Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.apache.commons.text; import java.util.Arrays; /** * A matcher class that can be queried to determine if a character array * portion matches. * <p> * This class comes complete with various factory methods. * If these do not suffice, you can subclass and implement your own matcher. * * @since 1.0 */ public abstract class StrMatcher { /** * Matches the comma character. */ private static final StrMatcher COMMA_MATCHER = new CharMatcher(','); /** * Matches the tab character. */ private static final StrMatcher TAB_MATCHER = new CharMatcher('\t'); /** * Matches the space character. */ private static final StrMatcher SPACE_MATCHER = new CharMatcher(' '); /** * Matches the same characters as StringTokenizer, * namely space, tab, newline, formfeed. */ private static final StrMatcher SPLIT_MATCHER = new CharSetMatcher(" \t\n\r\f".toCharArray()); /** * Matches the String trim() whitespace characters. */ private static final StrMatcher TRIM_MATCHER = new TrimMatcher(); /** * Matches the double quote character. */ private static final StrMatcher SINGLE_QUOTE_MATCHER = new CharMatcher('\''); /** * Matches the double quote character. */ private static final StrMatcher DOUBLE_QUOTE_MATCHER = new CharMatcher('"'); /** * Matches the single or double quote character. */ private static final StrMatcher QUOTE_MATCHER = new CharSetMatcher("'\"".toCharArray()); /** * Matches no characters. */ private static final StrMatcher NONE_MATCHER = new NoMatcher(); // ----------------------------------------------------------------------- /** * Returns a matcher which matches the comma character. * * @return a matcher for a comma */ public static StrMatcher commaMatcher() { return COMMA_MATCHER; } /** * Returns a matcher which matches the tab character. * * @return a matcher for a tab */ public static StrMatcher tabMatcher() { return TAB_MATCHER; } /** * Returns a matcher which matches the space character. * * @return a matcher for a space */ public static StrMatcher spaceMatcher() { return SPACE_MATCHER; } /** * Matches the same characters as StringTokenizer, * namely space, tab, newline and formfeed. * * @return the split matcher */ public static StrMatcher splitMatcher() { return SPLIT_MATCHER; } /** * Matches the String trim() whitespace characters. * * @return the trim matcher */ public static StrMatcher trimMatcher() { return TRIM_MATCHER; } /** * Returns a matcher which matches the single quote character. * * @return a matcher for a single quote */ public static StrMatcher singleQuoteMatcher() { return SINGLE_QUOTE_MATCHER; } /** * Returns a matcher which matches the double quote character. * * @return a matcher for a double quote */ public static StrMatcher doubleQuoteMatcher() { return DOUBLE_QUOTE_MATCHER; } /** * Returns a matcher which matches the single or double quote character. * * @return a matcher for a single or double quote */ public static StrMatcher quoteMatcher() { return QUOTE_MATCHER; } /** * Matches no characters. * * @return a matcher that matches nothing */ public static StrMatcher noneMatcher() { return NONE_MATCHER; } /** * Constructor that creates a matcher from a character. * * @param ch the character to match, must not be null * @return a new Matcher for the given char */ public static StrMatcher charMatcher(final char ch) { return new CharMatcher(ch); } /** * Constructor that creates a matcher from a set of characters. * * @param chars the characters to match, null or empty matches nothing * @return a new matcher for the given char[] */ public static StrMatcher charSetMatcher(final char... chars) { if (chars == null || chars.length == 0) { return NONE_MATCHER; } if (chars.length == 1) { return new CharMatcher(chars[0]); } return new CharSetMatcher(chars); } /** * Constructor that creates a matcher from a string representing a set of characters. * * @param chars the characters to match, null or empty matches nothing * @return a new Matcher for the given characters */ public static StrMatcher charSetMatcher(final String chars) { if (chars == null || chars.length() == 0) { return NONE_MATCHER; } if (chars.length() == 1) { return new CharMatcher(chars.charAt(0)); } return new CharSetMatcher(chars.toCharArray()); } /** * Constructor that creates a matcher from a string. * * @param str the string to match, null or empty matches nothing * @return a new Matcher for the given String */ public static StrMatcher stringMatcher(final String str) { if (str == null || str.length() == 0) { return NONE_MATCHER; } return new StringMatcher(str); } //----------------------------------------------------------------------- /** * Constructor. */ protected StrMatcher() { super(); } /** * Returns the number of matching characters, zero for no match. * <p> * This method is called to check for a match. * The parameter <code>pos</code> represents the current position to be * checked in the string <code>buffer</code> (a character array which must * not be changed). * The API guarantees that <code>pos</code> is a valid index for <code>buffer</code>. * <p> * The character array may be larger than the active area to be matched. * Only values in the buffer between the specified indices may be accessed. * <p> * The matching code may check one character or many. * It may check characters preceding <code>pos</code> as well as those * after, so long as no checks exceed the bounds specified. * <p> * It must return zero for no match, or a positive number if a match was found. * The number indicates the number of characters that matched. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index (exclusive) of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ public abstract int isMatch(char[] buffer, int pos, int bufferStart, int bufferEnd); /** * Returns the number of matching characters, zero for no match. * <p> * This method is called to check for a match. * The parameter <code>pos</code> represents the current position to be * checked in the string <code>buffer</code> (a character array which must * not be changed). * The API guarantees that <code>pos</code> is a valid index for <code>buffer</code>. * <p> * The matching code may check one character or many. * It may check characters preceding <code>pos</code> as well as those after. * <p> * It must return zero for no match, or a positive number if a match was found. * The number indicates the number of characters that matched. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @return the number of matching characters, zero for no match */ public int isMatch(final char[] buffer, final int pos) { return isMatch(buffer, pos, 0, buffer.length); } //----------------------------------------------------------------------- /** * Class used to define a set of characters for matching purposes. */ static final class CharSetMatcher extends StrMatcher { /** The set of characters to match. */ private final char[] chars; /** * Constructor that creates a matcher from a character array. * * @param chars the characters to match, must not be null */ CharSetMatcher(final char chars[]) { super(); this.chars = chars.clone(); Arrays.sort(this.chars); } /** * Returns whether or not the given character matches. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ @Override public int isMatch(final char[] buffer, final int pos, final int bufferStart, final int bufferEnd) { return Arrays.binarySearch(chars, buffer[pos]) >= 0 ? 1 : 0; } } //----------------------------------------------------------------------- /** * Class used to define a character for matching purposes. */ static final class CharMatcher extends StrMatcher { /** The character to match. */ private final char ch; /** * Constructor that creates a matcher that matches a single character. * * @param ch the character to match */ CharMatcher(final char ch) { super(); this.ch = ch; } /** * Returns whether or not the given character matches. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ @Override public int isMatch(final char[] buffer, final int pos, final int bufferStart, final int bufferEnd) { return ch == buffer[pos] ? 1 : 0; } } //----------------------------------------------------------------------- /** * Class used to define a set of characters for matching purposes. */ static final class StringMatcher extends StrMatcher { /** The string to match, as a character array. */ private final char[] chars; /** * Constructor that creates a matcher from a String. * * @param str the string to match, must not be null */ StringMatcher(final String str) { super(); chars = str.toCharArray(); } /** * Returns whether or not the given text matches the stored string. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ @Override public int isMatch(final char[] buffer, int pos, final int bufferStart, final int bufferEnd) { final int len = chars.length; if (pos + len > bufferEnd) { return 0; } for (int i = 0; i < chars.length; i++, pos++) { if (chars[i] != buffer[pos]) { return 0; } } return len; } @Override public String toString() { return super.toString() + ' ' + Arrays.toString(chars); } } //----------------------------------------------------------------------- /** * Class used to match no characters. */ static final class NoMatcher extends StrMatcher { /** * Constructs a new instance of <code>NoMatcher</code>. */ NoMatcher() { super(); } /** * Always returns <code>false</code>. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ @Override public int isMatch(final char[] buffer, final int pos, final int bufferStart, final int bufferEnd) { return 0; } } //----------------------------------------------------------------------- /** * Class used to match whitespace as per trim(). */ static final class TrimMatcher extends StrMatcher { /** * Constructs a new instance of <code>TrimMatcher</code>. */ TrimMatcher() { super(); } /** * Returns whether or not the given character matches. * * @param buffer the text content to match against, do not change * @param pos the starting position for the match, valid for buffer * @param bufferStart the first active index in the buffer, valid for buffer * @param bufferEnd the end index of the active buffer, valid for buffer * @return the number of matching characters, zero for no match */ @Override public int isMatch(final char[] buffer, final int pos, final int bufferStart, final int bufferEnd) { return buffer[pos] <= 32 ? 1 : 0; } } }