From e7a2512aa3666e1b891dc7dfc5a0cb28fd66bea9 Mon Sep 17 00:00:00 2001 From: "Tadashi G. Takaoka" Date: Tue, 15 Mar 2011 11:46:32 -0700 Subject: [PATCH] Add Utils.equalsIgnoreCase methods This change also corrects usage of "frequency", "priority" and "score" * Frequency is the relative probability in dictionary. * Score is the relative probability in suggestions. * Priority is kind a sorted score. Change-Id: Iafb135a4ecdb401cc505014a07c74dfcac44d699 --- java/proguard.flags | 4 + .../inputmethod/latin/AutoCorrection.java | 10 +- .../inputmethod/latin/BinaryDictionary.java | 30 +++--- .../android/inputmethod/latin/Dictionary.java | 8 +- .../latin/ExpandableDictionary.java | 2 +- .../android/inputmethod/latin/Suggest.java | 100 +++++++----------- .../com/android/inputmethod/latin/Utils.java | 66 +++++++++++- 7 files changed, 134 insertions(+), 86 deletions(-) diff --git a/java/proguard.flags b/java/proguard.flags index 729f4ad61..914bd7595 100644 --- a/java/proguard.flags +++ b/java/proguard.flags @@ -18,3 +18,7 @@ -keep class com.android.inputmethod.latin.AutoCorrection { java.lang.CharSequence getAutoCorrectionWord(); } + +-keep class com.android.inputmethod.latin.Utils { + boolean equalsIgnoreCase(...); +} diff --git a/java/src/com/android/inputmethod/latin/AutoCorrection.java b/java/src/com/android/inputmethod/latin/AutoCorrection.java index 092f7ad63..d3119792c 100644 --- a/java/src/com/android/inputmethod/latin/AutoCorrection.java +++ b/java/src/com/android/inputmethod/latin/AutoCorrection.java @@ -48,7 +48,7 @@ public class AutoCorrection { } public void updateAutoCorrectionStatus(Map dictionaries, - WordComposer wordComposer, ArrayList suggestions, int[] priorities, + WordComposer wordComposer, ArrayList suggestions, int[] sortedScores, CharSequence typedWord, double autoCorrectionThreshold, int correctionMode, CharSequence quickFixedWord, CharSequence whitelistedWord) { if (hasAutoCorrectionForWhitelistedWord(whitelistedWord)) { @@ -62,7 +62,7 @@ public class AutoCorrection { mHasAutoCorrection = true; mAutoCorrectionWord = quickFixedWord; } else if (hasAutoCorrectionForBinaryDictionary(wordComposer, suggestions, correctionMode, - priorities, typedWord, autoCorrectionThreshold)) { + sortedScores, typedWord, autoCorrectionThreshold)) { mHasAutoCorrection = true; mAutoCorrectionWord = suggestions.get(0); } @@ -114,13 +114,13 @@ public class AutoCorrection { } private boolean hasAutoCorrectionForBinaryDictionary(WordComposer wordComposer, - ArrayList suggestions, int correctionMode, int[] priorities, + ArrayList suggestions, int correctionMode, int[] sortedScores, CharSequence typedWord, double autoCorrectionThreshold) { if (wordComposer.size() > 1 && (correctionMode == Suggest.CORRECTION_FULL || correctionMode == Suggest.CORRECTION_FULL_BIGRAM) - && typedWord != null && suggestions.size() > 0 && priorities.length > 0) { + && typedWord != null && suggestions.size() > 0 && sortedScores.length > 0) { final CharSequence autoCorrectionCandidate = suggestions.get(0); - final int autoCorrectionCandidateScore = priorities[0]; + final int autoCorrectionCandidateScore = sortedScores[0]; // TODO: when the normalized score of the first suggestion is nearly equals to // the normalized score of the second suggestion, behave less aggressive. mNormalizedScore = Utils.calcNormalizedScore( diff --git a/java/src/com/android/inputmethod/latin/BinaryDictionary.java b/java/src/com/android/inputmethod/latin/BinaryDictionary.java index 08ddd25fa..c5491af47 100644 --- a/java/src/com/android/inputmethod/latin/BinaryDictionary.java +++ b/java/src/com/android/inputmethod/latin/BinaryDictionary.java @@ -54,8 +54,8 @@ public class BinaryDictionary extends Dictionary { private final int[] mInputCodes = new int[MAX_WORD_LENGTH * MAX_PROXIMITY_CHARS_SIZE]; private final char[] mOutputChars = new char[MAX_WORD_LENGTH * MAX_WORDS]; private final char[] mOutputChars_bigrams = new char[MAX_WORD_LENGTH * MAX_BIGRAMS]; - private final int[] mFrequencies = new int[MAX_WORDS]; - private final int[] mFrequencies_bigrams = new int[MAX_BIGRAMS]; + private final int[] mScores = new int[MAX_WORDS]; + private final int[] mBigramScores = new int[MAX_BIGRAMS]; private final KeyboardSwitcher mKeyboardSwitcher = KeyboardSwitcher.getInstance(); private final SubtypeSwitcher mSubtypeSwitcher = SubtypeSwitcher.getInstance(); @@ -149,14 +149,14 @@ public class BinaryDictionary extends Dictionary { private native boolean isValidWordNative(int nativeData, char[] word, int wordLength); private native int getSuggestionsNative(int dict, int proximityInfo, int[] xCoordinates, int[] yCoordinates, int[] inputCodes, int codesSize, int flags, char[] outputChars, - int[] frequencies); + int[] scores); private native int getBigramsNative(int dict, char[] prevWord, int prevWordLength, - int[] inputCodes, int inputCodesLength, char[] outputChars, int[] frequencies, + int[] inputCodes, int inputCodesLength, char[] outputChars, int[] scores, int maxWordLength, int maxBigrams, int maxAlternatives); private final void loadDictionary(String path, long startOffset, long length) { mNativeDict = openNative(path, startOffset, length, - TYPED_LETTER_MULTIPLIER, FULL_WORD_FREQ_MULTIPLIER, + TYPED_LETTER_MULTIPLIER, FULL_WORD_SCORE_MULTIPLIER, MAX_WORD_LENGTH, MAX_WORDS, MAX_PROXIMITY_CHARS_SIZE); mDictLength = length; } @@ -168,7 +168,7 @@ public class BinaryDictionary extends Dictionary { char[] chars = previousWord.toString().toCharArray(); Arrays.fill(mOutputChars_bigrams, (char) 0); - Arrays.fill(mFrequencies_bigrams, 0); + Arrays.fill(mBigramScores, 0); int codesSize = codes.size(); Arrays.fill(mInputCodes, -1); @@ -177,18 +177,18 @@ public class BinaryDictionary extends Dictionary { Math.min(alternatives.length, MAX_PROXIMITY_CHARS_SIZE)); int count = getBigramsNative(mNativeDict, chars, chars.length, mInputCodes, codesSize, - mOutputChars_bigrams, mFrequencies_bigrams, MAX_WORD_LENGTH, MAX_BIGRAMS, + mOutputChars_bigrams, mBigramScores, MAX_WORD_LENGTH, MAX_BIGRAMS, MAX_PROXIMITY_CHARS_SIZE); for (int j = 0; j < count; ++j) { - if (mFrequencies_bigrams[j] < 1) break; + if (mBigramScores[j] < 1) break; final int start = j * MAX_WORD_LENGTH; int len = 0; while (len < MAX_WORD_LENGTH && mOutputChars_bigrams[start + len] != 0) { ++len; } if (len > 0) { - callback.addWord(mOutputChars_bigrams, start, len, mFrequencies_bigrams[j], + callback.addWord(mOutputChars_bigrams, start, len, mBigramScores[j], mDicTypeId, DataType.BIGRAM); } } @@ -197,17 +197,17 @@ public class BinaryDictionary extends Dictionary { @Override public void getWords(final WordComposer codes, final WordCallback callback) { final int count = getSuggestions(codes, mKeyboardSwitcher.getLatinKeyboard(), - mOutputChars, mFrequencies); + mOutputChars, mScores); for (int j = 0; j < count; ++j) { - if (mFrequencies[j] < 1) break; + if (mScores[j] < 1) break; final int start = j * MAX_WORD_LENGTH; int len = 0; while (len < MAX_WORD_LENGTH && mOutputChars[start + len] != 0) { ++len; } if (len > 0) { - callback.addWord(mOutputChars, start, len, mFrequencies[j], mDicTypeId, + callback.addWord(mOutputChars, start, len, mScores[j], mDicTypeId, DataType.UNIGRAM); } } @@ -218,7 +218,7 @@ public class BinaryDictionary extends Dictionary { } /* package for test */ int getSuggestions(final WordComposer codes, final Keyboard keyboard, - char[] outputChars, int[] frequencies) { + char[] outputChars, int[] scores) { if (!isValidDictionary()) return -1; final int codesSize = codes.size(); @@ -232,12 +232,12 @@ public class BinaryDictionary extends Dictionary { Math.min(alternatives.length, MAX_PROXIMITY_CHARS_SIZE)); } Arrays.fill(outputChars, (char) 0); - Arrays.fill(frequencies, 0); + Arrays.fill(scores, 0); return getSuggestionsNative( mNativeDict, keyboard.getProximityInfo(), codes.getXCoordinates(), codes.getYCoordinates(), mInputCodes, codesSize, - mFlags, outputChars, frequencies); + mFlags, outputChars, scores); } @Override diff --git a/java/src/com/android/inputmethod/latin/Dictionary.java b/java/src/com/android/inputmethod/latin/Dictionary.java index 56f0cc503..ac43d6477 100644 --- a/java/src/com/android/inputmethod/latin/Dictionary.java +++ b/java/src/com/android/inputmethod/latin/Dictionary.java @@ -29,7 +29,7 @@ public abstract class Dictionary { /** * The weight to give to a word if it's length is the same as the number of typed characters. */ - protected static final int FULL_WORD_FREQ_MULTIPLIER = 2; + protected static final int FULL_WORD_SCORE_MULTIPLIER = 2; public static enum DataType { UNIGRAM, BIGRAM @@ -42,17 +42,17 @@ public abstract class Dictionary { public interface WordCallback { /** * Adds a word to a list of suggestions. The word is expected to be ordered based on - * the provided frequency. + * the provided score. * @param word the character array containing the word * @param wordOffset starting offset of the word in the character array * @param wordLength length of valid characters in the character array - * @param frequency the frequency of occurrence. This is normalized between 1 and 255, but + * @param score the score of occurrence. This is normalized between 1 and 255, but * can exceed those limits * @param dicTypeId of the dictionary where word was from * @param dataType tells type of this data * @return true if the word was added, false if no more words are required */ - boolean addWord(char[] word, int wordOffset, int wordLength, int frequency, int dicTypeId, + boolean addWord(char[] word, int wordOffset, int wordLength, int score, int dicTypeId, DataType dataType); } diff --git a/java/src/com/android/inputmethod/latin/ExpandableDictionary.java b/java/src/com/android/inputmethod/latin/ExpandableDictionary.java index 0318175f6..d87fbce51 100644 --- a/java/src/com/android/inputmethod/latin/ExpandableDictionary.java +++ b/java/src/com/android/inputmethod/latin/ExpandableDictionary.java @@ -327,7 +327,7 @@ public class ExpandableDictionary extends Dictionary { final int finalFreq; if (skipPos < 0) { finalFreq = freq * snr * addedAttenuation - * FULL_WORD_FREQ_MULTIPLIER; + * FULL_WORD_SCORE_MULTIPLIER; } else { finalFreq = computeSkippedWordFinalFreq(freq, snr * addedAttenuation, mInputLength); diff --git a/java/src/com/android/inputmethod/latin/Suggest.java b/java/src/com/android/inputmethod/latin/Suggest.java index 0de474e59..94ee2c50f 100644 --- a/java/src/com/android/inputmethod/latin/Suggest.java +++ b/java/src/com/android/inputmethod/latin/Suggest.java @@ -47,7 +47,7 @@ public class Suggest implements Dictionary.WordCallback { /** * Words that appear in both bigram and unigram data gets multiplier ranging from - * BIGRAM_MULTIPLIER_MIN to BIGRAM_MULTIPLIER_MAX depending on the frequency score from + * BIGRAM_MULTIPLIER_MIN to BIGRAM_MULTIPLIER_MAX depending on the score from * bigram data. */ public static final double BIGRAM_MULTIPLIER_MIN = 1.2; @@ -92,13 +92,13 @@ public class Suggest implements Dictionary.WordCallback { private boolean mQuickFixesEnabled; private double mAutoCorrectionThreshold; - private int[] mPriorities = new int[mPrefMaxSuggestions]; - private int[] mBigramPriorities = new int[PREF_MAX_BIGRAMS]; + private int[] mScores = new int[mPrefMaxSuggestions]; + private int[] mBigramScores = new int[PREF_MAX_BIGRAMS]; private ArrayList mSuggestions = new ArrayList(); ArrayList mBigramSuggestions = new ArrayList(); private ArrayList mStringPool = new ArrayList(); - private String mLowerOriginalWord; + private CharSequence mTypedWord; // TODO: Remove these member variables by passing more context to addWord() callback method private boolean mIsFirstCharCapitalized; @@ -207,8 +207,8 @@ public class Suggest implements Dictionary.WordCallback { throw new IllegalArgumentException("maxSuggestions must be between 1 and 100"); } mPrefMaxSuggestions = maxSuggestions; - mPriorities = new int[mPrefMaxSuggestions]; - mBigramPriorities = new int[PREF_MAX_BIGRAMS]; + mScores = new int[mPrefMaxSuggestions]; + mBigramScores = new int[PREF_MAX_BIGRAMS]; collectGarbage(mSuggestions, mPrefMaxSuggestions); while (mStringPool.size() < mPrefMaxSuggestions) { StringBuilder sb = new StringBuilder(getApproxMaxWordLength()); @@ -256,25 +256,23 @@ public class Suggest implements Dictionary.WordCallback { mIsFirstCharCapitalized = wordComposer.isFirstCharCapitalized(); mIsAllUpperCase = wordComposer.isAllUpperCase(); collectGarbage(mSuggestions, mPrefMaxSuggestions); - Arrays.fill(mPriorities, 0); + Arrays.fill(mScores, 0); // Save a lowercase version of the original word CharSequence typedWord = wordComposer.getTypedWord(); if (typedWord != null) { final String typedWordString = typedWord.toString(); typedWord = typedWordString; - mLowerOriginalWord = typedWordString.toLowerCase(); // Treating USER_TYPED as UNIGRAM suggestion for logging now. LatinImeLogger.onAddSuggestedWord(typedWordString, Suggest.DIC_USER_TYPED, Dictionary.DataType.UNIGRAM); - } else { - mLowerOriginalWord = ""; } + mTypedWord = typedWord; if (wordComposer.size() == 1 && (mCorrectionMode == CORRECTION_FULL_BIGRAM || mCorrectionMode == CORRECTION_BASIC)) { // At first character typed, search only the bigrams - Arrays.fill(mBigramPriorities, 0); + Arrays.fill(mBigramScores, 0); collectGarbage(mBigramSuggestions, PREF_MAX_BIGRAMS); if (!TextUtils.isEmpty(prevWordForBigram)) { @@ -346,7 +344,7 @@ public class Suggest implements Dictionary.WordCallback { mWhiteListDictionary.getWhiteListedWord(typedWordString)); mAutoCorrection.updateAutoCorrectionStatus(mUnigramDictionaries, wordComposer, - mSuggestions, mPriorities, typedWord, mAutoCorrectionThreshold, mCorrectionMode, + mSuggestions, mScores, typedWord, mAutoCorrectionThreshold, mCorrectionMode, autoText, whitelistedWord); if (autoText != null) { @@ -364,26 +362,25 @@ public class Suggest implements Dictionary.WordCallback { if (DBG) { double normalizedScore = mAutoCorrection.getNormalizedScore(); - ArrayList frequencyInfoList = + ArrayList scoreInfoList = new ArrayList(); - frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo("+", false)); - final int priorityLength = mPriorities.length; - for (int i = 0; i < priorityLength; ++i) { + scoreInfoList.add(new SuggestedWords.SuggestedWordInfo("+", false)); + for (int i = 0; i < mScores.length; ++i) { if (normalizedScore > 0) { - final String priorityThreshold = Integer.toString(mPriorities[i]) + " (" + + final String scoreThreshold = Integer.toString(mScores[i]) + " (" + normalizedScore + ")"; - frequencyInfoList.add( - new SuggestedWords.SuggestedWordInfo(priorityThreshold, false)); + scoreInfoList.add( + new SuggestedWords.SuggestedWordInfo(scoreThreshold, false)); normalizedScore = 0.0; } else { - final String priority = Integer.toString(mPriorities[i]); - frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo(priority, false)); + final String score = Integer.toString(mScores[i]); + scoreInfoList.add(new SuggestedWords.SuggestedWordInfo(score, false)); } } - for (int i = priorityLength; i < mSuggestions.size(); ++i) { - frequencyInfoList.add(new SuggestedWords.SuggestedWordInfo("--", false)); + for (int i = mScores.length; i < mSuggestions.size(); ++i) { + scoreInfoList.add(new SuggestedWords.SuggestedWordInfo("--", false)); } - return new SuggestedWords.Builder().addWords(mSuggestions, frequencyInfoList); + return new SuggestedWords.Builder().addWords(mSuggestions, scoreInfoList); } return new SuggestedWords.Builder().addWords(mSuggestions, null); } @@ -419,52 +416,37 @@ public class Suggest implements Dictionary.WordCallback { return mAutoCorrection.hasAutoCorrection(); } - private static boolean compareCaseInsensitive(final String lowerOriginalWord, - final char[] word, final int offset, final int length) { - final int originalLength = lowerOriginalWord.length(); - if (originalLength == length && Character.isUpperCase(word[offset])) { - for (int i = 0; i < originalLength; i++) { - if (lowerOriginalWord.charAt(i) != Character.toLowerCase(word[offset+i])) { - return false; - } - } - return true; - } - return false; - } - @Override - public boolean addWord(final char[] word, final int offset, final int length, int freq, + public boolean addWord(final char[] word, final int offset, final int length, int score, final int dicTypeId, final Dictionary.DataType dataType) { Dictionary.DataType dataTypeForLog = dataType; - ArrayList suggestions; - int[] priorities; - int prefMaxSuggestions; + final ArrayList suggestions; + final int[] sortedScores; + final int prefMaxSuggestions; if(dataType == Dictionary.DataType.BIGRAM) { suggestions = mBigramSuggestions; - priorities = mBigramPriorities; + sortedScores = mBigramScores; prefMaxSuggestions = PREF_MAX_BIGRAMS; } else { suggestions = mSuggestions; - priorities = mPriorities; + sortedScores = mScores; prefMaxSuggestions = mPrefMaxSuggestions; } int pos = 0; // Check if it's the same word, only caps are different - if (compareCaseInsensitive(mLowerOriginalWord, word, offset, length)) { + if (Utils.equalsIgnoreCase(mTypedWord, word, offset, length)) { // TODO: remove this surrounding if clause and move this logic to // getSuggestedWordBuilder. if (suggestions.size() > 0) { - final String currentHighestWordLowerCase = - suggestions.get(0).toString().toLowerCase(); + final String currentHighestWord = suggestions.get(0).toString(); // If the current highest word is also equal to typed word, we need to compare // frequency to determine the insertion position. This does not ensure strictly // correct ordering, but ensures the top score is on top which is enough for // removing duplicates correctly. - if (compareCaseInsensitive(currentHighestWordLowerCase, word, offset, length) - && freq <= priorities[0]) { + if (Utils.equalsIgnoreCase(currentHighestWord, word, offset, length) + && score <= sortedScores[0]) { pos = 1; } } @@ -475,24 +457,24 @@ public class Suggest implements Dictionary.WordCallback { if(bigramSuggestion >= 0) { dataTypeForLog = Dictionary.DataType.BIGRAM; // turn freq from bigram into multiplier specified above - double multiplier = (((double) mBigramPriorities[bigramSuggestion]) + double multiplier = (((double) mBigramScores[bigramSuggestion]) / MAXIMUM_BIGRAM_FREQUENCY) * (BIGRAM_MULTIPLIER_MAX - BIGRAM_MULTIPLIER_MIN) + BIGRAM_MULTIPLIER_MIN; /* Log.d(TAG,"bigram num: " + bigramSuggestion + " wordB: " + mBigramSuggestions.get(bigramSuggestion).toString() - + " currentPriority: " + freq + " bigramPriority: " - + mBigramPriorities[bigramSuggestion] + + " currentScore: " + score + " bigramScore: " + + mBigramScores[bigramSuggestion] + " multiplier: " + multiplier); */ - freq = (int)Math.round((freq * multiplier)); + score = (int)Math.round((score * multiplier)); } } - // Check the last one's priority and bail - if (priorities[prefMaxSuggestions - 1] >= freq) return true; + // Check the last one's score and bail + if (sortedScores[prefMaxSuggestions - 1] >= score) return true; while (pos < prefMaxSuggestions) { - if (priorities[pos] < freq - || (priorities[pos] == freq && length < suggestions.get(pos).length())) { + if (sortedScores[pos] < score + || (sortedScores[pos] == score && length < suggestions.get(pos).length())) { break; } pos++; @@ -502,8 +484,8 @@ public class Suggest implements Dictionary.WordCallback { return true; } - System.arraycopy(priorities, pos, priorities, pos + 1, prefMaxSuggestions - pos - 1); - priorities[pos] = freq; + System.arraycopy(sortedScores, pos, sortedScores, pos + 1, prefMaxSuggestions - pos - 1); + sortedScores[pos] = score; int poolSize = mStringPool.size(); StringBuilder sb = poolSize > 0 ? (StringBuilder) mStringPool.remove(poolSize - 1) : new StringBuilder(getApproxMaxWordLength()); diff --git a/java/src/com/android/inputmethod/latin/Utils.java b/java/src/com/android/inputmethod/latin/Utils.java index 727e3f16d..608d7e967 100644 --- a/java/src/com/android/inputmethod/latin/Utils.java +++ b/java/src/com/android/inputmethod/latin/Utils.java @@ -285,7 +285,7 @@ public class Utils { // In dictionary.cpp, getSuggestion() method, // suggestion scores are computed using the below formula. - // original score (called 'frequency') + // original score // := pow(mTypedLetterMultiplier (this is defined 2), // (the number of matched characters between typed word and suggested word)) // * (individual word's score which defined in the unigram dictionary, @@ -295,7 +295,7 @@ public class Utils { // (full match up to min(before.length(), after.length()) // => Then multiply by FULL_MATCHED_WORDS_PROMOTION_RATE (this is defined 1.2) // - If the word is a true full match except for differences in accents or - // capitalization, then treat it as if the frequency was 255. + // capitalization, then treat it as if the score was 255. // - If before.length() == after.length() // => multiply by mFullWordMultiplier (this is defined 2)) // So, maximum original score is pow(2, min(before.length(), after.length())) * 255 * 2 * 1.2 @@ -561,4 +561,66 @@ public class Utils { Log.e(TAG, "Could not load native library jni_latinime"); } } + + /** + * Returns true if a and b are equal ignoring the case of the character. + * @param a first character to check + * @param b second character to check + * @return {@code true} if a and b are equal, {@code false} otherwise. + */ + public static boolean equalsIgnoreCase(char a, char b) { + // Some language, such as Turkish, need testing both cases. + return a == b + || Character.toLowerCase(a) == Character.toLowerCase(b) + || Character.toUpperCase(a) == Character.toUpperCase(b); + } + + /** + * Returns true if a and b are equal ignoring the case of the characters, including if they are + * both null. + * @param a first CharSequence to check + * @param b second CharSequence to check + * @return {@code true} if a and b are equal, {@code false} otherwise. + */ + public static boolean equalsIgnoreCase(CharSequence a, CharSequence b) { + if (a == b) + return true; // including both a and b are null. + if (a == null || b == null) + return false; + final int length = a.length(); + if (length != b.length()) + return false; + for (int i = 0; i < length; i++) { + if (!equalsIgnoreCase(a.charAt(i), b.charAt(i))) + return false; + } + return true; + } + + /** + * Returns true if a and b are equal ignoring the case of the characters, including if a is null + * and b is zero length. + * @param a CharSequence to check + * @param b character array to check + * @param offset start offset of array b + * @param length length of characters in array b + * @return {@code true} if a and b are equal, {@code false} otherwise. + * @throws IndexOutOfBoundsException + * if {@code offset < 0 || length < 0 || offset + length > data.length}. + * @throws NullPointerException if {@code b == null}. + */ + public static boolean equalsIgnoreCase(CharSequence a, char[] b, int offset, int length) { + if (offset < 0 || length < 0 || length > b.length - offset) + throw new IndexOutOfBoundsException("array.length=" + b.length + " offset=" + offset + + " length=" + length); + if (a == null) + return length == 0; // including a is null and b is zero length. + if (a.length() != length) + return false; + for (int i = 0; i < length; i++) { + if (!equalsIgnoreCase(a.charAt(i), b[offset + i])) + return false; + } + return true; + } }