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. */ public class Main { /** * <p>Case insensitive check if a String starts with a specified prefix.</p> * * <p><code>null</code>s are handled without exceptions. Two <code>null</code> * references are considered to be equal. The comparison is case insensitive.</p> * * <pre> * StringUtils.startsWithIgnoreCase(null, null) = true * StringUtils.startsWithIgnoreCase(null, "abcdef") = false * StringUtils.startsWithIgnoreCase("abc", null) = false * StringUtils.startsWithIgnoreCase("abc", "abcdef") = true * StringUtils.startsWithIgnoreCase("abc", "ABCDEF") = true * </pre> * * @see java.lang.String#startsWith(String) * @param str the String to check, may be null * @param prefix the prefix to find, may be null * @return <code>true</code> if the String starts with the prefix, case insensitive, or * both <code>null</code> * @since 2.4 */ public static boolean startsWithIgnoreCase(String str, String prefix) { return startsWith(str, prefix, true); } /** * <p>Check if a String starts with a specified prefix (optionally case insensitive).</p> * * @see java.lang.String#startsWith(String) * @param str the String to check, may be null * @param prefix the prefix to find, may be null * @param ignoreCase inidicates whether the compare should ignore case * (case insensitive) or not. * @return <code>true</code> if the String starts with the prefix or * both <code>null</code> */ private static boolean startsWith(String str, String prefix, boolean ignoreCase) { if (str == null || prefix == null) { return (str == null && prefix == null); } if (prefix.length() > str.length()) { return false; } return str.regionMatches(ignoreCase, 0, prefix, 0, prefix.length()); } // Empty checks //----------------------------------------------------------------------- /** * <p>Checks if a String is empty ("") or null.</p> * * <pre> * StringUtils.isEmpty(null) = true * StringUtils.isEmpty("") = true * StringUtils.isEmpty(" ") = false * StringUtils.isEmpty("bob") = false * StringUtils.isEmpty(" bob ") = false * </pre> * * <p>NOTE: This method changed in Lang version 2.0. * It no longer trims the String. * That functionality is available in isBlank().</p> * * @param str the String to check, may be null * @return <code>true</code> if the String is empty or null */ public static boolean isEmpty(String str) { return str == null || str.length() == 0; } }