.* @return The padding string added to each side.*/public String patch_addPadding(LinkedList<Patch> patches) {int paddingLength = this.Patch_Margin;String nullPadding = "";for (int x = 1; x <= paddingLength; x++) {nullPadding += String.valueOf((char) x);}// Bump all the patches forward.for (Patch aPatch : patches) {aPatch.start1 += paddingLength;aPatch.start2 += paddingLength;}// Add some padding on start of first diff.Patch patch = patches.getFirst();LinkedList<Diff> diffs = patch.diffs;if (diffs.isEmpty() || diffs.getFirst().operation != Operation.EQUAL) {// Add nullPadding equality.diffs.addFirst(new Diff(Operation.EQUAL, nullPadding));patch.start1 -= paddingLength;  // Should be 0.patch.start2 -= paddingLength;  // Should be 0.patch.length1 += paddingLength;patch.length2 += paddingLength;} else if (paddingLength > diffs.getFirst().text.length()) {// Grow first equality.Diff firstDiff = diffs.getFirst();int extraLength = paddingLength - firstDiff.text.length();firstDiff.text = nullPadding.substring(firstDiff.text.length())+ firstDiff.text;patch.start1 -= extraLength;patch.start2 -= extraLength;patch.length1 += extraLength;patch.length2 += extraLength;}// Add some padding on end of last diff.patch = patches.getLast();diffs = patch.diffs;if (diffs.isEmpty() || diffs.getLast().operation != Operation.EQUAL) {// Add nullPadding equality.diffs.addLast(new Diff(Operation.EQUAL, nullPadding));patch.length1 += paddingLength;patch.length2 += paddingLength;} else if (paddingLength > diffs.getLast().text.length()) {// Grow last equality.Diff lastDiff = diffs.getLast();int extraLength = paddingLength - lastDiff.text.length();lastDiff.text += nullPadding.substring(0, extraLength);patch.length1 += extraLength;patch.length2 += extraLength;}return nullPadding;}/*** Look through the patches and break up any which are longer than the* maximum limit of the match algorithm.* @param patches LinkedList of Patch objects.*/public void patch_splitMax(LinkedList<Patch> patches) {int patch_size;String precontext, postcontext;Patch patch;int start1, start2;boolean empty;Operation diff_type;String diff_text;ListIterator<Patch> pointer = patches.listIterator();Patch bigpatch = pointer.hasNext() ? pointer.next() : null;while (bigpatch != null) {if (bigpatch.length1 <= Match_MaxBits) {bigpatch = pointer.hasNext() ? pointer.next() : null;continue;}// Remove the big old patch.pointer.remove();patch_size = Match_MaxBits;start1 = bigpatch.start1;start2 = bigpatch.start2;precontext = "";while (!bigpatch.diffs.isEmpty()) {// Create one of several smaller patches.patch = new Patch();empty = true;patch.start1 = start1 - precontext.length();patch.start2 = start2 - precontext.length();if (precontext.length() != 0) {patch.length1 = patch.length2 = precontext.length();patch.diffs.add(new Diff(Operation.EQUAL, precontext));}while (!bigpatch.diffs.isEmpty()&& patch.length1 < patch_size - Patch_Margin) {diff_type = bigpatch.diffs.getFirst().operation;diff_text = bigpatch.diffs.getFirst().text;if (diff_type == Operation.INSERT) {// Insertions are harmless.patch.length2 += diff_text.length();start2 += diff_text.length();patch.diffs.addLast(bigpatch.diffs.removeFirst());empty = false;} else if (diff_type == Operation.DELETE && patch.diffs.size() == 1&& patch.diffs.getFirst().operation == Operation.EQUAL&& diff_text.length() > 2 * patch_size) {// This is a large deletion.  Let it pass in one chunk.patch.length1 += diff_text.length();start1 += diff_text.length();empty = false;patch.diffs.add(new Diff(diff_type, diff_text));bigpatch.diffs.removeFirst();} else {// Deletion or equality.  Only take as much as we can stomach.diff_text = diff_text.substring(0, Math.min(diff_text.length(),patch_size - patch.length1 - Patch_Margin));patch.length1 += diff_text.length();start1 += diff_text.length();if (diff_type == Operation.EQUAL) {patch.length2 += diff_text.length();start2 += diff_text.length();} else {empty = false;}patch.diffs.add(new Diff(diff_type, diff_text));if (diff_text.equals(bigpatch.diffs.getFirst().text)) {bigpatch.diffs.removeFirst();} else {bigpatch.diffs.getFirst().text = bigpatch.diffs.getFirst().text.substring(diff_text.length());}}}// Compute the head context for the next patch.precontext = diff_text2(patch.diffs);precontext = precontext.substring(Math.max(0, precontext.length()- Patch_Margin));// Append the end context for this patch.if (diff_text1(bigpatch.diffs).length() > Patch_Margin) {postcontext = diff_text1(bigpatch.diffs).substring(0, Patch_Margin);} else {postcontext = diff_text1(bigpatch.diffs);}if (postcontext.length() != 0) {patch.length1 += postcontext.length();patch.length2 += postcontext.length();if (!patch.diffs.isEmpty()&& patch.diffs.getLast().operation == Operation.EQUAL) {patch.diffs.getLast().text += postcontext;} else {patch.diffs.add(new Diff(Operation.EQUAL, postcontext));}}if (!empty) {pointer.add(patch);}}bigpatch = pointer.hasNext() ? pointer.next() : null;}}/*** Take a list of patches and return a textual representation.* @param patches List of Patch objects.* @return Text representation of patches.*/public String patch_toText(List<Patch> patches) {StringBuilder text = new StringBuilder();for (Patch aPatch : patches) {text.append(aPatch);}return text.toString();}/*** Parse a textual representation of patches and return a List of Patch* objects.* @param textline Text representation of patches.* @return List of Patch objects.* @throws IllegalArgumentException If invalid input.*/public List<Patch> patch_fromText(String textline)throws IllegalArgumentException {List<Patch> patches = new LinkedList<Patch>();if (textline.length() == 0) {return patches;}List<String> textList = Arrays.asList(textline.split("\n"));LinkedList<String> text = new LinkedList<String>(textList);Patch patch;Pattern patchHeader= Pattern.compile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$");Matcher m;char sign;String line;while (!text.isEmpty()) {m = patchHeader.matcher(text.getFirst());if (!m.matches()) {throw new IllegalArgumentException("Invalid patch string: " + text.getFirst());}patch = new Patch();patches.add(patch);patch.start1 = Integer.parseInt(m.group(1));if (m.group(2).length() == 0) {patch.start1--;patch.length1 = 1;} else if ("0".equals(m.group(2))) {patch.length1 = 0;} else {patch.start1--;patch.length1 = Integer.parseInt(m.group(2));}patch.start2 = Integer.parseInt(m.group(3));if (m.group(4).length() == 0) {patch.start2--;patch.length2 = 1;} else if ("0".equals(m.group(4))) {patch.length2 = 0;} else {patch.start2--;patch.length2 = Integer.parseInt(m.group(4));}text.removeFirst();while (!text.isEmpty()) {try {sign = text.getFirst().charAt(0);} catch (IndexOutOfBoundsException e) {// Blank line?  Whatever.text.removeFirst();continue;}line = text.getFirst().substring(1);line = line.replace("+", "%2B");  // decode would change all "+" to " "try {line = URLDecoder.decode(line, "UTF-8");} catch (UnsupportedEncodingException e) {// Not likely on modern system.throw new Error("This system does not support UTF-8.", e);} catch (IllegalArgumentException e) {// Malformed URI sequence.throw new IllegalArgumentException("Illegal escape in patch_fromText: " + line, e);}if (sign == '-') {// Deletion.patch.diffs.add(new Diff(Operation.DELETE, line));} else if (sign == '+') {// Insertion.patch.diffs.add(new Diff(Operation.INSERT, line));} else if (sign == ' ') {// Minor equality.patch.diffs.add(new Diff(Operation.EQUAL, line));} else if (sign == '@') {// Start of next patch.break;} else {// WTF?throw new IllegalArgumentException("Invalid patch mode '" + sign + "' in: " + line);}text.removeFirst();}}return patches;}/*** Class representing one diff operation.*/public static class Diff {/*** One of: INSERT, DELETE or EQUAL.*/public Operation operation;/*** The text associated with this diff operation.*/public String text;/*** Constructor.  Initializes the diff with the provided values.* @param operation One of INSERT, DELETE or EQUAL.* @param text The text being applied.*/public Diff(Operation operation, String text) {// Construct a diff with the specified operation and text.this.operation = operation;this.text = text;}/*** Display a human-readable version of this Diff.* @return text version.*/@Overridepublic String toString() {String prettyText = this.text.replace('\n', '\u00b6');return "Diff(" + this.operation + ",\"" + prettyText + "\")";}/*** Is this Diff equivalent to another Diff?* @param d Another Diff to compare against.* @return true or false.*/@Overridepublic boolean equals(Object d) {try {return (((Diff) d).operation == this.operation)&& (((Diff) d).text.equals(this.text));} catch (ClassCastException e) {return false;}}}/*** Class representing one patch operation.*/public static class Patch {public LinkedList<Diff> diffs;public int start1;public int start2;public int length1;public int length2;/*** Constructor.  Initializes with an empty list of diffs.*/public Patch() {this.diffs = new LinkedList<Diff>();}/*** Emmulate GNU diff's format.* Header: @@ -382,8 +481,9 @@* Indicies are printed as 1-based, not 0-based.* @return The GNU diff string.*/@Overridepublic String toString() {String coords1, coords2;if (this.length1 == 0) {coords1 = this.start1 + ",0";} else if (this.length1 == 1) {coords1 = Integer.toString(this.start1 + 1);} else {coords1 = (this.start1 + 1) + "," + this.length1;}if (this.length2 == 0) {coords2 = this.start2 + ",0";} else if (this.length2 == 1) {coords2 = Integer.toString(this.start2 + 1);} else {coords2 = (this.start2 + 1) + "," + this.length2;}StringBuilder text = new StringBuilder();text.append("@@ -").append(coords1).append(" +").append(coords2).append(" @@\n");// Escape the body of the patch with %xx notation.for (Diff aDiff : this.diffs) {switch (aDiff.operation) {case INSERT:text.append('+');break;case DELETE:text.append('-');break;case EQUAL:text.append(' ');break;}try {text.append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' ')).append("\n");} catch (UnsupportedEncodingException e) {// Not likely on modern system.throw new Error("This system does not support UTF-8.", e);}}return unescapeForEncodeUriCompatability(text.toString());}}/*** Unescape selected chars for compatability with JavaScript's encodeURI.* In speed critical applications this could be dropped since the* receiving application will certainly decode these fine.* Note that this function is case-sensitive.  Thus "%3f" would not be* unescaped.  But this is ok because it is only called with the output of* URLEncoder.encode which returns uppercase hex.** Example: "%3F" -> "?", "%24" -> "$", etc.** @param str The string to escape.* @return The escaped string.*/private static String unescapeForEncodeUriCompatability(String str) {return str.replace("%21", "!").replace("%7E", "~").replace("%27", "'").replace("%28", "(").replace("%29", ")").replace("%3B", ";").replace("%2F", "/").replace("%3F", "?").replace("%3A", ":").replace("%40", "@").replace("%26", "&").replace("%3D", "=").replace("%2B", "+").replace("%24", "$").replace("%2C", ",").replace("%23", "#");}public  String getHtmlDiffString(String text1,String text2){return diff_prettyHtml(diff_main(text1,text2));}public static void main(String[] args){DiffMatchPatch dmp = new DiffMatchPatch();String text1 = "我方在“福市财政资金补助项目管理系统”的项目实施过程，为保证该项目的工程进度、质量，符合数办项目的实施管理规范与要求。";String text2 = "我方在“福州市财政资金补助项目管理系统”的项目实施过程，为保证该haha项目的工程进度、质量，符合目的实施管理规范与要求。";System.out.println(dmp.getHtmlDiffString(text1,text2));}
}

效果：

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