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.lang3; /** * <p>Operations on {@code CharSet} instances.</p> * * <p>This class handles {@code null} input gracefully. * An exception will not be thrown for a {@code null} input. * Each method documents its behaviour in more detail.</p> * * <p>#ThreadSafe#</p> * @see CharSet * @since 1.0 * @version $Id$ */ public class CharSetUtils { /** * <p>CharSetUtils instances should NOT be constructed in standard programming. * Instead, the class should be used as {@code CharSetUtils.evaluateSet(null);}.</p> * * <p>This constructor is public to permit tools that require a JavaBean instance * to operate.</p> */ public CharSetUtils() { super(); } // 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 CharSet#getInstance(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 the modified String, {@code null} if null string input */ public static String squeeze(final String str, final String... set) { if (StringUtils.isEmpty(str) || deepEmpty(set)) { return str; } final CharSet chars = CharSet.getInstance(set); final StringBuilder buffer = new StringBuilder(str.length()); final char[] chrs = str.toCharArray(); final int sz = chrs.length; char lastChar = ' '; char ch = ' '; for (int i = 0; i < sz; i++) { ch = chrs[i]; // Compare with contains() last for performance. if (ch == lastChar && i != 0 && chars.contains(ch)) { continue; } buffer.append(ch); lastChar = ch; } return buffer.toString(); } // ContainsAny //----------------------------------------------------------------------- /** * <p>Takes an argument in set-syntax, see evaluateSet, * and identifies whether any of the characters are present in the specified string.</p> * * <pre> * CharSetUtils.containsAny(null, *) = false * CharSetUtils.containsAny("", *) = false * CharSetUtils.containsAny(*, null) = false * CharSetUtils.containsAny(*, "") = false * CharSetUtils.containsAny("hello", "k-p") = true * CharSetUtils.containsAny("hello", "a-d") = false * </pre> * * @see CharSet#getInstance(java.lang.String...) for set-syntax. * @param str String to look for characters in, may be null * @param set String[] set of characters to identify, may be null * @return whether or not the characters in the set are in the primary string * @since 3.2 */ public static boolean containsAny(final String str, final String... set) { if (StringUtils.isEmpty(str) || deepEmpty(set)) { return false; } final CharSet chars = CharSet.getInstance(set); for (final char c : str.toCharArray()) { if (chars.contains(c)) { return true; } } return false; } // 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 CharSet#getInstance(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 the character count, zero if null string input */ public static int count(final String str, final String... set) { if (StringUtils.isEmpty(str) || deepEmpty(set)) { return 0; } final CharSet chars = CharSet.getInstance(set); int count = 0; for (final char c : str.toCharArray()) { if (chars.contains(c)) { 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 CharSet#getInstance(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 the modified String, {@code null} if null string input * @since 2.0 */ public static String keep(final String str, final String... set) { if (str == null) { return null; } if (str.isEmpty() || deepEmpty(set)) { return StringUtils.EMPTY; } 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 CharSet#getInstance(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 the modified String, {@code null} if null string input */ public static String delete(final String str, final String... set) { if (StringUtils.isEmpty(str) || deepEmpty(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 the modified String, not null */ private static String modify(final String str, final String[] set, final boolean expect) { final CharSet chars = CharSet.getInstance(set); final StringBuilder buffer = new StringBuilder(str.length()); final char[] chrs = str.toCharArray(); final int sz = chrs.length; for (int i = 0; i < sz; i++) { if (chars.contains(chrs[i]) == expect) { buffer.append(chrs[i]); } } return buffer.toString(); } /** * Determines whether or not all the Strings in an array are * empty or not. * * @param strings String[] whose elements are being checked for emptiness * @return whether or not the String is empty */ private static boolean deepEmpty(final String[] strings) { if (strings != null) { for (final String s : strings) { if (StringUtils.isNotEmpty(s)) { return false; } } } return true; } }