文本对比

需求：直观的展示运行结果返回的文本内容对比。

有现成的轮子，google-diff-match-patch。github地址。

/** Diff Match and Patch* Copyright 2018 The diff-match-patch Authors.* https://github.com/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.*/package name.fraser.neil.plaintext;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 [email protected] (Neil Fraser)*//*** Class containing the diff, match and patch methods.* Also contains the behaviour settings.*/
public class diff_match_patch {// 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;/*** 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 do* the contents have to be 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 short 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 lineArray;protected LinesToCharsResult(String chars1, String chars2,List 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_main(String text1, String text2) {return diff_main(text1, text2, true);}/*** Find the differences between two texts.* @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_main(String text1, String text2,boolean checklines) {// Set a deadline by which time the diff must be complete.long deadline;if (Diff_Timeout <= 0) {deadline = Long.MAX_VALUE;} else {deadline = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);}return diff_main(text1, text2, checklines, deadline);}/*** 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.* @param deadline Time when the diff should be complete by.  Used*     internally for recursive calls.  Users should set DiffTimeout instead.* @return Linked List of Diff objects.*/private LinkedList diff_main(String text1, String text2,boolean checklines, long deadline) {// Check for null inputs.if (text1 == null || text2 == null) {throw new IllegalArgumentException("Null inputs. (diff_main)");}// Check for equality (speedup).LinkedList diffs;if (text1.equals(text2)) {diffs = new LinkedList();if (text1.length() != 0) {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 block.diffs = diff_compute(text1, text2, checklines, deadline);// Restore the prefix and suffix.if (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.* @param deadline Time when the diff should be complete by.* @return Linked List of Diff objects.*/private LinkedList diff_compute(String text1, String text2,boolean checklines, long deadline) {LinkedList diffs = new LinkedList();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;}if (shorttext.length() == 1) {// Single character string.// After the previous speedup, the character can't be an equality.diffs.add(new Diff(Operation.DELETE, text1));diffs.add(new Diff(Operation.INSERT, text2));return diffs;}// 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 diffs_a = diff_main(text1_a, text2_a,checklines, deadline);LinkedList diffs_b = diff_main(text1_b, text2_b,checklines, deadline);// Merge the results.diffs = diffs_a;diffs.add(new Diff(Operation.EQUAL, mid_common));diffs.addAll(diffs_b);return diffs;}if (checklines && text1.length() > 100 && text2.length() > 100) {return diff_lineMode(text1, text2, deadline);}return diff_bisect(text1, text2, deadline);}/*** Do a quick line-level diff on both strings, then rediff the parts for* greater accuracy.* This speedup can produce non-minimal diffs.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @param deadline Time when the diff should be complete by.* @return Linked List of Diff objects.*/private LinkedList diff_lineMode(String text1, String text2,long deadline) {// Scan the text on a line-by-line basis first.LinesToCharsResult a = diff_linesToChars(text1, text2);text1 = a.chars1;text2 = a.chars2;List linearray = a.lineArray;LinkedList diffs = diff_main(text1, text2, false, deadline);// 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 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 subDiff : diff_main(text_delete, text_insert, false,deadline)) {pointer.add(subDiff);}}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;}/*** Find the 'middle snake' of a diff, split the problem in two* and return the recursively constructed diff.* See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @param deadline Time at which to bail if not yet complete.* @return LinkedList of Diff objects.*/protected LinkedList diff_bisect(String text1, String text2,long deadline) {// 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) / 2;int v_offset = max_d;int v_length = 2 * max_d;int[] v1 = new int[v_length];int[] v2 = new int[v_length];for (int x = 0; x < v_length; x++) {v1[x] = -1;v2[x] = -1;}v1[v_offset + 1] = 0;v2[v_offset + 1] = 0;int delta = text1_length - text2_length;// If the total number of characters is odd, then the front path will// collide with the reverse path.boolean front = (delta % 2 != 0);// Offsets for start and end of k loop.// Prevents mapping of space beyond the grid.int k1start = 0;int k1end = 0;int k2start = 0;int k2end = 0;for (int d = 0; d < max_d; d++) {// Bail out if deadline is reached.if (System.currentTimeMillis() > deadline) {break;}// Walk the front path one step.for (int k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {int k1_offset = v_offset + k1;int x1;if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {x1 = v1[k1_offset + 1];} else {x1 = v1[k1_offset - 1] + 1;}int y1 = x1 - k1;while (x1 < text1_length && y1 < text2_length&& text1.charAt(x1) == text2.charAt(y1)) {x1++;y1++;}v1[k1_offset] = x1;if (x1 > text1_length) {// Ran off the right of the graph.k1end += 2;} else if (y1 > text2_length) {// Ran off the bottom of the graph.k1start += 2;} else if (front) {int k2_offset = v_offset + delta - k1;if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {// Mirror x2 onto top-left coordinate system.int x2 = text1_length - v2[k2_offset];if (x1 >= x2) {// Overlap detected.return diff_bisectSplit(text1, text2, x1, y1, deadline);}}}}// Walk the reverse path one step.for (int k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {int k2_offset = v_offset + k2;int x2;if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {x2 = v2[k2_offset + 1];} else {x2 = v2[k2_offset - 1] + 1;}int y2 = x2 - k2;while (x2 < text1_length && y2 < text2_length&& text1.charAt(text1_length - x2 - 1)== text2.charAt(text2_length - y2 - 1)) {x2++;y2++;}v2[k2_offset] = x2;if (x2 > text1_length) {// Ran off the left of the graph.k2end += 2;} else if (y2 > text2_length) {// Ran off the top of the graph.k2start += 2;} else if (!front) {int k1_offset = v_offset + delta - k2;if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {int x1 = v1[k1_offset];int y1 = v_offset + x1 - k1_offset;// Mirror x2 onto top-left coordinate system.x2 = text1_length - x2;if (x1 >= x2) {// Overlap detected.return diff_bisectSplit(text1, text2, x1, y1, deadline);}}}}}// Diff took too long and hit the deadline or// number of diffs equals number of characters, no commonality at all.LinkedList diffs = new LinkedList();diffs.add(new Diff(Operation.DELETE, text1));diffs.add(new Diff(Operation.INSERT, text2));return diffs;}/*** Given the location of the 'middle snake', split the diff in two parts* and recurse.* @param text1 Old string to be diffed.* @param text2 New string to be diffed.* @param x Index of split point in text1.* @param y Index of split point in text2.* @param deadline Time at which to bail if not yet complete.* @return LinkedList of Diff objects.*/private LinkedList diff_bisectSplit(String text1, String text2,int x, int y, long deadline) {String text1a = text1.substring(0, x);String text2a = text2.substring(0, y);String text1b = text1.substring(x);String text2b = text2.substring(y);// Compute both diffs serially.LinkedList diffs = diff_main(text1a, text2a, false, deadline);LinkedList diffsb = diff_main(text1b, text2b, false, deadline);diffs.addAll(diffsb);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 lineArray = new ArrayList();Map lineHash = new HashMap();// e.g. linearray[4] == "Hello
"// e.g. linehash.get("Hello
") == 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("");// Allocate 2/3rds of the space for text1, the rest for text2.String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash, 40000);String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash, 65535);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.* @param maxLines Maximum length of lineArray.* @return Encoded string.*/private String diff_linesToCharsMunge(String text, List lineArray,Map lineHash, int maxLines) {int lineStart = 0;int lineEnd = -1;String line;StringBuilder chars = new StringBuilder();// Walk the text, pulling out a substring for each line.// text.split('
') 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('
', lineStart);if (lineEnd == -1) {lineEnd = text.length() - 1;}line = text.substring(lineStart, lineEnd + 1);if (lineHash.containsKey(line)) {chars.append(String.valueOf((char) (int) lineHash.get(line)));} else {if (lineArray.size() == maxLines) {// Bail out at 65535 because// String.valueOf((char) 65536).equals(String.valueOf(((char) 0)))line = text.substring(lineStart);lineEnd = text.length();}lineArray.add(line);lineHash.put(line, lineArray.size() - 1);chars.append(String.valueOf((char) (lineArray.size() - 1)));}lineStart = lineEnd + 1;}return chars.toString();}/*** Rehydrate the text in a diff from a string of line hashes to real lines of* text.* @param diffs List of Diff objects.* @param lineArray List of unique strings.*/protected void diff_charsToLines(List diffs,List lineArray) {StringBuilder text;for (Diff diff : diffs) {text = new StringBuilder();for (int j = 0; j < diff.text.length(); j++) {text.append(lineArray.get(diff.text.charAt(j)));}diff.text = text.toString();}}/*** 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: https://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: https://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;}/*** Determine if the suffix of one string is the prefix of another.* @param text1 First string.* @param text2 Second string.* @return The number of characters common to the end of the first*     string and the start of the second string.*/protected int diff_commonOverlap(String text1, String text2) {// Cache the text lengths to prevent multiple calls.int text1_length = text1.length();int text2_length = text2.length();// Eliminate the null case.if (text1_length == 0 || text2_length == 0) {return 0;}// Truncate the longer string.if (text1_length > text2_length) {text1 = text1.substring(text1_length - text2_length);} else if (text1_length < text2_length) {text2 = text2.substring(0, text1_length);}int text_length = Math.min(text1_length, text2_length);// Quick check for the worst case.if (text1.equals(text2)) {return text_length;}// Start by looking for a single character match// and increase length until no match is found.// Performance analysis: https://neil.fraser.name/news/2010/11/04/int best = 0;int length = 1;while (true) {String pattern = text1.substring(text_length - length);int found = text2.indexOf(pattern);if (found == -1) {return best;}length += found;if (found == 0 || text1.substring(text_length - length).equals(text2.substring(0, length))) {best = length;length++;}}}/*** Do the two texts share a substring which is at least half the length of* the longer text?* This speedup can produce non-minimal diffs.* @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) {if (Diff_Timeout <= 0) {// Don't risk returning a non-optimal diff if we have unlimited time.return null;}String longtext = text1.length() > text2.length() ? text1 : text2;String shorttext = text1.length() > text2.length() ? text2 : text1;if (longtext.length() < 4 || shorttext.length() * 2 < longtext.length()) {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() * 2 >= longtext.length()) {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 diffs) {if (diffs.isEmpty()) {return;}boolean changes = false;Deque equalities = new ArrayDeque();  // Double-ended queue of qualities.String lastEquality = null; // Always equal to equalities.peek().textListIterator pointer = diffs.listIterator();// Number of characters that changed prior to the equality.int length_insertions1 = 0;int length_deletions1 = 0;// Number of characters that changed after the equality.int length_insertions2 = 0;int length_deletions2 = 0;Diff thisDiff = pointer.next();while (thisDiff != null) {if (thisDiff.operation == Operation.EQUAL) {// Equality found.
        equalities.push(thisDiff);length_insertions1 = length_insertions2;length_deletions1 = length_deletions2;length_insertions2 = 0;length_deletions2 = 0;lastEquality = thisDiff.text;} else {// An insertion or deletion.if (thisDiff.operation == Operation.INSERT) {length_insertions2 += thisDiff.text.length();} else {length_deletions2 += thisDiff.text.length();}// Eliminate an equality that is smaller or equal to the edits on both// sides of it.if (lastEquality != null && (lastEquality.length()<= Math.max(length_insertions1, length_deletions1))&& (lastEquality.length()<= Math.max(length_insertions2, length_deletions2))) {//System.out.println("Splitting: '" + lastEquality + "'");// Walk back to offending equality.while (thisDiff != equalities.peek()) {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.isEmpty()) {// Throw away the previous equality (it needs to be reevaluated).
            equalities.pop();}if (equalities.isEmpty()) {// 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.peek();while (thisDiff != pointer.previous()) {// Intentionally empty loop.
            }}length_insertions1 = 0;  // Reset the counters.length_insertions2 = 0;length_deletions1 = 0;length_deletions2 = 0;lastEquality = null;changes = true;}}thisDiff = pointer.hasNext() ? pointer.next() : null;}// Normalize the diff.if (changes) {diff_cleanupMerge(diffs);}diff_cleanupSemanticLossless(diffs);// Find any overlaps between deletions and insertions.// e.g: abcxxxxxxdef//   -> abcxxxdef// e.g: xxxabcdefxxx//   -> defxxxabc// Only extract an overlap if it is as big as the edit ahead or behind it.pointer = diffs.listIterator();Diff prevDiff = null;thisDiff = null;if (pointer.hasNext()) {prevDiff = pointer.next();if (pointer.hasNext()) {thisDiff = pointer.next();}}while (thisDiff != null) {if (prevDiff.operation == Operation.DELETE &&thisDiff.operation == Operation.INSERT) {String deletion = prevDiff.text;String insertion = thisDiff.text;int overlap_length1 = this.diff_commonOverlap(deletion, insertion);int overlap_length2 = this.diff_commonOverlap(insertion, deletion);if (overlap_length1 >= overlap_length2) {if (overlap_length1 >= deletion.length() / 2.0 ||overlap_length1 >= insertion.length() / 2.0) {// Overlap found. Insert an equality and trim the surrounding edits.
            pointer.previous();pointer.add(new Diff(Operation.EQUAL,insertion.substring(0, overlap_length1)));prevDiff.text =deletion.substring(0, deletion.length() - overlap_length1);thisDiff.text = insertion.substring(overlap_length1);// pointer.add inserts the element before the cursor, so there is// no need to step past the new element.
          }} else {if (overlap_length2 >= deletion.length() / 2.0 ||overlap_length2 >= insertion.length() / 2.0) {// Reverse overlap found.// Insert an equality and swap and trim the surrounding edits.
            pointer.previous();pointer.add(new Diff(Operation.EQUAL,deletion.substring(0, overlap_length2)));prevDiff.operation = Operation.INSERT;prevDiff.text =insertion.substring(0, insertion.length() - overlap_length2);thisDiff.operation = Operation.DELETE;thisDiff.text = deletion.substring(overlap_length2);// pointer.add inserts the element before the cursor, so there is// no need to step past the new element.
          }}thisDiff = pointer.hasNext() ? pointer.next() : null;}prevDiff = thisDiff;thisDiff = pointer.hasNext() ? pointer.next() : null;}}/*** 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 cat came. -> The cat came.* @param diffs LinkedList of Diff objects.*/public void diff_cleanupSemanticLossless(LinkedList diffs) {String equality1, edit, equality2;String commonString;int commonOffset;int score, bestScore;String bestEquality1, bestEdit, bestEquality2;// Create a new iterator at the start.ListIterator 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 6 (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 6;}// 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.char char1 = one.charAt(one.length() - 1);char char2 = two.charAt(0);boolean nonAlphaNumeric1 = !Character.isLetterOrDigit(char1);boolean nonAlphaNumeric2 = !Character.isLetterOrDigit(char2);boolean whitespace1 = nonAlphaNumeric1 && Character.isWhitespace(char1);boolean whitespace2 = nonAlphaNumeric2 && Character.isWhitespace(char2);boolean lineBreak1 = whitespace1&& Character.getType(char1) == Character.CONTROL;boolean lineBreak2 = whitespace2&& Character.getType(char2) == Character.CONTROL;boolean blankLine1 = lineBreak1 && BLANKLINEEND.matcher(one).find();boolean blankLine2 = lineBreak2 && BLANKLINESTART.matcher(two).find();if (blankLine1 || blankLine2) {// Five points for blank lines.return 5;} else if (lineBreak1 || lineBreak2) {// Four points for line breaks.return 4;} else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {// Three points for end of sentences.return 3;} else if (whitespace1 || whitespace2) {// Two points for whitespace.return 2;} else if (nonAlphaNumeric1 || nonAlphaNumeric2) {// One point for non-alphanumeric.return 1;}return 0;}// Define some regex patterns for matching boundaries.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 diffs) {if (diffs.isEmpty()) {return;}boolean changes = false;Deque equalities = new ArrayDeque();  // Double-ended queue of equalities.String lastEquality = null; // Always equal to equalities.peek().textListIterator 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 unsplittable.while (thisDiff != null) {if (thisDiff.operation == Operation.EQUAL) {// Equality found.if (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 deletion.if (thisDiff.operation == Operation.DELETE) {post_del = true;} else {post_ins = true;}/** Five types to be split:* ABXYCD* AXCD* ABXC* AXCD* ABXC*/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.peek()) {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.isEmpty()) {// Throw away the previous equality (it needs to be reevaluated).
              equalities.pop();}if (equalities.isEmpty()) {// 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.peek();}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 diffs) {diffs.add(new Diff(Operation.EQUAL, ""));  // Add a dummy entry at the end.ListIterator 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 + count_insert > 1) {boolean both_types = 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 (both_types) {// 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;}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: ABAC -> ABAC*/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 List of Diff objects.* @param loc Location within text1.* @return Location within text2.*/public int diff_xIndex(List 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 List of Diff objects.* @return HTML representation.*/public String diff_prettyHtml(List diffs) {StringBuilder html = new StringBuilder();for (Diff aDiff : diffs) {String text = aDiff.text.replace("&", "&").replace("<", "<").replace(">", ">").replace("
", "¶
");switch (aDiff.operation) {case INSERT:html.append("").append(text).append("");break;case DELETE:html.append("").append(text).append("");break;case EQUAL:html.append("").append(text).append("");break;}}return html.toString();}/*** Compute and return the source text (all equalities and deletions).* @param diffs List of Diff objects.* @return Source text.*/public String diff_text1(List 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 List of Diff objects.* @return Destination text.*/public String diff_text2(List 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 List of Diff objects.* @return Number of changes.*/public int diff_levenshtein(List 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	-2	+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.* Operations are tab-separated.  Inserted text is escaped using %xx notation.* @param diffs List of Diff objects.* @return Delta text.*/public String diff_toDelta(List 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("	");} 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("	");break;case EQUAL:text.append("=").append(aDiff.text.length()).append("	");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 objects or null if invalid.* @throws IllegalArgumentException If invalid input.*/public LinkedList diff_fromDelta(String text1, String delta)throws IllegalArgumentException {LinkedList diffs = new LinkedList();int pointer = 0;  // Cursor in text1String[] tokens = delta.split("	");for (String token : tokens) {if (token.length() == 0) {// Blank tokens are ok (from a trailing 	).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) {// Check for null inputs.if (text == null || pattern == null) {throw new IllegalArgumentException("Null inputs. (match_main)");}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 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 match_alphabet(String pattern) {Map s = new HashMap();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_make(String text1, String text2) {if (text1 == null || text2 == null) {throw new IllegalArgumentException("Null inputs. (patch_make)");}// No diffs provided, compute our own.LinkedList 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 objects for text1 to text2.* @return LinkedList of Patch objects.*/public LinkedList patch_make(LinkedList diffs) {if (diffs == null) {throw new IllegalArgumentException("Null inputs. (patch_make)");}// 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 objects for text1 to text2.* @return LinkedList of Patch objects.* @deprecated Prefer patch_make(String text1, LinkedList diffs).*/@Deprecated public LinkedList patch_make(String text1, String text2,LinkedList 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 objects for text1 to text2.* @return LinkedList of Patch objects.*/public LinkedList patch_make(String text1, LinkedList diffs) {if (text1 == null || diffs == null) {throw new IllegalArgumentException("Null inputs. (patch_make)");}LinkedList patches = new LinkedList();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 && !patch.diffs.isEmpty()) {// 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.// https://github.com/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_deepCopy(LinkedList patches) {LinkedList patchesCopy = new LinkedList();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 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 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 patches) {short paddingLength = this.Patch_Margin;String nullPadding = "";for (short 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 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.* Intended to be called only from within patch_apply.* @param patches LinkedList of Patch objects.*/public void patch_splitMax(LinkedList patches) {short patch_size = Match_MaxBits;String precontext, postcontext;Patch patch;int start1, start2;boolean empty;Operation diff_type;String diff_text;ListIterator 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();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 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_fromText(String textline)throws IllegalArgumentException {List patches = new LinkedList();if (textline.length() == 0) {return patches;}List textList = Arrays.asList(textline.split("
"));LinkedList text = new LinkedList(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 (m.group(2).equals("0")) {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 (m.group(4).equals("0")) {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.*/public String toString() {String prettyText = this.text.replace('
', 'u00b6');return "Diff(" + this.operation + ","" + prettyText + "")";}/*** Create a numeric hash value for a Diff.* This function is not used by DMP.* @return Hash value.*/@Overridepublic int hashCode() {final int prime = 31;int result = (operation == null) ? 0 : operation.hashCode();result += prime * ((text == null) ? 0 : text.hashCode());return result;}/*** Is this Diff equivalent to another Diff?* @param obj Another Diff to compare against.* @return true or false.*/@Overridepublic boolean equals(Object obj) {if (this == obj) {return true;}if (obj == null) {return false;}if (getClass() != obj.getClass()) {return false;}Diff other = (Diff) obj;if (operation != other.operation) {return false;}if (text == null) {if (other.text != null) {return false;}} else if (!text.equals(other.text)) {return false;}return true;}}/*** Class representing one patch operation.*/public static class Patch {public LinkedList 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();}/*** Emulate GNU diff's format.* Header: @@ -382,8 +481,9 @@* Indices are printed as 1-based, not 0-based.* @return The GNU diff string.*/public 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(" @@
");// 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("
");} 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", "#");}
}

拿到这个算法类，再写个工具类来完成使用封装。

package com.boomoom.common.util.diff;import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;import com.boomoom.common.util.diff.diff_match_patch.Diff;
import com.boomoom.common.util.diff.diff_match_patch.Operation;public class CompareUtil {public static String HIGH_LIGHT_FORMAT = "%s";public static String NEW_LINE_FLAG = "
";public static CompareResult compare(String leftStr, String rightStr) {List beList = rememberSpacing(leftStr);List afList = rememberSpacing(rightStr);leftStr = leftStr.replace(" ", "");rightStr = rightStr.replace(" ","");LinkedList diffList = new diff_match_patch().diff_main(leftStr, rightStr);StringBuffer left = new StringBuffer();StringBuffer right = new StringBuffer();Integer indexBe = 0;Integer indexAf = 0;for (Diff diff : diffList) {StringBuffer diffTextBe = new StringBuffer(diff.text);StringBuffer diffTextAf = new StringBuffer(diff.text);if (diff.operation.equals(Operation.EQUAL)) {addSpacing(beList, indexBe, diffTextBe);addSpacing(afList, indexAf, diffTextAf);left.append(diffTextBe);right.append(diffTextAf);indexBe += diffTextBe.length();indexAf += diffTextAf.length();}indexBe = appendString(Operation.DELETE, diff, left, beList, indexBe);indexAf = appendString(Operation.INSERT, diff, right, afList, indexAf);}return new CompareResult(left.toString(), right.toString());}private static List rememberSpacing(String str) {List list = new ArrayList<>();for (int i = 0; i < str.length(); i++) {if (' ' == str.charAt(i)) {list.add(i);}}return list;}private static void addSpacing(List list, Integer index, StringBuffer str) {for (Integer o : list) {if (o >= index && o < index + str.length()) {str.insert(o - index, ' ');}}}private static Integer appendString(Operation type, Diff diff, StringBuffer sbOne, List list, Integer i) {if (diff.operation.equals(type)) {StringBuffer sb = new StringBuffer(diff.text);for (Integer o : list) {if (o >= i && o < i + sb.length()) {sb.insert(o - i, ' ');}}sbOne.append(highLight(sb.toString()));return i + sb.length();}return i;}private static String highLight(String str) {if (!str.contains(NEW_LINE_FLAG)) {return highLightFormat(str);}if (str.equals(NEW_LINE_FLAG)) {return NEW_LINE_FLAG;}String[] tempList = str.split(NEW_LINE_FLAG);int length = tempList.length;StringBuffer sb = new StringBuffer();for (int i = 0; i < length; i++) {if (StringUtil.isNotBlank(tempList[i])) {sb.append(highLightFormat(tempList[i]));}if (length == 1 || (i < length -1)) {sb.append(NEW_LINE_FLAG);}}return sb.toString();}private static String highLightFormat(String str) {return String.format(HIGH_LIGHT_FORMAT, str);}public static void main(String[] args) throws Exception {String left = "/home/admin/tempA/101
20180101_L.txt";String right = "/home/admin/tempB/20180205_R.txt";CompareResult result = compare(left, right);System.out.println(result.getLeftResult());System.out.println("--------------------");System.out.println(result.getRightResult());}
}