    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     *      http://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     */
    017    package org.apache.commons.lang3;
    018
    019    /**
    020     * Null-safe CharSequence utility methods.
    021     *
    022     * @author Gary Gregory
    023     * @version $Id: CharSequenceUtils.java 967237 2010-07-23 20:08:57Z mbenson $
    024     */
    025    public class CharSequenceUtils {
    026
    027        /**
    028         * Gets a CharSequence length or <code>0</code> if the CharSequence is
    029         * <code>null</code>.
    030         *
    031         * @param cs
    032         *            a CharSequence or <code>null</code>
    033         * @return CharSequence length or <code>0</code> if the CharSequence is
    034         *         <code>null</code>.
    035         * @since 3.0
    036         */
    037        public static int length(CharSequence cs) {
    038            return cs == null ? 0 : cs.length();
    039        }
    040
    041        /**
    042         * Returns a new <code>CharSequence</code> that is a subsequence of this
    043         * sequence starting with the <code>char</code> value at the specified
    044         * index. The length (in <code>char</code>s) of the returned sequence is
    045         * <code>length() - start</code>, so if <code>start == end</code> then an
    046         * empty sequence is returned. </p>
    047         *
    048         * @param cs
    049         *            the specified subsequence, may be null
    050         * @param start
    051         *            the start index, inclusive
    052         * @return a new subsequence or null
    053         *
    054         * @throws IndexOutOfBoundsException
    055         *             if <code>start</code> is negative or if <code>start</code> is
    056         *             greater than <code>length()</code>
    057         * @since 3.0
    058         */
    059        public static CharSequence subSequence(CharSequence cs, int start) {
    060            return cs == null ? null : cs.subSequence(start, cs.length());
    061        }
    062    }