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.lang; /** * <p>Operations on <code>CharSet</code>s.</p> * * <p>This class handles <code>null</code> input gracefully. * An exception will not be thrown for a <code>null</code> input. * Each method documents its behaviour in more detail.</p> * * @see CharSet * @author Stephen Colebourne * @author Phil Steitz * @author Gary Gregory * @since 1.0 * @version $Id: CharSetUtils.java 471626 2006-11-06 04:02:09Z bayard $ */ public class CharSetUtils { /** * <p>CharSetUtils instances should NOT be constructed in standard programming. * Instead, the class should be used as <code>CharSetUtils.evaluateSet(null);</code>.</p> * * <p>This constructor is public to permit tools that require a JavaBean instance * to operate.</p> */ public CharSetUtils() { super(); } // Factory //----------------------------------------------------------------------- /** * <p>Creates a <code>CharSet</code> instance which allows a certain amount of * set logic to be performed.</p> * <p>The syntax is:</p> * <ul> * <li>"aeio" which implies 'a','e',..</li> * <li>"^e" implies not e.</li> * <li>"ej-m" implies e,j->m. e,j,k,l,m.</li> * </ul> * * <pre> * CharSetUtils.evaluateSet(null) = null * CharSetUtils.evaluateSet([]) = CharSet matching nothing * CharSetUtils.evaluateSet(["a-e"]) = CharSet matching a,b,c,d,e * </pre> * * @param set the set, may be null * @return a CharSet instance, <code>null</code> if null input * @deprecated Use {@link CharSet#getInstance(String)}. * Method will be removed in Commons Lang 3.0. */ public static CharSet evaluateSet(String[] set) { if (set == null) { return null; } return new CharSet(set); } // Squeeze //----------------------------------------------------------------------- /** * <p>Squeezes any repetitions of a character that is mentioned in the * supplied set.</p> * * <pre> * CharSetUtils.squeeze(null, *) = null * CharSetUtils.squeeze("", *) = "" * CharSetUtils.squeeze(*, null) = * * CharSetUtils.squeeze(*, "") = * * CharSetUtils.squeeze("hello", "k-p") = "helo" * CharSetUtils.squeeze("hello", "a-e") = "hello" * </pre> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str the string to squeeze, may be null * @param set the character set to use for manipulation, may be null * @return modified String, <code>null</code> if null string input */ public static String squeeze(String str, String set) { if (StringUtils.isEmpty(str) || StringUtils.isEmpty(set)) { return str; } String[] strs = new String[1]; strs[0] = set; return squeeze(str, strs); } /** * <p>Squeezes any repetitions of a character that is mentioned in the * supplied set.</p> * * <p>An example is:</p> * <ul> * <li>squeeze("hello", {"el"}) => "helo"</li> * </ul> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str the string to squeeze, may be null * @param set the character set to use for manipulation, may be null * @return modified String, <code>null</code> if null string input */ public static String squeeze(String str, String[] set) { if (StringUtils.isEmpty(str) || ArrayUtils.isEmpty(set)) { return str; } CharSet chars = evaluateSet(set); StringBuffer buffer = new StringBuffer(str.length()); char[] chrs = str.toCharArray(); int sz = chrs.length; char lastChar = ' '; char ch = ' '; for (int i = 0; i < sz; i++) { ch = chrs[i]; if (chars.contains(ch)) { if ((ch == lastChar) && (i != 0)) { continue; } } buffer.append(ch); lastChar = ch; } return buffer.toString(); } // Count //----------------------------------------------------------------------- /** * <p>Takes an argument in set-syntax, see evaluateSet, * and returns the number of characters present in the specified string.</p> * * <pre> * CharSetUtils.count(null, *) = 0 * CharSetUtils.count("", *) = 0 * CharSetUtils.count(*, null) = 0 * CharSetUtils.count(*, "") = 0 * CharSetUtils.count("hello", "k-p") = 3 * CharSetUtils.count("hello", "a-e") = 1 * </pre> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to count characters in, may be null * @param set String set of characters to count, may be null * @return character count, zero if null string input */ public static int count(String str, String set) { if (StringUtils.isEmpty(str) || StringUtils.isEmpty(set)) { return 0; } String[] strs = new String[1]; strs[0] = set; return count(str, strs); } /** * <p>Takes an argument in set-syntax, see evaluateSet, * and returns the number of characters present in the specified string.</p> * * <p>An example would be:</p> * <ul> * <li>count("hello", {"c-f", "o"}) returns 2.</li> * </ul> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to count characters in, may be null * @param set String[] set of characters to count, may be null * @return character count, zero if null string input */ public static int count(String str, String[] set) { if (StringUtils.isEmpty(str) || ArrayUtils.isEmpty(set)) { return 0; } CharSet chars = evaluateSet(set); int count = 0; char[] chrs = str.toCharArray(); int sz = chrs.length; for (int i = 0; i < sz; i++) { if (chars.contains(chrs[i])) { count++; } } return count; } // Keep //----------------------------------------------------------------------- /** * <p>Takes an argument in set-syntax, see evaluateSet, * and keeps any of characters present in the specified string.</p> * * <pre> * CharSetUtils.keep(null, *) = null * CharSetUtils.keep("", *) = "" * CharSetUtils.keep(*, null) = "" * CharSetUtils.keep(*, "") = "" * CharSetUtils.keep("hello", "hl") = "hll" * CharSetUtils.keep("hello", "le") = "ell" * </pre> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to keep characters from, may be null * @param set String set of characters to keep, may be null * @return modified String, <code>null</code> if null string input * @since 2.0 */ public static String keep(String str, String set) { if (str == null) { return null; } if (str.length() == 0 || StringUtils.isEmpty(set)) { return ""; } String[] strs = new String[1]; strs[0] = set; return keep(str, strs); } /** * <p>Takes an argument in set-syntax, see evaluateSet, * and keeps any of characters present in the specified string.</p> * * <p>An example would be:</p> * <ul> * <li>keep("hello", {"c-f", "o"}) * returns "eo"</li> * </ul> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to keep characters from, may be null * @param set String[] set of characters to keep, may be null * @return modified String, <code>null</code> if null string input * @since 2.0 */ public static String keep(String str, String[] set) { if (str == null) { return null; } if (str.length() == 0 || ArrayUtils.isEmpty(set)) { return ""; } return modify(str, set, true); } // Delete //----------------------------------------------------------------------- /** * <p>Takes an argument in set-syntax, see evaluateSet, * and deletes any of characters present in the specified string.</p> * * <pre> * CharSetUtils.delete(null, *) = null * CharSetUtils.delete("", *) = "" * CharSetUtils.delete(*, null) = * * CharSetUtils.delete(*, "") = * * CharSetUtils.delete("hello", "hl") = "eo" * CharSetUtils.delete("hello", "le") = "ho" * </pre> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to delete characters from, may be null * @param set String set of characters to delete, may be null * @return modified String, <code>null</code> if null string input */ public static String delete(String str, String set) { if (StringUtils.isEmpty(str) || StringUtils.isEmpty(set)) { return str; } String[] strs = new String[1]; strs[0] = set; return delete(str, strs); } /** * <p>Takes an argument in set-syntax, see evaluateSet, * and deletes any of characters present in the specified string.</p> * * <p>An example would be:</p> * <ul> * <li>delete("hello", {"c-f", "o"}) returns * "hll"</li> * </ul> * * @see #evaluateSet(java.lang.String[]) for set-syntax. * @param str String to delete characters from, may be null * @param set String[] set of characters to delete, may be null * @return modified String, <code>null</code> if null string input */ public static String delete(String str, String[] set) { if (StringUtils.isEmpty(str) || ArrayUtils.isEmpty(set)) { return str; } return modify(str, set, false); } //----------------------------------------------------------------------- /** * Implementation of delete and keep * * @param str String to modify characters within * @param set String[] set of characters to modify * @param expect whether to evaluate on match, or non-match * @return modified String */ private static String modify(String str, String[] set, boolean expect) { CharSet chars = evaluateSet(set); StringBuffer buffer = new StringBuffer(str.length()); char[] chrs = str.toCharArray(); int sz = chrs.length; for (int i = 0; i < sz; i++) { if (chars.contains(chrs[i]) == expect) { buffer.append(chrs[i]); } } return buffer.toString(); } // Translate //----------------------------------------------------------------------- /** * <p>Translate characters in a String. * This is a multi character search and replace routine.</p> * * <p>An example is:</p> * <ul> * <li>translate("hello", "ho", "jy") * => jelly</li> * </ul> * * <p>If the length of characters to search for is greater than the * length of characters to replace, then the last character is * used.</p> * * <pre> * CharSetUtils.translate(null, *, *) = null * CharSetUtils.translate("", *, *) = "" * </pre> * * @param str String to replace characters in, may be null * @param searchChars a set of characters to search for, must not be null * @param replaceChars a set of characters to replace, must not be null or empty ("") * @return translated String, <code>null</code> if null string input * @throws NullPointerException if <code>searchChars</code> or <code>replaceChars</code> * is <code>null</code> * @throws ArrayIndexOutOfBoundsException if <code>replaceChars</code> is empty ("") * @deprecated Use {@link StringUtils#replaceChars(String, String, String)}. * Method will be removed in Commons Lang 3.0. * NOTE: StringUtils#replaceChars behaves differently when 'searchChars' is longer * than 'replaceChars'. CharSetUtils#translate will use the last char of the replacement * string whereas StringUtils#replaceChars will delete */ public static String translate(String str, String searchChars, String replaceChars) { if (StringUtils.isEmpty(str)) { return str; } StringBuffer buffer = new StringBuffer(str.length()); char[] chrs = str.toCharArray(); char[] withChrs = replaceChars.toCharArray(); int sz = chrs.length; int withMax = replaceChars.length() - 1; for (int i = 0; i < sz; i++) { int idx = searchChars.indexOf(chrs[i]); if (idx != -1) { if (idx > withMax) { idx = withMax; } buffer.append(withChrs[idx]); } else { buffer.append(chrs[i]); } } return buffer.toString(); } }