Apache Commons Text LetterCase

/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
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 * <http://www.apache.org/>.
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 */
package org.apache.commons.text;

import java.util.Locale;

/**
 * Enumerates letter cases and converts strings.
 *
 * @author <a href="mailto:ggregory@rocketsoftware.com">Gary Gregory</a>
 */
public enum LetterCase {

    LOWER {
        @Override
        public char[] toCaseString(final char[] source, final Locale locale) {
            return String.valueOf(source).toLowerCase(locale).toCharArray();
        }

        @Override
        public String toCaseString(final String source, final Locale locale) {
            return source.toLowerCase(locale);
        }

    },
    UPPER {
        @Override
        public char[] toCaseString(final char[] source, final Locale locale) {
            return String.valueOf(source).toUpperCase(locale).toCharArray();
        }

        @Override
        public String toCaseString(final String source, final Locale locale) {
            return source.toUpperCase(locale);
        }
    };

    /**
     * Converts from the given {@code source} string to the case specified by this enum using the default {@code locale}.
     *
     * @param source
     *            the string to convert
     * @param locale
     *            the locale to use for conversion.
     * @return a converted string.
     */
    public char[] toCaseString(final char[] source) {
        return toCaseString(source, Locale.getDefault());
    }

    /**
     * Converts from the given {@code source} char[] to the case specified by this enum using the given {@code locale}.
     *
     * @param source
     *            the char[] to convert
     * @param locale
     *            the locale to use for conversion.
     * @return a converted char[].
     */
    public abstract char[] toCaseString(char[] source, Locale locale);

    /**
     * Converts from the given {@code source} string to the case specified by this enum using the default {@code locale}.
     *
     * @param source
     *            the string to convert
     * @param locale
     *            the locale to use for conversion.
     * @return a converted string.
     */
    public String toCaseString(final String source) {
        return toCaseString(source, Locale.getDefault());
    }

    /**
     * Converts from the given {@code source} string to the case specified by this enum using the given {@code locale}.
     *
     * @param source
     *            the string to convert
     * @param locale
     *            the locale to use for conversion.
     * @return a converted string.
     */
    public abstract String toCaseString(String source, Locale locale);

}