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. */ /** * Operations on {@link java.lang.String} that are * <code>null</code> safe. * * @see java.lang.String * @author <a href="http://jakarta.apache.org/turbine/">Apache Jakarta Turbine</a> * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a> * @author Daniel L. Rall * @author <a href="mailto:gcoladonato@yahoo.com">Greg Coladonato</a> * @author <a href="mailto:ed@apache.org">Ed Korthof</a> * @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a> * @author Stephen Colebourne * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a> * @author Holger Krauth * @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a> * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> * @author Arun Mammen Thomas * @author Gary Gregory * @author Phil Steitz * @author Al Chou * @author Michael Davey * @author Reuben Sivan * @author Chris Hyzer * @author Scott Johnson * @since 1.0 * @version $Id: StringUtils.java 635447 2008-03-10 06:27:09Z bayard $ */ public class Main { /** * Checks if String contains a search String irrespective of case, * handling <code>null</code>. This method uses * {@link #contains(String, String)}. * * A <code>null</code> String will return <code>false</code>. * * <pre> * StringUtils.contains(null, *) = false * StringUtils.contains(*, null) = false * StringUtils.contains("", "") = true * StringUtils.contains("abc", "") = true * StringUtils.contains("abc", "a") = true * StringUtils.contains("abc", "z") = false * StringUtils.contains("abc", "A") = true * StringUtils.contains("abc", "Z") = false * </pre> * * @param str the String to check, may be null * @param searchStr the String to find, may be null * @return true if the String contains the search String irrespective of * case or false if not or <code>null</code> string input */ public static boolean containsIgnoreCase(String str, String searchStr) { if (str == null || searchStr == null) { return false; } return contains(str.toUpperCase(), searchStr.toUpperCase()); } /** * Checks if String contains a search String, handling <code>null</code>. * This method uses {@link String#indexOf(String)}. * * A <code>null</code> String will return <code>false</code>. * * <pre> * StringUtils.contains(null, *) = false * StringUtils.contains(*, null) = false * StringUtils.contains("", "") = true * StringUtils.contains("abc", "") = true * StringUtils.contains("abc", "a") = true * StringUtils.contains("abc", "z") = false * </pre> * * @param str the String to check, may be null * @param searchStr the String to find, may be null * @return true if the String contains the search String, * false if not or <code>null</code> string input * @since 2.0 */ public static boolean contains(String str, String searchStr) { if (str == null || searchStr == null) { return false; } return str.indexOf(searchStr) >= 0; } // Empty checks //----------------------------------------------------------------------- /** * Checks if a String is empty ("") or null. * * <pre> * StringUtils.isEmpty(null) = true * StringUtils.isEmpty("") = true * StringUtils.isEmpty(" ") = false * StringUtils.isEmpty("bob") = false * StringUtils.isEmpty(" bob ") = false * </pre> * * NOTE: This method changed in Lang version 2.0. * It no longer trims the String. * That functionality is available in isBlank(). * * @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; } }