    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      https://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.text;
    018
    019import java.util.HashSet;
    020import java.util.Set;
    021
    022import org.apache.commons.lang3.ArrayUtils;
    023import org.apache.commons.lang3.StringUtils;
    024
    025/**
    026 * Case manipulation operations on Strings that contain words.
    027 *
    028 * <p>This class tries to handle {@code null} input gracefully.
    029 * An exception will not be thrown for a {@code null} input.
    030 * Each method documents its behavior in more detail.</p>
    031 *
    032 * @since 1.2
    033 */
    034public class CaseUtils {
    035
    036    /**
    037     * Converts all the delimiter separated words in a String into camelCase,
    038     * that is each word is made up of a title case character and then a series of
    039     * lowercase characters.
    040     *
    041     * <p>The delimiters represent a set of characters understood to separate words.
    042     * The first non-delimiter character after a delimiter will be capitalized. The first String
    043     * character may or may not be capitalized and it's determined by the user input for capitalizeFirstLetter
    044     * variable.</p>
    045     *
    046     * <p>A {@code null} input String returns {@code null}.</p>
    047     *
    048     * <p>A input string with only delimiter characters returns {@code ""}.</p>
    049     *
    050     * Capitalization uses the Unicode title case, normally equivalent to
    051     * upper case and cannot perform locale-sensitive mappings.
    052     *
    053     * <pre>
    054     * CaseUtils.toCamelCase(null, false)                                 = null
    055     * CaseUtils.toCamelCase("", false, *)                                = ""
    056     * CaseUtils.toCamelCase(*, false, null)                              = *
    057     * CaseUtils.toCamelCase(*, true, new char[0])                        = *
    058     * CaseUtils.toCamelCase("To.Camel.Case", false, new char[]{'.'})     = "toCamelCase"
    059     * CaseUtils.toCamelCase(" to @ Camel case", true, new char[]{'@'})   = "ToCamelCase"
    060     * CaseUtils.toCamelCase(" @to @ Camel case", false, new char[]{'@'}) = "toCamelCase"
    061     * CaseUtils.toCamelCase(" @", false, new char[]{'@'})                = ""
    062     * </pre>
    063     *
    064     * @param str  the String to be converted to camelCase, may be null
    065     * @param capitalizeFirstLetter boolean that determines if the first character of first word should be title case.
    066     * @param delimiters  set of characters to determine capitalization, null and/or empty array means whitespace
    067     * @return camelCase of String, {@code null} if null String input
    068     */
    069    public static String toCamelCase(String str, final boolean capitalizeFirstLetter, final char... delimiters) {
    070        if (StringUtils.isEmpty(str)) {
    071            return str;
    072        }
    073        str = str.toLowerCase();
    074        final int strLen = str.length();
    075        final int[] newCodePoints = new int[strLen];
    076        int outOffset = 0;
    077        final Set<Integer> delimiterSet = toDelimiterSet(delimiters);
    078        boolean capitalizeNext = capitalizeFirstLetter;
    079        for (int index = 0; index < strLen;) {
    080            final int codePoint = str.codePointAt(index);
    081
    082            if (delimiterSet.contains(codePoint)) {
    083                capitalizeNext = outOffset != 0;
    084                index += Character.charCount(codePoint);
    085            } else if (capitalizeNext || outOffset == 0 && capitalizeFirstLetter) {
    086                final int titleCaseCodePoint = Character.toTitleCase(codePoint);
    087                newCodePoints[outOffset++] = titleCaseCodePoint;
    088                index += Character.charCount(titleCaseCodePoint);
    089                capitalizeNext = false;
    090            } else {
    091                newCodePoints[outOffset++] = codePoint;
    092                index += Character.charCount(codePoint);
    093            }
    094        }
    095
    096        return new String(newCodePoints, 0, outOffset);
    097    }
    098
    099    /**
    100     * Converts an array of delimiters to a hash set of code points. Code point of space(32) is added
    101     * as the default value. The generated hash set provides O(1) lookup time.
    102     *
    103     * @param delimiters  set of characters to determine capitalization, null means whitespace
    104     * @return Set<Integer>
    105     */
    106    private static Set<Integer> toDelimiterSet(final char[] delimiters) {
    107        final Set<Integer> delimiterHashSet = new HashSet<>();
    108        delimiterHashSet.add(Character.codePointAt(new char[]{' '}, 0));
    109        if (ArrayUtils.isEmpty(delimiters)) {
    110            return delimiterHashSet;
    111        }
    112
    113        for (int index = 0; index < delimiters.length; index++) {
    114            delimiterHashSet.add(Character.codePointAt(delimiters, index));
    115        }
    116        return delimiterHashSet;
    117    }
    118
    119    /**
    120     * {@code CaseUtils} instances should NOT be constructed in
    121     * standard programming. Instead, the class should be used as
    122     * {@code CaseUtils.toCamelCase("foo bar", true, new char[]{'-'});}.
    123     *
    124     * <p>This constructor is public to permit tools that require a JavaBean
    125     * instance to operate.</p>
    126     */
    127    public CaseUtils() {
    128    }
    129}
    130